2 * Kernel Probes (KProbes)
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 * Copyright (C) IBM Corporation, 2002, 2004
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
23 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24 * interface to access function arguments.
25 * 2004-Oct Jim Keniston <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
26 * <prasanna@in.ibm.com> adapted for x86_64 from i386.
27 * 2005-Mar Roland McGrath <roland@redhat.com>
28 * Fixed to handle %rip-relative addressing mode correctly.
29 * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
30 * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
31 * <prasanna@in.ibm.com> added function-return probes.
32 * 2005-May Rusty Lynch <rusty.lynch@intel.com>
33 * Added function return probes functionality
34 * 2006-Feb Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added
35 * kprobe-booster and kretprobe-booster for i386.
36 * 2007-Dec Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster
37 * and kretprobe-booster for x86-64
38 * 2007-Dec Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven
39 * <arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com>
40 * unified x86 kprobes code.
43 #include <linux/kprobes.h>
44 #include <linux/ptrace.h>
45 #include <linux/string.h>
46 #include <linux/slab.h>
47 #include <linux/hardirq.h>
48 #include <linux/preempt.h>
49 #include <linux/module.h>
50 #include <linux/kdebug.h>
51 #include <linux/kallsyms.h>
52 #include <linux/ftrace.h>
54 #include <asm/cacheflush.h>
56 #include <asm/pgtable.h>
57 #include <asm/uaccess.h>
58 #include <asm/alternative.h>
60 #include <asm/debugreg.h>
62 void jprobe_return_end(void);
64 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
65 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
67 #define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
69 #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
70 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
71 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
72 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
73 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
76 * Undefined/reserved opcodes, conditional jump, Opcode Extension
77 * Groups, and some special opcodes can not boost.
79 static const u32 twobyte_is_boostable[256 / 32] = {
80 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
81 /* ---------------------------------------------- */
82 W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
83 W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
84 W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
85 W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
86 W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
87 W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
88 W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
89 W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
90 W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
91 W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
92 W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
93 W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
94 W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
95 W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
96 W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
97 W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
98 /* ----------------------------------------------- */
99 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
103 struct kretprobe_blackpoint kretprobe_blacklist[] = {
104 {"__switch_to", }, /* This function switches only current task, but
105 doesn't switch kernel stack.*/
106 {NULL, NULL} /* Terminator */
108 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
110 static void __kprobes __synthesize_relative_insn(void *from, void *to, u8 op)
112 struct __arch_relative_insn {
115 } __attribute__((packed)) *insn;
117 insn = (struct __arch_relative_insn *)from;
118 insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
122 /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
123 static void __kprobes synthesize_reljump(void *from, void *to)
125 __synthesize_relative_insn(from, to, RELATIVEJUMP_OPCODE);
129 * Check for the REX prefix which can only exist on X86_64
130 * X86_32 always returns 0
132 static int __kprobes is_REX_prefix(kprobe_opcode_t *insn)
135 if ((*insn & 0xf0) == 0x40)
142 * Returns non-zero if opcode is boostable.
143 * RIP relative instructions are adjusted at copying time in 64 bits mode
145 static int __kprobes can_boost(kprobe_opcode_t *opcodes)
147 kprobe_opcode_t opcode;
148 kprobe_opcode_t *orig_opcodes = opcodes;
150 if (search_exception_tables((unsigned long)opcodes))
151 return 0; /* Page fault may occur on this address. */
154 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
156 opcode = *(opcodes++);
158 /* 2nd-byte opcode */
159 if (opcode == 0x0f) {
160 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
162 return test_bit(*opcodes,
163 (unsigned long *)twobyte_is_boostable);
166 switch (opcode & 0xf0) {
169 goto retry; /* REX prefix is boostable */
172 if (0x63 < opcode && opcode < 0x67)
173 goto retry; /* prefixes */
174 /* can't boost Address-size override and bound */
175 return (opcode != 0x62 && opcode != 0x67);
177 return 0; /* can't boost conditional jump */
179 /* can't boost software-interruptions */
180 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
182 /* can boost AA* and XLAT */
183 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
185 /* can boost in/out and absolute jmps */
186 return ((opcode & 0x04) || opcode == 0xea);
188 if ((opcode & 0x0c) == 0 && opcode != 0xf1)
189 goto retry; /* lock/rep(ne) prefix */
190 /* clear and set flags are boostable */
191 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
193 /* segment override prefixes are boostable */
194 if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
195 goto retry; /* prefixes */
196 /* CS override prefix and call are not boostable */
197 return (opcode != 0x2e && opcode != 0x9a);
201 /* Recover the probed instruction at addr for further analysis. */
202 static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
205 kp = get_kprobe((void *)addr);
210 * Basically, kp->ainsn.insn has an original instruction.
