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1/*
2 * User-space Probes (UProbes)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2008-2012
19 * Authors:
20 * Srikar Dronamraju
21 * Jim Keniston
22 * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
23 */
24
25#include <linux/kernel.h>
26#include <linux/highmem.h>
27#include <linux/pagemap.h> /* read_mapping_page */
28#include <linux/slab.h>
29#include <linux/sched.h>
30#include <linux/rmap.h> /* anon_vma_prepare */
31#include <linux/mmu_notifier.h> /* set_pte_at_notify */
32#include <linux/swap.h> /* try_to_free_swap */
33#include <linux/ptrace.h> /* user_enable_single_step */
34#include <linux/kdebug.h> /* notifier mechanism */
35
36#include <linux/uprobes.h>
37
38#define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
39#define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
40
41static struct srcu_struct uprobes_srcu;
42static struct rb_root uprobes_tree = RB_ROOT;
43
44static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
45
46#define UPROBES_HASH_SZ 13
47
48/* serialize (un)register */
49static struct mutex uprobes_mutex[UPROBES_HASH_SZ];
50
51#define uprobes_hash(v) (&uprobes_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
52
53/* serialize uprobe->pending_list */
54static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
55#define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
56
57/*
58 * uprobe_events allows us to skip the uprobe_mmap if there are no uprobe
59 * events active at this time. Probably a fine grained per inode count is
60 * better?
61 */
62static atomic_t uprobe_events = ATOMIC_INIT(0);
63
64/*
65 * Maintain a temporary per vma info that can be used to search if a vma
66 * has already been handled. This structure is introduced since extending
67 * vm_area_struct wasnt recommended.
68 */
69struct vma_info {
70 struct list_head probe_list;
71 struct mm_struct *mm;
72 loff_t vaddr;
73};
74
75struct uprobe {
76 struct rb_node rb_node; /* node in the rb tree */
77 atomic_t ref;
78 struct rw_semaphore consumer_rwsem;
79 struct list_head pending_list;
80 struct uprobe_consumer *consumers;
81 struct inode *inode; /* Also hold a ref to inode */
82 loff_t offset;
83 int flags;
84 struct arch_uprobe arch;
85};
86
87/*
88 * valid_vma: Verify if the specified vma is an executable vma
89 * Relax restrictions while unregistering: vm_flags might have
90 * changed after breakpoint was inserted.
91 * - is_register: indicates if we are in register context.
92 * - Return 1 if the specified virtual address is in an
93 * executable vma.
94 */
95static bool valid_vma(struct vm_area_struct *vma, bool is_register)
96{
97 if (!vma->vm_file)
98 return false;
99
100 if (!is_register)
101 return true;
102
103 if ((vma->vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)) == (VM_READ|VM_EXEC))
104 return true;
105
106 return false;
107}
108
109static loff_t vma_address(struct vm_area_struct *vma, loff_t offset)
110{
111 loff_t vaddr;
112
113 vaddr = vma->vm_start + offset;
114 vaddr -= vma->vm_pgoff << PAGE_SHIFT;
115
116 return vaddr;
117}
118
119/**
120 * __replace_page - replace page in vma by new page.
121 * based on replace_page in mm/ksm.c
122 *
123 * @vma: vma that holds the pte pointing to page
124 * @page: the cowed page we are replacing by kpage
125 * @kpage: the modified page we replace page by
126 *
127 * Returns 0 on success, -EFAULT on failure.
128 */
129static int __replace_page(struct vm_area_struct *vma, struct page *page, struct page *kpage)
130{
131 struct mm_struct *mm = vma->vm_mm;
132 pgd_t *pgd;
133 pud_t *pud;
134 pmd_t *pmd;
135 pte_t *ptep;
136 spinlock_t *ptl;
137 unsigned long addr;
138 int err = -EFAULT;
139
140 addr = page_address_in_vma(page, vma);
141 if (addr == -EFAULT)
142 goto out;
143
144 pgd = pgd_offset(mm, addr);
145 if (!pgd_present(*pgd))
146 goto out;
147
148 pud = pud_offset(pgd, addr);
149 if (!pud_present(*pud))
150 goto out;
151
152 pmd = pmd_offset(pud, addr);
153 if (!pmd_present(*pmd))
154 goto out;
155
156 ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
157 if (!ptep)
158 goto out;
159
160 get_page(kpage);
161 page_add_new_anon_rmap(kpage, vma, addr);
162
163 if (!PageAnon(page)) {
164 dec_mm_counter(mm, MM_FILEPAGES);
165 inc_mm_counter(mm, MM_ANONPAGES);
166 }
167
168 flush_cache_page(vma, addr, pte_pfn(*ptep));
169 ptep_clear_flush(vma, addr, ptep);
170 set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
171
172 page_remove_rmap(page);
173 if (!page_mapped(page))
174 try_to_free_swap(page);
175 put_page(page);
176 pte_unmap_unlock(ptep, ptl);
177 err = 0;
178
179out:
180 return err;
181}
182
183/**
184 * is_swbp_insn - check if instruction is breakpoint instruction.
185 * @insn: instruction to be checked.
186 * Default implementation of is_swbp_insn
187 * Returns true if @insn is a breakpoint instruction.
188 */
189bool __weak is_swbp_insn(uprobe_opcode_t *insn)
190{
191 return *insn == UPROBE_SWBP_INSN;
192}
193
194/*
195 * NOTE:
196 * Expect the breakpoint instruction to be the smallest size instruction for
197 * the architecture. If an arch has variable length instruction and the
198 * breakpoint instruction is not of the smallest length instruction
199 * supported by that architecture then we need to modify read_opcode /
200 * write_opcode accordingly. This would never be a problem for archs that
201 * have fixed length instructions.
202 */
203
204/*
205 * write_opcode - write the opcode at a given virtual address.
206 * @auprobe: arch breakpointing information.
207 * @mm: the probed process address space.
208 * @vaddr: the virtual address to store the opcode.
209 * @opcode: opcode to be written at @vaddr.
210 *
211 * Called with mm->mmap_sem held (for read and with a reference to
212 * mm).
213 *
214 * For mm @mm, write the opcode at @vaddr.
215 * Return 0 (success) or a negative errno.
216 */
217static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
218 unsigned long vaddr, uprobe_opcode_t opcode)
219{
220 struct page *old_page, *new_page;
221 struct address_space *mapping;
222 void *vaddr_old, *vaddr_new;
223 struct vm_area_struct *vma;
224 struct uprobe *uprobe;
225 loff_t addr;
226 int ret;
227
228 /* Read the page with vaddr into memory */
229 ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
230 if (ret <= 0)
231 return ret;
232
233 ret = -EINVAL;
234
235 /*
236 * We are interested in text pages only. Our pages of interest
237 * should be mapped for read and execute only. We desist from
238 * adding probes in write mapped pages since the breakpoints
239 * might end up in the file copy.
240 */
241 if (!valid_vma(vma, is_swbp_insn(&opcode)))
242 goto put_out;
243
244 uprobe = container_of(auprobe, struct uprobe, arch);
245 mapping = uprobe->inode->i_mapping;
246 if (mapping != vma->vm_file->f_mapping)
247 goto put_out;
248
249 addr = vma_address(vma, uprobe->offset);
250 if (vaddr != (unsigned long)addr)
251 goto put_out;
252
253 ret = -ENOMEM;
254 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
255 if (!new_page)
256 goto put_out;
257
258 __SetPageUptodate(new_page);
259
260 /*
261 * lock page will serialize against do_wp_page()'s
262 * PageAnon() handling
263 */
264 lock_page(old_page);
265 /* copy the page now that we've got it stable */
266 vaddr_old = kmap_atomic(old_page);
267 vaddr_new = kmap_atomic(new_page);
268
269 memcpy(vaddr_new, vaddr_old, PAGE_SIZE);
270
271 /* poke the new insn in, ASSUMES we don't cross page boundary */
272 vaddr &= ~PAGE_MASK;
273 BUG_ON(vaddr + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
274 memcpy(vaddr_new + vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
275
276 kunmap_atomic(vaddr_new);
277 kunmap_atomic(vaddr_old);
278
279 ret = anon_vma_prepare(vma);
280 if (ret)
281 goto unlock_out;
282
283 lock_page(new_page);
284 ret = __replace_page(vma, old_page, new_page);
285 unlock_page(new_page);
286
287unlock_out:
288 unlock_page(old_page);
289 page_cache_release(new_page);
290
291put_out:
292 put_page(old_page);
293
294 return ret;
295}
296
297/**
298 * read_opcode - read the opcode at a given virtual address.
299 * @mm: the probed process address space.
300 * @vaddr: the virtual address to read the opcode.
301 * @opcode: location to store the read opcode.
302 *
303 * Called with mm->mmap_sem held (for read and with a reference to
304 * mm.
305 *
306 * For mm @mm, read the opcode at @vaddr and store it in @opcode.
307 * Return 0 (success) or a negative errno.
308 */
309static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode)
310{
311 struct page *page;
312 void *vaddr_new;
313 int ret;
314
315 ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
316 if (ret <= 0)
317 return ret;
318
319 lock_page(page);
320 vaddr_new = kmap_atomic(page);
321 vaddr &= ~PAGE_MASK;
322 memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
323 kunmap_atomic(vaddr_new);
324 unlock_page(page);
325
326 put_page(page);
327
328 return 0;
329}
330
331static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
332{
333 uprobe_opcode_t opcode;
334 int result;
335
336 result = read_opcode(mm, vaddr, &opcode);
337 if (result)
338 return result;
339
340 if (is_swbp_insn(&opcode))
341 return 1;
342
343 return 0;
344}
345
346/**
347 * set_swbp - store breakpoint at a given address.
348 * @auprobe: arch specific probepoint information.
349 * @mm: the probed process address space.
350 * @vaddr: the virtual address to insert the opcode.
351 *
352 * For mm @mm, store the breakpoint instruction at @vaddr.
353 * Return 0 (success) or a negative errno.
354 */
355int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
356{
357 int result;
358
359 result = is_swbp_at_addr(mm, vaddr);
360 if (result == 1)
361 return -EEXIST;
362
363 if (result)
364 return result;
365
366 return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
367}
368
369/**
370 * set_orig_insn - Restore the original instruction.
371 * @mm: the probed process address space.
372 * @auprobe: arch specific probepoint information.
373 * @vaddr: the virtual address to insert the opcode.
374 * @verify: if true, verify existance of breakpoint instruction.
375 *
376 * For mm @mm, restore the original opcode (opcode) at @vaddr.
377 * Return 0 (success) or a negative errno.
378 */
379int __weak
380set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, bool verify)
381{
382 if (verify) {
383 int result;
384
385 result = is_swbp_at_addr(mm, vaddr);
386 if (!result)
387 return -EINVAL;
388
389 if (result != 1)
390 return result;
391 }
392 return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
393}
394
395static int match_uprobe(struct uprobe *l, struct uprobe *r)
396{
397 if (l->inode < r->inode)
398 return -1;
399
400 if (l->inode > r->inode)
401 return 1;
402
403 if (l->offset < r->offset)
404 return -1;
405
406 if (l->offset > r->offset)
407 return 1;
408
409 return 0;
410}
411
412static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
413{
414 struct uprobe u = { .inode = inode, .offset = offset };
415 struct rb_node *n = uprobes_tree.rb_node;
416 struct uprobe *uprobe;
417 int match;
418
419 while (n) {
420 uprobe = rb_entry(n, struct uprobe, rb_node);
421 match = match_uprobe(&u, uprobe);
422 if (!match) {
423 atomic_inc(&uprobe->ref);
424 return uprobe;
425 }
426
427 if (match < 0)
428 n = n->rb_left;
429 else
430 n = n->rb_right;
431 }
432 return NULL;
433}
434
435/*
436 * Find a uprobe corresponding to a given inode:offset
437 * Acquires uprobes_treelock
438 */
439static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
440{
441 struct uprobe *uprobe;
442 unsigned long flags;
443
444 spin_lock_irqsave(&uprobes_treelock, flags);
445 uprobe = __find_uprobe(inode, offset);
446 spin_unlock_irqrestore(&uprobes_treelock, flags);
447
448 return uprobe;
449}
450
451static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
452{
453 struct rb_node **p = &uprobes_tree.rb_node;
454 struct rb_node *parent = NULL;
455 struct uprobe *u;
456 int match;
457
458 while (*p) {
459 parent = *p;
460 u = rb_entry(parent, struct uprobe, rb_node);
461 match = match_uprobe(uprobe, u);
462 if (!match) {
463 atomic_inc(&u->ref);
464 return u;
465 }
466
467 if (match < 0)
468 p = &parent->rb_left;
469 else
470 p = &parent->rb_right;
471
472 }
473
474 u = NULL;
475 rb_link_node(&uprobe->rb_node, parent, p);
476 rb_insert_color(&uprobe->rb_node, &uprobes_tree);
477 /* get access + creation ref */
478 atomic_set(&uprobe->ref, 2);
479
480 return u;
481}
482
483/*
484 * Acquire uprobes_treelock.
485 * Matching uprobe already exists in rbtree;
486 * increment (access refcount) and return the matching uprobe.
487 *
488 * No matching uprobe; insert the uprobe in rb_tree;
489 * get a double refcount (access + creation) and return NULL.
490 */
491static struct uprobe *insert_uprobe(struct uprobe *uprobe)
492{
493 unsigned long flags;
494 struct uprobe *u;
495
496 spin_lock_irqsave(&uprobes_treelock, flags);
497 u = __insert_uprobe(uprobe);
498 spin_unlock_irqrestore(&uprobes_treelock, flags);
499
500 /* For now assume that the instruction need not be single-stepped */
501 uprobe->flags |= UPROBE_SKIP_SSTEP;
502
503 return u;
504}
505
506static void put_uprobe(struct uprobe *uprobe)
507{
508 if (atomic_dec_and_test(&uprobe->ref))
509 kfree(uprobe);
510}
511
512static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
513{
514 struct uprobe *uprobe, *cur_uprobe;
515
516 uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
517 if (!uprobe)
518 return NULL;
519
520 uprobe->inode = igrab(inode);
521 uprobe->offset = offset;
522 init_rwsem(&uprobe->consumer_rwsem);
523 INIT_LIST_HEAD(&uprobe->pending_list);
524
525 /* add to uprobes_tree, sorted on inode:offset */
526 cur_uprobe = insert_uprobe(uprobe);
527
528 /* a uprobe exists for this inode:offset combination */
529 if (cur_uprobe) {
530 kfree(uprobe);
531 uprobe = cur_uprobe;
532 iput(inode);
533 } else {
534 atomic_inc(&uprobe_events);
535 }
536
537 return uprobe;
538}
539
540static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
541{
542 struct uprobe_consumer *uc;
543
544 if (!(uprobe->flags & UPROBE_RUN_HANDLER))
545 return;
546
547 down_read(&uprobe->consumer_rwsem);
548 for (uc = uprobe->consumers; uc; uc = uc->next) {
549 if (!uc->filter || uc->filter(uc, current))
550 uc->handler(uc, regs);
551 }
552 up_read(&uprobe->consumer_rwsem);
553}
554
555/* Returns the previous consumer */
556static struct uprobe_consumer *
557consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
558{
559 down_write(&uprobe->consumer_rwsem);
560 uc->next = uprobe->consumers;
561 uprobe->consumers = uc;
562 up_write(&uprobe->consumer_rwsem);
563
564 return uc->next;
565}
566
567/*
568 * For uprobe @uprobe, delete the consumer @uc.
