2 * arch/arm/kernel/kprobes.c
6 * Abhishek Sagar <sagar.abhishek@gmail.com>
7 * Copyright (C) 2006, 2007 Motorola Inc.
9 * Nicolas Pitre <nico@marvell.com>
10 * Copyright (C) 2007 Marvell Ltd.
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License version 2 as
14 * published by the Free Software Foundation.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 * General Public License for more details.
22 #include <linux/kernel.h>
23 #include <linux/kprobes.h>
24 #include <linux/module.h>
25 #include <linux/slab.h>
26 #include <linux/stop_machine.h>
27 #include <linux/sched/debug.h>
28 #include <linux/stringify.h>
29 #include <asm/traps.h>
30 #include <asm/opcodes.h>
31 #include <asm/cacheflush.h>
32 #include <linux/percpu.h>
33 #include <linux/bug.h>
34 #include <asm/patch.h>
36 #include "../decode-arm.h"
37 #include "../decode-thumb.h"
40 #define MIN_STACK_SIZE(addr) \
41 min((unsigned long)MAX_STACK_SIZE, \
42 (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
44 #define flush_insns(addr, size) \
45 flush_icache_range((unsigned long)(addr), \
46 (unsigned long)(addr) + \
49 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
50 #define JPROBE_MAGIC_ADDR 0xffffffff
52 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
53 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
56 int __kprobes arch_prepare_kprobe(struct kprobe *p)
59 kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
60 unsigned long addr = (unsigned long)p->addr;
62 kprobe_decode_insn_t *decode_insn;
63 const union decode_action *actions;
65 const struct decode_checker **checkers;
67 if (in_exception_text(addr))
70 #ifdef CONFIG_THUMB2_KERNEL
72 addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
73 insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
74 if (is_wide_instruction(insn)) {
75 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
76 insn = __opcode_thumb32_compose(insn, inst2);
77 decode_insn = thumb32_probes_decode_insn;
78 actions = kprobes_t32_actions;
79 checkers = kprobes_t32_checkers;
81 decode_insn = thumb16_probes_decode_insn;
82 actions = kprobes_t16_actions;
83 checkers = kprobes_t16_checkers;
85 #else /* !CONFIG_THUMB2_KERNEL */
89 insn = __mem_to_opcode_arm(*p->addr);
90 decode_insn = arm_probes_decode_insn;
91 actions = kprobes_arm_actions;
92 checkers = kprobes_arm_checkers;
96 p->ainsn.insn = tmp_insn;
98 switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
99 case INSN_REJECTED: /* not supported */
102 case INSN_GOOD: /* instruction uses slot */
103 p->ainsn.insn = get_insn_slot();
106 for (is = 0; is < MAX_INSN_SIZE; ++is)
107 p->ainsn.insn[is] = tmp_insn[is];
108 flush_insns(p->ainsn.insn,
109 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
110 p->ainsn.insn_fn = (probes_insn_fn_t *)
111 ((uintptr_t)p->ainsn.insn | thumb);
114 case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
115 p->ainsn.insn = NULL;
120 * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
121 * 'str r0, [sp, #-68]' should also be prohibited.