211 * However, RIP-relative instruction can not do single-stepping
212 * at different place, __copy_instruction() tweaks the displacement of
213 * that instruction. In that case, we can't recover the instruction
214 * from the kp->ainsn.insn.
216 * On the other hand, kp->opcode has a copy of the first byte of
217 * the probed instruction, which is overwritten by int3. And
218 * the instruction at kp->addr is not modified by kprobes except
219 * for the first byte, we can recover the original instruction
220 * from it and kp->opcode.
222 memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
227 /* Dummy buffers for kallsyms_lookup */
228 static char __dummy_buf[KSYM_NAME_LEN];
230 /* Check if paddr is at an instruction boundary */
231 static int __kprobes can_probe(unsigned long paddr)
234 unsigned long addr, offset = 0;
236 kprobe_opcode_t buf[MAX_INSN_SIZE];
238 if (!kallsyms_lookup(paddr, NULL, &offset, NULL, __dummy_buf))
241 /* Decode instructions */
242 addr = paddr - offset;
243 while (addr < paddr) {
244 kernel_insn_init(&insn, (void *)addr);
245 insn_get_opcode(&insn);
248 * Check if the instruction has been modified by another
249 * kprobe, in which case we replace the breakpoint by the
250 * original instruction in our buffer.
252 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
253 ret = recover_probed_instruction(buf, addr);
256 * Another debugging subsystem might insert
257 * this breakpoint. In that case, we can't
261 kernel_insn_init(&insn, buf);
263 insn_get_length(&insn);
267 return (addr == paddr);
271 * Returns non-zero if opcode modifies the interrupt flag.
273 static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
278 case 0xcf: /* iret/iretd */
279 case 0x9d: /* popf/popfd */
284 * on X86_64, 0x40-0x4f are REX prefixes so we need to look
285 * at the next byte instead.. but of course not recurse infinitely
287 if (is_REX_prefix(insn))
288 return is_IF_modifier(++insn);
294 * Copy an instruction and adjust the displacement if the instruction
295 * uses the %rip-relative addressing mode.
296 * If it does, Return the address of the 32-bit displacement word.
297 * If not, return null.
298 * Only applicable to 64-bit x86.
300 static int __kprobes __copy_instruction(u8 *dest, u8 *src, int recover)
304 kprobe_opcode_t buf[MAX_INSN_SIZE];
306 kernel_insn_init(&insn, src);
308 insn_get_opcode(&insn);
309 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
310 ret = recover_probed_instruction(buf,
314 kernel_insn_init(&insn, buf);
317 insn_get_length(&insn);
318 memcpy(dest, insn.kaddr, insn.length);
321 if (insn_rip_relative(&insn)) {
324 kernel_insn_init(&insn, dest);
325 insn_get_displacement(&insn);
327 * The copied instruction uses the %rip-relative addressing
328 * mode. Adjust the displacement for the difference between
329 * the original location of this instruction and the location
330 * of the copy that will actually be run. The tricky bit here
331 * is making sure that the sign extension happens correctly in
332 * this calculation, since we need a signed 32-bit result to
333 * be sign-extended to 64 bits when it's added to the %rip
334 * value and yield the same 64-bit result that the sign-
335 * extension of the original signed 32-bit displacement would
338 newdisp = (u8 *) src + (s64) insn.displacement.value -
340 BUG_ON((s64) (s32) newdisp != newdisp); /* Sanity check. */
341 disp = (u8 *) dest + insn_offset_displacement(&insn);
342 *(s32 *) disp = (s32) newdisp;
348 static void __kprobes arch_copy_kprobe(struct kprobe *p)
351 * Copy an instruction without recovering int3, because it will be
352 * put by another subsystem.
