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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright IBM Corp. 2002, 2006
6 *
7 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
8 */
9
10#include <linux/kprobes.h>
11#include <linux/ptrace.h>
12#include <linux/preempt.h>
13#include <linux/stop_machine.h>
14#include <linux/kdebug.h>
15#include <linux/uaccess.h>
16#include <linux/extable.h>
17#include <linux/module.h>
18#include <linux/slab.h>
19#include <linux/hardirq.h>
20#include <linux/ftrace.h>
21#include <asm/set_memory.h>
22#include <asm/sections.h>
23#include <asm/dis.h>
24
25DEFINE_PER_CPU(struct kprobe *, current_kprobe);
26DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
27
28struct kretprobe_blackpoint kretprobe_blacklist[] = { };
29
30DEFINE_INSN_CACHE_OPS(dmainsn);
31
32static void *alloc_dmainsn_page(void)
33{
34 void *page;
35
36 page = (void *) __get_free_page(GFP_KERNEL | GFP_DMA);
37 if (page)
38 set_memory_x((unsigned long) page, 1);
39 return page;
40}
41
42static void free_dmainsn_page(void *page)
43{
44 set_memory_nx((unsigned long) page, 1);
45 free_page((unsigned long)page);
46}
47
48struct kprobe_insn_cache kprobe_dmainsn_slots = {
49 .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
50 .alloc = alloc_dmainsn_page,
51 .free = free_dmainsn_page,
52 .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
53 .insn_size = MAX_INSN_SIZE,
54};
55
56static void copy_instruction(struct kprobe *p)
57{
58 unsigned long ip = (unsigned long) p->addr;
59 s64 disp, new_disp;
60 u64 addr, new_addr;
61
62 if (ftrace_location(ip) == ip) {
63 /*
64 * If kprobes patches the instruction that is morphed by
65 * ftrace make sure that kprobes always sees the branch
66 * "jg .+24" that skips the mcount block or the "brcl 0,0"
67 * in case of hotpatch.
68 */
69 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
70 p->ainsn.is_ftrace_insn = 1;
71 } else
72 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
73 p->opcode = p->ainsn.insn[0];
74 if (!probe_is_insn_relative_long(p->ainsn.insn))
75 return;
76 /*
77 * For pc-relative instructions in RIL-b or RIL-c format patch the
78 * RI2 displacement field. We have already made sure that the insn
79 * slot for the patched instruction is within the same 2GB area
80 * as the original instruction (either kernel image or module area).
81 * Therefore the new displacement will always fit.
82 */
83 disp = *(s32 *)&p->ainsn.insn[1];
84 addr = (u64)(unsigned long)p->addr;
85 new_addr = (u64)(unsigned long)p->ainsn.insn;
86 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
87 *(s32 *)&p->ainsn.insn[1] = new_disp;
88}
89NOKPROBE_SYMBOL(copy_instruction);
90
91static inline int is_kernel_addr(void *addr)
92{
93 return addr < (void *)_end;
94}
95
96static int s390_get_insn_slot(struct kprobe *p)
97{
98 /*
99 * Get an insn slot that is within the same 2GB area like the original
100 * instruction. That way instructions with a 32bit signed displacement
101 * field can be patched and executed within the insn slot.
102 */
103 p->ainsn.insn = NULL;
104 if (is_kernel_addr(p->addr))
105 p->ainsn.insn = get_dmainsn_slot();
106 else if (is_module_addr(p->addr))
107 p->ainsn.insn = get_insn_slot();
108 return p->ainsn.insn ? 0 : -ENOMEM;
109}
110NOKPROBE_SYMBOL(s390_get_insn_slot);
111
112static void s390_free_insn_slot(struct kprobe *p)
113{
114 if (!p->ainsn.insn)
115 return;
116 if (is_kernel_addr(p->addr))
117 free_dmainsn_slot(p->ainsn.insn, 0);
118 else
119 free_insn_slot(p->ainsn.insn, 0);
120 p->ainsn.insn = NULL;
121}
122NOKPROBE_SYMBOL(s390_free_insn_slot);
123
124int arch_prepare_kprobe(struct kprobe *p)
125{
126 if ((unsigned long) p->addr & 0x01)
127 return -EINVAL;
128 /* Make sure the probe isn't going on a difficult instruction */
129 if (probe_is_prohibited_opcode(p->addr))
130 return -EINVAL;
131 if (s390_get_insn_slot(p))
132 return -ENOMEM;
133 copy_instruction(p);
134 return 0;
135}
136NOKPROBE_SYMBOL(arch_prepare_kprobe);
137
138int arch_check_ftrace_location(struct kprobe *p)
139{
140 return 0;
141}
142
143struct swap_insn_args {
144 struct kprobe *p;
145 unsigned int arm_kprobe : 1;
146};
147
148static int swap_instruction(void *data)
149{
150 struct swap_insn_args *args = data;
151 struct ftrace_insn new_insn, *insn;
152 struct kprobe *p = args->p;
153 size_t len;
154
155 new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
