2 * arch/arm64/kernel/probes/kprobes.c
4 * Kprobes support for ARM64
6 * Copyright (C) 2013 Linaro Limited.
7 * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
19 #include <linux/kasan.h>
20 #include <linux/kernel.h>
21 #include <linux/kprobes.h>
22 #include <linux/module.h>
23 #include <linux/slab.h>
24 #include <linux/stop_machine.h>
25 #include <linux/stringify.h>
26 #include <asm/traps.h>
27 #include <asm/ptrace.h>
28 #include <asm/cacheflush.h>
29 #include <asm/debug-monitors.h>
30 #include <asm/system_misc.h>
32 #include <asm/uaccess.h>
34 #include <asm-generic/sections.h>
36 #include "decode-insn.h"
38 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
39 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
42 post_kprobe_handler(struct kprobe_ctlblk
*, struct pt_regs
*);
44 static void __kprobes
arch_prepare_ss_slot(struct kprobe
*p
)
46 /* prepare insn slot */
47 p
->ainsn
.insn
[0] = cpu_to_le32(p
->opcode
);
49 flush_icache_range((uintptr_t) (p
->ainsn
.insn
),
50 (uintptr_t) (p
->ainsn
.insn
) +
51 MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
54 * Needs restoring of return address after stepping xol.
56 p
->ainsn
.restore
= (unsigned long) p
->addr
+
57 sizeof(kprobe_opcode_t
);
60 static void __kprobes
arch_prepare_simulate(struct kprobe
*p
)
62 /* This instructions is not executed xol. No need to adjust the PC */
66 static void __kprobes
arch_simulate_insn(struct kprobe
*p
, struct pt_regs
*regs
)
68 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
71 p
->ainsn
.handler((u32
)p
->opcode
, (long)p
->addr
, regs
);
73 /* single step simulated, now go for post processing */
74 post_kprobe_handler(kcb
, regs
);
77 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
79 unsigned long probe_addr
= (unsigned long)p
->addr
;
80 extern char __start_rodata
[];
81 extern char __end_rodata
[];
86 /* copy instruction */
87 p
->opcode
= le32_to_cpu(*p
->addr
);
89 if (in_exception_text(probe_addr
))
91 if (probe_addr
>= (unsigned long) __start_rodata
&&
92 probe_addr
<= (unsigned long) __end_rodata
)
95 /* decode instruction */
96 switch (arm_kprobe_decode_insn(p
->addr
, &p
->ainsn
)) {
97 case INSN_REJECTED
: /* insn not supported */
100 case INSN_GOOD_NO_SLOT
: /* insn need simulation */
101 p
->ainsn
.insn
= NULL
;
104 case INSN_GOOD
: /* instruction uses slot */
105 p
->ainsn
.insn
= get_insn_slot();
111 /* prepare the instruction */
113 arch_prepare_ss_slot(p
);
115 arch_prepare_simulate(p
);
120 static int __kprobes
patch_text(kprobe_opcode_t
*addr
, u32 opcode
)
125 addrs
[0] = (void *)addr
;
126 insns
[0] = (u32
)opcode
;
128 return aarch64_insn_patch_text(addrs
, insns
, 1);
131 /* arm kprobe: install breakpoint in text */
132 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
134 patch_text(p
->addr
, BRK64_OPCODE_KPROBES
);
137 /* disarm kprobe: remove breakpoint from text */
138 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
140 patch_text(p
->addr
, p
->opcode
);
143 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
146 free_insn_slot(p
->ainsn
.insn
, 0);
147 p
->ainsn
.insn
= NULL
;
151 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
153 kcb
->prev_kprobe
.kp
= kprobe_running();
154 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
157 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
159 __this_cpu_write(current_kprobe
, kcb
->prev_kprobe
.kp
);
160 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
163 static void __kprobes
set_current_kprobe(struct kprobe
*p
)
165 __this_cpu_write(current_kprobe
, p
);
169 * The D-flag (Debug mask) is set (masked) upon debug exception entry.
170 * Kprobes needs to clear (unmask) D-flag -ONLY- in case of recursive
171 * probe i.e. when probe hit from kprobe handler context upon
172 * executing the pre/post handlers. In this case we return with
173 * D-flag clear so that single-stepping can be carried-out.
175 * Leave D-flag set in all other cases.
177 static void __kprobes
178 spsr_set_debug_flag(struct pt_regs
*regs
, int mask
)
180 unsigned long spsr
= regs
->pstate
;
191 * Interrupts need to be disabled before single-step mode is set, and not
192 * reenabled until after single-step mode ends.
193 * Without disabling interrupt on local CPU, there is a chance of
194 * interrupt occurrence in the period of exception return and start of
195 * out-of-line single-step, that result in wrongly single stepping
196 * into the interrupt handler.
