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
);
269 if (!p
->ainsn
.insn_check_cc(regs
->ARM_cpsr
)) {
271 * Probe hit but conditional execution check failed,
272 * so just skip the instruction and continue as if
273 * nothing had happened.
274 * In this case, we can skip recursing check too.
276 singlestep_skip(p
, regs
);
278 /* Kprobe is pending, so we're recursing. */
279 switch (kcb
->kprobe_status
) {
280 case KPROBE_HIT_ACTIVE
:
281 case KPROBE_HIT_SSDONE
:
283 /* A pre- or post-handler probe got us here. */
284 kprobes_inc_nmissed_count(p
);
285 save_previous_kprobe(kcb
);
286 set_current_kprobe(p
);
287 kcb
->kprobe_status
= KPROBE_REENTER
;
288 singlestep(p
, regs
, kcb
);
289 restore_previous_kprobe(kcb
);
292 /* A nested probe was hit in FIQ, it is a BUG */
293 pr_warn("Unrecoverable kprobe detected at %p.\n",
297 /* impossible cases */
301 /* Probe hit and conditional execution check ok. */
302 set_current_kprobe(p
);
303 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
306 * If we have no pre-handler or it returned 0, we
307 * continue with normal processing. If we have a
308 * pre-handler and it returned non-zero, it prepped
309 * for calling the break_handler below on re-entry,
310 * so get out doing nothing more here.
312 if (!p
->pre_handler
|| !p
->pre_handler(p
, regs
)) {
313 kcb
->kprobe_status
= KPROBE_HIT_SS
;
314 singlestep(p
, regs
, kcb
);
315 if (p
->post_handler
) {
316 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
317 p
->post_handler(p
, regs
, 0);
319 reset_current_kprobe();
323 /* We probably hit a jprobe. Call its break handler. */
324 if (cur
->break_handler
&& cur
->break_handler(cur
, regs
)) {
325 kcb
->kprobe_status
= KPROBE_HIT_SS
;
326 singlestep(cur
, regs
, kcb
);
327 if (cur
->post_handler
) {
328 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
329 cur
->post_handler(cur
, regs
, 0);
332 reset_current_kprobe();
335 * The probe was removed and a race is in progress.
336 * There is nothing we can do about it. Let's restart
337 * the instruction. By the time we can restart, the
338 * real instruction will be there.
343 static int __kprobes
kprobe_trap_handler(struct pt_regs
*regs
, unsigned int instr
)
346 local_irq_save(flags
);
347 kprobe_handler(regs
);
348 local_irq_restore(flags
);
352 int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, unsigned int fsr
)
354 struct kprobe
*cur
= kprobe_running();
355 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
357 switch (kcb
->kprobe_status
) {
361 * We are here because the instruction being single
362 * stepped caused a page fault. We reset the current
363 * kprobe and the PC to point back to the probe address
364 * and allow the page fault handler to continue as a
367 regs
->ARM_pc
= (long)cur
->addr
;
368 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
369 restore_previous_kprobe(kcb
);
371 reset_current_kprobe();
375 case KPROBE_HIT_ACTIVE
:
376 case KPROBE_HIT_SSDONE
:
378 * We increment the nmissed count for accounting,
379 * we can also use npre/npostfault count for accounting
380 * these specific fault cases.
382 kprobes_inc_nmissed_count(cur
);
385 * We come here because instructions in the pre/post
386 * handler caused the page_fault, this could happen
387 * if handler tries to access user space by
388 * copy_from_user(), get_user() etc. Let the
389 * user-specified handler try to fix it.
391 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, fsr
))
402 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
403 unsigned long val
, void *data
)
406 * notify_die() is currently never called on ARM,
407 * so this callback is currently empty.