569 * Return true if the @uc is deleted successfully
570 * or return false.
571 */
572static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
573{
574 struct uprobe_consumer **con;
575 bool ret = false;
576
577 down_write(&uprobe->consumer_rwsem);
578 for (con = &uprobe->consumers; *con; con = &(*con)->next) {
579 if (*con == uc) {
580 *con = uc->next;
581 ret = true;
582 break;
583 }
584 }
585 up_write(&uprobe->consumer_rwsem);
586
587 return ret;
588}
589
590static int
591__copy_insn(struct address_space *mapping, struct vm_area_struct *vma, char *insn,
592 unsigned long nbytes, unsigned long offset)
593{
594 struct file *filp = vma->vm_file;
595 struct page *page;
596 void *vaddr;
597 unsigned long off1;
598 unsigned long idx;
599
600 if (!filp)
601 return -EINVAL;
602
603 idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT);
604 off1 = offset &= ~PAGE_MASK;
605
606 /*
607 * Ensure that the page that has the original instruction is
608 * populated and in page-cache.
609 */
610 page = read_mapping_page(mapping, idx, filp);
611 if (IS_ERR(page))
612 return PTR_ERR(page);
613
614 vaddr = kmap_atomic(page);
615 memcpy(insn, vaddr + off1, nbytes);
616 kunmap_atomic(vaddr);
617 page_cache_release(page);
618
619 return 0;
620}
621
622static int
623copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long addr)
624{
625 struct address_space *mapping;
626 unsigned long nbytes;
627 int bytes;
628
629 addr &= ~PAGE_MASK;
630 nbytes = PAGE_SIZE - addr;
631 mapping = uprobe->inode->i_mapping;
632
633 /* Instruction at end of binary; copy only available bytes */
634 if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
635 bytes = uprobe->inode->i_size - uprobe->offset;
636 else
637 bytes = MAX_UINSN_BYTES;
638
639 /* Instruction at the page-boundary; copy bytes in second page */
640 if (nbytes < bytes) {
641 if (__copy_insn(mapping, vma, uprobe->arch.insn + nbytes,
642 bytes - nbytes, uprobe->offset + nbytes))
643 return -ENOMEM;
644
645 bytes = nbytes;
646 }
647 return __copy_insn(mapping, vma, uprobe->arch.insn, bytes, uprobe->offset);
648}
649
650/*
651 * How mm->uprobes_state.count gets updated
652 * uprobe_mmap() increments the count if
653 * - it successfully adds a breakpoint.
654 * - it cannot add a breakpoint, but sees that there is a underlying
655 * breakpoint (via a is_swbp_at_addr()).
656 *
657 * uprobe_munmap() decrements the count if
658 * - it sees a underlying breakpoint, (via is_swbp_at_addr)
659 * (Subsequent uprobe_unregister wouldnt find the breakpoint
660 * unless a uprobe_mmap kicks in, since the old vma would be
661 * dropped just after uprobe_munmap.)
662 *
663 * uprobe_register increments the count if:
664 * - it successfully adds a breakpoint.
665 *
666 * uprobe_unregister decrements the count if:
667 * - it sees a underlying breakpoint and removes successfully.
668 * (via is_swbp_at_addr)
669 * (Subsequent uprobe_munmap wouldnt find the breakpoint
670 * since there is no underlying breakpoint after the
671 * breakpoint removal.)
672 */
673static int
674install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
675 struct vm_area_struct *vma, loff_t vaddr)
676{
677 unsigned long addr;
678 int ret;
679
680 /*
681 * If probe is being deleted, unregister thread could be done with
682 * the vma-rmap-walk through. Adding a probe now can be fatal since
683 * nobody will be able to cleanup. Also we could be from fork or
684 * mremap path, where the probe might have already been inserted.
685 * Hence behave as if probe already existed.
686 */
687 if (!uprobe->consumers)
688 return -EEXIST;
689
690 addr = (unsigned long)vaddr;
691
692 if (!(uprobe->flags & UPROBE_COPY_INSN)) {
693 ret = copy_insn(uprobe, vma, addr);
694 if (ret)
695 return ret;
696
697 if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
698 return -EEXIST;
699
700 ret = arch_uprobe_analyze_insn(&uprobe->arch, mm);
701 if (ret)
702 return ret;
703
704 uprobe->flags |= UPROBE_COPY_INSN;
705 }
706
707 /*
708 * Ideally, should be updating the probe count after the breakpoint
709 * has been successfully inserted. However a thread could hit the
710 * breakpoint we just inserted even before the probe count is
711 * incremented. If this is the first breakpoint placed, breakpoint
712 * notifier might ignore uprobes and pass the trap to the thread.
713 * Hence increment before and decrement on failure.
714 */
715 atomic_inc(&mm->uprobes_state.count);
716 ret = set_swbp(&uprobe->arch, mm, addr);
717 if (ret)
718 atomic_dec(&mm->uprobes_state.count);
719
720 return ret;
721}
722
723static void
724remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, loff_t vaddr)
725{
726 if (!set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true))
727 atomic_dec(&mm->uprobes_state.count);
728}
729
730/*
731 * There could be threads that have hit the breakpoint and are entering the
732 * notifier code and trying to acquire the uprobes_treelock. The thread
733 * calling delete_uprobe() that is removing the uprobe from the rb_tree can
734 * race with these threads and might acquire the uprobes_treelock compared
735 * to some of the breakpoint hit threads. In such a case, the breakpoint
736 * hit threads will not find the uprobe. The current unregistering thread
737 * waits till all other threads have hit a breakpoint, to acquire the
738 * uprobes_treelock before the uprobe is removed from the rbtree.
739 */
740static void delete_uprobe(struct uprobe *uprobe)
741{
742 unsigned long flags;
743
744 synchronize_srcu(&uprobes_srcu);
745 spin_lock_irqsave(&uprobes_treelock, flags);
746 rb_erase(&uprobe->rb_node, &uprobes_tree);
747 spin_unlock_irqrestore(&uprobes_treelock, flags);
748 iput(uprobe->inode);
749 put_uprobe(uprobe);
750 atomic_dec(&uprobe_events);
751}
752
753static struct vma_info *
754__find_next_vma_info(struct address_space *mapping, struct list_head *head,
755 struct vma_info *vi, loff_t offset, bool is_register)
756{
757 struct prio_tree_iter iter;
758 struct vm_area_struct *vma;
759 struct vma_info *tmpvi;
760 unsigned long pgoff;
761 int existing_vma;
762 loff_t vaddr;
763
764 pgoff = offset >> PAGE_SHIFT;
765
766 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
767 if (!valid_vma(vma, is_register))
768 continue;
769
770 existing_vma = 0;
771 vaddr = vma_address(vma, offset);
772
773 list_for_each_entry(tmpvi, head, probe_list) {
774 if (tmpvi->mm == vma->vm_mm && tmpvi->vaddr == vaddr) {
775 existing_vma = 1;
776 break;
777 }
778 }
779
780 /*
781 * Another vma needs a probe to be installed. However skip
782 * installing the probe if the vma is about to be unlinked.
783 */
784 if (!existing_vma && atomic_inc_not_zero(&vma->vm_mm->mm_users)) {
785 vi->mm = vma->vm_mm;
786 vi->vaddr = vaddr;
787 list_add(&vi->probe_list, head);
788
789 return vi;
790 }
791 }
792
793 return NULL;
794}
795
796/*
797 * Iterate in the rmap prio tree and find a vma where a probe has not
798 * yet been inserted.
799 */
800static struct vma_info *
801find_next_vma_info(struct address_space *mapping, struct list_head *head,
802 loff_t offset, bool is_register)
803{
804 struct vma_info *vi, *retvi;
805
806 vi = kzalloc(sizeof(struct vma_info), GFP_KERNEL);
807 if (!vi)
808 return ERR_PTR(-ENOMEM);
809
810 mutex_lock(&mapping->i_mmap_mutex);
811 retvi = __find_next_vma_info(mapping, head, vi, offset, is_register);
812 mutex_unlock(&mapping->i_mmap_mutex);
813
814 if (!retvi)
815 kfree(vi);
816
817 return retvi;
818}
819
820static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
821{
822 struct list_head try_list;
823 struct vm_area_struct *vma;
824 struct address_space *mapping;
825 struct vma_info *vi, *tmpvi;
826 struct mm_struct *mm;
827 loff_t vaddr;
828 int ret;
829
830 mapping = uprobe->inode->i_mapping;
831 INIT_LIST_HEAD(&try_list);
832
833 ret = 0;
834
835 for (;;) {
836 vi = find_next_vma_info(mapping, &try_list, uprobe->offset, is_register);
837 if (!vi)
838 break;
839
840 if (IS_ERR(vi)) {
841 ret = PTR_ERR(vi);
842 break;
843 }
844
845 mm = vi->mm;
846 down_read(&mm->mmap_sem);
847 vma = find_vma(mm, (unsigned long)vi->vaddr);
848 if (!vma || !valid_vma(vma, is_register)) {
849 list_del(&vi->probe_list);
850 kfree(vi);
851 up_read(&mm->mmap_sem);
852 mmput(mm);
853 continue;
854 }
855 vaddr = vma_address(vma, uprobe->offset);
856 if (vma->vm_file->f_mapping->host != uprobe->inode ||
857 vaddr != vi->vaddr) {
858 list_del(&vi->probe_list);
859 kfree(vi);
860 up_read(&mm->mmap_sem);
861 mmput(mm);
862 continue;
863 }
864
865 if (is_register)
866 ret = install_breakpoint(uprobe, mm, vma, vi->vaddr);
867 else
868 remove_breakpoint(uprobe, mm, vi->vaddr);
869
870 up_read(&mm->mmap_sem);
871 mmput(mm);
872 if (is_register) {
873 if (ret && ret == -EEXIST)
874 ret = 0;
875 if (ret)
876 break;
877 }
878 }
879
880 list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
881 list_del(&vi->probe_list);
882 kfree(vi);
883 }
884
885 return ret;
886}
887
888static int __uprobe_register(struct uprobe *uprobe)
889{
890 return register_for_each_vma(uprobe, true);
891}
892
893static void __uprobe_unregister(struct uprobe *uprobe)
894{
895 if (!register_for_each_vma(uprobe, false))
896 delete_uprobe(uprobe);
897
898 /* TODO : cant unregister? schedule a worker thread */
899}
900
901/*
902 * uprobe_register - register a probe
903 * @inode: the file in which the probe has to be placed.
904 * @offset: offset from the start of the file.
905 * @uc: information on howto handle the probe..
906 *
907 * Apart from the access refcount, uprobe_register() takes a creation
908 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
909 * inserted into the rbtree (i.e first consumer for a @inode:@offset
910 * tuple). Creation refcount stops uprobe_unregister from freeing the
911 * @uprobe even before the register operation is complete. Creation
912 * refcount is released when the last @uc for the @uprobe
913 * unregisters.
914 *
915 * Return errno if it cannot successully install probes
916 * else return 0 (success)
917 */
918int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
919{
920 struct uprobe *uprobe;
921 int ret;
922
923 if (!inode || !uc || uc->next)
924 return -EINVAL;
925
926 if (offset > i_size_read(inode))
927 return -EINVAL;
928
929 ret = 0;
930 mutex_lock(uprobes_hash(inode));
931 uprobe = alloc_uprobe(inode, offset);
932
933 if (uprobe && !consumer_add(uprobe, uc)) {
934 ret = __uprobe_register(uprobe);
935 if (ret) {
936 uprobe->consumers = NULL;
937 __uprobe_unregister(uprobe);
938 } else {
939 uprobe->flags |= UPROBE_RUN_HANDLER;
940 }
941 }
942
943 mutex_unlock(uprobes_hash(inode));
944 put_uprobe(uprobe);
945
946 return ret;
947}
948
949/*
950 * uprobe_unregister - unregister a already registered probe.
951 * @inode: the file in which the probe has to be removed.
952 * @offset: offset from the start of the file.
953 * @uc: identify which probe if multiple probes are colocated.
954 */
955void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
956{
957 struct uprobe *uprobe;
958
959 if (!inode || !uc)
960 return;
961
962 uprobe = find_uprobe(inode, offset);
963 if (!uprobe)
964 return;
965
966 mutex_lock(uprobes_hash(inode));
967
968 if (consumer_del(uprobe, uc)) {
969 if (!uprobe->consumers) {
970 __uprobe_unregister(uprobe);
971 uprobe->flags &= ~UPROBE_RUN_HANDLER;
972 }
973 }
974
975 mutex_unlock(uprobes_hash(inode));
976 if (uprobe)
977 put_uprobe(uprobe);
978}
979
980/*
981 * Of all the nodes that correspond to the given inode, return the node
982 * with the least offset.
983 */
984static struct rb_node *find_least_offset_node(struct inode *inode)
985{
986 struct uprobe u = { .inode = inode, .offset = 0};
987 struct rb_node *n = uprobes_tree.rb_node;
988 struct rb_node *close_node = NULL;
989 struct uprobe *uprobe;
990 int match;
991
992 while (n) {
993 uprobe = rb_entry(n, struct uprobe, rb_node);
994 match = match_uprobe(&u, uprobe);
995
996 if (uprobe->inode == inode)
997 close_node = n;
998
999 if (!match)
1000 return close_node;
1001
1002 if (match < 0)
1003 n = n->rb_left;
1004 else
1005 n = n->rb_right;
1006 }
1007
1008 return close_node;
1009}
1010
1011/*
1012 * For a given inode, build a list of probes that need to be inserted.
1013 */
1014static void build_probe_list(struct inode *inode, struct list_head *head)
1015{
1016 struct uprobe *uprobe;
1017 unsigned long flags;
1018 struct rb_node *n;
1019
1020 spin_lock_irqsave(&uprobes_treelock, flags);
1021
1022 n = find_least_offset_node(inode);
1023
1024 for (; n; n = rb_next(n)) {
1025 uprobe = rb_entry(n, struct uprobe, rb_node);
1026 if (uprobe->inode != inode)
1027 break;
1028
1029 list_add(&uprobe->pending_list, head);
1030 atomic_inc(&uprobe->ref);
1031 }
1032
1033 spin_unlock_irqrestore(&uprobes_treelock, flags);
1034}
1035
1036/*
1037 * Called from mmap_region.
