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/stringify.h>
28 #include <asm/traps.h>
29 #include <asm/cacheflush.h>
33 #define MIN_STACK_SIZE(addr) \
34 min((unsigned long)MAX_STACK_SIZE, \
35 (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
37 #define flush_insns(addr, cnt) \
38 flush_icache_range((unsigned long)(addr), \
39 (unsigned long)(addr) + \
40 sizeof(kprobe_opcode_t) * (cnt))
42 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
43 #define JPROBE_MAGIC_ADDR 0xffffffff
45 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
46 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
49 int __kprobes arch_prepare_kprobe(struct kprobe *p)
52 kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
53 unsigned long addr = (unsigned long)p->addr;
54 kprobe_decode_insn_t *decode_insn;
57 if (in_exception_text(addr))
60 #ifdef CONFIG_THUMB2_KERNEL
61 addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
62 insn = ((u16 *)addr)[0];
63 if (is_wide_instruction(insn)) {
65 insn |= ((u16 *)addr)[1];
66 decode_insn = thumb32_kprobe_decode_insn;
68 decode_insn = thumb16_kprobe_decode_insn;
69 #else /* !CONFIG_THUMB2_KERNEL */
73 decode_insn = arm_kprobe_decode_insn;
77 p->ainsn.insn = tmp_insn;
79 switch ((*decode_insn)(insn, &p->ainsn)) {
80 case INSN_REJECTED: /* not supported */
83 case INSN_GOOD: /* instruction uses slot */
84 p->ainsn.insn = get_insn_slot();
87 for (is = 0; is < MAX_INSN_SIZE; ++is)
88 p->ainsn.insn[is] = tmp_insn[is];
89 flush_insns(p->ainsn.insn, MAX_INSN_SIZE);
92 case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
100 void __kprobes arch_arm_kprobe(struct kprobe *p)
102 *p->addr = KPROBE_BREAKPOINT_INSTRUCTION;
103 flush_insns(p->addr, 1);
107 * The actual disarming is done here on each CPU and synchronized using
108 * stop_machine. This synchronization is necessary on SMP to avoid removing
109 * a probe between the moment the 'Undefined Instruction' exception is raised
110 * and the moment the exception handler reads the faulting instruction from
113 int __kprobes __arch_disarm_kprobe(void *p)
115 struct kprobe *kp = p;
116 *kp->addr = kp->opcode;
117 flush_insns(kp->addr, 1);
121 void __kprobes arch_disarm_kprobe(struct kprobe *p)
123 stop_machine(__arch_disarm_kprobe, p, &cpu_online_map);
126 void __kprobes arch_remove_kprobe(struct kprobe *p)
129 free_insn_slot(p->ainsn.insn, 0);
130 p->ainsn.insn = NULL;
134 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
136 kcb->prev_kprobe.kp = kprobe_running();
137 kcb->prev_kprobe.status = kcb->kprobe_status;
140 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
142 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
143 kcb->kprobe_status = kcb->prev_kprobe.status;
146 static void __kprobes set_current_kprobe(struct kprobe *p)
148 __get_cpu_var(current_kprobe) = p;
151 static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs,
152 struct kprobe_ctlblk *kcb)
155 if (p->ainsn.insn_check_cc(regs->ARM_cpsr))
156 p->ainsn.insn_handler(p, regs);
160 * Called with IRQs disabled. IRQs must remain disabled from that point
161 * all the way until processing this kprobe is complete. The current
162 * kprobes implementation cannot process more than one nested level of
163 * kprobe, and that level is reserved for user kprobe handlers, so we can't
164 * risk encountering a new kprobe in an interrupt handler.
166 void __kprobes kprobe_handler(struct pt_regs *regs)
168 struct kprobe *p, *cur;
169 struct kprobe_ctlblk *kcb;
170 kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->ARM_pc;
172 kcb = get_kprobe_ctlblk();
173 cur = kprobe_running();
174 p = get_kprobe(addr);
178 /* Kprobe is pending, so we're recursing. */
179 switch (kcb->kprobe_status) {
180 case KPROBE_HIT_ACTIVE:
181 case KPROBE_HIT_SSDONE:
182 /* A pre- or post-handler probe got us here. */
183 kprobes_inc_nmissed_count(p);
184 save_previous_kprobe(kcb);
185 set_current_kprobe(p);
186 kcb->kprobe_status = KPROBE_REENTER;
187 singlestep(p, regs, kcb);
188 restore_previous_kprobe(kcb);
191 /* impossible cases */
195 set_current_kprobe(p);
196 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
199 * If we have no pre-handler or it returned 0, we
200 * continue with normal processing. If we have a
201 * pre-handler and it returned non-zero, it prepped
202 * for calling the break_handler below on re-entry,
203 * so get out doing nothing more here.
