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.
42 #include <linux/kprobes.h>
43 #include <linux/ptrace.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/hardirq.h>
47 #include <linux/preempt.h>
48 #include <linux/sched/debug.h>
49 #include <linux/extable.h>
50 #include <linux/kdebug.h>
51 #include <linux/kallsyms.h>
52 #include <linux/ftrace.h>
53 #include <linux/frame.h>
54 #include <linux/kasan.h>
56 #include <asm/text-patching.h>
57 #include <asm/cacheflush.h>
59 #include <asm/pgtable.h>
60 #include <linux/uaccess.h>
61 #include <asm/alternative.h>
63 #include <asm/debugreg.h>
67 void jprobe_return_end(void);
69 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
70 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
72 #define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs))
74 #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
75 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
76 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
77 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
78 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
81 * Undefined/reserved opcodes, conditional jump, Opcode Extension
82 * Groups, and some special opcodes can not boost.
83 * This is non-const and volatile to keep gcc from statically
84 * optimizing it out, as variable_test_bit makes gcc think only
85 * *(unsigned long*) is used.
87 static volatile u32 twobyte_is_boostable
[256 / 32] = {
88 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
89 /* ---------------------------------------------- */
90 W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
91 W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
92 W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
93 W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
94 W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
95 W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
96 W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
97 W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
98 W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
99 W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
100 W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
101 W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
102 W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
103 W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
104 W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
105 W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
106 /* ----------------------------------------------- */
107 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
111 struct kretprobe_blackpoint kretprobe_blacklist
[] = {
112 {"__switch_to", }, /* This function switches only current task, but
113 doesn't switch kernel stack.*/
114 {NULL
, NULL
} /* Terminator */
117 const int kretprobe_blacklist_size
= ARRAY_SIZE(kretprobe_blacklist
);
119 static nokprobe_inline
void
120 __synthesize_relative_insn(void *from
, void *to
, u8 op
)
122 struct __arch_relative_insn
{
127 insn
= (struct __arch_relative_insn
*)from
;
128 insn
->raddr
= (s32
)((long)(to
) - ((long)(from
) + 5));
132 /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
133 void synthesize_reljump(void *from
, void *to
)
135 __synthesize_relative_insn(from
, to
, RELATIVEJUMP_OPCODE
);
137 NOKPROBE_SYMBOL(synthesize_reljump
);
139 /* Insert a call instruction at address 'from', which calls address 'to'.*/
140 void synthesize_relcall(void *from
, void *to
)
142 __synthesize_relative_insn(from
, to
, RELATIVECALL_OPCODE
);
144 NOKPROBE_SYMBOL(synthesize_relcall
);
147 * Skip the prefixes of the instruction.
149 static kprobe_opcode_t
*skip_prefixes(kprobe_opcode_t
*insn
)
153 attr
= inat_get_opcode_attribute((insn_byte_t
)*insn
);
154 while (inat_is_legacy_prefix(attr
)) {
156 attr
= inat_get_opcode_attribute((insn_byte_t
)*insn
);
159 if (inat_is_rex_prefix(attr
))
164 NOKPROBE_SYMBOL(skip_prefixes
);
167 * Returns non-zero if opcode is boostable.
168 * RIP relative instructions are adjusted at copying time in 64 bits mode
170 int can_boost(kprobe_opcode_t
*opcodes
, void *addr
)
172 kprobe_opcode_t opcode
;
173 kprobe_opcode_t
*orig_opcodes
= opcodes
;
175 if (search_exception_tables((unsigned long)addr
))
176 return 0; /* Page fault may occur on this address. */
179 if (opcodes
- orig_opcodes
> MAX_INSN_SIZE
- 1)
181 opcode
= *(opcodes
++);
183 /* 2nd-byte opcode */
184 if (opcode
== 0x0f) {
185 if (opcodes
- orig_opcodes
> MAX_INSN_SIZE
- 1)
187 return test_bit(*opcodes
,
188 (unsigned long *)twobyte_is_boostable
);
191 switch (opcode
& 0xf0) {
194 goto retry
; /* REX prefix is boostable */
197 if (0x63 < opcode
&& opcode
< 0x67)
198 goto retry
; /* prefixes */
199 /* can't boost Address-size override and bound */
200 return (opcode
!= 0x62 && opcode
!= 0x67);
202 return 0; /* can't boost conditional jump */
204 /* can't boost software-interruptions */
205 return (0xc1 < opcode
&& opcode
< 0xcc) || opcode
== 0xcf;
207 /* can boost AA* and XLAT */
208 return (opcode
== 0xd4 || opcode
== 0xd5 || opcode
== 0xd7);
210 /* can boost in/out and absolute jmps */
211 return ((opcode
& 0x04) || opcode
== 0xea);
213 if ((opcode
& 0x0c) == 0 && opcode
!= 0xf1)
214 goto retry
; /* lock/rep(ne) prefix */
215 /* clear and set flags are boostable */
216 return (opcode
== 0xf5 || (0xf7 < opcode
&& opcode
< 0xfe));
218 /* segment override prefixes are boostable */
219 if (opcode
== 0x26 || opcode
== 0x36 || opcode
== 0x3e)
220 goto retry
; /* prefixes */
221 /* CS override prefix and call are not boostable */
222 return (opcode
!= 0x2e && opcode
!= 0x9a);
227 __recover_probed_insn(kprobe_opcode_t
*buf
, unsigned long addr
)
232 kp
= get_kprobe((void *)addr
);
233 faddr
= ftrace_location(addr
);
235 * Addresses inside the ftrace location are refused by
236 * arch_check_ftrace_location(). Something went terribly wrong
237 * if such an address is checked here.