1038 * called with mm->mmap_sem acquired.
1039 *
1040 * Return -ve no if we fail to insert probes and we cannot
1041 * bail-out.
1042 * Return 0 otherwise. i.e:
1043 *
1044 * - successful insertion of probes
1045 * - (or) no possible probes to be inserted.
1046 * - (or) insertion of probes failed but we can bail-out.
1047 */
1048int uprobe_mmap(struct vm_area_struct *vma)
1049{
1050 struct list_head tmp_list;
1051 struct uprobe *uprobe, *u;
1052 struct inode *inode;
1053 int ret, count;
1054
1055 if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
1056 return 0;
1057
1058 inode = vma->vm_file->f_mapping->host;
1059 if (!inode)
1060 return 0;
1061
1062 INIT_LIST_HEAD(&tmp_list);
1063 mutex_lock(uprobes_mmap_hash(inode));
1064 build_probe_list(inode, &tmp_list);
1065
1066 ret = 0;
1067 count = 0;
1068
1069 list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1070 loff_t vaddr;
1071
1072 list_del(&uprobe->pending_list);
1073 if (!ret) {
1074 vaddr = vma_address(vma, uprobe->offset);
1075
1076 if (vaddr < vma->vm_start || vaddr >= vma->vm_end) {
1077 put_uprobe(uprobe);
1078 continue;
1079 }
1080
1081 ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1082
1083 /* Ignore double add: */
1084 if (ret == -EEXIST) {
1085 ret = 0;
1086
1087 if (!is_swbp_at_addr(vma->vm_mm, vaddr))
1088 continue;
1089
1090 /*
1091 * Unable to insert a breakpoint, but
1092 * breakpoint lies underneath. Increment the
1093 * probe count.
1094 */
1095 atomic_inc(&vma->vm_mm->uprobes_state.count);
1096 }
1097
1098 if (!ret)
1099 count++;
1100 }
1101 put_uprobe(uprobe);
1102 }
1103
1104 mutex_unlock(uprobes_mmap_hash(inode));
1105
1106 if (ret)
1107 atomic_sub(count, &vma->vm_mm->uprobes_state.count);
1108
1109 return ret;
1110}
1111
1112/*
1113 * Called in context of a munmap of a vma.
1114 */
1115void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1116{
1117 struct list_head tmp_list;
1118 struct uprobe *uprobe, *u;
1119 struct inode *inode;
1120
1121 if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
1122 return;
1123
1124 if (!atomic_read(&vma->vm_mm->uprobes_state.count))
1125 return;
1126
1127 inode = vma->vm_file->f_mapping->host;
1128 if (!inode)
1129 return;
1130
1131 INIT_LIST_HEAD(&tmp_list);
1132 mutex_lock(uprobes_mmap_hash(inode));
1133 build_probe_list(inode, &tmp_list);
1134
1135 list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1136 loff_t vaddr;
1137
1138 list_del(&uprobe->pending_list);
1139 vaddr = vma_address(vma, uprobe->offset);
1140
1141 if (vaddr >= start && vaddr < end) {
1142 /*
1143 * An unregister could have removed the probe before
1144 * unmap. So check before we decrement the count.
1145 */
1146 if (is_swbp_at_addr(vma->vm_mm, vaddr) == 1)
1147 atomic_dec(&vma->vm_mm->uprobes_state.count);
1148 }
1149 put_uprobe(uprobe);
1150 }
1151 mutex_unlock(uprobes_mmap_hash(inode));
1152}
1153
1154/* Slot allocation for XOL */
1155static int xol_add_vma(struct xol_area *area)
1156{
1157 struct mm_struct *mm;
1158 int ret;
1159
1160 area->page = alloc_page(GFP_HIGHUSER);
1161 if (!area->page)
1162 return -ENOMEM;
1163
1164 ret = -EALREADY;
1165 mm = current->mm;
1166
1167 down_write(&mm->mmap_sem);
1168 if (mm->uprobes_state.xol_area)
1169 goto fail;
1170
1171 ret = -ENOMEM;
1172
1173 /* Try to map as high as possible, this is only a hint. */
1174 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0);
1175 if (area->vaddr & ~PAGE_MASK) {
1176 ret = area->vaddr;
1177 goto fail;
1178 }
1179
1180 ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1181 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page);
1182 if (ret)
1183 goto fail;
1184
1185 smp_wmb(); /* pairs with get_xol_area() */
1186 mm->uprobes_state.xol_area = area;
1187 ret = 0;
1188
1189fail:
1190 up_write(&mm->mmap_sem);
1191 if (ret)
1192 __free_page(area->page);
1193
1194 return ret;
1195}
1196
1197static struct xol_area *get_xol_area(struct mm_struct *mm)
1198{
1199 struct xol_area *area;
1200
1201 area = mm->uprobes_state.xol_area;
1202 smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
1203
1204 return area;
1205}
1206
1207/*
1208 * xol_alloc_area - Allocate process's xol_area.
1209 * This area will be used for storing instructions for execution out of
1210 * line.
1211 *
1212 * Returns the allocated area or NULL.
1213 */
1214static struct xol_area *xol_alloc_area(void)
1215{
1216 struct xol_area *area;
1217
1218 area = kzalloc(sizeof(*area), GFP_KERNEL);
1219 if (unlikely(!area))
1220 return NULL;
1221
1222 area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL);
1223
1224 if (!area->bitmap)
1225 goto fail;
1226
1227 init_waitqueue_head(&area->wq);
1228 if (!xol_add_vma(area))
1229 return area;
1230
1231fail:
1232 kfree(area->bitmap);
1233 kfree(area);
1234
1235 return get_xol_area(current->mm);
1236}
1237
1238/*
1239 * uprobe_clear_state - Free the area allocated for slots.
1240 */
1241void uprobe_clear_state(struct mm_struct *mm)
1242{
1243 struct xol_area *area = mm->uprobes_state.xol_area;
1244
1245 if (!area)
1246 return;
1247
1248 put_page(area->page);
1249 kfree(area->bitmap);
1250 kfree(area);
1251}
1252
1253/*
1254 * uprobe_reset_state - Free the area allocated for slots.
1255 */
1256void uprobe_reset_state(struct mm_struct *mm)
1257{
1258 mm->uprobes_state.xol_area = NULL;
1259 atomic_set(&mm->uprobes_state.count, 0);
1260}
1261
1262/*
1263 * - search for a free slot.
1264 */
1265static unsigned long xol_take_insn_slot(struct xol_area *area)
1266{
1267 unsigned long slot_addr;
1268 int slot_nr;
1269
1270 do {
1271 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1272 if (slot_nr < UINSNS_PER_PAGE) {
1273 if (!test_and_set_bit(slot_nr, area->bitmap))
1274 break;
1275
1276 slot_nr = UINSNS_PER_PAGE;
1277 continue;
1278 }
1279 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1280 } while (slot_nr >= UINSNS_PER_PAGE);
1281
1282 slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1283 atomic_inc(&area->slot_count);
1284
1285 return slot_addr;
1286}
1287
1288/*
1289 * xol_get_insn_slot - If was not allocated a slot, then
1290 * allocate a slot.
1291 * Returns the allocated slot address or 0.
1292 */
1293static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot_addr)
1294{
1295 struct xol_area *area;
1296 unsigned long offset;
1297 void *vaddr;
1298
1299 area = get_xol_area(current->mm);
1300 if (!area) {
1301 area = xol_alloc_area();
1302 if (!area)
1303 return 0;
1304 }
1305 current->utask->xol_vaddr = xol_take_insn_slot(area);
1306
1307 /*
1308 * Initialize the slot if xol_vaddr points to valid
1309 * instruction slot.
1310 */
1311 if (unlikely(!current->utask->xol_vaddr))
1312 return 0;
1313
1314 current->utask->vaddr = slot_addr;
1315 offset = current->utask->xol_vaddr & ~PAGE_MASK;
1316 vaddr = kmap_atomic(area->page);
1317 memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
1318 kunmap_atomic(vaddr);
1319
1320 return current->utask->xol_vaddr;
1321}
1322
1323/*
1324 * xol_free_insn_slot - If slot was earlier allocated by
1325 * @xol_get_insn_slot(), make the slot available for
1326 * subsequent requests.
1327 */
1328static void xol_free_insn_slot(struct task_struct *tsk)
1329{
1330 struct xol_area *area;
1331 unsigned long vma_end;
1332 unsigned long slot_addr;
1333
1334 if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1335 return;
1336
1337 slot_addr = tsk->utask->xol_vaddr;
1338
1339 if (unlikely(!slot_addr || IS_ERR_VALUE(slot_addr)))
1340 return;
1341
1342 area = tsk->mm->uprobes_state.xol_area;
1343 vma_end = area->vaddr + PAGE_SIZE;
1344 if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1345 unsigned long offset;
1346 int slot_nr;
1347
1348 offset = slot_addr - area->vaddr;
1349 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1350 if (slot_nr >= UINSNS_PER_PAGE)
1351 return;
1352
1353 clear_bit(slot_nr, area->bitmap);
1354 atomic_dec(&area->slot_count);
1355 if (waitqueue_active(&area->wq))
1356 wake_up(&area->wq);
1357
1358 tsk->utask->xol_vaddr = 0;
1359 }
1360}
1361
1362/**
1363 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1364 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1365 * instruction.
1366 * Return the address of the breakpoint instruction.
1367 */
1368unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1369{
1370 return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1371}
1372
1373/*
1374 * Called with no locks held.
1375 * Called in context of a exiting or a exec-ing thread.
1376 */
1377void uprobe_free_utask(struct task_struct *t)
1378{
1379 struct uprobe_task *utask = t->utask;
1380
1381 if (t->uprobe_srcu_id != -1)
1382 srcu_read_unlock_raw(&uprobes_srcu, t->uprobe_srcu_id);
1383
1384 if (!utask)
1385 return;
1386
1387 if (utask->active_uprobe)
1388 put_uprobe(utask->active_uprobe);
1389
1390 xol_free_insn_slot(t);
1391 kfree(utask);
1392 t->utask = NULL;
1393}
1394
1395/*
1396 * Called in context of a new clone/fork from copy_process.
1397 */
1398void uprobe_copy_process(struct task_struct *t)
1399{
1400 t->utask = NULL;
1401 t->uprobe_srcu_id = -1;
1402}
1403
1404/*
1405 * Allocate a uprobe_task object for the task.
1406 * Called when the thread hits a breakpoint for the first time.
1407 *
1408 * Returns:
1409 * - pointer to new uprobe_task on success
1410 * - NULL otherwise
1411 */
1412static struct uprobe_task *add_utask(void)
1413{
1414 struct uprobe_task *utask;
1415
1416 utask = kzalloc(sizeof *utask, GFP_KERNEL);
1417 if (unlikely(!utask))
1418 return NULL;
1419
1420 utask->active_uprobe = NULL;
1421 current->utask = utask;
1422 return utask;
1423}
1424
1425/* Prepare to single-step probed instruction out of line. */
1426static int
1427pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr)
1428{
1429 if (xol_get_insn_slot(uprobe, vaddr) && !arch_uprobe_pre_xol(&uprobe->arch, regs))
1430 return 0;
1431
1432 return -EFAULT;
1433}
1434
1435/*
1436 * If we are singlestepping, then ensure this thread is not connected to
1437 * non-fatal signals until completion of singlestep. When xol insn itself
1438 * triggers the signal, restart the original insn even if the task is
1439 * already SIGKILL'ed (since coredump should report the correct ip). This
1440 * is even more important if the task has a handler for SIGSEGV/etc, The
1441 * _same_ instruction should be repeated again after return from the signal
1442 * handler, and SSTEP can never finish in this case.
1443 */
1444bool uprobe_deny_signal(void)
1445{
1446 struct task_struct *t = current;
1447 struct uprobe_task *utask = t->utask;
1448
1449 if (likely(!utask || !utask->active_uprobe))
1450 return false;
1451
1452 WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1453
1454 if (signal_pending(t)) {
1455 spin_lock_irq(&t->sighand->siglock);
1456 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1457 spin_unlock_irq(&t->sighand->siglock);
1458
1459 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1460 utask->state = UTASK_SSTEP_TRAPPED;
1461 set_tsk_thread_flag(t, TIF_UPROBE);
1462 set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
1463 }
1464 }
1465
1466 return true;
1467}
1468
1469/*
1470 * Avoid singlestepping the original instruction if the original instruction
1471 * is a NOP or can be emulated.
1472 */
1473static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
1474{
1475 if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
1476 return true;
1477
1478 uprobe->flags &= ~UPROBE_SKIP_SSTEP;
1479 return false;
1480}
1481
1482/*
1483 * Run handler and ask thread to singlestep.
1484 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
1485 */
1486static void handle_swbp(struct pt_regs *regs)
1487{
1488 struct vm_area_struct *vma;
1489 struct uprobe_task *utask;
1490 struct uprobe *uprobe;
1491 struct mm_struct *mm;
1492 unsigned long bp_vaddr;
1493
1494 uprobe = NULL;
1495 bp_vaddr = uprobe_get_swbp_addr(regs);
1496 mm = current->mm;
1497 down_read(&mm->mmap_sem);
1498 vma = find_vma(mm, bp_vaddr);
1499
1500 if (vma && vma->vm_start <= bp_vaddr && valid_vma(vma, false)) {
1501 struct inode *inode;
1502 loff_t offset;
1503
1504 inode = vma->vm_file->f_mapping->host;
1505 offset = bp_vaddr - vma->vm_start;
1506 offset += (vma->vm_pgoff << PAGE_SHIFT);
1507 uprobe = find_uprobe(inode, offset);
1508 }
1509
1510 srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);
1511 current->uprobe_srcu_id = -1;
1512 up_read(&mm->mmap_sem);
1513
1514 if (!uprobe) {
1515 /* No matching uprobe; signal SIGTRAP. */
1516 send_sig(SIGTRAP, current, 0);
1517 return;
1518 }
1519
1520 utask = current->utask;
1521 if (!utask) {
1522 utask = add_utask();
1523 /* Cannot allocate; re-execute the instruction. */
1524 if (!utask)
1525 goto cleanup_ret;
1526 }
1527 utask->active_uprobe = uprobe;
1528 handler_chain(uprobe, regs);
1529 if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
1530 goto cleanup_ret;
1531
1532 utask->state = UTASK_SSTEP;
1533 if (!pre_ssout(uprobe, regs, bp_vaddr)) {
1534 user_enable_single_step(current);
1535 return;
1536 }
1537
1538cleanup_ret:
1539 if (utask) {
1540 utask->active_uprobe = NULL;
1541 utask->state = UTASK_RUNNING;
1542 }
1543 if (uprobe) {
1544 if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
1545
1546 /*
1547 * cannot singlestep; cannot skip instruction;
1548 * re-execute the instruction.