413 * When a retprobed function returns, trampoline_handler() is called,
414 * calling the kretprobe's handler. We construct a struct pt_regs to
415 * give a view of registers r0-r11 to the user return-handler. This is
416 * not a complete pt_regs structure, but that should be plenty sufficient
417 * for kretprobe handlers which should normally be interested in r0 only
420 void __naked __kprobes
kretprobe_trampoline(void)
422 __asm__
__volatile__ (
423 "stmdb sp!, {r0 - r11} \n\t"
425 "bl trampoline_handler \n\t"
427 "ldmia sp!, {r0 - r11} \n\t"
428 #ifdef CONFIG_THUMB2_KERNEL
436 /* Called from kretprobe_trampoline */
437 static __used __kprobes
void *trampoline_handler(struct pt_regs
*regs
)
439 struct kretprobe_instance
*ri
= NULL
;
440 struct hlist_head
*head
, empty_rp
;
441 struct hlist_node
*tmp
;
442 unsigned long flags
, orig_ret_address
= 0;
443 unsigned long trampoline_address
= (unsigned long)&kretprobe_trampoline
;
444 kprobe_opcode_t
*correct_ret_addr
= NULL
;
446 INIT_HLIST_HEAD(&empty_rp
);
447 kretprobe_hash_lock(current
, &head
, &flags
);
450 * It is possible to have multiple instances associated with a given
451 * task either because multiple functions in the call path have
452 * a return probe installed on them, and/or more than one return
453 * probe was registered for a target function.
455 * We can handle this because:
456 * - instances are always inserted at the head of the list
457 * - when multiple return probes are registered for the same
458 * function, the first instance's ret_addr will point to the
459 * real return address, and all the rest will point to
460 * kretprobe_trampoline
462 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
463 if (ri
->task
!= current
)
464 /* another task is sharing our hash bucket */
467 orig_ret_address
= (unsigned long)ri
->ret_addr
;
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
);
480 correct_ret_addr
= ri
->ret_addr
;
481 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
482 if (ri
->task
!= current
)
483 /* another task is sharing our hash bucket */
486 orig_ret_address
= (unsigned long)ri
->ret_addr
;
487 if (ri
->rp
&& ri
->rp
->handler
) {
488 __this_cpu_write(current_kprobe
, &ri
->rp
->kp
);
489 get_kprobe_ctlblk()->kprobe_status
= KPROBE_HIT_ACTIVE
;
490 ri
->ret_addr
= correct_ret_addr
;
491 ri
->rp
->handler(ri
, regs
);
492 __this_cpu_write(current_kprobe
, NULL
);
495 recycle_rp_inst(ri
, &empty_rp
);
497 if (orig_ret_address
!= trampoline_address
)
499 * This is the real return address. Any other
500 * instances associated with this task are for
501 * other calls deeper on the call stack
506 kretprobe_hash_unlock(current
, &flags
);
508 hlist_for_each_entry_safe(ri
, tmp
, &empty_rp
, hlist
) {
509 hlist_del(&ri
->hlist
);
513 return (void *)orig_ret_address
;
516 void __kprobes
arch_prepare_kretprobe(struct kretprobe_instance
*ri
,
517 struct pt_regs
*regs
)
519 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->ARM_lr
;
521 /* Replace the return addr with trampoline addr. */
522 regs
->ARM_lr
= (unsigned long)&kretprobe_trampoline
;
525 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
527 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
528 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
529 long sp_addr
= regs
->ARM_sp
;
532 kcb
->jprobe_saved_regs
= *regs
;
533 memcpy(kcb
->jprobes_stack
, (void *)sp_addr
, MIN_STACK_SIZE(sp_addr
));
534 regs
->ARM_pc
= (long)jp
->entry
;
536 cpsr
= regs
->ARM_cpsr
| PSR_I_BIT
;
537 #ifdef CONFIG_THUMB2_KERNEL
538 /* Set correct Thumb state in cpsr */
539 if (regs
->ARM_pc
& 1)
544 regs
->ARM_cpsr
= cpsr
;
550 void __kprobes
jprobe_return(void)
552 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
554 __asm__
__volatile__ (
556 * Setup an empty pt_regs. Fill SP and PC fields as
557 * they're needed by longjmp_break_handler.
559 * We allocate some slack between the original SP and start of
560 * our fabricated regs. To be precise we want to have worst case
561 * covered which is STMFD with all 16 regs so we allocate 2 *
562 * sizeof(struct_pt_regs)).
564 * This is to prevent any simulated instruction from writing
565 * over the regs when they are accessing the stack.