198 static void __kprobes
kprobes_save_local_irqflag(struct kprobe_ctlblk
*kcb
,
199 struct pt_regs
*regs
)
201 kcb
->saved_irqflag
= regs
->pstate
;
202 regs
->pstate
|= PSR_I_BIT
;
205 static void __kprobes
kprobes_restore_local_irqflag(struct kprobe_ctlblk
*kcb
,
206 struct pt_regs
*regs
)
208 if (kcb
->saved_irqflag
& PSR_I_BIT
)
209 regs
->pstate
|= PSR_I_BIT
;
211 regs
->pstate
&= ~PSR_I_BIT
;
214 static void __kprobes
215 set_ss_context(struct kprobe_ctlblk
*kcb
, unsigned long addr
)
217 kcb
->ss_ctx
.ss_pending
= true;
218 kcb
->ss_ctx
.match_addr
= addr
+ sizeof(kprobe_opcode_t
);
221 static void __kprobes
clear_ss_context(struct kprobe_ctlblk
*kcb
)
223 kcb
->ss_ctx
.ss_pending
= false;
224 kcb
->ss_ctx
.match_addr
= 0;
227 static void __kprobes
setup_singlestep(struct kprobe
*p
,
228 struct pt_regs
*regs
,
229 struct kprobe_ctlblk
*kcb
, int reenter
)
234 save_previous_kprobe(kcb
);
235 set_current_kprobe(p
);
236 kcb
->kprobe_status
= KPROBE_REENTER
;
238 kcb
->kprobe_status
= KPROBE_HIT_SS
;
243 /* prepare for single stepping */
244 slot
= (unsigned long)p
->ainsn
.insn
;
246 set_ss_context(kcb
, slot
); /* mark pending ss */
248 if (kcb
->kprobe_status
== KPROBE_REENTER
)
249 spsr_set_debug_flag(regs
, 0);
251 WARN_ON(regs
->pstate
& PSR_D_BIT
);
253 /* IRQs and single stepping do not mix well. */
254 kprobes_save_local_irqflag(kcb
, regs
);
255 kernel_enable_single_step(regs
);
256 instruction_pointer_set(regs
, slot
);
258 /* insn simulation */
259 arch_simulate_insn(p
, regs
);
263 static int __kprobes
reenter_kprobe(struct kprobe
*p
,
264 struct pt_regs
*regs
,
265 struct kprobe_ctlblk
*kcb
)
267 switch (kcb
->kprobe_status
) {
268 case KPROBE_HIT_SSDONE
:
269 case KPROBE_HIT_ACTIVE
:
270 kprobes_inc_nmissed_count(p
);
271 setup_singlestep(p
, regs
, kcb
, 1);
275 pr_warn("Unrecoverable kprobe detected at %p.\n", p
->addr
);
287 static void __kprobes
288 post_kprobe_handler(struct kprobe_ctlblk
*kcb
, struct pt_regs
*regs
)
290 struct kprobe
*cur
= kprobe_running();
295 /* return addr restore if non-branching insn */
296 if (cur
->ainsn
.restore
!= 0)
297 instruction_pointer_set(regs
, cur
->ainsn
.restore
);
299 /* restore back original saved kprobe variables and continue */
300 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
301 restore_previous_kprobe(kcb
);
304 /* call post handler */
305 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
306 if (cur
->post_handler
) {
307 /* post_handler can hit breakpoint and single step
308 * again, so we enable D-flag for recursive exception.
310 cur
->post_handler(cur
, regs
, 0);
313 reset_current_kprobe();
316 int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, unsigned int fsr
)
318 struct kprobe
*cur
= kprobe_running();
319 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
321 switch (kcb
->kprobe_status
) {
325 * We are here because the instruction being single
326 * stepped caused a page fault. We reset the current
327 * kprobe and the ip points back to the probe address
328 * and allow the page fault handler to continue as a
331 instruction_pointer_set(regs
, (unsigned long) cur
->addr
);
332 if (!instruction_pointer(regs
))
335 kernel_disable_single_step();
336 if (kcb
->kprobe_status
== KPROBE_REENTER
)
337 spsr_set_debug_flag(regs
, 1);
339 if (kcb
->kprobe_status
== KPROBE_REENTER
)
340 restore_previous_kprobe(kcb
);
342 reset_current_kprobe();
345 case KPROBE_HIT_ACTIVE
:
346 case KPROBE_HIT_SSDONE
:
348 * We increment the nmissed count for accounting,
349 * we can also use npre/npostfault count for accounting
350 * these specific fault cases.