205 if (!p->pre_handler || !p->pre_handler(p, regs)) {
206 kcb->kprobe_status = KPROBE_HIT_SS;
207 singlestep(p, regs, kcb);
208 if (p->post_handler) {
209 kcb->kprobe_status = KPROBE_HIT_SSDONE;
210 p->post_handler(p, regs, 0);
212 reset_current_kprobe();
216 /* We probably hit a jprobe. Call its break handler. */
217 if (cur->break_handler && cur->break_handler(cur, regs)) {
218 kcb->kprobe_status = KPROBE_HIT_SS;
219 singlestep(cur, regs, kcb);
220 if (cur->post_handler) {
221 kcb->kprobe_status = KPROBE_HIT_SSDONE;
222 cur->post_handler(cur, regs, 0);
225 reset_current_kprobe();
228 * The probe was removed and a race is in progress.
229 * There is nothing we can do about it. Let's restart
230 * the instruction. By the time we can restart, the
231 * real instruction will be there.
236 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
239 local_irq_save(flags);
240 kprobe_handler(regs);
241 local_irq_restore(flags);
245 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
247 struct kprobe *cur = kprobe_running();
248 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
250 switch (kcb->kprobe_status) {
254 * We are here because the instruction being single
255 * stepped caused a page fault. We reset the current
256 * kprobe and the PC to point back to the probe address
257 * and allow the page fault handler to continue as a
260 regs->ARM_pc = (long)cur->addr;
261 if (kcb->kprobe_status == KPROBE_REENTER) {
262 restore_previous_kprobe(kcb);
264 reset_current_kprobe();
268 case KPROBE_HIT_ACTIVE:
269 case KPROBE_HIT_SSDONE:
271 * We increment the nmissed count for accounting,
272 * we can also use npre/npostfault count for accounting
273 * these specific fault cases.
275 kprobes_inc_nmissed_count(cur);
278 * We come here because instructions in the pre/post
279 * handler caused the page_fault, this could happen
280 * if handler tries to access user space by
281 * copy_from_user(), get_user() etc. Let the
282 * user-specified handler try to fix it.
284 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
295 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
296 unsigned long val, void *data)
299 * notify_die() is currently never called on ARM,
300 * so this callback is currently empty.
306 * When a retprobed function returns, trampoline_handler() is called,
307 * calling the kretprobe's handler. We construct a struct pt_regs to
308 * give a view of registers r0-r11 to the user return-handler. This is
309 * not a complete pt_regs structure, but that should be plenty sufficient
310 * for kretprobe handlers which should normally be interested in r0 only
313 void __naked __kprobes kretprobe_trampoline(void)
315 __asm__ __volatile__ (
316 "stmdb sp!, {r0 - r11} \n\t"
318 "bl trampoline_handler \n\t"
320 "ldmia sp!, {r0 - r11} \n\t"
321 #ifdef CONFIG_THUMB2_KERNEL
329 /* Called from kretprobe_trampoline */
330 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
332 struct kretprobe_instance *ri = NULL;
333 struct hlist_head *head, empty_rp;
334 struct hlist_node *node, *tmp;
335 unsigned long flags, orig_ret_address = 0;
336 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
338 INIT_HLIST_HEAD(&empty_rp);
339 kretprobe_hash_lock(current, &head, &flags);
342 * It is possible to have multiple instances associated with a given
343 * task either because multiple functions in the call path have
344 * a return probe installed on them, and/or more than one return
345 * probe was registered for a target function.
