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>
11 #define pr_fmt(fmt) "kprobes: " fmt
13 #include <linux/extable.h>
14 #include <linux/kasan.h>
15 #include <linux/kernel.h>
16 #include <linux/kprobes.h>
17 #include <linux/sched/debug.h>
18 #include <linux/set_memory.h>
19 #include <linux/slab.h>
20 #include <linux/stop_machine.h>
21 #include <linux/stringify.h>
22 #include <linux/uaccess.h>
23 #include <linux/vmalloc.h>
25 #include <asm/cacheflush.h>
26 #include <asm/daifflags.h>
27 #include <asm/debug-monitors.h>
30 #include <asm/patching.h>
31 #include <asm/ptrace.h>
32 #include <asm/sections.h>
33 #include <asm/system_misc.h>
34 #include <asm/traps.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 *, struct kprobe_ctlblk *, struct pt_regs *);
44 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
46 kprobe_opcode_t *addr = p->ainsn.api.insn;
49 * Prepare insn slot, Mark Rutland points out it depends on a coupe of
52 * - That the I-cache maintenance for these instructions is complete
53 * *before* the kprobe BRK is written (and aarch64_insn_patch_text_nosync()
54 * ensures this, but just omits causing a Context-Synchronization-Event
57 * - That the kprobe BRK results in an exception (and consequently a
58 * Context-Synchronoization-Event), which ensures that the CPU will
59 * fetch thesingle-step slot instructions *after* this, ensuring that
60 * the new instructions are used
62 * It supposes to place ISB after patching to guarantee I-cache maintenance
63 * is observed on all CPUS, however, single-step slot is installed in
64 * the BRK exception handler, so it is unnecessary to generate
65 * Contex-Synchronization-Event via ISB again.
67 aarch64_insn_patch_text_nosync(addr, p->opcode);
68 aarch64_insn_patch_text_nosync(addr + 1, BRK64_OPCODE_KPROBES_SS);
71 * Needs restoring of return address after stepping xol.
73 p->ainsn.api.restore = (unsigned long) p->addr +
74 sizeof(kprobe_opcode_t);
77 static void __kprobes arch_prepare_simulate(struct kprobe *p)
79 /* This instructions is not executed xol. No need to adjust the PC */
80 p->ainsn.api.restore = 0;
83 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
85 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
87 if (p->ainsn.api.handler)
88 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
90 /* single step simulated, now go for post processing */
91 post_kprobe_handler(p, kcb, regs);
94 int __kprobes arch_prepare_kprobe(struct kprobe *p)
96 unsigned long probe_addr = (unsigned long)p->addr;
101 /* copy instruction */
102 p->opcode = le32_to_cpu(*p->addr);
104 if (search_exception_tables(probe_addr))
107 /* decode instruction */
108 switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
109 case INSN_REJECTED: /* insn not supported */
112 case INSN_GOOD_NO_SLOT: /* insn need simulation */
113 p->ainsn.api.insn = NULL;
116 case INSN_GOOD: /* instruction uses slot */
117 p->ainsn.api.insn = get_insn_slot();
118 if (!p->ainsn.api.insn)
123 /* prepare the instruction */
124 if (p->ainsn.api.insn)
125 arch_prepare_ss_slot(p);
127 arch_prepare_simulate(p);
132 void *alloc_insn_page(void)
134 return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
135 GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
136 NUMA_NO_NODE, __builtin_return_address(0));
139 /* arm kprobe: install breakpoint in text */
140 void __kprobes arch_arm_kprobe(struct kprobe *p)
142 void *addr = p->addr;
143 u32 insn = BRK64_OPCODE_KPROBES;
145 aarch64_insn_patch_text(&addr, &insn, 1);
148 /* disarm kprobe: remove breakpoint from text */
149 void __kprobes arch_disarm_kprobe(struct kprobe *p)
151 void *addr = p->addr;
153 aarch64_insn_patch_text(&addr, &p->opcode, 1);
156 void __kprobes arch_remove_kprobe(struct kprobe *p)
158 if (p->ainsn.api.insn) {
159 free_insn_slot(p->ainsn.api.insn, 0);
160 p->ainsn.api.insn = NULL;
164 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
166 kcb->prev_kprobe.kp = kprobe_running();
167 kcb->prev_kprobe.status = kcb->kprobe_status;
170 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
172 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
173 kcb->kprobe_status = kcb->prev_kprobe.status;
176 static void __kprobes set_current_kprobe(struct kprobe *p)
178 __this_cpu_write(current_kprobe, p);
182 * Mask all of DAIF while executing the instruction out-of-line, to keep things
183 * simple and avoid nesting exceptions. Interrupts do have to be disabled since
184 * the kprobe state is per-CPU and doesn't get migrated.