1549 */
1550 instruction_pointer_set(regs, bp_vaddr);
1551
1552 put_uprobe(uprobe);
1553 }
1554}
1555
1556/*
1557 * Perform required fix-ups and disable singlestep.
1558 * Allow pending signals to take effect.
1559 */
1560static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
1561{
1562 struct uprobe *uprobe;
1563
1564 uprobe = utask->active_uprobe;
1565 if (utask->state == UTASK_SSTEP_ACK)
1566 arch_uprobe_post_xol(&uprobe->arch, regs);
1567 else if (utask->state == UTASK_SSTEP_TRAPPED)
1568 arch_uprobe_abort_xol(&uprobe->arch, regs);
1569 else
1570 WARN_ON_ONCE(1);
1571
1572 put_uprobe(uprobe);
1573 utask->active_uprobe = NULL;
1574 utask->state = UTASK_RUNNING;
1575 user_disable_single_step(current);
1576 xol_free_insn_slot(current);
1577
1578 spin_lock_irq(¤t->sighand->siglock);
1579 recalc_sigpending(); /* see uprobe_deny_signal() */
1580 spin_unlock_irq(¤t->sighand->siglock);
1581}
1582
1583/*
1584 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on
1585 * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
1586 * allows the thread to return from interrupt.
1587 *
1588 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
1589 * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from
1590 * interrupt.
1591 *
1592 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
1593 * uprobe_notify_resume().
1594 */
1595void uprobe_notify_resume(struct pt_regs *regs)
1596{
1597 struct uprobe_task *utask;
1598
1599 utask = current->utask;
1600 if (!utask || utask->state == UTASK_BP_HIT)
1601 handle_swbp(regs);
1602 else
1603 handle_singlestep(utask, regs);
1604}
1605
1606/*
1607 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
1608 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
1609 */
1610int uprobe_pre_sstep_notifier(struct pt_regs *regs)
1611{
1612 struct uprobe_task *utask;
1613
1614 if (!current->mm || !atomic_read(¤t->mm->uprobes_state.count))
1615 /* task is currently not uprobed */
1616 return 0;
1617
1618 utask = current->utask;
1619 if (utask)
1620 utask->state = UTASK_BP_HIT;
1621
1622 set_thread_flag(TIF_UPROBE);
1623 current->uprobe_srcu_id = srcu_read_lock_raw(&uprobes_srcu);
1624
1625 return 1;
1626}
1627
1628/*
1629 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
1630 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
1631 */
1632int uprobe_post_sstep_notifier(struct pt_regs *regs)
1633{
1634 struct uprobe_task *utask = current->utask;
1635
1636 if (!current->mm || !utask || !utask->active_uprobe)
1637 /* task is currently not uprobed */
1638 return 0;
1639
1640 utask->state = UTASK_SSTEP_ACK;
1641 set_thread_flag(TIF_UPROBE);
1642 return 1;
1643}
1644
1645static struct notifier_block uprobe_exception_nb = {
1646 .notifier_call = arch_uprobe_exception_notify,
1647 .priority = INT_MAX-1, /* notified after kprobes, kgdb */
1648};
1649
1650static int __init init_uprobes(void)
1651{
1652 int i;
1653
1654 for (i = 0; i < UPROBES_HASH_SZ; i++) {
1655 mutex_init(&uprobes_mutex[i]);
1656 mutex_init(&uprobes_mmap_mutex[i]);
1657 }
1658 init_srcu_struct(&uprobes_srcu);
1659
1660 return register_die_notifier(&uprobe_exception_nb);
1661}
1662module_init(init_uprobes);
1663
1664static void __exit exit_uprobes(void)
1665{
1666}
1667module_exit(exit_uprobes);
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * User-space Probes (UProbes)
4 *
5 * Copyright (C) IBM Corporation, 2008-2012
6 * Authors:
7 * Srikar Dronamraju
8 * Jim Keniston
9 * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
10 */
11
12#include <linux/kernel.h>
13#include <linux/highmem.h>
14#include <linux/pagemap.h> /* read_mapping_page */
15#include <linux/slab.h>
16#include <linux/sched.h>
17#include <linux/sched/mm.h>
18#include <linux/sched/coredump.h>
19#include <linux/export.h>
20#include <linux/rmap.h> /* anon_vma_prepare */
21#include <linux/mmu_notifier.h> /* set_pte_at_notify */
22#include <linux/swap.h> /* try_to_free_swap */
23#include <linux/ptrace.h> /* user_enable_single_step */
24#include <linux/kdebug.h> /* notifier mechanism */
25#include "../../mm/internal.h" /* munlock_vma_page */
26#include <linux/percpu-rwsem.h>
27#include <linux/task_work.h>
28#include <linux/shmem_fs.h>
29#include <linux/khugepaged.h>
30
31#include <linux/uprobes.h>
32
33#define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
34#define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
35
36static struct rb_root uprobes_tree = RB_ROOT;
37/*
38 * allows us to skip the uprobe_mmap if there are no uprobe events active
39 * at this time. Probably a fine grained per inode count is better?
40 */
41#define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree)
42
43static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
44
45#define UPROBES_HASH_SZ 13
46/* serialize uprobe->pending_list */
47static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
48#define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
49
50DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem);
51
52/* Have a copy of original instruction */
53#define UPROBE_COPY_INSN 0
54
55struct uprobe {
56 struct rb_node rb_node; /* node in the rb tree */
57 refcount_t ref;
58 struct rw_semaphore register_rwsem;
59 struct rw_semaphore consumer_rwsem;
60 struct list_head pending_list;
61 struct uprobe_consumer *consumers;
62 struct inode *inode; /* Also hold a ref to inode */
63 loff_t offset;
64 loff_t ref_ctr_offset;
65 unsigned long flags;
66
67 /*
68 * The generic code assumes that it has two members of unknown type
69 * owned by the arch-specific code:
70 *
71 * insn - copy_insn() saves the original instruction here for
72 * arch_uprobe_analyze_insn().
73 *
74 * ixol - potentially modified instruction to execute out of
75 * line, copied to xol_area by xol_get_insn_slot().
76 */
77 struct arch_uprobe arch;
78};
79
80struct delayed_uprobe {
81 struct list_head list;
82 struct uprobe *uprobe;
83 struct mm_struct *mm;
84};
85
86static DEFINE_MUTEX(delayed_uprobe_lock);
87static LIST_HEAD(delayed_uprobe_list);
88
89/*
90 * Execute out of line area: anonymous executable mapping installed
91 * by the probed task to execute the copy of the original instruction
92 * mangled by set_swbp().
93 *
94 * On a breakpoint hit, thread contests for a slot. It frees the
95 * slot after singlestep. Currently a fixed number of slots are
96 * allocated.
97 */
98struct xol_area {
99 wait_queue_head_t wq; /* if all slots are busy */
100 atomic_t slot_count; /* number of in-use slots */
101 unsigned long *bitmap; /* 0 = free slot */
102
103 struct vm_special_mapping xol_mapping;
104 struct page *pages[2];
105 /*
106 * We keep the vma's vm_start rather than a pointer to the vma
107 * itself. The probed process or a naughty kernel module could make
108 * the vma go away, and we must handle that reasonably gracefully.
109 */
110 unsigned long vaddr; /* Page(s) of instruction slots */
111};
112
113/*
114 * valid_vma: Verify if the specified vma is an executable vma
115 * Relax restrictions while unregistering: vm_flags might have
116 * changed after breakpoint was inserted.
117 * - is_register: indicates if we are in register context.
118 * - Return 1 if the specified virtual address is in an
119 * executable vma.
120 */
121static bool valid_vma(struct vm_area_struct *vma, bool is_register)
122{
123 vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE;
124
125 if (is_register)
126 flags |= VM_WRITE;
127
128 return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
129}
130
131static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
132{
133 return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
134}
135
136static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
137{
138 return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start);
139}
140
141/**
142 * __replace_page - replace page in vma by new page.
143 * based on replace_page in mm/ksm.c
144 *
145 * @vma: vma that holds the pte pointing to page
146 * @addr: address the old @page is mapped at
147 * @old_page: the page we are replacing by new_page
148 * @new_page: the modified page we replace page by
149 *
150 * If @new_page is NULL, only unmap @old_page.
151 *
152 * Returns 0 on success, negative error code otherwise.
153 */
154static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
155 struct page *old_page, struct page *new_page)
156{
157 struct mm_struct *mm = vma->vm_mm;
158 struct page_vma_mapped_walk pvmw = {
159 .page = compound_head(old_page),
160 .vma = vma,
161 .address = addr,
162 };
163 int err;
164 struct mmu_notifier_range range;
165 struct mem_cgroup *memcg;
166
167 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr,
168 addr + PAGE_SIZE);
169
170 if (new_page) {
171 err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL,
172 &memcg, false);
173 if (err)
174 return err;
175 }
176
177 /* For try_to_free_swap() and munlock_vma_page() below */
178 lock_page(old_page);
179
180 mmu_notifier_invalidate_range_start(&range);
181 err = -EAGAIN;
182 if (!page_vma_mapped_walk(&pvmw)) {
183 if (new_page)
184 mem_cgroup_cancel_charge(new_page, memcg, false);
185 goto unlock;
186 }
187 VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
188
189 if (new_page) {
190 get_page(new_page);
191 page_add_new_anon_rmap(new_page, vma, addr, false);
192 mem_cgroup_commit_charge(new_page, memcg, false, false);
193 lru_cache_add_active_or_unevictable(new_page, vma);
194 } else
195 /* no new page, just dec_mm_counter for old_page */
196 dec_mm_counter(mm, MM_ANONPAGES);
197
198 if (!PageAnon(old_page)) {
199 dec_mm_counter(mm, mm_counter_file(old_page));
200 inc_mm_counter(mm, MM_ANONPAGES);
201 }
202
203 flush_cache_page(vma, addr, pte_pfn(*pvmw.pte));
204 ptep_clear_flush_notify(vma, addr, pvmw.pte);
205 if (new_page)
206 set_pte_at_notify(mm, addr, pvmw.pte,
207 mk_pte(new_page, vma->vm_page_prot));
208
209 page_remove_rmap(old_page, false);
210 if (!page_mapped(old_page))
211 try_to_free_swap(old_page);
212 page_vma_mapped_walk_done(&pvmw);
213
214 if (vma->vm_flags & VM_LOCKED)
215 munlock_vma_page(old_page);
216 put_page(old_page);
217
218 err = 0;
219 unlock:
220 mmu_notifier_invalidate_range_end(&range);
221 unlock_page(old_page);
222 return err;
223}
224
225/**
226 * is_swbp_insn - check if instruction is breakpoint instruction.
227 * @insn: instruction to be checked.
228 * Default implementation of is_swbp_insn
229 * Returns true if @insn is a breakpoint instruction.
230 */
231bool __weak is_swbp_insn(uprobe_opcode_t *insn)
232{
233 return *insn == UPROBE_SWBP_INSN;
234}
235
236/**
237 * is_trap_insn - check if instruction is breakpoint instruction.
238 * @insn: instruction to be checked.
239 * Default implementation of is_trap_insn
240 * Returns true if @insn is a breakpoint instruction.
241 *
242 * This function is needed for the case where an architecture has multiple
243 * trap instructions (like powerpc).
244 */
245bool __weak is_trap_insn(uprobe_opcode_t *insn)
246{
247 return is_swbp_insn(insn);
248}
249
250static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len)
251{
252 void *kaddr = kmap_atomic(page);
253 memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
254 kunmap_atomic(kaddr);
255}
256
257static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
258{
259 void *kaddr = kmap_atomic(page);
260 memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
261 kunmap_atomic(kaddr);
262}
263
264static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
265{
266 uprobe_opcode_t old_opcode;
267 bool is_swbp;
268
269 /*
270 * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here.
271 * We do not check if it is any other 'trap variant' which could
272 * be conditional trap instruction such as the one powerpc supports.
273 *
274 * The logic is that we do not care if the underlying instruction
275 * is a trap variant; uprobes always wins over any other (gdb)
276 * breakpoint.
277 */
278 copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE);
279 is_swbp = is_swbp_insn(&old_opcode);
280
281 if (is_swbp_insn(new_opcode)) {
282 if (is_swbp) /* register: already installed? */
283 return 0;
284 } else {
285 if (!is_swbp) /* unregister: was it changed by us? */
286 return 0;
287 }
288
289 return 1;
290}
291
292static struct delayed_uprobe *
293delayed_uprobe_check(struct uprobe *uprobe, struct mm_struct *mm)
294{
295 struct delayed_uprobe *du;
296
297 list_for_each_entry(du, &delayed_uprobe_list, list)
298 if (du->uprobe == uprobe && du->mm == mm)
299 return du;
300 return NULL;
301}
302
303static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm)
304{
305 struct delayed_uprobe *du;
306
307 if (delayed_uprobe_check(uprobe, mm))
308 return 0;
309
310 du = kzalloc(sizeof(*du), GFP_KERNEL);
311 if (!du)
312 return -ENOMEM;
313
314 du->uprobe = uprobe;
315 du->mm = mm;
316 list_add(&du->list, &delayed_uprobe_list);
317 return 0;
318}
319
320static void delayed_uprobe_delete(struct delayed_uprobe *du)
321{
322 if (WARN_ON(!du))
323 return;
324 list_del(&du->list);
325 kfree(du);
326}
327
328static void delayed_uprobe_remove(struct uprobe *uprobe, struct mm_struct *mm)
329{
330 struct list_head *pos, *q;
331 struct delayed_uprobe *du;
332
333 if (!uprobe && !mm)
334 return;
335
336 list_for_each_safe(pos, q, &delayed_uprobe_list) {
337 du = list_entry(pos, struct delayed_uprobe, list);
338
339 if (uprobe && du->uprobe != uprobe)
340 continue;
341 if (mm && du->mm != mm)
342 continue;
343
344 delayed_uprobe_delete(du);
345 }
346}
347
348static bool valid_ref_ctr_vma(struct uprobe *uprobe,
349 struct vm_area_struct *vma)
350{
351 unsigned long vaddr = offset_to_vaddr(vma, uprobe->ref_ctr_offset);
352
353 return uprobe->ref_ctr_offset &&
354 vma->vm_file &&
355 file_inode(vma->vm_file) == uprobe->inode &&
356 (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
357 vma->vm_start <= vaddr &&
358 vma->vm_end > vaddr;
359}
360
361static struct vm_area_struct *
362find_ref_ctr_vma(struct uprobe *uprobe, struct mm_struct *mm)
363{
364 struct vm_area_struct *tmp;
365
366 for (tmp = mm->mmap; tmp; tmp = tmp->vm_next)
367 if (valid_ref_ctr_vma(uprobe, tmp))
368 return tmp;
369
370 return NULL;
371}
372
373static int
374__update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
375{
376 void *kaddr;
377 struct page *page;
378 struct vm_area_struct *vma;
379 int ret;
380 short *ptr;
381
382 if (!vaddr || !d)
383 return -EINVAL;
384
385 ret = get_user_pages_remote(NULL, mm, vaddr, 1,
386 FOLL_WRITE, &page, &vma, NULL);
387 if (unlikely(ret <= 0)) {
388 /*
389 * We are asking for 1 page. If get_user_pages_remote() fails,
390 * it may return 0, in that case we have to return error.