156 len = sizeof(new_insn.opc);
157 if (!p->ainsn.is_ftrace_insn)
158 goto skip_ftrace;
159 len = sizeof(new_insn);
160 insn = (struct ftrace_insn *) p->addr;
161 if (args->arm_kprobe) {
162 if (is_ftrace_nop(insn))
163 new_insn.disp = KPROBE_ON_FTRACE_NOP;
164 else
165 new_insn.disp = KPROBE_ON_FTRACE_CALL;
166 } else {
167 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
168 if (insn->disp == KPROBE_ON_FTRACE_NOP)
169 ftrace_generate_nop_insn(&new_insn);
170 }
171skip_ftrace:
172 s390_kernel_write(p->addr, &new_insn, len);
173 return 0;
174}
175NOKPROBE_SYMBOL(swap_instruction);
176
177void arch_arm_kprobe(struct kprobe *p)
178{
179 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
180
181 stop_machine_cpuslocked(swap_instruction, &args, NULL);
182}
183NOKPROBE_SYMBOL(arch_arm_kprobe);
184
185void arch_disarm_kprobe(struct kprobe *p)
186{
187 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
188
189 stop_machine_cpuslocked(swap_instruction, &args, NULL);
190}
191NOKPROBE_SYMBOL(arch_disarm_kprobe);
192
193void arch_remove_kprobe(struct kprobe *p)
194{
195 s390_free_insn_slot(p);
196}
197NOKPROBE_SYMBOL(arch_remove_kprobe);
198
199static void enable_singlestep(struct kprobe_ctlblk *kcb,
200 struct pt_regs *regs,
201 unsigned long ip)
202{
203 struct per_regs per_kprobe;
204
205 /* Set up the PER control registers %cr9-%cr11 */
206 per_kprobe.control = PER_EVENT_IFETCH;
207 per_kprobe.start = ip;
208 per_kprobe.end = ip;
209
210 /* Save control regs and psw mask */
211 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
212 kcb->kprobe_saved_imask = regs->psw.mask &
213 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
214
215 /* Set PER control regs, turns on single step for the given address */
216 __ctl_load(per_kprobe, 9, 11);
217 regs->psw.mask |= PSW_MASK_PER;
218 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
219 regs->psw.addr = ip;
220}
221NOKPROBE_SYMBOL(enable_singlestep);
222
223static void disable_singlestep(struct kprobe_ctlblk *kcb,
224 struct pt_regs *regs,
225 unsigned long ip)
226{
227 /* Restore control regs and psw mask, set new psw address */
228 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
229 regs->psw.mask &= ~PSW_MASK_PER;
230 regs->psw.mask |= kcb->kprobe_saved_imask;
231 regs->psw.addr = ip;
232}
233NOKPROBE_SYMBOL(disable_singlestep);
234
235/*
236 * Activate a kprobe by storing its pointer to current_kprobe. The
237 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
238 * two kprobes can be active, see KPROBE_REENTER.
239 */
240static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
241{
242 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
243 kcb->prev_kprobe.status = kcb->kprobe_status;
244 __this_cpu_write(current_kprobe, p);
245}
246NOKPROBE_SYMBOL(push_kprobe);
247
248/*
249 * Deactivate a kprobe by backing up to the previous state. If the
250 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
251 * for any other state prev_kprobe.kp will be NULL.
252 */
253static void pop_kprobe(struct kprobe_ctlblk *kcb)
254{
255 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
256 kcb->kprobe_status = kcb->prev_kprobe.status;
257}
258NOKPROBE_SYMBOL(pop_kprobe);
259
260void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
261{
262 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
263
264 /* Replace the return addr with trampoline addr */
265 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
266}
267NOKPROBE_SYMBOL(arch_prepare_kretprobe);
268
269static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
270{
271 switch (kcb->kprobe_status) {
272 case KPROBE_HIT_SSDONE:
273 case KPROBE_HIT_ACTIVE:
274 kprobes_inc_nmissed_count(p);
275 break;
276 case KPROBE_HIT_SS:
277 case KPROBE_REENTER:
278 default:
279 /*
280 * A kprobe on the code path to single step an instruction
281 * is a BUG. The code path resides in the .kprobes.text
282 * section and is executed with interrupts disabled.
283 */
284 pr_err("Invalid kprobe detected.\n");
285 dump_kprobe(p);
286 BUG();
287 }
288}
289NOKPROBE_SYMBOL(kprobe_reenter_check);
290
291static int kprobe_handler(struct pt_regs *regs)
292{
293 struct kprobe_ctlblk *kcb;
294 struct kprobe *p;
295
296 /*
297 * We want to disable preemption for the entire duration of kprobe
298 * processing. That includes the calls to the pre/post handlers
299 * and single stepping the kprobe instruction.