354 __copy_instruction(p->ainsn.insn, p->addr, 0);
356 if (can_boost(p->addr))
357 p->ainsn.boostable = 0;
359 p->ainsn.boostable = -1;
361 p->opcode = *p->addr;
364 int __kprobes arch_prepare_kprobe(struct kprobe *p)
366 if (alternatives_text_reserved(p->addr, p->addr))
369 if (!can_probe((unsigned long)p->addr))
371 /* insn: must be on special executable page on x86. */
372 p->ainsn.insn = get_insn_slot();
379 void __kprobes arch_arm_kprobe(struct kprobe *p)
381 text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
384 void __kprobes arch_disarm_kprobe(struct kprobe *p)
386 text_poke(p->addr, &p->opcode, 1);
389 void __kprobes arch_remove_kprobe(struct kprobe *p)
392 free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1));
393 p->ainsn.insn = NULL;
397 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
399 kcb->prev_kprobe.kp = kprobe_running();
400 kcb->prev_kprobe.status = kcb->kprobe_status;
401 kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
402 kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
405 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
407 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
408 kcb->kprobe_status = kcb->prev_kprobe.status;
409 kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
410 kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
413 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
414 struct kprobe_ctlblk *kcb)
416 __get_cpu_var(current_kprobe) = p;
417 kcb->kprobe_saved_flags = kcb->kprobe_old_flags
418 = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
419 if (is_IF_modifier(p->ainsn.insn))
420 kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
423 static void __kprobes clear_btf(void)
425 if (test_thread_flag(TIF_DEBUGCTLMSR))
426 update_debugctlmsr(0);
429 static void __kprobes restore_btf(void)
431 if (test_thread_flag(TIF_DEBUGCTLMSR))
432 update_debugctlmsr(current->thread.debugctlmsr);
435 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
436 struct pt_regs *regs)
438 unsigned long *sara = stack_addr(regs);
440 ri->ret_addr = (kprobe_opcode_t *) *sara;
442 /* Replace the return addr with trampoline addr */
443 *sara = (unsigned long) &kretprobe_trampoline;
446 #ifdef CONFIG_OPTPROBES
447 static int __kprobes setup_detour_execution(struct kprobe *p,
448 struct pt_regs *regs,
451 #define setup_detour_execution(p, regs, reenter) (0)
454 static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
455 struct kprobe_ctlblk *kcb, int reenter)
457 if (setup_detour_execution(p, regs, reenter))
460 #if !defined(CONFIG_PREEMPT)
461 if (p->ainsn.boostable == 1 && !p->post_handler) {
462 /* Boost up -- we can execute copied instructions directly */
464 reset_current_kprobe();
466 * Reentering boosted probe doesn't reset current_kprobe,
467 * nor set current_kprobe, because it doesn't use single
470 regs->ip = (unsigned long)p->ainsn.insn;
471 preempt_enable_no_resched();
476 save_previous_kprobe(kcb);
477 set_current_kprobe(p, regs, kcb);
478 kcb->kprobe_status = KPROBE_REENTER;
480 kcb->kprobe_status = KPROBE_HIT_SS;
481 /* Prepare real single stepping */
483 regs->flags |= X86_EFLAGS_TF;
484 regs->flags &= ~X86_EFLAGS_IF;
485 /* single step inline if the instruction is an int3 */
486 if (p->opcode == BREAKPOINT_INSTRUCTION)
487 regs->ip = (unsigned long)p->addr;
489 regs->ip = (unsigned long)p->ainsn.insn;
493 * We have reentered the kprobe_handler(), since another probe was hit while
494 * within the handler. We save the original kprobes variables and just single
495 * step on the instruction of the new probe without calling any user handlers.
497 static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
498 struct kprobe_ctlblk *kcb)
500 switch (kcb->kprobe_status) {
501 case KPROBE_HIT_SSDONE:
502 case KPROBE_HIT_ACTIVE:
503 kprobes_inc_nmissed_count(p);
504 setup_singlestep(p, regs, kcb, 1);
507 /* A probe has been hit in the codepath leading up to, or just
508 * after, single-stepping of a probed instruction. This entire
509 * codepath should strictly reside in .kprobes.text section.
510 * Raise a BUG or we'll continue in an endless reentering loop
511 * and eventually a stack overflow.
513 printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n",
518 /* impossible cases */
527 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
528 * remain disabled throughout this function.
530 static int __kprobes kprobe_handler(struct pt_regs *regs)
532 kprobe_opcode_t *addr;
534 struct kprobe_ctlblk *kcb;
536 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
538 * We don't want to be preempted for the entire
539 * duration of kprobe processing. We conditionally
540 * re-enable preemption at the end of this function,
541 * and also in reenter_kprobe() and setup_singlestep().