391 */
392 return ret == 0 ? -EBUSY : ret;
393 }
394
395 kaddr = kmap_atomic(page);
396 ptr = kaddr + (vaddr & ~PAGE_MASK);
397
398 if (unlikely(*ptr + d < 0)) {
399 pr_warn("ref_ctr going negative. vaddr: 0x%lx, "
400 "curr val: %d, delta: %d\n", vaddr, *ptr, d);
401 ret = -EINVAL;
402 goto out;
403 }
404
405 *ptr += d;
406 ret = 0;
407out:
408 kunmap_atomic(kaddr);
409 put_page(page);
410 return ret;
411}
412
413static void update_ref_ctr_warn(struct uprobe *uprobe,
414 struct mm_struct *mm, short d)
415{
416 pr_warn("ref_ctr %s failed for inode: 0x%lx offset: "
417 "0x%llx ref_ctr_offset: 0x%llx of mm: 0x%pK\n",
418 d > 0 ? "increment" : "decrement", uprobe->inode->i_ino,
419 (unsigned long long) uprobe->offset,
420 (unsigned long long) uprobe->ref_ctr_offset, mm);
421}
422
423static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm,
424 short d)
425{
426 struct vm_area_struct *rc_vma;
427 unsigned long rc_vaddr;
428 int ret = 0;
429
430 rc_vma = find_ref_ctr_vma(uprobe, mm);
431
432 if (rc_vma) {
433 rc_vaddr = offset_to_vaddr(rc_vma, uprobe->ref_ctr_offset);
434 ret = __update_ref_ctr(mm, rc_vaddr, d);
435 if (ret)
436 update_ref_ctr_warn(uprobe, mm, d);
437
438 if (d > 0)
439 return ret;
440 }
441
442 mutex_lock(&delayed_uprobe_lock);
443 if (d > 0)
444 ret = delayed_uprobe_add(uprobe, mm);
445 else
446 delayed_uprobe_remove(uprobe, mm);
447 mutex_unlock(&delayed_uprobe_lock);
448
449 return ret;
450}
451
452/*
453 * NOTE:
454 * Expect the breakpoint instruction to be the smallest size instruction for
455 * the architecture. If an arch has variable length instruction and the
456 * breakpoint instruction is not of the smallest length instruction
457 * supported by that architecture then we need to modify is_trap_at_addr and
458 * uprobe_write_opcode accordingly. This would never be a problem for archs
459 * that have fixed length instructions.
460 *
461 * uprobe_write_opcode - write the opcode at a given virtual address.
462 * @mm: the probed process address space.
463 * @vaddr: the virtual address to store the opcode.
464 * @opcode: opcode to be written at @vaddr.
465 *
466 * Called with mm->mmap_sem held for write.
467 * Return 0 (success) or a negative errno.
468 */
469int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
470 unsigned long vaddr, uprobe_opcode_t opcode)
471{
472 struct uprobe *uprobe;
473 struct page *old_page, *new_page;
474 struct vm_area_struct *vma;
475 int ret, is_register, ref_ctr_updated = 0;
476 bool orig_page_huge = false;
477 unsigned int gup_flags = FOLL_FORCE;
478
479 is_register = is_swbp_insn(&opcode);
480 uprobe = container_of(auprobe, struct uprobe, arch);
481
482retry:
483 if (is_register)
484 gup_flags |= FOLL_SPLIT_PMD;
485 /* Read the page with vaddr into memory */
486 ret = get_user_pages_remote(NULL, mm, vaddr, 1, gup_flags,
487 &old_page, &vma, NULL);
488 if (ret <= 0)
489 return ret;
490
491 ret = verify_opcode(old_page, vaddr, &opcode);
492 if (ret <= 0)
493 goto put_old;
494
495 if (WARN(!is_register && PageCompound(old_page),
496 "uprobe unregister should never work on compound page\n")) {
497 ret = -EINVAL;
498 goto put_old;
499 }
500
501 /* We are going to replace instruction, update ref_ctr. */
502 if (!ref_ctr_updated && uprobe->ref_ctr_offset) {
503 ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1);
504 if (ret)
505 goto put_old;
506
507 ref_ctr_updated = 1;
508 }
509
510 ret = 0;
511 if (!is_register && !PageAnon(old_page))
512 goto put_old;
513
514 ret = anon_vma_prepare(vma);
515 if (ret)
516 goto put_old;
517
518 ret = -ENOMEM;
519 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
520 if (!new_page)
521 goto put_old;
522
523 __SetPageUptodate(new_page);
524 copy_highpage(new_page, old_page);
525 copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
526
527 if (!is_register) {
528 struct page *orig_page;
529 pgoff_t index;
530
531 VM_BUG_ON_PAGE(!PageAnon(old_page), old_page);
532
533 index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT;
534 orig_page = find_get_page(vma->vm_file->f_inode->i_mapping,
535 index);
536
537 if (orig_page) {
538 if (PageUptodate(orig_page) &&
539 pages_identical(new_page, orig_page)) {
540 /* let go new_page */
541 put_page(new_page);
542 new_page = NULL;
543
544 if (PageCompound(orig_page))
545 orig_page_huge = true;
546 }
547 put_page(orig_page);
548 }
549 }
550
551 ret = __replace_page(vma, vaddr, old_page, new_page);
552 if (new_page)
553 put_page(new_page);
554put_old:
555 put_page(old_page);
556
557 if (unlikely(ret == -EAGAIN))
558 goto retry;
559
560 /* Revert back reference counter if instruction update failed. */
561 if (ret && is_register && ref_ctr_updated)
562 update_ref_ctr(uprobe, mm, -1);
563
564 /* try collapse pmd for compound page */
565 if (!ret && orig_page_huge)
566 collapse_pte_mapped_thp(mm, vaddr);
567
568 return ret;
569}
570
571/**
572 * set_swbp - store breakpoint at a given address.
573 * @auprobe: arch specific probepoint information.
574 * @mm: the probed process address space.
575 * @vaddr: the virtual address to insert the opcode.
576 *
577 * For mm @mm, store the breakpoint instruction at @vaddr.
578 * Return 0 (success) or a negative errno.
579 */
580int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
581{
582 return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
583}
584
585/**
586 * set_orig_insn - Restore the original instruction.
587 * @mm: the probed process address space.
588 * @auprobe: arch specific probepoint information.
589 * @vaddr: the virtual address to insert the opcode.
590 *
591 * For mm @mm, restore the original opcode (opcode) at @vaddr.
592 * Return 0 (success) or a negative errno.
593 */
594int __weak
595set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
596{
597 return uprobe_write_opcode(auprobe, mm, vaddr,
598 *(uprobe_opcode_t *)&auprobe->insn);
599}
600
601static struct uprobe *get_uprobe(struct uprobe *uprobe)
602{
603 refcount_inc(&uprobe->ref);
604 return uprobe;
605}
606
607static void put_uprobe(struct uprobe *uprobe)
608{
609 if (refcount_dec_and_test(&uprobe->ref)) {
610 /*
611 * If application munmap(exec_vma) before uprobe_unregister()
612 * gets called, we don't get a chance to remove uprobe from
613 * delayed_uprobe_list from remove_breakpoint(). Do it here.
614 */
615 mutex_lock(&delayed_uprobe_lock);
616 delayed_uprobe_remove(uprobe, NULL);
617 mutex_unlock(&delayed_uprobe_lock);
618 kfree(uprobe);
619 }
620}
621
622static int match_uprobe(struct uprobe *l, struct uprobe *r)
623{
624 if (l->inode < r->inode)
625 return -1;
626
627 if (l->inode > r->inode)
628 return 1;
629
630 if (l->offset < r->offset)
631 return -1;
632
633 if (l->offset > r->offset)
634 return 1;
635
636 return 0;
637}
638
639static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
640{
641 struct uprobe u = { .inode = inode, .offset = offset };
642 struct rb_node *n = uprobes_tree.rb_node;
643 struct uprobe *uprobe;
644 int match;
645
646 while (n) {
647 uprobe = rb_entry(n, struct uprobe, rb_node);
648 match = match_uprobe(&u, uprobe);
649 if (!match)
650 return get_uprobe(uprobe);
651
652 if (match < 0)
653 n = n->rb_left;
654 else
655 n = n->rb_right;
656 }
657 return NULL;
658}
659
660/*
661 * Find a uprobe corresponding to a given inode:offset
662 * Acquires uprobes_treelock
663 */
664static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
665{
666 struct uprobe *uprobe;
667
668 spin_lock(&uprobes_treelock);
669 uprobe = __find_uprobe(inode, offset);
670 spin_unlock(&uprobes_treelock);
671
672 return uprobe;
673}
674
675static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
676{
677 struct rb_node **p = &uprobes_tree.rb_node;
678 struct rb_node *parent = NULL;
679 struct uprobe *u;
680 int match;
681
682 while (*p) {
683 parent = *p;
684 u = rb_entry(parent, struct uprobe, rb_node);
685 match = match_uprobe(uprobe, u);
686 if (!match)
687 return get_uprobe(u);
688
689 if (match < 0)
690 p = &parent->rb_left;
691 else
692 p = &parent->rb_right;
693
694 }
695
696 u = NULL;
697 rb_link_node(&uprobe->rb_node, parent, p);
698 rb_insert_color(&uprobe->rb_node, &uprobes_tree);
699 /* get access + creation ref */
700 refcount_set(&uprobe->ref, 2);
701
702 return u;
703}
704
705/*
706 * Acquire uprobes_treelock.
707 * Matching uprobe already exists in rbtree;
708 * increment (access refcount) and return the matching uprobe.
709 *
710 * No matching uprobe; insert the uprobe in rb_tree;
711 * get a double refcount (access + creation) and return NULL.
712 */
713static struct uprobe *insert_uprobe(struct uprobe *uprobe)
714{
715 struct uprobe *u;
716
717 spin_lock(&uprobes_treelock);
718 u = __insert_uprobe(uprobe);
719 spin_unlock(&uprobes_treelock);
720
721 return u;
722}
723
724static void
725ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe)
726{
727 pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx "
728 "ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n",
729 uprobe->inode->i_ino, (unsigned long long) uprobe->offset,
730 (unsigned long long) cur_uprobe->ref_ctr_offset,
731 (unsigned long long) uprobe->ref_ctr_offset);
732}
733
734static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
735 loff_t ref_ctr_offset)
736{
737 struct uprobe *uprobe, *cur_uprobe;
738
739 uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
740 if (!uprobe)
741 return NULL;
742
743 uprobe->inode = inode;
744 uprobe->offset = offset;
745 uprobe->ref_ctr_offset = ref_ctr_offset;
746 init_rwsem(&uprobe->register_rwsem);
747 init_rwsem(&uprobe->consumer_rwsem);
748
749 /* add to uprobes_tree, sorted on inode:offset */
750 cur_uprobe = insert_uprobe(uprobe);
751 /* a uprobe exists for this inode:offset combination */
752 if (cur_uprobe) {
753 if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
754 ref_ctr_mismatch_warn(cur_uprobe, uprobe);
755 put_uprobe(cur_uprobe);
756 kfree(uprobe);
757 return ERR_PTR(-EINVAL);
758 }
759 kfree(uprobe);
760 uprobe = cur_uprobe;
761 }
762
763 return uprobe;
764}
765
766static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
767{
768 down_write(&uprobe->consumer_rwsem);
769 uc->next = uprobe->consumers;
770 uprobe->consumers = uc;
771 up_write(&uprobe->consumer_rwsem);
772}
773
774/*
775 * For uprobe @uprobe, delete the consumer @uc.
776 * Return true if the @uc is deleted successfully
777 * or return false.
778 */
779static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
780{
781 struct uprobe_consumer **con;
782 bool ret = false;
783
784 down_write(&uprobe->consumer_rwsem);
785 for (con = &uprobe->consumers; *con; con = &(*con)->next) {
786 if (*con == uc) {
787 *con = uc->next;
788 ret = true;
789 break;
790 }
791 }
792 up_write(&uprobe->consumer_rwsem);
793
794 return ret;
795}
796
797static int __copy_insn(struct address_space *mapping, struct file *filp,
798 void *insn, int nbytes, loff_t offset)
799{
800 struct page *page;
801 /*
802 * Ensure that the page that has the original instruction is populated
803 * and in page-cache. If ->readpage == NULL it must be shmem_mapping(),
804 * see uprobe_register().
805 */
806 if (mapping->a_ops->readpage)
807 page = read_mapping_page(mapping, offset >> PAGE_SHIFT, filp);
808 else
809 page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
810 if (IS_ERR(page))
811 return PTR_ERR(page);
812
813 copy_from_page(page, offset, insn, nbytes);
814 put_page(page);
815
816 return 0;
817}
818
819static int copy_insn(struct uprobe *uprobe, struct file *filp)
820{
821 struct address_space *mapping = uprobe->inode->i_mapping;
822 loff_t offs = uprobe->offset;
823 void *insn = &uprobe->arch.insn;
824 int size = sizeof(uprobe->arch.insn);
825 int len, err = -EIO;
826
827 /* Copy only available bytes, -EIO if nothing was read */
828 do {
829 if (offs >= i_size_read(uprobe->inode))
830 break;
831
832 len = min_t(int, size, PAGE_SIZE - (offs & ~PAGE_MASK));
833 err = __copy_insn(mapping, filp, insn, len, offs);
834 if (err)
835 break;
836
837 insn += len;
838 offs += len;
839 size -= len;
840 } while (size);
841
842 return err;
843}
844
845static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
846 struct mm_struct *mm, unsigned long vaddr)
847{
848 int ret = 0;
849
850 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
851 return ret;
852
853 /* TODO: move this into _register, until then we abuse this sem. */
854 down_write(&uprobe->consumer_rwsem);
855 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
856 goto out;
857
858 ret = copy_insn(uprobe, file);
859 if (ret)
860 goto out;
861
862 ret = -ENOTSUPP;
863 if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn))
864 goto out;
865
866 ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
867 if (ret)
868 goto out;
869
870 /* uprobe_write_opcode() assumes we don't cross page boundary */
871 BUG_ON((uprobe->offset & ~PAGE_MASK) +
872 UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
873
874 smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
875 set_bit(UPROBE_COPY_INSN, &uprobe->flags);
876
877 out:
878 up_write(&uprobe->consumer_rwsem);
879
880 return ret;
881}
882
883static inline bool consumer_filter(struct uprobe_consumer *uc,
884 enum uprobe_filter_ctx ctx, struct mm_struct *mm)
885{
886 return !uc->filter || uc->filter(uc, ctx, mm);
887}
888
889static bool filter_chain(struct uprobe *uprobe,
890 enum uprobe_filter_ctx ctx, struct mm_struct *mm)
891{
892 struct uprobe_consumer *uc;
893 bool ret = false;
894
895 down_read(&uprobe->consumer_rwsem);
896 for (uc = uprobe->consumers; uc; uc = uc->next) {
897 ret = consumer_filter(uc, ctx, mm);
898 if (ret)
899 break;
900 }
901 up_read(&uprobe->consumer_rwsem);
902
903 return ret;
904}
905
906static int
907install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
908 struct vm_area_struct *vma, unsigned long vaddr)
909{
910 bool first_uprobe;
911 int ret;
912
913 ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
914 if (ret)
915 return ret;
916
917 /*
918 * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
919 * the task can hit this breakpoint right after __replace_page().