300 */
301 preempt_disable();
302 kcb = get_kprobe_ctlblk();
303 p = get_kprobe((void *)(regs->psw.addr - 2));
304
305 if (p) {
306 if (kprobe_running()) {
307 /*
308 * We have hit a kprobe while another is still
309 * active. This can happen in the pre and post
310 * handler. Single step the instruction of the
311 * new probe but do not call any handler function
312 * of this secondary kprobe.
313 * push_kprobe and pop_kprobe saves and restores
314 * the currently active kprobe.
315 */
316 kprobe_reenter_check(kcb, p);
317 push_kprobe(kcb, p);
318 kcb->kprobe_status = KPROBE_REENTER;
319 } else {
320 /*
321 * If we have no pre-handler or it returned 0, we
322 * continue with single stepping. If we have a
323 * pre-handler and it returned non-zero, it prepped
324 * for calling the break_handler below on re-entry
325 * for jprobe processing, so get out doing nothing
326 * more here.
327 */
328 push_kprobe(kcb, p);
329 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
330 if (p->pre_handler && p->pre_handler(p, regs))
331 return 1;
332 kcb->kprobe_status = KPROBE_HIT_SS;
333 }
334 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
335 return 1;
336 } else if (kprobe_running()) {
337 p = __this_cpu_read(current_kprobe);
338 if (p->break_handler && p->break_handler(p, regs)) {
339 /*
340 * Continuation after the jprobe completed and
341 * caused the jprobe_return trap. The jprobe
342 * break_handler "returns" to the original
343 * function that still has the kprobe breakpoint
344 * installed. We continue with single stepping.
345 */
346 kcb->kprobe_status = KPROBE_HIT_SS;
347 enable_singlestep(kcb, regs,
348 (unsigned long) p->ainsn.insn);
349 return 1;
350 } /* else:
351 * No kprobe at this address and the current kprobe
352 * has no break handler (no jprobe!). The kernel just
353 * exploded, let the standard trap handler pick up the
354 * pieces.
355 */
356 } /* else:
357 * No kprobe at this address and no active kprobe. The trap has
358 * not been caused by a kprobe breakpoint. The race of breakpoint
359 * vs. kprobe remove does not exist because on s390 as we use
360 * stop_machine to arm/disarm the breakpoints.
361 */
362 preempt_enable_no_resched();
363 return 0;
364}
365NOKPROBE_SYMBOL(kprobe_handler);
366
367/*
368 * Function return probe trampoline:
369 * - init_kprobes() establishes a probepoint here
370 * - When the probed function returns, this probe
371 * causes the handlers to fire
372 */
373static void __used kretprobe_trampoline_holder(void)
374{
375 asm volatile(".global kretprobe_trampoline\n"
376 "kretprobe_trampoline: bcr 0,0\n");
377}
378
379/*
380 * Called when the probe at kretprobe trampoline is hit
381 */
382static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
383{
384 struct kretprobe_instance *ri;
385 struct hlist_head *head, empty_rp;
386 struct hlist_node *tmp;
387 unsigned long flags, orig_ret_address;
388 unsigned long trampoline_address;
389 kprobe_opcode_t *correct_ret_addr;
390
391 INIT_HLIST_HEAD(&empty_rp);
392 kretprobe_hash_lock(current, &head, &flags);
393
394 /*
395 * It is possible to have multiple instances associated with a given
396 * task either because an multiple functions in the call path
397 * have a return probe installed on them, and/or more than one return
398 * return probe was registered for a target function.
399 *
400 * We can handle this because:
401 * - instances are always inserted at the head of the list
402 * - when multiple return probes are registered for the same
403 * function, the first instance's ret_addr will point to the
404 * real return address, and all the rest will point to
405 * kretprobe_trampoline
406 */
407 ri = NULL;
408 orig_ret_address = 0;
409 correct_ret_addr = NULL;
410 trampoline_address = (unsigned long) &kretprobe_trampoline;
411 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
412 if (ri->task != current)
413 /* another task is sharing our hash bucket */
414 continue;
415
416 orig_ret_address = (unsigned long) ri->ret_addr;
417
418 if (orig_ret_address != trampoline_address)
419 /*
420 * This is the real return address. Any other
421 * instances associated with this task are for
422 * other calls deeper on the call stack
423 */
424 break;
425 }
426
427 kretprobe_assert(ri, orig_ret_address, trampoline_address);
428
429 correct_ret_addr = ri->ret_addr;
430 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
431 if (ri->task != current)
432 /* another task is sharing our hash bucket */
433 continue;
434
435 orig_ret_address = (unsigned long) ri->ret_addr;
436
437 if (ri->rp && ri->rp->handler) {
438 ri->ret_addr = correct_ret_addr;
439 ri->rp->handler(ri, regs);
440 }
441
442 recycle_rp_inst(ri, &empty_rp);
443
444 if (orig_ret_address != trampoline_address)
445 /*
446 * This is the real return address. Any other
447 * instances associated with this task are for
448 * other calls deeper on the call stack
449 */
450 break;
451 }
452
453 regs->psw.addr = orig_ret_address;
454
455 pop_kprobe(get_kprobe_ctlblk());
456 kretprobe_hash_unlock(current, &flags);
457 preempt_enable_no_resched();
458
459 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
460 hlist_del(&ri->hlist);
461 kfree(ri);
462 }
463 /*
464 * By returning a non-zero value, we are telling
465 * kprobe_handler() that we don't want the post_handler
466 * to run (and have re-enabled preemption)
467 */
468 return 1;
469}
470NOKPROBE_SYMBOL(trampoline_probe_handler);
471
472/*
473 * Called after single-stepping. p->addr is the address of the
474 * instruction whose first byte has been replaced by the "breakpoint"
475 * instruction. To avoid the SMP problems that can occur when we
476 * temporarily put back the original opcode to single-step, we
477 * single-stepped a copy of the instruction. The address of this
478 * copy is p->ainsn.insn.