124 if ((p->ainsn.stack_space < 0) ||
125 (p->ainsn.stack_space > MAX_STACK_SIZE))
131 void __kprobes arch_arm_kprobe(struct kprobe *p)
136 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
137 /* Remove any Thumb flag */
138 addr = (void *)((uintptr_t)p->addr & ~1);
140 if (is_wide_instruction(p->opcode))
141 brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
143 brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
145 kprobe_opcode_t insn = p->opcode;
148 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
150 if (insn >= 0xe0000000)
151 brkp |= 0xe0000000; /* Unconditional instruction */
153 brkp |= insn & 0xf0000000; /* Copy condition from insn */
156 patch_text(addr, brkp);
160 * The actual disarming is done here on each CPU and synchronized using
161 * stop_machine. This synchronization is necessary on SMP to avoid removing
162 * a probe between the moment the 'Undefined Instruction' exception is raised
163 * and the moment the exception handler reads the faulting instruction from
164 * memory. It is also needed to atomically set the two half-words of a 32-bit
172 static int __kprobes_remove_breakpoint(void *data)
174 struct patch *p = data;
175 __patch_text(p->addr, p->insn);
179 void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
185 stop_machine(__kprobes_remove_breakpoint, &p, cpu_online_mask);
188 void __kprobes arch_disarm_kprobe(struct kprobe *p)
190 kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
194 void __kprobes arch_remove_kprobe(struct kprobe *p)
197 free_insn_slot(p->ainsn.insn, 0);
198 p->ainsn.insn = NULL;
202 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
204 kcb->prev_kprobe.kp = kprobe_running();
205 kcb->prev_kprobe.status = kcb->kprobe_status;
208 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
210 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
211 kcb->kprobe_status = kcb->prev_kprobe.status;
214 static void __kprobes set_current_kprobe(struct kprobe *p)
216 __this_cpu_write(current_kprobe, p);
219 static void __kprobes
220 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
222 #ifdef CONFIG_THUMB2_KERNEL
223 regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
224 if (is_wide_instruction(p->opcode))
233 static inline void __kprobes
234 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
236 p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
240 * Called with IRQs disabled. IRQs must remain disabled from that point
241 * all the way until processing this kprobe is complete. The current
242 * kprobes implementation cannot process more than one nested level of
243 * kprobe, and that level is reserved for user kprobe handlers, so we can't
244 * risk encountering a new kprobe in an interrupt handler.
246 void __kprobes kprobe_handler(struct pt_regs *regs)
248 struct kprobe *p, *cur;
249 struct kprobe_ctlblk *kcb;
251 kcb = get_kprobe_ctlblk();
252 cur = kprobe_running();
254 #ifdef CONFIG_THUMB2_KERNEL
256 * First look for a probe which was registered using an address with
257 * bit 0 set, this is the usual situation for pointers to Thumb code.
258 * If not found, fallback to looking for one with bit 0 clear.
260 p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
262 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
264 #else /* ! CONFIG_THUMB2_KERNEL */
265 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
270 /* Kprobe is pending, so we're recursing. */
271 switch (kcb->kprobe_status) {
272 case KPROBE_HIT_ACTIVE:
273 case KPROBE_HIT_SSDONE:
274 /* A pre- or post-handler probe got us here. */
275 kprobes_inc_nmissed_count(p);
276 save_previous_kprobe(kcb);
277 set_current_kprobe(p);
278 kcb->kprobe_status = KPROBE_REENTER;
279 singlestep(p, regs, kcb);
280 restore_previous_kprobe(kcb);
283 /* impossible cases */
286 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
287 /* Probe hit and conditional execution check ok. */
288 set_current_kprobe(p);
289 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
292 * If we have no pre-handler or it returned 0, we
293 * continue with normal processing. If we have a
294 * pre-handler and it returned non-zero, it prepped
295 * for calling the break_handler below on re-entry,
296 * so get out doing nothing more here.
298 if (!p->pre_handler || !p->pre_handler(p, regs)) {
299 kcb->kprobe_status = KPROBE_HIT_SS;
300 singlestep(p, regs, kcb);
301 if (p->post_handler) {
302 kcb->kprobe_status = KPROBE_HIT_SSDONE;
303 p->post_handler(p, regs, 0);
305 reset_current_kprobe();
309 * Probe hit but conditional execution check failed,
310 * so just skip the instruction and continue as if
311 * nothing had happened.
313 singlestep_skip(p, regs);
316 /* We probably hit a jprobe. Call its break handler. */
317 if (cur->break_handler && cur->break_handler(cur, regs)) {
318 kcb->kprobe_status = KPROBE_HIT_SS;
319 singlestep(cur, regs, kcb);
320 if (cur->post_handler) {
321 kcb->kprobe_status = KPROBE_HIT_SSDONE;
322 cur->post_handler(cur, regs, 0);
325 reset_current_kprobe();
328 * The probe was removed and a race is in progress.
329 * There is nothing we can do about it. Let's restart
330 * the instruction. By the time we can restart, the
331 * real instruction will be there.