920 */
921 first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
922 if (first_uprobe)
923 set_bit(MMF_HAS_UPROBES, &mm->flags);
924
925 ret = set_swbp(&uprobe->arch, mm, vaddr);
926 if (!ret)
927 clear_bit(MMF_RECALC_UPROBES, &mm->flags);
928 else if (first_uprobe)
929 clear_bit(MMF_HAS_UPROBES, &mm->flags);
930
931 return ret;
932}
933
934static int
935remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
936{
937 set_bit(MMF_RECALC_UPROBES, &mm->flags);
938 return set_orig_insn(&uprobe->arch, mm, vaddr);
939}
940
941static inline bool uprobe_is_active(struct uprobe *uprobe)
942{
943 return !RB_EMPTY_NODE(&uprobe->rb_node);
944}
945/*
946 * There could be threads that have already hit the breakpoint. They
947 * will recheck the current insn and restart if find_uprobe() fails.
948 * See find_active_uprobe().
949 */
950static void delete_uprobe(struct uprobe *uprobe)
951{
952 if (WARN_ON(!uprobe_is_active(uprobe)))
953 return;
954
955 spin_lock(&uprobes_treelock);
956 rb_erase(&uprobe->rb_node, &uprobes_tree);
957 spin_unlock(&uprobes_treelock);
958 RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
959 put_uprobe(uprobe);
960}
961
962struct map_info {
963 struct map_info *next;
964 struct mm_struct *mm;
965 unsigned long vaddr;
966};
967
968static inline struct map_info *free_map_info(struct map_info *info)
969{
970 struct map_info *next = info->next;
971 kfree(info);
972 return next;
973}
974
975static struct map_info *
976build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
977{
978 unsigned long pgoff = offset >> PAGE_SHIFT;
979 struct vm_area_struct *vma;
980 struct map_info *curr = NULL;
981 struct map_info *prev = NULL;
982 struct map_info *info;
983 int more = 0;
984
985 again:
986 i_mmap_lock_read(mapping);
987 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
988 if (!valid_vma(vma, is_register))
989 continue;
990
991 if (!prev && !more) {
992 /*
993 * Needs GFP_NOWAIT to avoid i_mmap_rwsem recursion through
994 * reclaim. This is optimistic, no harm done if it fails.
995 */
996 prev = kmalloc(sizeof(struct map_info),
997 GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
998 if (prev)
999 prev->next = NULL;
1000 }
1001 if (!prev) {
1002 more++;
1003 continue;
1004 }
1005
1006 if (!mmget_not_zero(vma->vm_mm))
1007 continue;
1008
1009 info = prev;
1010 prev = prev->next;
1011 info->next = curr;
1012 curr = info;
1013
1014 info->mm = vma->vm_mm;
1015 info->vaddr = offset_to_vaddr(vma, offset);
1016 }
1017 i_mmap_unlock_read(mapping);
1018
1019 if (!more)
1020 goto out;
1021
1022 prev = curr;
1023 while (curr) {
1024 mmput(curr->mm);
1025 curr = curr->next;
1026 }
1027
1028 do {
1029 info = kmalloc(sizeof(struct map_info), GFP_KERNEL);
1030 if (!info) {
1031 curr = ERR_PTR(-ENOMEM);
1032 goto out;
1033 }
1034 info->next = prev;
1035 prev = info;
1036 } while (--more);
1037
1038 goto again;
1039 out:
1040 while (prev)
1041 prev = free_map_info(prev);
1042 return curr;
1043}
1044
1045static int
1046register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
1047{
1048 bool is_register = !!new;
1049 struct map_info *info;
1050 int err = 0;
1051
1052 percpu_down_write(&dup_mmap_sem);
1053 info = build_map_info(uprobe->inode->i_mapping,
1054 uprobe->offset, is_register);
1055 if (IS_ERR(info)) {
1056 err = PTR_ERR(info);
1057 goto out;
1058 }
1059
1060 while (info) {
1061 struct mm_struct *mm = info->mm;
1062 struct vm_area_struct *vma;
1063
1064 if (err && is_register)
1065 goto free;
1066
1067 down_write(&mm->mmap_sem);
1068 vma = find_vma(mm, info->vaddr);
1069 if (!vma || !valid_vma(vma, is_register) ||
1070 file_inode(vma->vm_file) != uprobe->inode)
1071 goto unlock;
1072
1073 if (vma->vm_start > info->vaddr ||
1074 vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
1075 goto unlock;
1076
1077 if (is_register) {
1078 /* consult only the "caller", new consumer. */
1079 if (consumer_filter(new,
1080 UPROBE_FILTER_REGISTER, mm))
1081 err = install_breakpoint(uprobe, mm, vma, info->vaddr);
1082 } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
1083 if (!filter_chain(uprobe,
1084 UPROBE_FILTER_UNREGISTER, mm))
1085 err |= remove_breakpoint(uprobe, mm, info->vaddr);
1086 }
1087
1088 unlock:
1089 up_write(&mm->mmap_sem);
1090 free:
1091 mmput(mm);
1092 info = free_map_info(info);
1093 }
1094 out:
1095 percpu_up_write(&dup_mmap_sem);
1096 return err;
1097}
1098
1099static void
1100__uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
1101{
1102 int err;
1103
1104 if (WARN_ON(!consumer_del(uprobe, uc)))
1105 return;
1106
1107 err = register_for_each_vma(uprobe, NULL);
1108 /* TODO : cant unregister? schedule a worker thread */
1109 if (!uprobe->consumers && !err)
1110 delete_uprobe(uprobe);
1111}
1112
1113/*
1114 * uprobe_unregister - unregister an already registered probe.
1115 * @inode: the file in which the probe has to be removed.
1116 * @offset: offset from the start of the file.
1117 * @uc: identify which probe if multiple probes are colocated.
1118 */
1119void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
1120{
1121 struct uprobe *uprobe;
1122
1123 uprobe = find_uprobe(inode, offset);
1124 if (WARN_ON(!uprobe))
1125 return;
1126
1127 down_write(&uprobe->register_rwsem);
1128 __uprobe_unregister(uprobe, uc);
1129 up_write(&uprobe->register_rwsem);
1130 put_uprobe(uprobe);
1131}
1132EXPORT_SYMBOL_GPL(uprobe_unregister);
1133
1134/*
1135 * __uprobe_register - register a probe
1136 * @inode: the file in which the probe has to be placed.
1137 * @offset: offset from the start of the file.
1138 * @uc: information on howto handle the probe..
1139 *
1140 * Apart from the access refcount, __uprobe_register() takes a creation
1141 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
1142 * inserted into the rbtree (i.e first consumer for a @inode:@offset
1143 * tuple). Creation refcount stops uprobe_unregister from freeing the
1144 * @uprobe even before the register operation is complete. Creation
1145 * refcount is released when the last @uc for the @uprobe
1146 * unregisters. Caller of __uprobe_register() is required to keep @inode
1147 * (and the containing mount) referenced.
1148 *
1149 * Return errno if it cannot successully install probes
1150 * else return 0 (success)
1151 */
1152static int __uprobe_register(struct inode *inode, loff_t offset,
1153 loff_t ref_ctr_offset, struct uprobe_consumer *uc)
1154{
1155 struct uprobe *uprobe;
1156 int ret;
1157
1158 /* Uprobe must have at least one set consumer */
1159 if (!uc->handler && !uc->ret_handler)
1160 return -EINVAL;
1161
1162 /* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
1163 if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping))
1164 return -EIO;
1165 /* Racy, just to catch the obvious mistakes */
1166 if (offset > i_size_read(inode))
1167 return -EINVAL;
1168
1169 retry:
1170 uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
1171 if (!uprobe)
1172 return -ENOMEM;
1173 if (IS_ERR(uprobe))
1174 return PTR_ERR(uprobe);
1175
1176 /*
1177 * We can race with uprobe_unregister()->delete_uprobe().
1178 * Check uprobe_is_active() and retry if it is false.
1179 */
1180 down_write(&uprobe->register_rwsem);
1181 ret = -EAGAIN;
1182 if (likely(uprobe_is_active(uprobe))) {
1183 consumer_add(uprobe, uc);
1184 ret = register_for_each_vma(uprobe, uc);
1185 if (ret)
1186 __uprobe_unregister(uprobe, uc);
1187 }
1188 up_write(&uprobe->register_rwsem);
1189 put_uprobe(uprobe);
1190
1191 if (unlikely(ret == -EAGAIN))
1192 goto retry;
1193 return ret;
1194}
1195
1196int uprobe_register(struct inode *inode, loff_t offset,
1197 struct uprobe_consumer *uc)
1198{
1199 return __uprobe_register(inode, offset, 0, uc);
1200}
1201EXPORT_SYMBOL_GPL(uprobe_register);
1202
1203int uprobe_register_refctr(struct inode *inode, loff_t offset,
1204 loff_t ref_ctr_offset, struct uprobe_consumer *uc)
1205{
1206 return __uprobe_register(inode, offset, ref_ctr_offset, uc);
1207}
1208EXPORT_SYMBOL_GPL(uprobe_register_refctr);
1209
1210/*
1211 * uprobe_apply - unregister an already registered probe.
1212 * @inode: the file in which the probe has to be removed.
1213 * @offset: offset from the start of the file.
1214 * @uc: consumer which wants to add more or remove some breakpoints
1215 * @add: add or remove the breakpoints
1216 */
1217int uprobe_apply(struct inode *inode, loff_t offset,
1218 struct uprobe_consumer *uc, bool add)
1219{
1220 struct uprobe *uprobe;
1221 struct uprobe_consumer *con;
1222 int ret = -ENOENT;
1223
1224 uprobe = find_uprobe(inode, offset);
1225 if (WARN_ON(!uprobe))
1226 return ret;
1227
1228 down_write(&uprobe->register_rwsem);
1229 for (con = uprobe->consumers; con && con != uc ; con = con->next)
1230 ;
1231 if (con)
1232 ret = register_for_each_vma(uprobe, add ? uc : NULL);
1233 up_write(&uprobe->register_rwsem);
1234 put_uprobe(uprobe);
1235
1236 return ret;
1237}
1238
1239static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
1240{
1241 struct vm_area_struct *vma;
1242 int err = 0;
1243
1244 down_read(&mm->mmap_sem);
1245 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1246 unsigned long vaddr;
1247 loff_t offset;
1248
1249 if (!valid_vma(vma, false) ||
1250 file_inode(vma->vm_file) != uprobe->inode)
1251 continue;
1252
1253 offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
1254 if (uprobe->offset < offset ||
1255 uprobe->offset >= offset + vma->vm_end - vma->vm_start)
1256 continue;
1257
1258 vaddr = offset_to_vaddr(vma, uprobe->offset);
1259 err |= remove_breakpoint(uprobe, mm, vaddr);
1260 }
1261 up_read(&mm->mmap_sem);
1262
1263 return err;
1264}
1265
1266static struct rb_node *
1267find_node_in_range(struct inode *inode, loff_t min, loff_t max)
1268{
1269 struct rb_node *n = uprobes_tree.rb_node;
1270
1271 while (n) {
1272 struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
1273
1274 if (inode < u->inode) {
1275 n = n->rb_left;
1276 } else if (inode > u->inode) {
1277 n = n->rb_right;
1278 } else {
1279 if (max < u->offset)
1280 n = n->rb_left;
1281 else if (min > u->offset)
1282 n = n->rb_right;
1283 else
1284 break;
1285 }
1286 }
1287
1288 return n;
1289}
1290
1291/*
1292 * For a given range in vma, build a list of probes that need to be inserted.
1293 */
1294static void build_probe_list(struct inode *inode,
1295 struct vm_area_struct *vma,
1296 unsigned long start, unsigned long end,
1297 struct list_head *head)
1298{
1299 loff_t min, max;
1300 struct rb_node *n, *t;
1301 struct uprobe *u;
1302
1303 INIT_LIST_HEAD(head);
1304 min = vaddr_to_offset(vma, start);
1305 max = min + (end - start) - 1;
1306
1307 spin_lock(&uprobes_treelock);
1308 n = find_node_in_range(inode, min, max);
1309 if (n) {
1310 for (t = n; t; t = rb_prev(t)) {
1311 u = rb_entry(t, struct uprobe, rb_node);
1312 if (u->inode != inode || u->offset < min)
1313 break;
1314 list_add(&u->pending_list, head);
1315 get_uprobe(u);
1316 }
1317 for (t = n; (t = rb_next(t)); ) {
1318 u = rb_entry(t, struct uprobe, rb_node);
1319 if (u->inode != inode || u->offset > max)
1320 break;
1321 list_add(&u->pending_list, head);
1322 get_uprobe(u);
1323 }
1324 }
1325 spin_unlock(&uprobes_treelock);
1326}
1327
1328/* @vma contains reference counter, not the probed instruction. */
1329static int delayed_ref_ctr_inc(struct vm_area_struct *vma)
1330{
1331 struct list_head *pos, *q;
1332 struct delayed_uprobe *du;
1333 unsigned long vaddr;
1334 int ret = 0, err = 0;
1335
1336 mutex_lock(&delayed_uprobe_lock);
1337 list_for_each_safe(pos, q, &delayed_uprobe_list) {
1338 du = list_entry(pos, struct delayed_uprobe, list);
1339
1340 if (du->mm != vma->vm_mm ||
1341 !valid_ref_ctr_vma(du->uprobe, vma))
1342 continue;
1343
1344 vaddr = offset_to_vaddr(vma, du->uprobe->ref_ctr_offset);
1345 ret = __update_ref_ctr(vma->vm_mm, vaddr, 1);
1346 if (ret) {
1347 update_ref_ctr_warn(du->uprobe, vma->vm_mm, 1);
1348 if (!err)
1349 err = ret;
1350 }
1351 delayed_uprobe_delete(du);
1352 }
1353 mutex_unlock(&delayed_uprobe_lock);
1354 return err;
1355}
1356
1357/*
1358 * Called from mmap_region/vma_adjust with mm->mmap_sem acquired.