545 kcb = get_kprobe_ctlblk();
546 p = get_kprobe(addr);
549 if (kprobe_running()) {
550 if (reenter_kprobe(p, regs, kcb))
553 set_current_kprobe(p, regs, kcb);
554 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
557 * If we have no pre-handler or it returned 0, we
558 * continue with normal processing. If we have a
559 * pre-handler and it returned non-zero, it prepped
560 * for calling the break_handler below on re-entry
561 * for jprobe processing, so get out doing nothing
564 if (!p->pre_handler || !p->pre_handler(p, regs))
565 setup_singlestep(p, regs, kcb, 0);
568 } else if (*addr != BREAKPOINT_INSTRUCTION) {
570 * The breakpoint instruction was removed right
571 * after we hit it. Another cpu has removed
572 * either a probepoint or a debugger breakpoint
573 * at this address. In either case, no further
574 * handling of this interrupt is appropriate.
575 * Back up over the (now missing) int3 and run
576 * the original instruction.
578 regs->ip = (unsigned long)addr;
579 preempt_enable_no_resched();
581 } else if (kprobe_running()) {
582 p = __get_cpu_var(current_kprobe);
583 if (p->break_handler && p->break_handler(p, regs)) {
584 setup_singlestep(p, regs, kcb, 0);
587 } /* else: not a kprobe fault; let the kernel handle it */
589 preempt_enable_no_resched();
594 #define SAVE_REGS_STRING \
595 /* Skip cs, ip, orig_ax. */ \
596 " subq $24, %rsp\n" \
612 #define RESTORE_REGS_STRING \
628 /* Skip orig_ax, ip, cs */ \
631 #define SAVE_REGS_STRING \
632 /* Skip cs, ip, orig_ax and gs. */ \
633 " subl $16, %esp\n" \
644 #define RESTORE_REGS_STRING \
652 /* Skip ds, es, fs, gs, orig_ax, and ip. Note: don't pop cs here*/\
657 * When a retprobed function returns, this code saves registers and
658 * calls trampoline_handler() runs, which calls the kretprobe's handler.
660 static void __used __kprobes kretprobe_trampoline_holder(void)
663 ".global kretprobe_trampoline\n"
664 "kretprobe_trampoline: \n"
666 /* We don't bother saving the ss register */
671 " call trampoline_handler\n"
672 /* Replace saved sp with true return address. */
673 " movq %rax, 152(%rsp)\n"
680 " call trampoline_handler\n"
681 /* Move flags to cs */
682 " movl 56(%esp), %edx\n"
683 " movl %edx, 52(%esp)\n"
684 /* Replace saved flags with true return address. */
685 " movl %eax, 56(%esp)\n"
693 * Called from kretprobe_trampoline
695 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
697 struct kretprobe_instance *ri = NULL;
698 struct hlist_head *head, empty_rp;
699 struct hlist_node *node, *tmp;
700 unsigned long flags, orig_ret_address = 0;
701 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
703 INIT_HLIST_HEAD(&empty_rp);
704 kretprobe_hash_lock(current, &head, &flags);
705 /* fixup registers */
707 regs->cs = __KERNEL_CS;
709 regs->cs = __KERNEL_CS | get_kernel_rpl();
712 regs->ip = trampoline_address;
713 regs->orig_ax = ~0UL;
716 * It is possible to have multiple instances associated with a given
717 * task either because multiple functions in the call path have
718 * return probes installed on them, and/or more than one
719 * return probe was registered for a target function.
721 * We can handle this because:
722 * - instances are always pushed into the head of the list
723 * - when multiple return probes are registered for the same
724 * function, the (chronologically) first instance's ret_addr
725 * will be the real return address, and all the rest will
726 * point to kretprobe_trampoline.
