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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);