1 // SPDX-License-Identifier: GPL-2.0-only
3 * arch/arm64/kernel/probes/kprobes.c
5 * Kprobes support for ARM64
7 * Copyright (C) 2013 Linaro Limited.
8 * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
10 #include <linux/kasan.h>
11 #include <linux/kernel.h>
12 #include <linux/kprobes.h>
13 #include <linux/extable.h>
14 #include <linux/slab.h>
15 #include <linux/stop_machine.h>
16 #include <linux/sched/debug.h>
17 #include <linux/set_memory.h>
18 #include <linux/stringify.h>
19 #include <linux/vmalloc.h>
20 #include <asm/traps.h>
21 #include <asm/ptrace.h>
22 #include <asm/cacheflush.h>
23 #include <asm/debug-monitors.h>
24 #include <asm/daifflags.h>
25 #include <asm/system_misc.h>
27 #include <linux/uaccess.h>
29 #include <asm/sections.h>
31 #include "decode-insn.h"
33 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
34 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
37 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
39 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
41 kprobe_opcode_t *addr = p->ainsn.api.insn;
42 void *addrs[] = {addr, addr + 1};
43 u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS};
45 /* prepare insn slot */
46 aarch64_insn_patch_text(addrs, insns, 2);
48 flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE));
51 * Needs restoring of return address after stepping xol.
53 p->ainsn.api.restore = (unsigned long) p->addr +
54 sizeof(kprobe_opcode_t);
57 static void __kprobes arch_prepare_simulate(struct kprobe *p)
59 /* This instructions is not executed xol. No need to adjust the PC */
60 p->ainsn.api.restore = 0;
63 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
65 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
67 if (p->ainsn.api.handler)
68 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
70 /* single step simulated, now go for post processing */
71 post_kprobe_handler(kcb, regs);
74 int __kprobes arch_prepare_kprobe(struct kprobe *p)
76 unsigned long probe_addr = (unsigned long)p->addr;
81 /* copy instruction */
82 p->opcode = le32_to_cpu(*p->addr);
84 if (search_exception_tables(probe_addr))
87 /* decode instruction */
88 switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
89 case INSN_REJECTED: /* insn not supported */
92 case INSN_GOOD_NO_SLOT: /* insn need simulation */
93 p->ainsn.api.insn = NULL;
96 case INSN_GOOD: /* instruction uses slot */
97 p->ainsn.api.insn = get_insn_slot();
98 if (!p->ainsn.api.insn)
103 /* prepare the instruction */
104 if (p->ainsn.api.insn)
105 arch_prepare_ss_slot(p);
107 arch_prepare_simulate(p);
112 void *alloc_insn_page(void)
116 page = vmalloc_exec(PAGE_SIZE);
118 set_memory_ro((unsigned long)page, 1);
119 set_vm_flush_reset_perms(page);
125 /* arm kprobe: install breakpoint in text */
126 void __kprobes arch_arm_kprobe(struct kprobe *p)
128 void *addr = p->addr;
129 u32 insn = BRK64_OPCODE_KPROBES;
131 aarch64_insn_patch_text(&addr, &insn, 1);
134 /* disarm kprobe: remove breakpoint from text */
135 void __kprobes arch_disarm_kprobe(struct kprobe *p)
137 void *addr = p->addr;
139 aarch64_insn_patch_text(&addr, &p->opcode, 1);
142 void __kprobes arch_remove_kprobe(struct kprobe *p)
144 if (p->ainsn.api.insn) {
145 free_insn_slot(p->ainsn.api.insn, 0);
146 p->ainsn.api.insn = NULL;
150 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
152 kcb->prev_kprobe.kp = kprobe_running();
153 kcb->prev_kprobe.status = kcb->kprobe_status;
156 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
158 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
159 kcb->kprobe_status = kcb->prev_kprobe.status;
162 static void __kprobes set_current_kprobe(struct kprobe *p)
164 __this_cpu_write(current_kprobe, p);
168 * Mask all of DAIF while executing the instruction out-of-line, to keep things
169 * simple and avoid nesting exceptions. Interrupts do have to be disabled since
170 * the kprobe state is per-CPU and doesn't get migrated.