728 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
729 if (ri->task != current)
730 /* another task is sharing our hash bucket */
733 if (ri->rp && ri->rp->handler) {
734 __get_cpu_var(current_kprobe) = &ri->rp->kp;
735 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
736 ri->rp->handler(ri, regs);
737 __get_cpu_var(current_kprobe) = NULL;
740 orig_ret_address = (unsigned long)ri->ret_addr;
741 recycle_rp_inst(ri, &empty_rp);
743 if (orig_ret_address != trampoline_address)
745 * This is the real return address. Any other
746 * instances associated with this task are for
747 * other calls deeper on the call stack
752 kretprobe_assert(ri, orig_ret_address, trampoline_address);
754 kretprobe_hash_unlock(current, &flags);
756 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
757 hlist_del(&ri->hlist);
760 return (void *)orig_ret_address;
764 * Called after single-stepping. p->addr is the address of the
765 * instruction whose first byte has been replaced by the "int 3"
766 * instruction. To avoid the SMP problems that can occur when we
767 * temporarily put back the original opcode to single-step, we
768 * single-stepped a copy of the instruction. The address of this
769 * copy is p->ainsn.insn.
771 * This function prepares to return from the post-single-step
772 * interrupt. We have to fix up the stack as follows:
774 * 0) Except in the case of absolute or indirect jump or call instructions,
775 * the new ip is relative to the copied instruction. We need to make
776 * it relative to the original instruction.
778 * 1) If the single-stepped instruction was pushfl, then the TF and IF
779 * flags are set in the just-pushed flags, and may need to be cleared.
781 * 2) If the single-stepped instruction was a call, the return address
782 * that is atop the stack is the address following the copied instruction.
783 * We need to make it the address following the original instruction.
785 * If this is the first time we've single-stepped the instruction at
786 * this probepoint, and the instruction is boostable, boost it: add a
787 * jump instruction after the copied instruction, that jumps to the next
788 * instruction after the probepoint.
790 static void __kprobes resume_execution(struct kprobe *p,
791 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
793 unsigned long *tos = stack_addr(regs);
794 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
795 unsigned long orig_ip = (unsigned long)p->addr;
796 kprobe_opcode_t *insn = p->ainsn.insn;
798 /*skip the REX prefix*/
799 if (is_REX_prefix(insn))
802 regs->flags &= ~X86_EFLAGS_TF;
804 case 0x9c: /* pushfl */
805 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
806 *tos |= kcb->kprobe_old_flags;
808 case 0xc2: /* iret/ret/lret */
813 case 0xea: /* jmp absolute -- ip is correct */
814 /* ip is already adjusted, no more changes required */
815 p->ainsn.boostable = 1;
817 case 0xe8: /* call relative - Fix return addr */
818 *tos = orig_ip + (*tos - copy_ip);
821 case 0x9a: /* call absolute -- same as call absolute, indirect */
822 *tos = orig_ip + (*tos - copy_ip);
826 if ((insn[1] & 0x30) == 0x10) {
828 * call absolute, indirect
829 * Fix return addr; ip is correct.
830 * But this is not boostable
832 *tos = orig_ip + (*tos - copy_ip);
834 } else if (((insn[1] & 0x31) == 0x20) ||
835 ((insn[1] & 0x31) == 0x21)) {
837 * jmp near and far, absolute indirect
838 * ip is correct. And this is boostable
840 p->ainsn.boostable = 1;
847 if (p->ainsn.boostable == 0) {
848 if ((regs->ip > copy_ip) &&
849 (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
851 * These instructions can be executed directly if it
852 * jumps back to correct address.
854 synthesize_reljump((void *)regs->ip,
855 (void *)orig_ip + (regs->ip - copy_ip));
856 p->ainsn.boostable = 1;
858 p->ainsn.boostable = -1;
862 regs->ip += orig_ip - copy_ip;
869 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
870 * remain disabled throughout this function.
872 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
874 struct kprobe *cur = kprobe_running();
875 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
880 resume_execution(cur, regs, kcb);
881 regs->flags |= kcb->kprobe_saved_flags;
883 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
884 kcb->kprobe_status = KPROBE_HIT_SSDONE;
885 cur->post_handler(cur, regs, 0);
888 /* Restore back the original saved kprobes variables and continue. */
889 if (kcb->kprobe_status == KPROBE_REENTER) {
890 restore_previous_kprobe(kcb);
893 reset_current_kprobe();
895 preempt_enable_no_resched();
898 * if somebody else is singlestepping across a probe point, flags
899 * will have TF set, in which case, continue the remaining processing
900 * of do_debug, as if this is not a probe hit.