567 #ifdef CONFIG_THUMB2_KERNEL
568 "sub r0, %0, %1 \n\t"
571 "sub sp, %0, %1 \n\t"
573 "ldr r0, ="__stringify(JPROBE_MAGIC_ADDR
)"\n\t"
574 "str %0, [sp, %2] \n\t"
575 "str r0, [sp, %3] \n\t"
577 "bl kprobe_handler \n\t"
580 * Return to the context saved by setjmp_pre_handler
581 * and restored by longjmp_break_handler.
583 #ifdef CONFIG_THUMB2_KERNEL
584 "ldr lr, [sp, %2] \n\t" /* lr = saved sp */
585 "ldrd r0, r1, [sp, %5] \n\t" /* r0,r1 = saved lr,pc */
586 "ldr r2, [sp, %4] \n\t" /* r2 = saved psr */
587 "stmdb lr!, {r0, r1, r2} \n\t" /* push saved lr and */
589 "ldmia sp, {r0 - r12} \n\t"
591 "ldr lr, [sp], #4 \n\t"
594 "ldr r0, [sp, %4] \n\t"
595 "msr cpsr_cxsf, r0 \n\t"
596 "ldmia sp, {r0 - pc} \n\t"
599 : "r" (kcb
->jprobe_saved_regs
.ARM_sp
),
600 "I" (sizeof(struct pt_regs
) * 2),
601 "J" (offsetof(struct pt_regs
, ARM_sp
)),
602 "J" (offsetof(struct pt_regs
, ARM_pc
)),
603 "J" (offsetof(struct pt_regs
, ARM_cpsr
)),
604 "J" (offsetof(struct pt_regs
, ARM_lr
))
608 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
610 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
611 long stack_addr
= kcb
->jprobe_saved_regs
.ARM_sp
;
612 long orig_sp
= regs
->ARM_sp
;
613 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
615 if (regs
->ARM_pc
== JPROBE_MAGIC_ADDR
) {
616 if (orig_sp
!= stack_addr
) {
617 struct pt_regs
*saved_regs
=
618 (struct pt_regs
*)kcb
->jprobe_saved_regs
.ARM_sp
;
619 printk("current sp %lx does not match saved sp %lx\n",
620 orig_sp
, stack_addr
);
621 printk("Saved registers for jprobe %p\n", jp
);
622 show_regs(saved_regs
);
623 printk("Current registers\n");
627 *regs
= kcb
->jprobe_saved_regs
;
628 memcpy((void *)stack_addr
, kcb
->jprobes_stack
,
629 MIN_STACK_SIZE(stack_addr
));
630 preempt_enable_no_resched();
636 int __kprobes
arch_trampoline_kprobe(struct kprobe
*p
)
641 #ifdef CONFIG_THUMB2_KERNEL
643 static struct undef_hook kprobes_thumb16_break_hook
= {
644 .instr_mask
= 0xffff,
645 .instr_val
= KPROBE_THUMB16_BREAKPOINT_INSTRUCTION
,
646 .cpsr_mask
= MODE_MASK
,
647 .cpsr_val
= SVC_MODE
,
648 .fn
= kprobe_trap_handler
,
651 static struct undef_hook kprobes_thumb32_break_hook
= {
652 .instr_mask
= 0xffffffff,
653 .instr_val
= KPROBE_THUMB32_BREAKPOINT_INSTRUCTION
,
654 .cpsr_mask
= MODE_MASK
,
655 .cpsr_val
= SVC_MODE
,
656 .fn
= kprobe_trap_handler
,
659 #else /* !CONFIG_THUMB2_KERNEL */
661 static struct undef_hook kprobes_arm_break_hook
= {
662 .instr_mask
= 0x0fffffff,
663 .instr_val
= KPROBE_ARM_BREAKPOINT_INSTRUCTION
,
664 .cpsr_mask
= MODE_MASK
,
665 .cpsr_val
= SVC_MODE
,
666 .fn
= kprobe_trap_handler
,
669 #endif /* !CONFIG_THUMB2_KERNEL */
671 int __init
arch_init_kprobes()
673 arm_probes_decode_init();
674 #ifdef CONFIG_THUMB2_KERNEL
675 register_undef_hook(&kprobes_thumb16_break_hook
);
676 register_undef_hook(&kprobes_thumb32_break_hook
);
678 register_undef_hook(&kprobes_arm_break_hook
);