352 kprobes_inc_nmissed_count(cur
);
355 * We come here because instructions in the pre/post
356 * handler caused the page_fault, this could happen
357 * if handler tries to access user space by
358 * copy_from_user(), get_user() etc. Let the
359 * user-specified handler try to fix it first.
361 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, fsr
))
365 * In case the user-specified fault handler returned
366 * zero, try to fix up.
368 if (fixup_exception(regs
))
374 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
375 unsigned long val
, void *data
)
380 static void __kprobes
kprobe_handler(struct pt_regs
*regs
)
382 struct kprobe
*p
, *cur_kprobe
;
383 struct kprobe_ctlblk
*kcb
;
384 unsigned long addr
= instruction_pointer(regs
);
386 kcb
= get_kprobe_ctlblk();
387 cur_kprobe
= kprobe_running();
389 p
= get_kprobe((kprobe_opcode_t
*) addr
);
393 if (reenter_kprobe(p
, regs
, kcb
))
397 set_current_kprobe(p
);
398 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
401 * If we have no pre-handler or it returned 0, we
402 * continue with normal processing. If we have a
403 * pre-handler and it returned non-zero, it prepped
404 * for calling the break_handler below on re-entry,
405 * so get out doing nothing more here.
407 * pre_handler can hit a breakpoint and can step thru
408 * before return, keep PSTATE D-flag enabled until
409 * pre_handler return back.
411 if (!p
->pre_handler
|| !p
->pre_handler(p
, regs
)) {
412 setup_singlestep(p
, regs
, kcb
, 0);
416 } else if ((le32_to_cpu(*(kprobe_opcode_t
*) addr
) ==
417 BRK64_OPCODE_KPROBES
) && cur_kprobe
) {
418 /* We probably hit a jprobe. Call its break handler. */
419 if (cur_kprobe
->break_handler
&&
420 cur_kprobe
->break_handler(cur_kprobe
, regs
)) {
421 setup_singlestep(cur_kprobe
, regs
, kcb
, 0);
426 * The breakpoint instruction was removed right
427 * after we hit it. Another cpu has removed
428 * either a probepoint or a debugger breakpoint
429 * at this address. In either case, no further
430 * handling of this interrupt is appropriate.
431 * Return back to original instruction, and continue.
436 kprobe_ss_hit(struct kprobe_ctlblk
*kcb
, unsigned long addr
)
438 if ((kcb
->ss_ctx
.ss_pending
)
439 && (kcb
->ss_ctx
.match_addr
== addr
)) {
440 clear_ss_context(kcb
); /* clear pending ss */
441 return DBG_HOOK_HANDLED
;
443 /* not ours, kprobes should ignore it */
444 return DBG_HOOK_ERROR
;
448 kprobe_single_step_handler(struct pt_regs
*regs
, unsigned int esr
)
450 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
453 /* return error if this is not our step */
454 retval
= kprobe_ss_hit(kcb
, instruction_pointer(regs
));
456 if (retval
== DBG_HOOK_HANDLED
) {
457 kprobes_restore_local_irqflag(kcb
, regs
);
458 kernel_disable_single_step();
460 if (kcb
->kprobe_status
== KPROBE_REENTER
)
461 spsr_set_debug_flag(regs
, 1);
463 post_kprobe_handler(kcb
, regs
);
470 kprobe_breakpoint_handler(struct pt_regs
*regs
, unsigned int esr
)
472 kprobe_handler(regs
);
473 return DBG_HOOK_HANDLED
;
476 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
478 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
479 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
481 kcb
->jprobe_saved_regs
= *regs
;
483 * Since we can't be sure where in the stack frame "stacked"
484 * pass-by-value arguments are stored we just don't try to
485 * duplicate any of the stack. Do not use jprobes on functions that
486 * use more than 64 bytes (after padding each to an 8 byte boundary)
487 * of arguments, or pass individual arguments larger than 16 bytes.
490 instruction_pointer_set(regs
, (unsigned long) jp
->entry
);
492 pause_graph_tracing();
496 void __kprobes
jprobe_return(void)
498 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
501 * Jprobe handler return by entering break exception,
502 * encoded same as kprobe, but with following conditions
503 * -a special PC to identify it from the other kprobes.