902 if (regs->flags & X86_EFLAGS_TF)
908 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
910 struct kprobe *cur = kprobe_running();
911 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
913 switch (kcb->kprobe_status) {
917 * We are here because the instruction being single
918 * stepped caused a page fault. We reset the current
919 * kprobe and the ip points back to the probe address
920 * and allow the page fault handler to continue as a
923 regs->ip = (unsigned long)cur->addr;
924 regs->flags |= kcb->kprobe_old_flags;
925 if (kcb->kprobe_status == KPROBE_REENTER)
926 restore_previous_kprobe(kcb);
928 reset_current_kprobe();
929 preempt_enable_no_resched();
931 case KPROBE_HIT_ACTIVE:
932 case KPROBE_HIT_SSDONE:
934 * We increment the nmissed count for accounting,
935 * we can also use npre/npostfault count for accounting
936 * these specific fault cases.
938 kprobes_inc_nmissed_count(cur);
941 * We come here because instructions in the pre/post
942 * handler caused the page_fault, this could happen
943 * if handler tries to access user space by
944 * copy_from_user(), get_user() etc. Let the
945 * user-specified handler try to fix it first.
947 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
951 * In case the user-specified fault handler returned
952 * zero, try to fix up.
954 if (fixup_exception(regs))
958 * fixup routine could not handle it,
959 * Let do_page_fault() fix it.
969 * Wrapper routine for handling exceptions.
971 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
972 unsigned long val, void *data)
974 struct die_args *args = data;
975 int ret = NOTIFY_DONE;
977 if (args->regs && user_mode_vm(args->regs))
982 if (kprobe_handler(args->regs))
986 if (post_kprobe_handler(args->regs)) {
988 * Reset the BS bit in dr6 (pointed by args->err) to
989 * denote completion of processing
991 (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
997 * To be potentially processing a kprobe fault and to
998 * trust the result from kprobe_running(), we have
999 * be non-preemptible.
1001 if (!preemptible() && kprobe_running() &&
1002 kprobe_fault_handler(args->regs, args->trapnr))
1011 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
1013 struct jprobe *jp = container_of(p, struct jprobe, kp);
1015 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1017 kcb->jprobe_saved_regs = *regs;
1018 kcb->jprobe_saved_sp = stack_addr(regs);
1019 addr = (unsigned long)(kcb->jprobe_saved_sp);
1022 * As Linus pointed out, gcc assumes that the callee
1023 * owns the argument space and could overwrite it, e.g.
1024 * tailcall optimization. So, to be absolutely safe
1025 * we also save and restore enough stack bytes to cover
1026 * the argument area.
1028 memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
1029 MIN_STACK_SIZE(addr));
1030 regs->flags &= ~X86_EFLAGS_IF;
1031 trace_hardirqs_off();
1032 regs->ip = (unsigned long)(jp->entry);
1036 void __kprobes jprobe_return(void)
1038 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1041 #ifdef CONFIG_X86_64
1042 " xchg %%rbx,%%rsp \n"
1044 " xchgl %%ebx,%%esp \n"
1047 " .globl jprobe_return_end\n"
1048 " jprobe_return_end: \n"
1050 (kcb->jprobe_saved_sp):"memory");
1053 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
1055 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1056 u8 *addr = (u8 *) (regs->ip - 1);
1057 struct jprobe *jp = container_of(p, struct jprobe, kp);
1059 if ((addr > (u8 *) jprobe_return) &&
1060 (addr < (u8 *) jprobe_return_end)) {
1061 if (stack_addr(regs) != kcb->jprobe_saved_sp) {
1062 struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
1064 "current sp %p does not match saved sp %p\n",
1065 stack_addr(regs), kcb->jprobe_saved_sp);
1066 printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
1067 show_registers(saved_regs);
1068 printk(KERN_ERR "Current registers\n");
1069 show_registers(regs);
1072 *regs = kcb->jprobe_saved_regs;
1073 memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp),
1075 MIN_STACK_SIZE(kcb->jprobe_saved_sp));
1076 preempt_enable_no_resched();
1083 #ifdef CONFIG_OPTPROBES
1085 /* Insert a call instruction at address 'from', which calls address 'to'.*/
1086 static void __kprobes synthesize_relcall(void *from, void *to)
