2 * Kernel Probes (KProbes)
3 * arch/mips/kernel/kprobes.c
5 * Copyright 2006 Sony Corp.
6 * Copyright 2010 Cavium Networks
8 * Some portions copied from the powerpc version.
10 * Copyright (C) IBM Corporation, 2002, 2004
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; version 2 of the License.
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
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26 #include <linux/kprobes.h>
27 #include <linux/preempt.h>
28 #include <linux/uaccess.h>
29 #include <linux/kdebug.h>
30 #include <linux/slab.h>
32 #include <asm/ptrace.h>
33 #include <asm/branch.h>
34 #include <asm/break.h>
37 static const union mips_instruction breakpoint_insn = {
40 .code = BRK_KPROBE_BP,
45 static const union mips_instruction breakpoint2_insn = {
48 .code = BRK_KPROBE_SSTEPBP,
53 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
54 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
56 static int __kprobes insn_has_delayslot(union mips_instruction insn)
58 switch (insn.i_format.opcode) {
61 * This group contains:
62 * jr and jalr are in r_format format.
65 switch (insn.r_format.func) {
74 * This group contains:
75 * bltz_op, bgez_op, bltzl_op, bgezl_op,
76 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
81 * These are unconditional and in j_format.
87 * These are conditional and in i_format.
99 * These are the FPA/cp1 branch instructions.
103 #ifdef CONFIG_CPU_CAVIUM_OCTEON
104 case lwc2_op: /* This is bbit0 on Octeon */
105 case ldc2_op: /* This is bbit032 on Octeon */
106 case swc2_op: /* This is bbit1 on Octeon */
107 case sdc2_op: /* This is bbit132 on Octeon */
118 * insn_has_ll_or_sc function checks whether instruction is ll or sc
119 * one; putting breakpoint on top of atomic ll/sc pair is bad idea;
120 * so we need to prevent it and refuse kprobes insertion for such
121 * instructions; cannot do much about breakpoint in the middle of
122 * ll/sc pair; it is upto user to avoid those places
124 static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)
128 switch (insn.i_format.opcode) {
141 int __kprobes arch_prepare_kprobe(struct kprobe *p)
143 union mips_instruction insn;
144 union mips_instruction prev_insn;
149 if (insn_has_ll_or_sc(insn)) {
150 pr_notice("Kprobes for ll and sc instructions are not"
156 if ((probe_kernel_read(&prev_insn, p->addr - 1,
157 sizeof(mips_instruction)) == 0) &&
158 insn_has_delayslot(prev_insn)) {
159 pr_notice("Kprobes for branch delayslot are not supported\n");
164 /* insn: must be on special executable page on mips. */
165 p->ainsn.insn = get_insn_slot();
166 if (!p->ainsn.insn) {
172 * In the kprobe->ainsn.insn[] array we store the original
173 * instruction at index zero and a break trap instruction at
176 * On MIPS arch if the instruction at probed address is a
177 * branch instruction, we need to execute the instruction at
178 * Branch Delayslot (BD) at the time of probe hit. As MIPS also
179 * doesn't have single stepping support, the BD instruction can
180 * not be executed in-line and it would be executed on SSOL slot
181 * using a normal breakpoint instruction in the next slot.
182 * So, read the instruction and save it for later execution.
184 if (insn_has_delayslot(insn))
185 memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t));
187 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
189 p->ainsn.insn[1] = breakpoint2_insn;
190 p->opcode = *p->addr;
196 void __kprobes arch_arm_kprobe(struct kprobe *p)
198 *p->addr = breakpoint_insn;
202 void __kprobes arch_disarm_kprobe(struct kprobe *p)
204 *p->addr = p->opcode;
208 void __kprobes arch_remove_kprobe(struct kprobe *p)
210 free_insn_slot(p->ainsn.insn, 0);
213 static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
215 kcb->prev_kprobe.kp = kprobe_running();
216 kcb->prev_kprobe.status = kcb->kprobe_status;
217 kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
218 kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
219 kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
222 static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
224 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
225 kcb->kprobe_status = kcb->prev_kprobe.status;
226 kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
227 kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
228 kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
231 static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
232 struct kprobe_ctlblk *kcb)
234 __get_cpu_var(current_kprobe) = p;
235 kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
236 kcb->kprobe_saved_epc = regs->cp0_epc;
240 * evaluate_branch_instrucion -
242 * Evaluate the branch instruction at probed address during probe hit. The
243 * result of evaluation would be the updated epc. The insturction in delayslot
244 * would actually be single stepped using a normal breakpoint) on SSOL slot.