479 */
480static void resume_execution(struct kprobe *p, struct pt_regs *regs)
481{
482 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
483 unsigned long ip = regs->psw.addr;
484 int fixup = probe_get_fixup_type(p->ainsn.insn);
485
486 /* Check if the kprobes location is an enabled ftrace caller */
487 if (p->ainsn.is_ftrace_insn) {
488 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
489 struct ftrace_insn call_insn;
490
491 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
492 /*
493 * A kprobe on an enabled ftrace call site actually single
494 * stepped an unconditional branch (ftrace nop equivalent).
495 * Now we need to fixup things and pretend that a brasl r0,...
496 * was executed instead.
497 */
498 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
499 ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
500 regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
501 }
502 }
503
504 if (fixup & FIXUP_PSW_NORMAL)
505 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
506
507 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
508 int ilen = insn_length(p->ainsn.insn[0] >> 8);
509 if (ip - (unsigned long) p->ainsn.insn == ilen)
510 ip = (unsigned long) p->addr + ilen;
511 }
512
513 if (fixup & FIXUP_RETURN_REGISTER) {
514 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
515 regs->gprs[reg] += (unsigned long) p->addr -
516 (unsigned long) p->ainsn.insn;
517 }
518
519 disable_singlestep(kcb, regs, ip);
520}
521NOKPROBE_SYMBOL(resume_execution);
522
523static int post_kprobe_handler(struct pt_regs *regs)
524{
525 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
526 struct kprobe *p = kprobe_running();
527
528 if (!p)
529 return 0;
530
531 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
532 kcb->kprobe_status = KPROBE_HIT_SSDONE;
533 p->post_handler(p, regs, 0);
534 }
535
536 resume_execution(p, regs);
537 pop_kprobe(kcb);
538 preempt_enable_no_resched();
539
540 /*
541 * if somebody else is singlestepping across a probe point, psw mask
542 * will have PER set, in which case, continue the remaining processing
543 * of do_single_step, as if this is not a probe hit.
544 */
545 if (regs->psw.mask & PSW_MASK_PER)
546 return 0;
547
548 return 1;
549}
550NOKPROBE_SYMBOL(post_kprobe_handler);
551
552static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
553{
554 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
555 struct kprobe *p = kprobe_running();
556 const struct exception_table_entry *entry;
557
558 switch(kcb->kprobe_status) {
559 case KPROBE_HIT_SS:
560 case KPROBE_REENTER:
561 /*
562 * We are here because the instruction being single
563 * stepped caused a page fault. We reset the current
564 * kprobe and the nip points back to the probe address
565 * and allow the page fault handler to continue as a
566 * normal page fault.
567 */
568 disable_singlestep(kcb, regs, (unsigned long) p->addr);
569 pop_kprobe(kcb);
570 preempt_enable_no_resched();
571 break;
572 case KPROBE_HIT_ACTIVE:
573 case KPROBE_HIT_SSDONE:
574 /*
575 * We increment the nmissed count for accounting,
576 * we can also use npre/npostfault count for accounting
577 * these specific fault cases.
578 */
579 kprobes_inc_nmissed_count(p);
580
581 /*
582 * We come here because instructions in the pre/post
583 * handler caused the page_fault, this could happen
584 * if handler tries to access user space by
585 * copy_from_user(), get_user() etc. Let the
586 * user-specified handler try to fix it first.
587 */
588 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
589 return 1;
590
591 /*
592 * In case the user-specified fault handler returned
593 * zero, try to fix up.
594 */
595 entry = search_exception_tables(regs->psw.addr);
596 if (entry) {
597 regs->psw.addr = extable_fixup(entry);
598 return 1;
599 }
600
601 /*
602 * fixup_exception() could not handle it,
603 * Let do_page_fault() fix it.