172 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
173 struct pt_regs *regs)
175 kcb->saved_irqflag = regs->pstate & DAIF_MASK;
176 regs->pstate |= DAIF_MASK;
179 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
180 struct pt_regs *regs)
182 regs->pstate &= ~DAIF_MASK;
183 regs->pstate |= kcb->saved_irqflag;
186 static void __kprobes
187 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr)
189 kcb->ss_ctx.ss_pending = true;
190 kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t);
193 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
195 kcb->ss_ctx.ss_pending = false;
196 kcb->ss_ctx.match_addr = 0;
199 static void __kprobes setup_singlestep(struct kprobe *p,
200 struct pt_regs *regs,
201 struct kprobe_ctlblk *kcb, int reenter)
206 save_previous_kprobe(kcb);
207 set_current_kprobe(p);
208 kcb->kprobe_status = KPROBE_REENTER;
210 kcb->kprobe_status = KPROBE_HIT_SS;
214 if (p->ainsn.api.insn) {
215 /* prepare for single stepping */
216 slot = (unsigned long)p->ainsn.api.insn;
218 set_ss_context(kcb, slot); /* mark pending ss */
219 kprobes_save_local_irqflag(kcb, regs);
220 instruction_pointer_set(regs, slot);
222 /* insn simulation */
223 arch_simulate_insn(p, regs);
227 static int __kprobes reenter_kprobe(struct kprobe *p,
228 struct pt_regs *regs,
229 struct kprobe_ctlblk *kcb)
231 switch (kcb->kprobe_status) {
232 case KPROBE_HIT_SSDONE:
233 case KPROBE_HIT_ACTIVE:
234 kprobes_inc_nmissed_count(p);
235 setup_singlestep(p, regs, kcb, 1);
239 pr_warn("Unrecoverable kprobe detected.\n");
251 static void __kprobes
252 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
254 struct kprobe *cur = kprobe_running();
259 /* return addr restore if non-branching insn */
260 if (cur->ainsn.api.restore != 0)
261 instruction_pointer_set(regs, cur->ainsn.api.restore);
263 /* restore back original saved kprobe variables and continue */
264 if (kcb->kprobe_status == KPROBE_REENTER) {
265 restore_previous_kprobe(kcb);
268 /* call post handler */
269 kcb->kprobe_status = KPROBE_HIT_SSDONE;
270 if (cur->post_handler)
271 cur->post_handler(cur, regs, 0);
273 reset_current_kprobe();
276 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
278 struct kprobe *cur = kprobe_running();
279 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
281 switch (kcb->kprobe_status) {
285 * We are here because the instruction being single
286 * stepped caused a page fault. We reset the current
287 * kprobe and the ip points back to the probe address
288 * and allow the page fault handler to continue as a
291 instruction_pointer_set(regs, (unsigned long) cur->addr);
292 if (!instruction_pointer(regs))
295 if (kcb->kprobe_status == KPROBE_REENTER)
296 restore_previous_kprobe(kcb);
298 reset_current_kprobe();
301 case KPROBE_HIT_ACTIVE:
302 case KPROBE_HIT_SSDONE:
304 * We increment the nmissed count for accounting,
305 * we can also use npre/npostfault count for accounting
306 * these specific fault cases.
308 kprobes_inc_nmissed_count(cur);
311 * We come here because instructions in the pre/post
312 * handler caused the page_fault, this could happen
313 * if handler tries to access user space by
314 * copy_from_user(), get_user() etc. Let the
315 * user-specified handler try to fix it first.
317 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
321 * In case the user-specified fault handler returned
322 * zero, try to fix up.
324 if (fixup_exception(regs))
330 static void __kprobes kprobe_handler(struct pt_regs *regs)
332 struct kprobe *p, *cur_kprobe;
333 struct kprobe_ctlblk *kcb;
334 unsigned long addr = instruction_pointer(regs);
336 kcb = get_kprobe_ctlblk();
337 cur_kprobe = kprobe_running();
339 p = get_kprobe((kprobe_opcode_t *) addr);
343 if (reenter_kprobe(p, regs, kcb))
347 set_current_kprobe(p);
348 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
351 * If we have no pre-handler or it returned 0, we
352 * continue with normal processing. If we have a
353 * pre-handler and it returned non-zero, it will
354 * modify the execution path and no need to single
355 * stepping. Let's just reset current kprobe and exit.
357 if (!p->pre_handler || !p->pre_handler(p, regs)) {
358 setup_singlestep(p, regs, kcb, 0);
360 reset_current_kprobe();
364 * The breakpoint instruction was removed right
365 * after we hit it. Another cpu has removed
366 * either a probepoint or a debugger breakpoint
367 * at this address. In either case, no further
368 * handling of this interrupt is appropriate.