336 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
339 local_irq_save(flags);
340 kprobe_handler(regs);
341 local_irq_restore(flags);
345 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
347 struct kprobe *cur = kprobe_running();
348 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
350 switch (kcb->kprobe_status) {
354 * We are here because the instruction being single
355 * stepped caused a page fault. We reset the current
356 * kprobe and the PC to point back to the probe address
357 * and allow the page fault handler to continue as a
360 regs->ARM_pc = (long)cur->addr;
361 if (kcb->kprobe_status == KPROBE_REENTER) {
362 restore_previous_kprobe(kcb);
364 reset_current_kprobe();
368 case KPROBE_HIT_ACTIVE:
369 case KPROBE_HIT_SSDONE:
371 * We increment the nmissed count for accounting,
372 * we can also use npre/npostfault count for accounting
373 * these specific fault cases.
375 kprobes_inc_nmissed_count(cur);
378 * We come here because instructions in the pre/post
379 * handler caused the page_fault, this could happen
380 * if handler tries to access user space by
381 * copy_from_user(), get_user() etc. Let the
382 * user-specified handler try to fix it.
384 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
395 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
396 unsigned long val, void *data)
399 * notify_die() is currently never called on ARM,
400 * so this callback is currently empty.
406 * When a retprobed function returns, trampoline_handler() is called,
407 * calling the kretprobe's handler. We construct a struct pt_regs to
408 * give a view of registers r0-r11 to the user return-handler. This is
409 * not a complete pt_regs structure, but that should be plenty sufficient
410 * for kretprobe handlers which should normally be interested in r0 only
413 void __naked __kprobes kretprobe_trampoline(void)
415 __asm__ __volatile__ (
416 "stmdb sp!, {r0 - r11} \n\t"
418 "bl trampoline_handler \n\t"
420 "ldmia sp!, {r0 - r11} \n\t"
421 #ifdef CONFIG_THUMB2_KERNEL
429 /* Called from kretprobe_trampoline */
430 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
432 struct kretprobe_instance *ri = NULL;
433 struct hlist_head *head, empty_rp;
434 struct hlist_node *tmp;
435 unsigned long flags, orig_ret_address = 0;
436 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
438 INIT_HLIST_HEAD(&empty_rp);
439 kretprobe_hash_lock(current, &head, &flags);
442 * It is possible to have multiple instances associated with a given
443 * task either because multiple functions in the call path have
444 * a return probe installed on them, and/or more than one return
445 * probe was registered for a target function.
447 * We can handle this because:
448 * - instances are always inserted at the head of the list
449 * - when multiple return probes are registered for the same
450 * function, the first instance's ret_addr will point to the
451 * real return address, and all the rest will point to
452 * kretprobe_trampoline
454 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
455 if (ri->task != current)
456 /* another task is sharing our hash bucket */
459 if (ri->rp && ri->rp->handler) {
460 __this_cpu_write(current_kprobe, &ri->rp->kp);
461 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
462 ri->rp->handler(ri, regs);
463 __this_cpu_write(current_kprobe, NULL);
466 orig_ret_address = (unsigned long)ri->ret_addr;
467 recycle_rp_inst(ri, &empty_rp);
469 if (orig_ret_address != trampoline_address)
471 * This is the real return address. Any other
472 * instances associated with this task are for
473 * other calls deeper on the call stack
478 kretprobe_assert(ri, orig_ret_address, trampoline_address);
479 kretprobe_hash_unlock(current, &flags);
481 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
482 hlist_del(&ri->hlist);
486 return (void *)orig_ret_address;
489 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
490 struct pt_regs *regs)
492 ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
494 /* Replace the return addr with trampoline addr. */
495 regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
498 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
500 struct jprobe *jp = container_of(p, struct jprobe, kp);
501 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
502 long sp_addr = regs->ARM_sp;
505 kcb->jprobe_saved_regs = *regs;
506 memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
507 regs->ARM_pc = (long)jp->entry;
509 cpsr = regs->ARM_cpsr | PSR_I_BIT;
510 #ifdef CONFIG_THUMB2_KERNEL
511 /* Set correct Thumb state in cpsr */
512 if (regs->ARM_pc & 1)
517 regs->ARM_cpsr = cpsr;
523 void __kprobes jprobe_return(void)
525 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
527 __asm__ __volatile__ (
529 * Setup an empty pt_regs. Fill SP and PC fields as
530 * they're needed by longjmp_break_handler.