604 */
605 break;
606 default:
607 break;
608 }
609 return 0;
610}
611NOKPROBE_SYMBOL(kprobe_trap_handler);
612
613int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
614{
615 int ret;
616
617 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
618 local_irq_disable();
619 ret = kprobe_trap_handler(regs, trapnr);
620 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
621 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
622 return ret;
623}
624NOKPROBE_SYMBOL(kprobe_fault_handler);
625
626/*
627 * Wrapper routine to for handling exceptions.
628 */
629int kprobe_exceptions_notify(struct notifier_block *self,
630 unsigned long val, void *data)
631{
632 struct die_args *args = (struct die_args *) data;
633 struct pt_regs *regs = args->regs;
634 int ret = NOTIFY_DONE;
635
636 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
637 local_irq_disable();
638
639 switch (val) {
640 case DIE_BPT:
641 if (kprobe_handler(regs))
642 ret = NOTIFY_STOP;
643 break;
644 case DIE_SSTEP:
645 if (post_kprobe_handler(regs))
646 ret = NOTIFY_STOP;
647 break;
648 case DIE_TRAP:
649 if (!preemptible() && kprobe_running() &&
650 kprobe_trap_handler(regs, args->trapnr))
651 ret = NOTIFY_STOP;
652 break;
653 default:
654 break;
655 }
656
657 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
658 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
659
660 return ret;
661}
662NOKPROBE_SYMBOL(kprobe_exceptions_notify);
663
664int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
665{
666 struct jprobe *jp = container_of(p, struct jprobe, kp);
667 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
668 unsigned long stack;
669
670 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
671
672 /* setup return addr to the jprobe handler routine */
673 regs->psw.addr = (unsigned long) jp->entry;
674 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
675
676 /* r15 is the stack pointer */
677 stack = (unsigned long) regs->gprs[15];
678
679 memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
680
681 /*
682 * jprobes use jprobe_return() which skips the normal return
683 * path of the function, and this messes up the accounting of the
684 * function graph tracer to get messed up.
685 *
686 * Pause function graph tracing while performing the jprobe function.
687 */
688 pause_graph_tracing();
689 return 1;
690}
691NOKPROBE_SYMBOL(setjmp_pre_handler);
692
693void jprobe_return(void)
694{
695 asm volatile(".word 0x0002");
696}
697NOKPROBE_SYMBOL(jprobe_return);
698
699int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
700{
701 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
702 unsigned long stack;
703
704 /* It's OK to start function graph tracing again */
705 unpause_graph_tracing();
706
707 stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
708
709 /* Put the regs back */
710 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
711 /* put the stack back */
712 memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
713 preempt_enable_no_resched();
714 return 1;
715}
716NOKPROBE_SYMBOL(longjmp_break_handler);
717
718static struct kprobe trampoline = {
719 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
720 .pre_handler = trampoline_probe_handler
721};
722
723int __init arch_init_kprobes(void)
724{
725 return register_kprobe(&trampoline);
726}
727
728int arch_trampoline_kprobe(struct kprobe *p)
729{
730 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
731}
732NOKPROBE_SYMBOL(arch_trampoline_kprobe);
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright IBM Corp. 2002, 2006
6 *
7 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
8 */
9
10#define pr_fmt(fmt) "kprobes: " fmt
11
12#include <linux/moduleloader.h>
13#include <linux/kprobes.h>
14#include <linux/ptrace.h>
15#include <linux/preempt.h>
16#include <linux/stop_machine.h>
17#include <linux/kdebug.h>
18#include <linux/uaccess.h>
19#include <linux/extable.h>
20#include <linux/module.h>
21#include <linux/slab.h>
22#include <linux/hardirq.h>
23#include <linux/ftrace.h>
24#include <asm/set_memory.h>
25#include <asm/sections.h>
26#include <asm/dis.h>
27#include "kprobes.h"
28#include "entry.h"
29
30DEFINE_PER_CPU(struct kprobe *, current_kprobe);
31DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
32
33struct kretprobe_blackpoint kretprobe_blacklist[] = { };
34
35static int insn_page_in_use;
36
37void *alloc_insn_page(void)
38{
39 void *page;
40
41 page = module_alloc(PAGE_SIZE);
42 if (!page)
43 return NULL;
44 set_memory_rox((unsigned long)page, 1);
45 return page;
46}
47
48static void *alloc_s390_insn_page(void)
49{
50 if (xchg(&insn_page_in_use, 1) == 1)
51 return NULL;
52 return &kprobes_insn_page;
53}
54
55static void free_s390_insn_page(void *page)
56{
57 xchg(&insn_page_in_use, 0);
58}
59
60struct kprobe_insn_cache kprobe_s390_insn_slots = {
61 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
62 .alloc = alloc_s390_insn_page,
63 .free = free_s390_insn_page,
64 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
65 .insn_size = MAX_INSN_SIZE,
66};
67
68static void copy_instruction(struct kprobe *p)
69{
70 kprobe_opcode_t insn[MAX_INSN_SIZE];
71 s64 disp, new_disp;
72 u64 addr, new_addr;
73 unsigned int len;
74
75 len = insn_length(*p->addr >> 8);
76 memcpy(&insn, p->addr, len);
77 p->opcode = insn[0];
78 if (probe_is_insn_relative_long(&insn[0])) {
79 /*
80 * For pc-relative instructions in RIL-b or RIL-c format patch
81 * the RI2 displacement field. We have already made sure that
82 * the insn slot for the patched instruction is within the same
83 * 2GB area as the original instruction (either kernel image or
84 * module area). Therefore the new displacement will always fit.