1088 __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE);
1091 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
1092 static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr,
1095 #ifdef CONFIG_X86_64
1101 *(unsigned long *)addr = val;
1104 void __kprobes kprobes_optinsn_template_holder(void)
1107 ".global optprobe_template_entry\n"
1108 "optprobe_template_entry: \n"
1109 #ifdef CONFIG_X86_64
1110 /* We don't bother saving the ss register */
1114 " movq %rsp, %rsi\n"
1115 ".global optprobe_template_val\n"
1116 "optprobe_template_val: \n"
1119 ".global optprobe_template_call\n"
1120 "optprobe_template_call: \n"
1122 /* Move flags to rsp */
1123 " movq 144(%rsp), %rdx\n"
1124 " movq %rdx, 152(%rsp)\n"
1126 /* Skip flags entry */
1129 #else /* CONFIG_X86_32 */
1132 " movl %esp, %edx\n"
1133 ".global optprobe_template_val\n"
1134 "optprobe_template_val: \n"
1136 ".global optprobe_template_call\n"
1137 "optprobe_template_call: \n"
1140 " addl $4, %esp\n" /* skip cs */
1143 ".global optprobe_template_end\n"
1144 "optprobe_template_end: \n");
1147 #define TMPL_MOVE_IDX \
1148 ((long)&optprobe_template_val - (long)&optprobe_template_entry)
1149 #define TMPL_CALL_IDX \
1150 ((long)&optprobe_template_call - (long)&optprobe_template_entry)
1151 #define TMPL_END_IDX \
1152 ((long)&optprobe_template_end - (long)&optprobe_template_entry)
1154 #define INT3_SIZE sizeof(kprobe_opcode_t)
1156 /* Optimized kprobe call back function: called from optinsn */
1157 static void __kprobes optimized_callback(struct optimized_kprobe *op,
1158 struct pt_regs *regs)
1160 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1163 if (kprobe_running()) {
1164 kprobes_inc_nmissed_count(&op->kp);
1166 /* Save skipped registers */
1167 #ifdef CONFIG_X86_64
1168 regs->cs = __KERNEL_CS;
1170 regs->cs = __KERNEL_CS | get_kernel_rpl();
1173 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
1174 regs->orig_ax = ~0UL;
1176 __get_cpu_var(current_kprobe) = &op->kp;
1177 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
1178 opt_pre_handler(&op->kp, regs);
1179 __get_cpu_var(current_kprobe) = NULL;
1181 preempt_enable_no_resched();
1184 static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
1188 while (len < RELATIVEJUMP_SIZE) {
1189 ret = __copy_instruction(dest + len, src + len, 1);
1190 if (!ret || !can_boost(dest + len))
1194 /* Check whether the address range is reserved */
1195 if (ftrace_text_reserved(src, src + len - 1) ||
1196 alternatives_text_reserved(src, src + len - 1))
1202 /* Check whether insn is indirect jump */
1203 static int __kprobes insn_is_indirect_jump(struct insn *insn)
1205 return ((insn->opcode.bytes[0] == 0xff &&
1206 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
1207 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
1210 /* Check whether insn jumps into specified address range */
1211 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
1213 unsigned long target = 0;
1215 switch (insn->opcode.bytes[0]) {
1216 case 0xe0: /* loopne */
1217 case 0xe1: /* loope */
1218 case 0xe2: /* loop */
1219 case 0xe3: /* jcxz */
1220 case 0xe9: /* near relative jump */
1221 case 0xeb: /* short relative jump */
1224 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
1228 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
1232 target = (unsigned long)insn->next_byte + insn->immediate.value;
1234 return (start <= target && target <= start + len);
1237 /* Decode whole function to ensure any instructions don't jump into target */
1238 static int __kprobes can_optimize(unsigned long paddr)
1241 unsigned long addr, size = 0, offset = 0;
1243 kprobe_opcode_t buf[MAX_INSN_SIZE];
1244 /* Dummy buffers for lookup_symbol_attrs */
1245 static char __dummy_buf[KSYM_NAME_LEN];
1247 /* Lookup symbol including addr */
1248 if (!kallsyms_lookup(paddr, &size, &offset, NULL, __dummy_buf))
1251 /* Check there is enough space for a relative jump. */
1252 if (size - offset < RELATIVEJUMP_SIZE)
1255 /* Decode instructions */
1256 addr = paddr - offset;
1257 while (addr < paddr - offset + size) { /* Decode until function end */
1258 if (search_exception_tables(addr))
1260 * Since some fixup code will jumps into this function,
1261 * we can't optimize kprobe in this function.