1359 *
1360 * Currently we ignore all errors and always return 0, the callers
1361 * can't handle the failure anyway.
1362 */
1363int uprobe_mmap(struct vm_area_struct *vma)
1364{
1365 struct list_head tmp_list;
1366 struct uprobe *uprobe, *u;
1367 struct inode *inode;
1368
1369 if (no_uprobe_events())
1370 return 0;
1371
1372 if (vma->vm_file &&
1373 (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
1374 test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags))
1375 delayed_ref_ctr_inc(vma);
1376
1377 if (!valid_vma(vma, true))
1378 return 0;
1379
1380 inode = file_inode(vma->vm_file);
1381 if (!inode)
1382 return 0;
1383
1384 mutex_lock(uprobes_mmap_hash(inode));
1385 build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
1386 /*
1387 * We can race with uprobe_unregister(), this uprobe can be already
1388 * removed. But in this case filter_chain() must return false, all
1389 * consumers have gone away.
1390 */
1391 list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1392 if (!fatal_signal_pending(current) &&
1393 filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
1394 unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
1395 install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1396 }
1397 put_uprobe(uprobe);
1398 }
1399 mutex_unlock(uprobes_mmap_hash(inode));
1400
1401 return 0;
1402}
1403
1404static bool
1405vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1406{
1407 loff_t min, max;
1408 struct inode *inode;
1409 struct rb_node *n;
1410
1411 inode = file_inode(vma->vm_file);
1412
1413 min = vaddr_to_offset(vma, start);
1414 max = min + (end - start) - 1;
1415
1416 spin_lock(&uprobes_treelock);
1417 n = find_node_in_range(inode, min, max);
1418 spin_unlock(&uprobes_treelock);
1419
1420 return !!n;
1421}
1422
1423/*
1424 * Called in context of a munmap of a vma.
1425 */
1426void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1427{
1428 if (no_uprobe_events() || !valid_vma(vma, false))
1429 return;
1430
1431 if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
1432 return;
1433
1434 if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||
1435 test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))
1436 return;
1437
1438 if (vma_has_uprobes(vma, start, end))
1439 set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
1440}
1441
1442/* Slot allocation for XOL */
1443static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
1444{
1445 struct vm_area_struct *vma;
1446 int ret;
1447
1448 if (down_write_killable(&mm->mmap_sem))
1449 return -EINTR;
1450
1451 if (mm->uprobes_state.xol_area) {
1452 ret = -EALREADY;
1453 goto fail;
1454 }
1455
1456 if (!area->vaddr) {
1457 /* Try to map as high as possible, this is only a hint. */
1458 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE,
1459 PAGE_SIZE, 0, 0);
1460 if (area->vaddr & ~PAGE_MASK) {
1461 ret = area->vaddr;
1462 goto fail;
1463 }
1464 }
1465
1466 vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1467 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
1468 &area->xol_mapping);
1469 if (IS_ERR(vma)) {
1470 ret = PTR_ERR(vma);
1471 goto fail;
1472 }
1473
1474 ret = 0;
1475 /* pairs with get_xol_area() */
1476 smp_store_release(&mm->uprobes_state.xol_area, area); /* ^^^ */
1477 fail:
1478 up_write(&mm->mmap_sem);
1479
1480 return ret;
1481}
1482
1483static struct xol_area *__create_xol_area(unsigned long vaddr)
1484{
1485 struct mm_struct *mm = current->mm;
1486 uprobe_opcode_t insn = UPROBE_SWBP_INSN;
1487 struct xol_area *area;
1488
1489 area = kmalloc(sizeof(*area), GFP_KERNEL);
1490 if (unlikely(!area))
1491 goto out;
1492
1493 area->bitmap = kcalloc(BITS_TO_LONGS(UINSNS_PER_PAGE), sizeof(long),
1494 GFP_KERNEL);
1495 if (!area->bitmap)
1496 goto free_area;
1497
1498 area->xol_mapping.name = "[uprobes]";
1499 area->xol_mapping.fault = NULL;
1500 area->xol_mapping.pages = area->pages;
1501 area->pages[0] = alloc_page(GFP_HIGHUSER);
1502 if (!area->pages[0])
1503 goto free_bitmap;
1504 area->pages[1] = NULL;
1505
1506 area->vaddr = vaddr;
1507 init_waitqueue_head(&area->wq);
1508 /* Reserve the 1st slot for get_trampoline_vaddr() */
1509 set_bit(0, area->bitmap);
1510 atomic_set(&area->slot_count, 1);
1511 arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE);
1512
1513 if (!xol_add_vma(mm, area))
1514 return area;
1515
1516 __free_page(area->pages[0]);
1517 free_bitmap:
1518 kfree(area->bitmap);
1519 free_area:
1520 kfree(area);
1521 out:
1522 return NULL;
1523}
1524
1525/*
1526 * get_xol_area - Allocate process's xol_area if necessary.
1527 * This area will be used for storing instructions for execution out of line.
1528 *
1529 * Returns the allocated area or NULL.
1530 */
1531static struct xol_area *get_xol_area(void)
1532{
1533 struct mm_struct *mm = current->mm;
1534 struct xol_area *area;
1535
1536 if (!mm->uprobes_state.xol_area)
1537 __create_xol_area(0);
1538
1539 /* Pairs with xol_add_vma() smp_store_release() */
1540 area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */
1541 return area;
1542}
1543
1544/*
1545 * uprobe_clear_state - Free the area allocated for slots.
1546 */
1547void uprobe_clear_state(struct mm_struct *mm)
1548{
1549 struct xol_area *area = mm->uprobes_state.xol_area;
1550
1551 mutex_lock(&delayed_uprobe_lock);
1552 delayed_uprobe_remove(NULL, mm);
1553 mutex_unlock(&delayed_uprobe_lock);
1554
1555 if (!area)
1556 return;
1557
1558 put_page(area->pages[0]);
1559 kfree(area->bitmap);
1560 kfree(area);
1561}
1562
1563void uprobe_start_dup_mmap(void)
1564{
1565 percpu_down_read(&dup_mmap_sem);
1566}
1567
1568void uprobe_end_dup_mmap(void)
1569{
1570 percpu_up_read(&dup_mmap_sem);
1571}
1572
1573void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
1574{
1575 if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {
1576 set_bit(MMF_HAS_UPROBES, &newmm->flags);
1577 /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */
1578 set_bit(MMF_RECALC_UPROBES, &newmm->flags);
1579 }
1580}
1581
1582/*
1583 * - search for a free slot.
1584 */
1585static unsigned long xol_take_insn_slot(struct xol_area *area)
1586{
1587 unsigned long slot_addr;
1588 int slot_nr;
1589
1590 do {
1591 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1592 if (slot_nr < UINSNS_PER_PAGE) {
1593 if (!test_and_set_bit(slot_nr, area->bitmap))
1594 break;
1595
1596 slot_nr = UINSNS_PER_PAGE;
1597 continue;
1598 }
1599 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1600 } while (slot_nr >= UINSNS_PER_PAGE);
1601
1602 slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1603 atomic_inc(&area->slot_count);
1604
1605 return slot_addr;
1606}
1607
1608/*
1609 * xol_get_insn_slot - allocate a slot for xol.
1610 * Returns the allocated slot address or 0.
1611 */
1612static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
1613{
1614 struct xol_area *area;
1615 unsigned long xol_vaddr;
1616
1617 area = get_xol_area();
1618 if (!area)
1619 return 0;
1620
1621 xol_vaddr = xol_take_insn_slot(area);
1622 if (unlikely(!xol_vaddr))
1623 return 0;
1624
1625 arch_uprobe_copy_ixol(area->pages[0], xol_vaddr,
1626 &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
1627
1628 return xol_vaddr;
1629}
1630
1631/*
1632 * xol_free_insn_slot - If slot was earlier allocated by
1633 * @xol_get_insn_slot(), make the slot available for
1634 * subsequent requests.
1635 */
1636static void xol_free_insn_slot(struct task_struct *tsk)
1637{
1638 struct xol_area *area;
1639 unsigned long vma_end;
1640 unsigned long slot_addr;
1641
1642 if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1643 return;
1644
1645 slot_addr = tsk->utask->xol_vaddr;
1646 if (unlikely(!slot_addr))
1647 return;
1648
1649 area = tsk->mm->uprobes_state.xol_area;
1650 vma_end = area->vaddr + PAGE_SIZE;
1651 if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1652 unsigned long offset;
1653 int slot_nr;
1654
1655 offset = slot_addr - area->vaddr;
1656 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1657 if (slot_nr >= UINSNS_PER_PAGE)
1658 return;
1659
1660 clear_bit(slot_nr, area->bitmap);
1661 atomic_dec(&area->slot_count);
1662 smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
1663 if (waitqueue_active(&area->wq))
1664 wake_up(&area->wq);
1665
1666 tsk->utask->xol_vaddr = 0;
1667 }
1668}
1669
1670void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
1671 void *src, unsigned long len)
1672{
1673 /* Initialize the slot */
1674 copy_to_page(page, vaddr, src, len);
1675
1676 /*
1677 * We probably need flush_icache_user_range() but it needs vma.
1678 * This should work on most of architectures by default. If
1679 * architecture needs to do something different it can define
1680 * its own version of the function.
1681 */
1682 flush_dcache_page(page);
1683}
1684
1685/**
1686 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1687 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1688 * instruction.
1689 * Return the address of the breakpoint instruction.
1690 */
1691unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1692{
1693 return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1694}
1695
1696unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
1697{
1698 struct uprobe_task *utask = current->utask;
1699
1700 if (unlikely(utask && utask->active_uprobe))
1701 return utask->vaddr;
1702
1703 return instruction_pointer(regs);
1704}
1705
1706static struct return_instance *free_ret_instance(struct return_instance *ri)
1707{
1708 struct return_instance *next = ri->next;
1709 put_uprobe(ri->uprobe);
1710 kfree(ri);
1711 return next;
1712}
1713
1714/*
1715 * Called with no locks held.
1716 * Called in context of an exiting or an exec-ing thread.
1717 */
1718void uprobe_free_utask(struct task_struct *t)
1719{
1720 struct uprobe_task *utask = t->utask;
1721 struct return_instance *ri;
1722
1723 if (!utask)
1724 return;
1725
1726 if (utask->active_uprobe)
1727 put_uprobe(utask->active_uprobe);
1728
1729 ri = utask->return_instances;
1730 while (ri)
1731 ri = free_ret_instance(ri);
1732
1733 xol_free_insn_slot(t);
1734 kfree(utask);
1735 t->utask = NULL;
1736}
1737
1738/*
1739 * Allocate a uprobe_task object for the task if if necessary.
1740 * Called when the thread hits a breakpoint.
1741 *
1742 * Returns:
1743 * - pointer to new uprobe_task on success
1744 * - NULL otherwise
1745 */
1746static struct uprobe_task *get_utask(void)
1747{
1748 if (!current->utask)
1749 current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1750 return current->utask;
1751}
1752
1753static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask)
1754{
1755 struct uprobe_task *n_utask;
1756 struct return_instance **p, *o, *n;
1757
1758 n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1759 if (!n_utask)
1760 return -ENOMEM;
1761 t->utask = n_utask;
1762
1763 p = &n_utask->return_instances;
1764 for (o = o_utask->return_instances; o; o = o->next) {
1765 n = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1766 if (!n)
1767 return -ENOMEM;
1768
1769 *n = *o;
1770 get_uprobe(n->uprobe);
1771 n->next = NULL;
1772
1773 *p = n;
1774 p = &n->next;
1775 n_utask->depth++;
1776 }
1777
1778 return 0;
1779}
1780
1781static void uprobe_warn(struct task_struct *t, const char *msg)
1782{
1783 pr_warn("uprobe: %s:%d failed to %s\n",
1784 current->comm, current->pid, msg);
1785}
1786
1787static void dup_xol_work(struct callback_head *work)
1788{
1789 if (current->flags & PF_EXITING)
1790 return;
1791
1792 if (!__create_xol_area(current->utask->dup_xol_addr) &&
1793 !fatal_signal_pending(current))
1794 uprobe_warn(current, "dup xol area");
1795}
1796
1797/*
1798 * Called in context of a new clone/fork from copy_process.
1799 */
1800void uprobe_copy_process(struct task_struct *t, unsigned long flags)
1801{
1802 struct uprobe_task *utask = current->utask;
1803 struct mm_struct *mm = current->mm;
1804 struct xol_area *area;
1805
1806 t->utask = NULL;
1807
1808 if (!utask || !utask->return_instances)
1809 return;
1810
1811 if (mm == t->mm && !(flags & CLONE_VFORK))
1812 return;
1813
1814 if (dup_utask(t, utask))
1815 return uprobe_warn(t, "dup ret instances");
1816
1817 /* The task can fork() after dup_xol_work() fails */
1818 area = mm->uprobes_state.xol_area;
1819 if (!area)
1820 return uprobe_warn(t, "dup xol area");
1821
1822 if (mm == t->mm)
1823 return;
1824
1825 t->utask->dup_xol_addr = area->vaddr;
1826 init_task_work(&t->utask->dup_xol_work, dup_xol_work);
1827 task_work_add(t, &t->utask->dup_xol_work, true);
1828}
1829
1830/*
1831 * Current area->vaddr notion assume the trampoline address is always
1832 * equal area->vaddr.
1833 *
1834 * Returns -1 in case the xol_area is not allocated.
1835 */
1836static unsigned long get_trampoline_vaddr(void)
1837{
1838 struct xol_area *area;
1839 unsigned long trampoline_vaddr = -1;
1840
1841 /* Pairs with xol_add_vma() smp_store_release() */
1842 area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */
1843 if (area)
1844 trampoline_vaddr = area->vaddr;
1845
1846 return trampoline_vaddr;
1847}
1848
1849static void cleanup_return_instances(struct uprobe_task *utask, bool chained,
1850 struct pt_regs *regs)
1851{
1852 struct return_instance *ri = utask->return_instances;
1853 enum rp_check ctx = chained ? RP_CHECK_CHAIN_CALL : RP_CHECK_CALL;
1854
1855 while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
1856 ri = free_ret_instance(ri);
1857 utask->depth--;
1858 }
1859 utask->return_instances = ri;
1860}
1861
1862static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
1863{
1864 struct return_instance *ri;
1865 struct uprobe_task *utask;
1866 unsigned long orig_ret_vaddr, trampoline_vaddr;
1867 bool chained;
1868
1869 if (!get_xol_area())
1870 return;
1871
1872 utask = get_utask();
1873 if (!utask)
1874 return;
1875
1876 if (utask->depth >= MAX_URETPROBE_DEPTH) {
1877 printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to"
1878 " nestedness limit pid/tgid=%d/%d\n",
1879 current->pid, current->tgid);
1880 return;
1881 }
1882
1883 ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1884 if (!ri)
1885 return;
1886
1887 trampoline_vaddr = get_trampoline_vaddr();
1888 orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
1889 if (orig_ret_vaddr == -1)
1890 goto fail;
1891
1892 /* drop the entries invalidated by longjmp() */
1893 chained = (orig_ret_vaddr == trampoline_vaddr);
1894 cleanup_return_instances(utask, chained, regs);
1895
1896 /*
1897 * We don't want to keep trampoline address in stack, rather keep the
1898 * original return address of first caller thru all the consequent
1899 * instances. This also makes breakpoint unwrapping easier.