246 * The result is also saved in the kprobe control block for later use,
247 * in case we need to execute the delayslot instruction. The latter will be
248 * false for NOP instruction in dealyslot and the branch-likely instructions
249 * when the branch is taken. And for those cases we set a flag as
250 * SKIP_DELAYSLOT in the kprobe control block
252 static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs,
253 struct kprobe_ctlblk *kcb)
255 union mips_instruction insn = p->opcode;
263 if (p->ainsn.insn->word == 0)
264 kcb->flags |= SKIP_DELAYSLOT;
266 kcb->flags &= ~SKIP_DELAYSLOT;
268 ret = __compute_return_epc_for_insn(regs, insn);
272 if (ret == BRANCH_LIKELY_TAKEN)
273 kcb->flags |= SKIP_DELAYSLOT;
275 kcb->target_epc = regs->cp0_epc;
280 pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm);
281 force_sig(SIGBUS, current);
286 static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
287 struct kprobe_ctlblk *kcb)
291 regs->cp0_status &= ~ST0_IE;
293 /* single step inline if the instruction is a break */
294 if (p->opcode.word == breakpoint_insn.word ||
295 p->opcode.word == breakpoint2_insn.word)
296 regs->cp0_epc = (unsigned long)p->addr;
297 else if (insn_has_delayslot(p->opcode)) {
298 ret = evaluate_branch_instruction(p, regs, kcb);
300 pr_notice("Kprobes: Error in evaluating branch\n");
304 regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
308 * Called after single-stepping. p->addr is the address of the
309 * instruction whose first byte has been replaced by the "break 0"
310 * instruction. To avoid the SMP problems that can occur when we
311 * temporarily put back the original opcode to single-step, we
312 * single-stepped a copy of the instruction. The address of this
313 * copy is p->ainsn.insn.
315 * This function prepares to return from the post-single-step
316 * breakpoint trap. In case of branch instructions, the target
317 * epc to be restored.
319 static void __kprobes resume_execution(struct kprobe *p,
320 struct pt_regs *regs,
321 struct kprobe_ctlblk *kcb)
323 if (insn_has_delayslot(p->opcode))
324 regs->cp0_epc = kcb->target_epc;
326 unsigned long orig_epc = kcb->kprobe_saved_epc;
327 regs->cp0_epc = orig_epc + 4;
331 static int __kprobes kprobe_handler(struct pt_regs *regs)
335 kprobe_opcode_t *addr;
336 struct kprobe_ctlblk *kcb;
338 addr = (kprobe_opcode_t *) regs->cp0_epc;
341 * We don't want to be preempted for the entire
342 * duration of kprobe processing
345 kcb = get_kprobe_ctlblk();
347 /* Check we're not actually recursing */
348 if (kprobe_running()) {
349 p = get_kprobe(addr);
351 if (kcb->kprobe_status == KPROBE_HIT_SS &&
352 p->ainsn.insn->word == breakpoint_insn.word) {
353 regs->cp0_status &= ~ST0_IE;
354 regs->cp0_status |= kcb->kprobe_saved_SR;
358 * We have reentered the kprobe_handler(), since
359 * another probe was hit while within the handler.
360 * We here save the original kprobes variables and
361 * just single step on the instruction of the new probe
362 * without calling any user handlers.
364 save_previous_kprobe(kcb);
365 set_current_kprobe(p, regs, kcb);
366 kprobes_inc_nmissed_count(p);
367 prepare_singlestep(p, regs, kcb);
368 kcb->kprobe_status = KPROBE_REENTER;
369 if (kcb->flags & SKIP_DELAYSLOT) {
370 resume_execution(p, regs, kcb);
371 restore_previous_kprobe(kcb);
372 preempt_enable_no_resched();
376 if (addr->word != breakpoint_insn.word) {
378 * The breakpoint instruction was removed by
379 * another cpu right after we hit, no further
380 * handling of this interrupt is appropriate
385 p = __get_cpu_var(current_kprobe);
386 if (p->break_handler && p->break_handler(p, regs))
392 p = get_kprobe(addr);
394 if (addr->word != breakpoint_insn.word) {
396 * The breakpoint instruction was removed right
397 * after we hit it. Another cpu has removed
398 * either a probepoint or a debugger breakpoint
399 * at this address. In either case, no further
400 * handling of this interrupt is appropriate.