504 * -restore stack addr to original saved pt_regs
506 asm volatile(" mov sp, %0 \n"
507 "jprobe_return_break: brk %1 \n"
509 : "r" (kcb
->jprobe_saved_regs
.sp
),
510 "I" (BRK64_ESR_KPROBES
)
516 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
518 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
519 long stack_addr
= kcb
->jprobe_saved_regs
.sp
;
520 long orig_sp
= kernel_stack_pointer(regs
);
521 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
522 extern const char jprobe_return_break
[];
524 if (instruction_pointer(regs
) != (u64
) jprobe_return_break
)
527 if (orig_sp
!= stack_addr
) {
528 struct pt_regs
*saved_regs
=
529 (struct pt_regs
*)kcb
->jprobe_saved_regs
.sp
;
530 pr_err("current sp %lx does not match saved sp %lx\n",
531 orig_sp
, stack_addr
);
532 pr_err("Saved registers for jprobe %p\n", jp
);
533 show_regs(saved_regs
);
534 pr_err("Current registers\n");
538 unpause_graph_tracing();
539 *regs
= kcb
->jprobe_saved_regs
;
540 preempt_enable_no_resched();
544 bool arch_within_kprobe_blacklist(unsigned long addr
)
546 extern char __idmap_text_start
[], __idmap_text_end
[];
547 extern char __hyp_idmap_text_start
[], __hyp_idmap_text_end
[];
549 if ((addr
>= (unsigned long)__kprobes_text_start
&&
550 addr
< (unsigned long)__kprobes_text_end
) ||
551 (addr
>= (unsigned long)__entry_text_start
&&
552 addr
< (unsigned long)__entry_text_end
) ||
553 (addr
>= (unsigned long)__idmap_text_start
&&
554 addr
< (unsigned long)__idmap_text_end
) ||
555 !!search_exception_tables(addr
))
558 if (!is_kernel_in_hyp_mode()) {
559 if ((addr
>= (unsigned long)__hyp_text_start
&&
560 addr
< (unsigned long)__hyp_text_end
) ||
561 (addr
>= (unsigned long)__hyp_idmap_text_start
&&
562 addr
< (unsigned long)__hyp_idmap_text_end
))
569 void __kprobes __used
*trampoline_probe_handler(struct pt_regs
*regs
)
571 struct kretprobe_instance
*ri
= NULL
;
572 struct hlist_head
*head
, empty_rp
;
573 struct hlist_node
*tmp
;
574 unsigned long flags
, orig_ret_address
= 0;
575 unsigned long trampoline_address
=
576 (unsigned long)&kretprobe_trampoline
;
577 kprobe_opcode_t
*correct_ret_addr
= NULL
;
579 INIT_HLIST_HEAD(&empty_rp
);
580 kretprobe_hash_lock(current
, &head
, &flags
);
583 * It is possible to have multiple instances associated with a given
584 * task either because multiple functions in the call path have
585 * return probes installed on them, and/or more than one
586 * return probe was registered for a target function.
588 * We can handle this because:
589 * - instances are always pushed into the head of the list
590 * - when multiple return probes are registered for the same
591 * function, the (chronologically) first instance's ret_addr
592 * will be the real return address, and all the rest will
593 * point to kretprobe_trampoline.
595 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
596 if (ri
->task
!= current
)
597 /* another task is sharing our hash bucket */
600 orig_ret_address
= (unsigned long)ri
->ret_addr
;
602 if (orig_ret_address
!= trampoline_address
)
604 * This is the real return address. Any other
605 * instances associated with this task are for
606 * other calls deeper on the call stack
611 kretprobe_assert(ri
, orig_ret_address
, trampoline_address
);
613 correct_ret_addr
= ri
->ret_addr
;
614 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
615 if (ri
->task
!= current
)
616 /* another task is sharing our hash bucket */
619 orig_ret_address
= (unsigned long)ri
->ret_addr
;
620 if (ri
->rp
&& ri
->rp
->handler
) {
621 __this_cpu_write(current_kprobe
, &ri
->rp
->kp
);
622 get_kprobe_ctlblk()->kprobe_status
= KPROBE_HIT_ACTIVE
;
623 ri
->ret_addr
= correct_ret_addr
;
624 ri
->rp
->handler(ri
, regs
);
625 __this_cpu_write(current_kprobe
, NULL
);
628 recycle_rp_inst(ri
, &empty_rp
);
630 if (orig_ret_address
!= trampoline_address
)
632 * This is the real return address. Any other
633 * instances associated with this task are for
634 * other calls deeper on the call stack
639 kretprobe_hash_unlock(current
, &flags
);
641 hlist_for_each_entry_safe(ri
, tmp
, &empty_rp
, hlist
) {
642 hlist_del(&ri
->hlist
);
645 return (void *)orig_ret_address
;
648 void __kprobes
arch_prepare_kretprobe(struct kretprobe_instance
*ri
,
649 struct pt_regs
*regs
)
651 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->regs
[30];
653 /* replace return addr (x30) with trampoline */
654 regs
->regs
[30] = (long)&kretprobe_trampoline
;
657 int __kprobes
arch_trampoline_kprobe(struct kprobe
*p
)
662 int __init
arch_init_kprobes(void)
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