1264 kernel_insn_init(&insn, (void *)addr);
1265 insn_get_opcode(&insn);
1266 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
1267 ret = recover_probed_instruction(buf, addr);
1270 kernel_insn_init(&insn, buf);
1272 insn_get_length(&insn);
1273 /* Recover address */
1274 insn.kaddr = (void *)addr;
1275 insn.next_byte = (void *)(addr + insn.length);
1276 /* Check any instructions don't jump into target */
1277 if (insn_is_indirect_jump(&insn) ||
1278 insn_jump_into_range(&insn, paddr + INT3_SIZE,
1279 RELATIVE_ADDR_SIZE))
1281 addr += insn.length;
1287 /* Check optimized_kprobe can actually be optimized. */
1288 int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
1293 for (i = 1; i < op->optinsn.size; i++) {
1294 p = get_kprobe(op->kp.addr + i);
1295 if (p && !kprobe_disabled(p))
1302 /* Check the addr is within the optimized instructions. */
1303 int __kprobes arch_within_optimized_kprobe(struct optimized_kprobe *op,
1306 return ((unsigned long)op->kp.addr <= addr &&
1307 (unsigned long)op->kp.addr + op->optinsn.size > addr);
1310 /* Free optimized instruction slot */
1312 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
1314 if (op->optinsn.insn) {
1315 free_optinsn_slot(op->optinsn.insn, dirty);
1316 op->optinsn.insn = NULL;
1317 op->optinsn.size = 0;
1321 void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)
1323 __arch_remove_optimized_kprobe(op, 1);
1327 * Copy replacing target instructions
1328 * Target instructions MUST be relocatable (checked inside)
1330 int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
1336 if (!can_optimize((unsigned long)op->kp.addr))
1339 op->optinsn.insn = get_optinsn_slot();
1340 if (!op->optinsn.insn)
1344 * Verify if the address gap is in 2GB range, because this uses
1347 rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
1348 if (abs(rel) > 0x7fffffff)
1351 buf = (u8 *)op->optinsn.insn;
1353 /* Copy instructions into the out-of-line buffer */
1354 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
1356 __arch_remove_optimized_kprobe(op, 0);
1359 op->optinsn.size = ret;
1361 /* Copy arch-dep-instance from template */
1362 memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
1364 /* Set probe information */
1365 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
1367 /* Set probe function call */
1368 synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
1370 /* Set returning jmp instruction at the tail of out-of-line buffer */
1371 synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
1372 (u8 *)op->kp.addr + op->optinsn.size);
1374 flush_icache_range((unsigned long) buf,
1375 (unsigned long) buf + TMPL_END_IDX +
1376 op->optinsn.size + RELATIVEJUMP_SIZE);
1380 /* Replace a breakpoint (int3) with a relative jump. */
1381 int __kprobes arch_optimize_kprobe(struct optimized_kprobe *op)
1383 unsigned char jmp_code[RELATIVEJUMP_SIZE];
1384 s32 rel = (s32)((long)op->optinsn.insn -
1385 ((long)op->kp.addr + RELATIVEJUMP_SIZE));
1387 /* Backup instructions which will be replaced by jump address */
1388 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
1389 RELATIVE_ADDR_SIZE);
1391 jmp_code[0] = RELATIVEJUMP_OPCODE;
1392 *(s32 *)(&jmp_code[1]) = rel;
1395 * text_poke_smp doesn't support NMI/MCE code modifying.
1396 * However, since kprobes itself also doesn't support NMI/MCE
1397 * code probing, it's not a problem.
1399 text_poke_smp(op->kp.addr, jmp_code, RELATIVEJUMP_SIZE);
1403 /* Replace a relative jump with a breakpoint (int3). */
1404 void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
1406 u8 buf[RELATIVEJUMP_SIZE];
1408 /* Set int3 to first byte for kprobes */
1409 buf[0] = BREAKPOINT_INSTRUCTION;
1410 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
1411 text_poke_smp(op->kp.addr, buf, RELATIVEJUMP_SIZE);
1414 static int __kprobes setup_detour_execution(struct kprobe *p,
1415 struct pt_regs *regs,
1418 struct optimized_kprobe *op;
1420 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
1421 /* This kprobe is really able to run optimized path. */
1422 op = container_of(p, struct optimized_kprobe, kp);
1423 /* Detour through copied instructions */
1424 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
1426 reset_current_kprobe();
1427 preempt_enable_no_resched();
1434 int __init arch_init_kprobes(void)
1439 int __kprobes arch_trampoline_kprobe(struct kprobe *p)