1900 */
1901 if (chained) {
1902 if (!utask->return_instances) {
1903 /*
1904 * This situation is not possible. Likely we have an
1905 * attack from user-space.
1906 */
1907 uprobe_warn(current, "handle tail call");
1908 goto fail;
1909 }
1910 orig_ret_vaddr = utask->return_instances->orig_ret_vaddr;
1911 }
1912
1913 ri->uprobe = get_uprobe(uprobe);
1914 ri->func = instruction_pointer(regs);
1915 ri->stack = user_stack_pointer(regs);
1916 ri->orig_ret_vaddr = orig_ret_vaddr;
1917 ri->chained = chained;
1918
1919 utask->depth++;
1920 ri->next = utask->return_instances;
1921 utask->return_instances = ri;
1922
1923 return;
1924 fail:
1925 kfree(ri);
1926}
1927
1928/* Prepare to single-step probed instruction out of line. */
1929static int
1930pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
1931{
1932 struct uprobe_task *utask;
1933 unsigned long xol_vaddr;
1934 int err;
1935
1936 utask = get_utask();
1937 if (!utask)
1938 return -ENOMEM;
1939
1940 xol_vaddr = xol_get_insn_slot(uprobe);
1941 if (!xol_vaddr)
1942 return -ENOMEM;
1943
1944 utask->xol_vaddr = xol_vaddr;
1945 utask->vaddr = bp_vaddr;
1946
1947 err = arch_uprobe_pre_xol(&uprobe->arch, regs);
1948 if (unlikely(err)) {
1949 xol_free_insn_slot(current);
1950 return err;
1951 }
1952
1953 utask->active_uprobe = uprobe;
1954 utask->state = UTASK_SSTEP;
1955 return 0;
1956}
1957
1958/*
1959 * If we are singlestepping, then ensure this thread is not connected to
1960 * non-fatal signals until completion of singlestep. When xol insn itself
1961 * triggers the signal, restart the original insn even if the task is
1962 * already SIGKILL'ed (since coredump should report the correct ip). This
1963 * is even more important if the task has a handler for SIGSEGV/etc, The
1964 * _same_ instruction should be repeated again after return from the signal
1965 * handler, and SSTEP can never finish in this case.
1966 */
1967bool uprobe_deny_signal(void)
1968{
1969 struct task_struct *t = current;
1970 struct uprobe_task *utask = t->utask;
1971
1972 if (likely(!utask || !utask->active_uprobe))
1973 return false;
1974
1975 WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1976
1977 if (signal_pending(t)) {
1978 spin_lock_irq(&t->sighand->siglock);
1979 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1980 spin_unlock_irq(&t->sighand->siglock);
1981
1982 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1983 utask->state = UTASK_SSTEP_TRAPPED;
1984 set_tsk_thread_flag(t, TIF_UPROBE);
1985 }
1986 }
1987
1988 return true;
1989}
1990
1991static void mmf_recalc_uprobes(struct mm_struct *mm)
1992{
1993 struct vm_area_struct *vma;
1994
1995 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1996 if (!valid_vma(vma, false))
1997 continue;
1998 /*
1999 * This is not strictly accurate, we can race with
2000 * uprobe_unregister() and see the already removed
2001 * uprobe if delete_uprobe() was not yet called.
2002 * Or this uprobe can be filtered out.
2003 */
2004 if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
2005 return;
2006 }
2007
2008 clear_bit(MMF_HAS_UPROBES, &mm->flags);
2009}
2010
2011static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
2012{
2013 struct page *page;
2014 uprobe_opcode_t opcode;
2015 int result;
2016
2017 pagefault_disable();
2018 result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
2019 pagefault_enable();
2020
2021 if (likely(result == 0))
2022 goto out;
2023
2024 /*
2025 * The NULL 'tsk' here ensures that any faults that occur here
2026 * will not be accounted to the task. 'mm' *is* current->mm,
2027 * but we treat this as a 'remote' access since it is
2028 * essentially a kernel access to the memory.
2029 */
2030 result = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &page,
2031 NULL, NULL);
2032 if (result < 0)
2033 return result;
2034
2035 copy_from_page(page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
2036 put_page(page);
2037 out:
2038 /* This needs to return true for any variant of the trap insn */
2039 return is_trap_insn(&opcode);
2040}
2041
2042static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
2043{
2044 struct mm_struct *mm = current->mm;
2045 struct uprobe *uprobe = NULL;
2046 struct vm_area_struct *vma;
2047
2048 down_read(&mm->mmap_sem);
2049 vma = find_vma(mm, bp_vaddr);
2050 if (vma && vma->vm_start <= bp_vaddr) {
2051 if (valid_vma(vma, false)) {
2052 struct inode *inode = file_inode(vma->vm_file);
2053 loff_t offset = vaddr_to_offset(vma, bp_vaddr);
2054
2055 uprobe = find_uprobe(inode, offset);
2056 }
2057
2058 if (!uprobe)
2059 *is_swbp = is_trap_at_addr(mm, bp_vaddr);
2060 } else {
2061 *is_swbp = -EFAULT;
2062 }
2063
2064 if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
2065 mmf_recalc_uprobes(mm);
2066 up_read(&mm->mmap_sem);
2067
2068 return uprobe;
2069}
2070
2071static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
2072{
2073 struct uprobe_consumer *uc;
2074 int remove = UPROBE_HANDLER_REMOVE;
2075 bool need_prep = false; /* prepare return uprobe, when needed */
2076
2077 down_read(&uprobe->register_rwsem);
2078 for (uc = uprobe->consumers; uc; uc = uc->next) {
2079 int rc = 0;
2080
2081 if (uc->handler) {
2082 rc = uc->handler(uc, regs);
2083 WARN(rc & ~UPROBE_HANDLER_MASK,
2084 "bad rc=0x%x from %ps()\n", rc, uc->handler);
2085 }
2086
2087 if (uc->ret_handler)
2088 need_prep = true;
2089
2090 remove &= rc;
2091 }
2092
2093 if (need_prep && !remove)
2094 prepare_uretprobe(uprobe, regs); /* put bp at return */
2095
2096 if (remove && uprobe->consumers) {
2097 WARN_ON(!uprobe_is_active(uprobe));
2098 unapply_uprobe(uprobe, current->mm);
2099 }
2100 up_read(&uprobe->register_rwsem);
2101}
2102
2103static void
2104handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
2105{
2106 struct uprobe *uprobe = ri->uprobe;
2107 struct uprobe_consumer *uc;
2108
2109 down_read(&uprobe->register_rwsem);
2110 for (uc = uprobe->consumers; uc; uc = uc->next) {
2111 if (uc->ret_handler)
2112 uc->ret_handler(uc, ri->func, regs);
2113 }
2114 up_read(&uprobe->register_rwsem);
2115}
2116
2117static struct return_instance *find_next_ret_chain(struct return_instance *ri)
2118{
2119 bool chained;
2120
2121 do {
2122 chained = ri->chained;
2123 ri = ri->next; /* can't be NULL if chained */
2124 } while (chained);
2125
2126 return ri;
2127}
2128
2129static void handle_trampoline(struct pt_regs *regs)
2130{
2131 struct uprobe_task *utask;
2132 struct return_instance *ri, *next;
2133 bool valid;
2134
2135 utask = current->utask;
2136 if (!utask)
2137 goto sigill;
2138
2139 ri = utask->return_instances;
2140 if (!ri)
2141 goto sigill;
2142
2143 do {
2144 /*
2145 * We should throw out the frames invalidated by longjmp().
2146 * If this chain is valid, then the next one should be alive
2147 * or NULL; the latter case means that nobody but ri->func
2148 * could hit this trampoline on return. TODO: sigaltstack().
2149 */
2150 next = find_next_ret_chain(ri);
2151 valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
2152
2153 instruction_pointer_set(regs, ri->orig_ret_vaddr);
2154 do {
2155 if (valid)
2156 handle_uretprobe_chain(ri, regs);
2157 ri = free_ret_instance(ri);
2158 utask->depth--;
2159 } while (ri != next);
2160 } while (!valid);
2161
2162 utask->return_instances = ri;
2163 return;
2164
2165 sigill:
2166 uprobe_warn(current, "handle uretprobe, sending SIGILL.");
2167 force_sig(SIGILL);
2168
2169}
2170
2171bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
2172{
2173 return false;
2174}
2175
2176bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
2177 struct pt_regs *regs)
2178{
2179 return true;
2180}
2181
2182/*
2183 * Run handler and ask thread to singlestep.
2184 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
2185 */
2186static void handle_swbp(struct pt_regs *regs)
2187{
2188 struct uprobe *uprobe;
2189 unsigned long bp_vaddr;
2190 int uninitialized_var(is_swbp);
2191
2192 bp_vaddr = uprobe_get_swbp_addr(regs);
2193 if (bp_vaddr == get_trampoline_vaddr())
2194 return handle_trampoline(regs);
2195
2196 uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
2197 if (!uprobe) {
2198 if (is_swbp > 0) {
2199 /* No matching uprobe; signal SIGTRAP. */
2200 send_sig(SIGTRAP, current, 0);
2201 } else {
2202 /*
2203 * Either we raced with uprobe_unregister() or we can't
2204 * access this memory. The latter is only possible if
2205 * another thread plays with our ->mm. In both cases
2206 * we can simply restart. If this vma was unmapped we
2207 * can pretend this insn was not executed yet and get
2208 * the (correct) SIGSEGV after restart.
2209 */
2210 instruction_pointer_set(regs, bp_vaddr);
2211 }
2212 return;
2213 }
2214
2215 /* change it in advance for ->handler() and restart */
2216 instruction_pointer_set(regs, bp_vaddr);
2217
2218 /*
2219 * TODO: move copy_insn/etc into _register and remove this hack.
2220 * After we hit the bp, _unregister + _register can install the
2221 * new and not-yet-analyzed uprobe at the same address, restart.
2222 */
2223 if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
2224 goto out;
2225
2226 /*
2227 * Pairs with the smp_wmb() in prepare_uprobe().
2228 *
2229 * Guarantees that if we see the UPROBE_COPY_INSN bit set, then
2230 * we must also see the stores to &uprobe->arch performed by the
2231 * prepare_uprobe() call.
2232 */
2233 smp_rmb();
2234
2235 /* Tracing handlers use ->utask to communicate with fetch methods */
2236 if (!get_utask())
2237 goto out;
2238
2239 if (arch_uprobe_ignore(&uprobe->arch, regs))
2240 goto out;
2241
2242 handler_chain(uprobe, regs);
2243
2244 if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
2245 goto out;
2246
2247 if (!pre_ssout(uprobe, regs, bp_vaddr))
2248 return;
2249
2250 /* arch_uprobe_skip_sstep() succeeded, or restart if can't singlestep */
2251out:
2252 put_uprobe(uprobe);
2253}
2254
2255/*
2256 * Perform required fix-ups and disable singlestep.
2257 * Allow pending signals to take effect.
2258 */
2259static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
2260{
2261 struct uprobe *uprobe;
2262 int err = 0;
2263
2264 uprobe = utask->active_uprobe;
2265 if (utask->state == UTASK_SSTEP_ACK)
2266 err = arch_uprobe_post_xol(&uprobe->arch, regs);
2267 else if (utask->state == UTASK_SSTEP_TRAPPED)
2268 arch_uprobe_abort_xol(&uprobe->arch, regs);
2269 else
2270 WARN_ON_ONCE(1);
2271
2272 put_uprobe(uprobe);
2273 utask->active_uprobe = NULL;
2274 utask->state = UTASK_RUNNING;
2275 xol_free_insn_slot(current);
2276
2277 spin_lock_irq(¤t->sighand->siglock);
2278 recalc_sigpending(); /* see uprobe_deny_signal() */
2279 spin_unlock_irq(¤t->sighand->siglock);
2280
2281 if (unlikely(err)) {
2282 uprobe_warn(current, "execute the probed insn, sending SIGILL.");
2283 force_sig(SIGILL);
2284 }
2285}
2286
2287/*
2288 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
2289 * allows the thread to return from interrupt. After that handle_swbp()
2290 * sets utask->active_uprobe.
2291 *
2292 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
2293 * and allows the thread to return from interrupt.
2294 *
2295 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
2296 * uprobe_notify_resume().
2297 */
2298void uprobe_notify_resume(struct pt_regs *regs)
2299{
2300 struct uprobe_task *utask;
2301
2302 clear_thread_flag(TIF_UPROBE);
2303
2304 utask = current->utask;
2305 if (utask && utask->active_uprobe)
2306 handle_singlestep(utask, regs);
2307 else
2308 handle_swbp(regs);
2309}
2310
2311/*
2312 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
2313 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
2314 */
2315int uprobe_pre_sstep_notifier(struct pt_regs *regs)
2316{
2317 if (!current->mm)
2318 return 0;
2319
2320 if (!test_bit(MMF_HAS_UPROBES, ¤t->mm->flags) &&
2321 (!current->utask || !current->utask->return_instances))
2322 return 0;
2323
2324 set_thread_flag(TIF_UPROBE);
2325 return 1;
2326}
2327
2328/*
2329 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
2330 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
2331 */
2332int uprobe_post_sstep_notifier(struct pt_regs *regs)
2333{
2334 struct uprobe_task *utask = current->utask;
2335
2336 if (!current->mm || !utask || !utask->active_uprobe)
2337 /* task is currently not uprobed */
2338 return 0;
2339
2340 utask->state = UTASK_SSTEP_ACK;
2341 set_thread_flag(TIF_UPROBE);
2342 return 1;
2343}
2344
2345static struct notifier_block uprobe_exception_nb = {
2346 .notifier_call = arch_uprobe_exception_notify,
2347 .priority = INT_MAX-1, /* notified after kprobes, kgdb */
2348};
2349
2350void __init uprobes_init(void)
2351{
2352 int i;
2353
2354 for (i = 0; i < UPROBES_HASH_SZ; i++)
2355 mutex_init(&uprobes_mmap_mutex[i]);
2356
2357 BUG_ON(register_die_notifier(&uprobe_exception_nb));
2358}