347 * We can handle this because:
348 * - instances are always inserted at the head of the list
349 * - when multiple return probes are registered for the same
350 * function, the first instance's ret_addr will point to the
351 * real return address, and all the rest will point to
352 * kretprobe_trampoline
354 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
355 if (ri->task != current)
356 /* another task is sharing our hash bucket */
359 if (ri->rp && ri->rp->handler) {
360 __get_cpu_var(current_kprobe) = &ri->rp->kp;
361 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
362 ri->rp->handler(ri, regs);
363 __get_cpu_var(current_kprobe) = NULL;
366 orig_ret_address = (unsigned long)ri->ret_addr;
367 recycle_rp_inst(ri, &empty_rp);
369 if (orig_ret_address != trampoline_address)
371 * This is the real return address. Any other
372 * instances associated with this task are for
373 * other calls deeper on the call stack
378 kretprobe_assert(ri, orig_ret_address, trampoline_address);
379 kretprobe_hash_unlock(current, &flags);
381 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
382 hlist_del(&ri->hlist);
386 return (void *)orig_ret_address;
389 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
390 struct pt_regs *regs)
392 ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
394 /* Replace the return addr with trampoline addr. */
395 regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
398 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
400 struct jprobe *jp = container_of(p, struct jprobe, kp);
401 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
402 long sp_addr = regs->ARM_sp;
405 kcb->jprobe_saved_regs = *regs;
406 memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
407 regs->ARM_pc = (long)jp->entry;
409 cpsr = regs->ARM_cpsr | PSR_I_BIT;
410 #ifdef CONFIG_THUMB2_KERNEL
411 /* Set correct Thumb state in cpsr */
412 if (regs->ARM_pc & 1)
417 regs->ARM_cpsr = cpsr;
423 void __kprobes jprobe_return(void)
425 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
427 __asm__ __volatile__ (
429 * Setup an empty pt_regs. Fill SP and PC fields as
430 * they're needed by longjmp_break_handler.
432 * We allocate some slack between the original SP and start of
433 * our fabricated regs. To be precise we want to have worst case
434 * covered which is STMFD with all 16 regs so we allocate 2 *
435 * sizeof(struct_pt_regs)).
437 * This is to prevent any simulated instruction from writing
438 * over the regs when they are accessing the stack.
440 #ifdef CONFIG_THUMB2_KERNEL
441 "sub r0, %0, %1 \n\t"
444 "sub sp, %0, %1 \n\t"
446 "ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
447 "str %0, [sp, %2] \n\t"
448 "str r0, [sp, %3] \n\t"
450 "bl kprobe_handler \n\t"
453 * Return to the context saved by setjmp_pre_handler
454 * and restored by longjmp_break_handler.
456 #ifdef CONFIG_THUMB2_KERNEL
457 "ldr lr, [sp, %2] \n\t" /* lr = saved sp */
458 "ldrd r0, r1, [sp, %5] \n\t" /* r0,r1 = saved lr,pc */
459 "ldr r2, [sp, %4] \n\t" /* r2 = saved psr */
460 "stmdb lr!, {r0, r1, r2} \n\t" /* push saved lr and */
462 "ldmia sp, {r0 - r12} \n\t"
464 "ldr lr, [sp], #4 \n\t"
467 "ldr r0, [sp, %4] \n\t"
468 "msr cpsr_cxsf, r0 \n\t"
469 "ldmia sp, {r0 - pc} \n\t"
472 : "r" (kcb->jprobe_saved_regs.ARM_sp),
473 "I" (sizeof(struct pt_regs) * 2),
474 "J" (offsetof(struct pt_regs, ARM_sp)),
475 "J" (offsetof(struct pt_regs, ARM_pc)),
476 "J" (offsetof(struct pt_regs, ARM_cpsr)),
477 "J" (offsetof(struct pt_regs, ARM_lr))
481 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
483 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
484 long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
485 long orig_sp = regs->ARM_sp;
486 struct jprobe *jp = container_of(p, struct jprobe, kp);
488 if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
489 if (orig_sp != stack_addr) {
490 struct pt_regs *saved_regs =
491 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
492 printk("current sp %lx does not match saved sp %lx\n",
493 orig_sp, stack_addr);
494 printk("Saved registers for jprobe %p\n", jp);
495 show_regs(saved_regs);
496 printk("Current registers\n");
500 *regs = kcb->jprobe_saved_regs;
501 memcpy((void *)stack_addr, kcb->jprobes_stack,
502 MIN_STACK_SIZE(stack_addr));
503 preempt_enable_no_resched();
509 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
514 static struct undef_hook kprobes_break_hook = {
515 .instr_mask = 0xffffffff,
516 .instr_val = KPROBE_BREAKPOINT_INSTRUCTION,
517 .cpsr_mask = MODE_MASK,
518 .cpsr_val = SVC_MODE,
519 .fn = kprobe_trap_handler,
522 int __init arch_init_kprobes()
524 arm_kprobe_decode_init();
525 register_undef_hook(&kprobes_break_hook);