85 */
86 disp = *(s32 *)&insn[1];
87 addr = (u64)(unsigned long)p->addr;
88 new_addr = (u64)(unsigned long)p->ainsn.insn;
89 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
90 *(s32 *)&insn[1] = new_disp;
91 }
92 s390_kernel_write(p->ainsn.insn, &insn, len);
93}
94NOKPROBE_SYMBOL(copy_instruction);
95
96static int s390_get_insn_slot(struct kprobe *p)
97{
98 /*
99 * Get an insn slot that is within the same 2GB area like the original
100 * instruction. That way instructions with a 32bit signed displacement
101 * field can be patched and executed within the insn slot.
102 */
103 p->ainsn.insn = NULL;
104 if (is_kernel((unsigned long)p->addr))
105 p->ainsn.insn = get_s390_insn_slot();
106 else if (is_module_addr(p->addr))
107 p->ainsn.insn = get_insn_slot();
108 return p->ainsn.insn ? 0 : -ENOMEM;
109}
110NOKPROBE_SYMBOL(s390_get_insn_slot);
111
112static void s390_free_insn_slot(struct kprobe *p)
113{
114 if (!p->ainsn.insn)
115 return;
116 if (is_kernel((unsigned long)p->addr))
117 free_s390_insn_slot(p->ainsn.insn, 0);
118 else
119 free_insn_slot(p->ainsn.insn, 0);
120 p->ainsn.insn = NULL;
121}
122NOKPROBE_SYMBOL(s390_free_insn_slot);
123
124/* Check if paddr is at an instruction boundary */
125static bool can_probe(unsigned long paddr)
126{
127 unsigned long addr, offset = 0;
128 kprobe_opcode_t insn;
129 struct kprobe *kp;
130
131 if (paddr & 0x01)
132 return false;
133
134 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
135 return false;
136
137 /* Decode instructions */
138 addr = paddr - offset;
139 while (addr < paddr) {
140 if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
141 return false;
142
143 if (insn >> 8 == 0) {
144 if (insn != BREAKPOINT_INSTRUCTION) {
145 /*
146 * Note that QEMU inserts opcode 0x0000 to implement
147 * software breakpoints for guests. Since the size of
148 * the original instruction is unknown, stop following
149 * instructions and prevent setting a kprobe.
150 */
151 return false;
152 }
153 /*
154 * Check if the instruction has been modified by another
155 * kprobe, in which case the original instruction is
156 * decoded.
157 */
158 kp = get_kprobe((void *)addr);
159 if (!kp) {
160 /* not a kprobe */
161 return false;
162 }
163 insn = kp->opcode;
164 }
165 addr += insn_length(insn >> 8);
166 }
167 return addr == paddr;
168}
169
170int arch_prepare_kprobe(struct kprobe *p)
171{
172 if (!can_probe((unsigned long)p->addr))
173 return -EINVAL;
174 /* Make sure the probe isn't going on a difficult instruction */
175 if (probe_is_prohibited_opcode(p->addr))
176 return -EINVAL;
177 if (s390_get_insn_slot(p))
178 return -ENOMEM;
179 copy_instruction(p);
180 return 0;
181}
182NOKPROBE_SYMBOL(arch_prepare_kprobe);
183
184struct swap_insn_args {
185 struct kprobe *p;
186 unsigned int arm_kprobe : 1;
187};
188
189static int swap_instruction(void *data)
190{
191 struct swap_insn_args *args = data;
192 struct kprobe *p = args->p;
193 u16 opc;
194
195 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
196 s390_kernel_write(p->addr, &opc, sizeof(opc));
197 return 0;
198}
199NOKPROBE_SYMBOL(swap_instruction);
200
201void arch_arm_kprobe(struct kprobe *p)
202{
203 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
204
205 stop_machine_cpuslocked(swap_instruction, &args, NULL);
206}
207NOKPROBE_SYMBOL(arch_arm_kprobe);
208
209void arch_disarm_kprobe(struct kprobe *p)
210{
211 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
212
213 stop_machine_cpuslocked(swap_instruction, &args, NULL);
214}
215NOKPROBE_SYMBOL(arch_disarm_kprobe);
216
217void arch_remove_kprobe(struct kprobe *p)
218{
219 s390_free_insn_slot(p);
220}
221NOKPROBE_SYMBOL(arch_remove_kprobe);
222
223static void enable_singlestep(struct kprobe_ctlblk *kcb,
224 struct pt_regs *regs,
225 unsigned long ip)
226{
227 union {
228 struct ctlreg regs[3];
229 struct {
230 struct ctlreg control;
231 struct ctlreg start;
232 struct ctlreg end;
233 };
234 } per_kprobe;
235
236 /* Set up the PER control registers %cr9-%cr11 */
237 per_kprobe.control.val = PER_EVENT_IFETCH;
238 per_kprobe.start.val = ip;
239 per_kprobe.end.val = ip;
240