404 /* Not one of ours: let kernel handle it */
408 set_current_kprobe(p, regs, kcb);
409 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
411 if (p->pre_handler && p->pre_handler(p, regs)) {
412 /* handler has already set things up, so skip ss setup */
417 prepare_singlestep(p, regs, kcb);
418 if (kcb->flags & SKIP_DELAYSLOT) {
419 kcb->kprobe_status = KPROBE_HIT_SSDONE;
421 p->post_handler(p, regs, 0);
422 resume_execution(p, regs, kcb);
423 preempt_enable_no_resched();
425 kcb->kprobe_status = KPROBE_HIT_SS;
430 preempt_enable_no_resched();
435 static inline int post_kprobe_handler(struct pt_regs *regs)
437 struct kprobe *cur = kprobe_running();
438 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
443 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
444 kcb->kprobe_status = KPROBE_HIT_SSDONE;
445 cur->post_handler(cur, regs, 0);
448 resume_execution(cur, regs, kcb);
450 regs->cp0_status |= kcb->kprobe_saved_SR;
452 /* Restore back the original saved kprobes variables and continue. */
453 if (kcb->kprobe_status == KPROBE_REENTER) {
454 restore_previous_kprobe(kcb);
457 reset_current_kprobe();
459 preempt_enable_no_resched();
464 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
466 struct kprobe *cur = kprobe_running();
467 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
469 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
472 if (kcb->kprobe_status & KPROBE_HIT_SS) {
473 resume_execution(cur, regs, kcb);
474 regs->cp0_status |= kcb->kprobe_old_SR;
476 reset_current_kprobe();
477 preempt_enable_no_resched();
483 * Wrapper routine for handling exceptions.
485 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
486 unsigned long val, void *data)
489 struct die_args *args = (struct die_args *)data;
490 int ret = NOTIFY_DONE;
494 if (kprobe_handler(args->regs))
498 if (post_kprobe_handler(args->regs))
503 /* kprobe_running() needs smp_processor_id() */
507 && kprobe_fault_handler(args->regs, args->trapnr))
517 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
519 struct jprobe *jp = container_of(p, struct jprobe, kp);
520 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
522 kcb->jprobe_saved_regs = *regs;
523 kcb->jprobe_saved_sp = regs->regs[29];
525 memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
526 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
528 regs->cp0_epc = (unsigned long)(jp->entry);
533 /* Defined in the inline asm below. */
534 void jprobe_return_end(void);
536 void __kprobes jprobe_return(void)
538 /* Assembler quirk necessitates this '0,code' business. */
541 ".globl jprobe_return_end\n"
542 "jprobe_return_end:\n"
543 : : "n" (BRK_KPROBE_BP) : "memory");
546 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
548 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
550 if (regs->cp0_epc >= (unsigned long)jprobe_return &&
551 regs->cp0_epc <= (unsigned long)jprobe_return_end) {
552 *regs = kcb->jprobe_saved_regs;
553 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
554 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
555 preempt_enable_no_resched();
563 * Function return probe trampoline:
564 * - init_kprobes() establishes a probepoint here
565 * - When the probed function returns, this probe causes the
568 static void __used kretprobe_trampoline_holder(void)
572 /* Keep the assembler from reordering and placing JR here. */
575 ".global kretprobe_trampoline\n"
576 "kretprobe_trampoline:\n\t"
582 void kretprobe_trampoline(void);
584 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
585 struct pt_regs *regs)
587 ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
589 /* Replace the return addr with trampoline addr */
590 regs->regs[31] = (unsigned long)kretprobe_trampoline;
594 * Called when the probe at kretprobe trampoline is hit
596 static int __kprobes trampoline_probe_handler(struct kprobe *p,
597 struct pt_regs *regs)
599 struct kretprobe_instance *ri = NULL;
600 struct hlist_head *head, empty_rp;
601 struct hlist_node *node, *tmp;
602 unsigned long flags, orig_ret_address = 0;
603 unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
605 INIT_HLIST_HEAD(&empty_rp);
606 kretprobe_hash_lock(current, &head, &flags);
609 * It is possible to have multiple instances associated with a given
610 * task either because an multiple functions in the call path
611 * have a return probe installed on them, and/or more than one return
612 * return probe was registered for a target function.
614 * We can handle this because:
615 * - instances are always inserted at the head of the list
616 * - when multiple return probes are registered for the same
617 * function, the first instance's ret_addr will point to the
618 * real return address, and all the rest will point to
619 * kretprobe_trampoline
621 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
622 if (ri->task != current)
623 /* another task is sharing our hash bucket */
626 if (ri->rp && ri->rp->handler)
627 ri->rp->handler(ri, regs);
629 orig_ret_address = (unsigned long)ri->ret_addr;
630 recycle_rp_inst(ri, &empty_rp);
632 if (orig_ret_address != trampoline_address)
634 * This is the real return address. Any other
635 * instances associated with this task are for
636 * other calls deeper on the call stack
641 kretprobe_assert(ri, orig_ret_address, trampoline_address);
642 instruction_pointer(regs) = orig_ret_address;
644 reset_current_kprobe();
645 kretprobe_hash_unlock(current, &flags);
646 preempt_enable_no_resched();
648 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
649 hlist_del(&ri->hlist);
653 * By returning a non-zero value, we are telling
654 * kprobe_handler() that we don't want the post_handler
655 * to run (and have re-enabled preemption)
660 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
662 if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
668 static struct kprobe trampoline_p = {
669 .addr = (kprobe_opcode_t *)kretprobe_trampoline,
670 .pre_handler = trampoline_probe_handler
673 int __init arch_init_kprobes(void)
675 return register_kprobe(&trampoline_p);