186 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
187 struct pt_regs *regs)
189 kcb->saved_irqflag = regs->pstate & DAIF_MASK;
190 regs->pstate |= DAIF_MASK;
193 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
194 struct pt_regs *regs)
196 regs->pstate &= ~DAIF_MASK;
197 regs->pstate |= kcb->saved_irqflag;
200 static void __kprobes setup_singlestep(struct kprobe *p,
201 struct pt_regs *regs,
202 struct kprobe_ctlblk *kcb, int reenter)
207 save_previous_kprobe(kcb);
208 set_current_kprobe(p);
209 kcb->kprobe_status = KPROBE_REENTER;
211 kcb->kprobe_status = KPROBE_HIT_SS;
215 if (p->ainsn.api.insn) {
216 /* prepare for single stepping */
217 slot = (unsigned long)p->ainsn.api.insn;
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("Failed to recover from reentered kprobes.\n");
251 static void __kprobes
252 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs)
254 /* return addr restore if non-branching insn */
255 if (cur->ainsn.api.restore != 0)
256 instruction_pointer_set(regs, cur->ainsn.api.restore);
258 /* restore back original saved kprobe variables and continue */
259 if (kcb->kprobe_status == KPROBE_REENTER) {
260 restore_previous_kprobe(kcb);
263 /* call post handler */
264 kcb->kprobe_status = KPROBE_HIT_SSDONE;
265 if (cur->post_handler)
266 cur->post_handler(cur, regs, 0);
268 reset_current_kprobe();
271 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
273 struct kprobe *cur = kprobe_running();
274 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
276 switch (kcb->kprobe_status) {
280 * We are here because the instruction being single
281 * stepped caused a page fault. We reset the current
282 * kprobe and the ip points back to the probe address
283 * and allow the page fault handler to continue as a
286 instruction_pointer_set(regs, (unsigned long) cur->addr);
287 BUG_ON(!instruction_pointer(regs));
289 if (kcb->kprobe_status == KPROBE_REENTER) {
290 restore_previous_kprobe(kcb);
292 kprobes_restore_local_irqflag(kcb, regs);
293 reset_current_kprobe();
302 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr)
304 struct kprobe *p, *cur_kprobe;
305 struct kprobe_ctlblk *kcb;
306 unsigned long addr = instruction_pointer(regs);
308 kcb = get_kprobe_ctlblk();
309 cur_kprobe = kprobe_running();
311 p = get_kprobe((kprobe_opcode_t *) addr);
312 if (WARN_ON_ONCE(!p)) {
314 * Something went wrong. This BRK used an immediate reserved
315 * for kprobes, but we couldn't find any corresponding probe.
317 return DBG_HOOK_ERROR;
321 /* Hit a kprobe inside another kprobe */
322 if (!reenter_kprobe(p, regs, kcb))
323 return DBG_HOOK_ERROR;
326 set_current_kprobe(p);
327 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
330 * If we have no pre-handler or it returned 0, we
331 * continue with normal processing. If we have a
332 * pre-handler and it returned non-zero, it will
333 * modify the execution path and not need to single-step
334 * Let's just reset current kprobe and exit.
336 if (!p->pre_handler || !p->pre_handler(p, regs))
337 setup_singlestep(p, regs, kcb, 0);
339 reset_current_kprobe();
342 return DBG_HOOK_HANDLED;
345 static struct break_hook kprobes_break_hook = {
346 .imm = KPROBES_BRK_IMM,
347 .fn = kprobe_breakpoint_handler,
351 kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned long esr)
353 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
354 unsigned long addr = instruction_pointer(regs);
355 struct kprobe *cur = kprobe_running();
357 if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
358 ((unsigned long)&cur->ainsn.api.insn[1] == addr)) {
359 kprobes_restore_local_irqflag(kcb, regs);
360 post_kprobe_handler(cur, kcb, regs);
362 return DBG_HOOK_HANDLED;
365 /* not ours, kprobes should ignore it */
366 return DBG_HOOK_ERROR;
369 static struct break_hook kprobes_break_ss_hook = {
370 .imm = KPROBES_BRK_SS_IMM,
371 .fn = kprobe_breakpoint_ss_handler,
375 * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
376 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
378 int __init arch_populate_kprobe_blacklist(void)
382 ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start,
383 (unsigned long)__entry_text_end);
386 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
387 (unsigned long)__irqentry_text_end);
390 ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start,
391 (unsigned long)__hyp_text_end);
392 if (ret || is_kernel_in_hyp_mode())
394 ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start,
395 (unsigned long)__hyp_idmap_text_end);
399 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
401 return (void *)kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
404 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
405 struct pt_regs *regs)
407 ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
408 ri->fp = (void *)regs->regs[29];
410 /* replace return addr (x30) with trampoline */
411 regs->regs[30] = (long)&__kretprobe_trampoline;
414 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
419 int __init arch_init_kprobes(void)
421 register_kernel_break_hook(&kprobes_break_hook);
422 register_kernel_break_hook(&kprobes_break_ss_hook);