241 /* Save control regs and psw mask */
242 __local_ctl_store(9, 11, kcb->kprobe_saved_ctl);
243 kcb->kprobe_saved_imask = regs->psw.mask &
244 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
245
246 /* Set PER control regs, turns on single step for the given address */
247 __local_ctl_load(9, 11, per_kprobe.regs);
248 regs->psw.mask |= PSW_MASK_PER;
249 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
250 regs->psw.addr = ip;
251}
252NOKPROBE_SYMBOL(enable_singlestep);
253
254static void disable_singlestep(struct kprobe_ctlblk *kcb,
255 struct pt_regs *regs,
256 unsigned long ip)
257{
258 /* Restore control regs and psw mask, set new psw address */
259 __local_ctl_load(9, 11, kcb->kprobe_saved_ctl);
260 regs->psw.mask &= ~PSW_MASK_PER;
261 regs->psw.mask |= kcb->kprobe_saved_imask;
262 regs->psw.addr = ip;
263}
264NOKPROBE_SYMBOL(disable_singlestep);
265
266/*
267 * Activate a kprobe by storing its pointer to current_kprobe. The
268 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
269 * two kprobes can be active, see KPROBE_REENTER.
270 */
271static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
272{
273 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
274 kcb->prev_kprobe.status = kcb->kprobe_status;
275 __this_cpu_write(current_kprobe, p);
276}
277NOKPROBE_SYMBOL(push_kprobe);
278
279/*
280 * Deactivate a kprobe by backing up to the previous state. If the
281 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
282 * for any other state prev_kprobe.kp will be NULL.
283 */
284static void pop_kprobe(struct kprobe_ctlblk *kcb)
285{
286 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
287 kcb->kprobe_status = kcb->prev_kprobe.status;
288 kcb->prev_kprobe.kp = NULL;
289}
290NOKPROBE_SYMBOL(pop_kprobe);
291
292static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
293{
294 switch (kcb->kprobe_status) {
295 case KPROBE_HIT_SSDONE:
296 case KPROBE_HIT_ACTIVE:
297 kprobes_inc_nmissed_count(p);
298 break;
299 case KPROBE_HIT_SS:
300 case KPROBE_REENTER:
301 default:
302 /*
303 * A kprobe on the code path to single step an instruction
304 * is a BUG. The code path resides in the .kprobes.text
305 * section and is executed with interrupts disabled.
306 */
307 pr_err("Failed to recover from reentered kprobes.\n");
308 dump_kprobe(p);
309 BUG();
310 }
311}
312NOKPROBE_SYMBOL(kprobe_reenter_check);
313
314static int kprobe_handler(struct pt_regs *regs)
315{
316 struct kprobe_ctlblk *kcb;
317 struct kprobe *p;
318
319 /*
320 * We want to disable preemption for the entire duration of kprobe
321 * processing. That includes the calls to the pre/post handlers
322 * and single stepping the kprobe instruction.
323 */
324 preempt_disable();
325 kcb = get_kprobe_ctlblk();
326 p = get_kprobe((void *)(regs->psw.addr - 2));
327
328 if (p) {
329 if (kprobe_running()) {
330 /*
331 * We have hit a kprobe while another is still
332 * active. This can happen in the pre and post
333 * handler. Single step the instruction of the
334 * new probe but do not call any handler function
335 * of this secondary kprobe.
336 * push_kprobe and pop_kprobe saves and restores
337 * the currently active kprobe.
338 */
339 kprobe_reenter_check(kcb, p);
340 push_kprobe(kcb, p);
341 kcb->kprobe_status = KPROBE_REENTER;
342 } else {
343 /*
344 * If we have no pre-handler or it returned 0, we
345 * continue with single stepping. If we have a
346 * pre-handler and it returned non-zero, it prepped
347 * for changing execution path, so get out doing
348 * nothing more here.
349 */
350 push_kprobe(kcb, p);
351 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
352 if (p->pre_handler && p->pre_handler(p, regs)) {
353 pop_kprobe(kcb);
354 preempt_enable_no_resched();
355 return 1;
356 }
357 kcb->kprobe_status = KPROBE_HIT_SS;
358 }
359 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
360 return 1;
361 } /* else:
362 * No kprobe at this address and no active kprobe. The trap has
363 * not been caused by a kprobe breakpoint. The race of breakpoint
364 * vs. kprobe remove does not exist because on s390 as we use
365 * stop_machine to arm/disarm the breakpoints.