369 * Return back to original instruction, and continue.
374 kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
376 if ((kcb->ss_ctx.ss_pending)
377 && (kcb->ss_ctx.match_addr == addr)) {
378 clear_ss_context(kcb); /* clear pending ss */
379 return DBG_HOOK_HANDLED;
381 /* not ours, kprobes should ignore it */
382 return DBG_HOOK_ERROR;
386 kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr)
388 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
391 /* return error if this is not our step */
392 retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
394 if (retval == DBG_HOOK_HANDLED) {
395 kprobes_restore_local_irqflag(kcb, regs);
396 post_kprobe_handler(kcb, regs);
402 static struct break_hook kprobes_break_ss_hook = {
403 .imm = KPROBES_BRK_SS_IMM,
404 .fn = kprobe_breakpoint_ss_handler,
408 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
410 kprobe_handler(regs);
411 return DBG_HOOK_HANDLED;
414 static struct break_hook kprobes_break_hook = {
415 .imm = KPROBES_BRK_IMM,
416 .fn = kprobe_breakpoint_handler,
420 * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
421 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
423 int __init arch_populate_kprobe_blacklist(void)
427 ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start,
428 (unsigned long)__entry_text_end);
431 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
432 (unsigned long)__irqentry_text_end);
435 ret = kprobe_add_area_blacklist((unsigned long)__exception_text_start,
436 (unsigned long)__exception_text_end);
439 ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start,
440 (unsigned long)__idmap_text_end);
443 ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start,
444 (unsigned long)__hyp_text_end);
445 if (ret || is_kernel_in_hyp_mode())
447 ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start,
448 (unsigned long)__hyp_idmap_text_end);
452 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
454 struct kretprobe_instance *ri = NULL;
455 struct hlist_head *head, empty_rp;
456 struct hlist_node *tmp;
457 unsigned long flags, orig_ret_address = 0;
458 unsigned long trampoline_address =
459 (unsigned long)&kretprobe_trampoline;
460 kprobe_opcode_t *correct_ret_addr = NULL;
462 INIT_HLIST_HEAD(&empty_rp);
463 kretprobe_hash_lock(current, &head, &flags);
466 * It is possible to have multiple instances associated with a given
467 * task either because multiple functions in the call path have
468 * return probes installed on them, and/or more than one
469 * return probe was registered for a target function.
471 * We can handle this because:
472 * - instances are always pushed into the head of the list
473 * - when multiple return probes are registered for the same
474 * function, the (chronologically) first instance's ret_addr
475 * will be the real return address, and all the rest will
476 * point to kretprobe_trampoline.
478 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
479 if (ri->task != current)
480 /* another task is sharing our hash bucket */
483 orig_ret_address = (unsigned long)ri->ret_addr;
485 if (orig_ret_address != trampoline_address)
487 * This is the real return address. Any other
488 * instances associated with this task are for
489 * other calls deeper on the call stack
494 kretprobe_assert(ri, orig_ret_address, trampoline_address);
496 correct_ret_addr = ri->ret_addr;
497 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
498 if (ri->task != current)
499 /* another task is sharing our hash bucket */
502 orig_ret_address = (unsigned long)ri->ret_addr;
503 if (ri->rp && ri->rp->handler) {
504 __this_cpu_write(current_kprobe, &ri->rp->kp);
505 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
506 ri->ret_addr = correct_ret_addr;
507 ri->rp->handler(ri, regs);
508 __this_cpu_write(current_kprobe, NULL);
511 recycle_rp_inst(ri, &empty_rp);
513 if (orig_ret_address != trampoline_address)
515 * This is the real return address. Any other
516 * instances associated with this task are for
517 * other calls deeper on the call stack
522 kretprobe_hash_unlock(current, &flags);
524 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
525 hlist_del(&ri->hlist);
528 return (void *)orig_ret_address;
531 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
532 struct pt_regs *regs)
534 ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
536 /* replace return addr (x30) with trampoline */
537 regs->regs[30] = (long)&kretprobe_trampoline;
540 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
545 int __init arch_init_kprobes(void)
547 register_kernel_break_hook(&kprobes_break_hook);
548 register_kernel_break_hook(&kprobes_break_ss_hook);