532 * We allocate some slack between the original SP and start of
533 * our fabricated regs. To be precise we want to have worst case
534 * covered which is STMFD with all 16 regs so we allocate 2 *
535 * sizeof(struct_pt_regs)).
537 * This is to prevent any simulated instruction from writing
538 * over the regs when they are accessing the stack.
540 #ifdef CONFIG_THUMB2_KERNEL
541 "sub r0, %0, %1 \n\t"
544 "sub sp, %0, %1 \n\t"
546 "ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
547 "str %0, [sp, %2] \n\t"
548 "str r0, [sp, %3] \n\t"
550 "bl kprobe_handler \n\t"
553 * Return to the context saved by setjmp_pre_handler
554 * and restored by longjmp_break_handler.
556 #ifdef CONFIG_THUMB2_KERNEL
557 "ldr lr, [sp, %2] \n\t" /* lr = saved sp */
558 "ldrd r0, r1, [sp, %5] \n\t" /* r0,r1 = saved lr,pc */
559 "ldr r2, [sp, %4] \n\t" /* r2 = saved psr */
560 "stmdb lr!, {r0, r1, r2} \n\t" /* push saved lr and */
562 "ldmia sp, {r0 - r12} \n\t"
564 "ldr lr, [sp], #4 \n\t"
567 "ldr r0, [sp, %4] \n\t"
568 "msr cpsr_cxsf, r0 \n\t"
569 "ldmia sp, {r0 - pc} \n\t"
572 : "r" (kcb->jprobe_saved_regs.ARM_sp),
573 "I" (sizeof(struct pt_regs) * 2),
574 "J" (offsetof(struct pt_regs, ARM_sp)),
575 "J" (offsetof(struct pt_regs, ARM_pc)),
576 "J" (offsetof(struct pt_regs, ARM_cpsr)),
577 "J" (offsetof(struct pt_regs, ARM_lr))
581 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
583 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
584 long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
585 long orig_sp = regs->ARM_sp;
586 struct jprobe *jp = container_of(p, struct jprobe, kp);
588 if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
589 if (orig_sp != stack_addr) {
590 struct pt_regs *saved_regs =
591 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
592 printk("current sp %lx does not match saved sp %lx\n",
593 orig_sp, stack_addr);
594 printk("Saved registers for jprobe %p\n", jp);
595 show_regs(saved_regs);
596 printk("Current registers\n");
600 *regs = kcb->jprobe_saved_regs;
601 memcpy((void *)stack_addr, kcb->jprobes_stack,
602 MIN_STACK_SIZE(stack_addr));
603 preempt_enable_no_resched();
609 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
614 #ifdef CONFIG_THUMB2_KERNEL
616 static struct undef_hook kprobes_thumb16_break_hook = {
617 .instr_mask = 0xffff,
618 .instr_val = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
619 .cpsr_mask = MODE_MASK,
620 .cpsr_val = SVC_MODE,
621 .fn = kprobe_trap_handler,
624 static struct undef_hook kprobes_thumb32_break_hook = {
625 .instr_mask = 0xffffffff,
626 .instr_val = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
627 .cpsr_mask = MODE_MASK,
628 .cpsr_val = SVC_MODE,
629 .fn = kprobe_trap_handler,
632 #else /* !CONFIG_THUMB2_KERNEL */
634 static struct undef_hook kprobes_arm_break_hook = {
635 .instr_mask = 0x0fffffff,
636 .instr_val = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
637 .cpsr_mask = MODE_MASK,
638 .cpsr_val = SVC_MODE,
639 .fn = kprobe_trap_handler,
642 #endif /* !CONFIG_THUMB2_KERNEL */
644 int __init arch_init_kprobes()
646 arm_probes_decode_init();
647 #ifdef CONFIG_THUMB2_KERNEL
648 register_undef_hook(&kprobes_thumb16_break_hook);
649 register_undef_hook(&kprobes_thumb32_break_hook);
651 register_undef_hook(&kprobes_arm_break_hook);