366 */
367 preempt_enable_no_resched();
368 return 0;
369}
370NOKPROBE_SYMBOL(kprobe_handler);
371
372/*
373 * Called after single-stepping. p->addr is the address of the
374 * instruction whose first byte has been replaced by the "breakpoint"
375 * instruction. To avoid the SMP problems that can occur when we
376 * temporarily put back the original opcode to single-step, we
377 * single-stepped a copy of the instruction. The address of this
378 * copy is p->ainsn.insn.
379 */
380static void resume_execution(struct kprobe *p, struct pt_regs *regs)
381{
382 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
383 unsigned long ip = regs->psw.addr;
384 int fixup = probe_get_fixup_type(p->ainsn.insn);
385
386 if (fixup & FIXUP_PSW_NORMAL)
387 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
388
389 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
390 int ilen = insn_length(p->ainsn.insn[0] >> 8);
391 if (ip - (unsigned long) p->ainsn.insn == ilen)
392 ip = (unsigned long) p->addr + ilen;
393 }
394
395 if (fixup & FIXUP_RETURN_REGISTER) {
396 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
397 regs->gprs[reg] += (unsigned long) p->addr -
398 (unsigned long) p->ainsn.insn;
399 }
400
401 disable_singlestep(kcb, regs, ip);
402}
403NOKPROBE_SYMBOL(resume_execution);
404
405static int post_kprobe_handler(struct pt_regs *regs)
406{
407 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
408 struct kprobe *p = kprobe_running();
409
410 if (!p)
411 return 0;
412
413 resume_execution(p, regs);
414 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
415 kcb->kprobe_status = KPROBE_HIT_SSDONE;
416 p->post_handler(p, regs, 0);
417 }
418 pop_kprobe(kcb);
419 preempt_enable_no_resched();
420
421 /*
422 * if somebody else is singlestepping across a probe point, psw mask
423 * will have PER set, in which case, continue the remaining processing
424 * of do_single_step, as if this is not a probe hit.
425 */
426 if (regs->psw.mask & PSW_MASK_PER)
427 return 0;
428
429 return 1;
430}
431NOKPROBE_SYMBOL(post_kprobe_handler);
432
433static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
434{
435 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
436 struct kprobe *p = kprobe_running();
437
438 switch(kcb->kprobe_status) {
439 case KPROBE_HIT_SS:
440 case KPROBE_REENTER:
441 /*
442 * We are here because the instruction being single
443 * stepped caused a page fault. We reset the current
444 * kprobe and the nip points back to the probe address
445 * and allow the page fault handler to continue as a
446 * normal page fault.
447 */
448 disable_singlestep(kcb, regs, (unsigned long) p->addr);
449 pop_kprobe(kcb);
450 preempt_enable_no_resched();
451 break;
452 case KPROBE_HIT_ACTIVE:
453 case KPROBE_HIT_SSDONE:
454 /*
455 * In case the user-specified fault handler returned
456 * zero, try to fix up.
457 */
458 if (fixup_exception(regs))
459 return 1;
460 /*
461 * fixup_exception() could not handle it,
462 * Let do_page_fault() fix it.
463 */
464 break;
465 default:
466 break;
467 }
468 return 0;
469}
470NOKPROBE_SYMBOL(kprobe_trap_handler);
471
472int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
473{
474 int ret;
475
476 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
477 local_irq_disable();
478 ret = kprobe_trap_handler(regs, trapnr);
479 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
480 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
481 return ret;
482}
483NOKPROBE_SYMBOL(kprobe_fault_handler);
484
485/*
486 * Wrapper routine to for handling exceptions.
487 */
488int kprobe_exceptions_notify(struct notifier_block *self,
489 unsigned long val, void *data)
490{
491 struct die_args *args = (struct die_args *) data;
492 struct pt_regs *regs = args->regs;
493 int ret = NOTIFY_DONE;
494
495 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
496 local_irq_disable();
497
498 switch (val) {
499 case DIE_BPT:
500 if (kprobe_handler(regs))
501 ret = NOTIFY_STOP;
502 break;
503 case DIE_SSTEP:
504 if (post_kprobe_handler(regs))
505 ret = NOTIFY_STOP;
506 break;
507 case DIE_TRAP:
508 if (!preemptible() && kprobe_running() &&
509 kprobe_trap_handler(regs, args->trapnr))
510 ret = NOTIFY_STOP;
511 break;
512 default:
513 break;
514 }
515
516 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
517 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
518
519 return ret;
520}
521NOKPROBE_SYMBOL(kprobe_exceptions_notify);
522
523int __init arch_init_kprobes(void)
524{
525 return 0;
526}
527
528int arch_trampoline_kprobe(struct kprobe *p)
529{
530 return 0;
531}
532NOKPROBE_SYMBOL(arch_trampoline_kprobe);