239 if (WARN_ON(faddr
&& faddr
!= addr
))
242 * Use the current code if it is not modified by Kprobe
243 * and it cannot be modified by ftrace.
249 * Basically, kp->ainsn.insn has an original instruction.
250 * However, RIP-relative instruction can not do single-stepping
251 * at different place, __copy_instruction() tweaks the displacement of
252 * that instruction. In that case, we can't recover the instruction
253 * from the kp->ainsn.insn.
255 * On the other hand, in case on normal Kprobe, kp->opcode has a copy
256 * of the first byte of the probed instruction, which is overwritten
257 * by int3. And the instruction at kp->addr is not modified by kprobes
258 * except for the first byte, we can recover the original instruction
259 * from it and kp->opcode.
261 * In case of Kprobes using ftrace, we do not have a copy of
262 * the original instruction. In fact, the ftrace location might
263 * be modified at anytime and even could be in an inconsistent state.
264 * Fortunately, we know that the original code is the ideal 5-byte
267 memcpy(buf
, (void *)addr
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
269 memcpy(buf
, ideal_nops
[NOP_ATOMIC5
], 5);
272 return (unsigned long)buf
;
276 * Recover the probed instruction at addr for further analysis.
277 * Caller must lock kprobes by kprobe_mutex, or disable preemption
278 * for preventing to release referencing kprobes.
279 * Returns zero if the instruction can not get recovered.
281 unsigned long recover_probed_instruction(kprobe_opcode_t
*buf
, unsigned long addr
)
283 unsigned long __addr
;
285 __addr
= __recover_optprobed_insn(buf
, addr
);
289 return __recover_probed_insn(buf
, addr
);
292 /* Check if paddr is at an instruction boundary */
293 static int can_probe(unsigned long paddr
)
295 unsigned long addr
, __addr
, offset
= 0;
297 kprobe_opcode_t buf
[MAX_INSN_SIZE
];
299 if (!kallsyms_lookup_size_offset(paddr
, NULL
, &offset
))
302 /* Decode instructions */
303 addr
= paddr
- offset
;
304 while (addr
< paddr
) {
306 * Check if the instruction has been modified by another
307 * kprobe, in which case we replace the breakpoint by the
308 * original instruction in our buffer.
309 * Also, jump optimization will change the breakpoint to
310 * relative-jump. Since the relative-jump itself is
311 * normally used, we just go through if there is no kprobe.
313 __addr
= recover_probed_instruction(buf
, addr
);
316 kernel_insn_init(&insn
, (void *)__addr
, MAX_INSN_SIZE
);
317 insn_get_length(&insn
);
320 * Another debugging subsystem might insert this breakpoint.
321 * In that case, we can't recover it.
323 if (insn
.opcode
.bytes
[0] == BREAKPOINT_INSTRUCTION
)
328 return (addr
== paddr
);
332 * Returns non-zero if opcode modifies the interrupt flag.
334 static int is_IF_modifier(kprobe_opcode_t
*insn
)
337 insn
= skip_prefixes(insn
);
342 case 0xcf: /* iret/iretd */
343 case 0x9d: /* popf/popfd */
351 * Copy an instruction and adjust the displacement if the instruction
352 * uses the %rip-relative addressing mode.
353 * If it does, Return the address of the 32-bit displacement word.
354 * If not, return null.
355 * Only applicable to 64-bit x86.
357 int __copy_instruction(u8
*dest
, u8
*src
)
360 kprobe_opcode_t buf
[MAX_INSN_SIZE
];
362 unsigned long recovered_insn
=
363 recover_probed_instruction(buf
, (unsigned long)src
);
367 kernel_insn_init(&insn
, (void *)recovered_insn
, MAX_INSN_SIZE
);
368 insn_get_length(&insn
);
369 length
= insn
.length
;
371 /* Another subsystem puts a breakpoint, failed to recover */
372 if (insn
.opcode
.bytes
[0] == BREAKPOINT_INSTRUCTION
)
374 memcpy(dest
, insn
.kaddr
, length
);
377 if (insn_rip_relative(&insn
)) {
380 kernel_insn_init(&insn
, dest
, length
);
381 insn_get_displacement(&insn
);
383 * The copied instruction uses the %rip-relative addressing
384 * mode. Adjust the displacement for the difference between
385 * the original location of this instruction and the location
386 * of the copy that will actually be run. The tricky bit here
387 * is making sure that the sign extension happens correctly in
388 * this calculation, since we need a signed 32-bit result to
389 * be sign-extended to 64 bits when it's added to the %rip
390 * value and yield the same 64-bit result that the sign-
391 * extension of the original signed 32-bit displacement would
394 newdisp
= (u8
*) src
+ (s64
) insn
.displacement
.value
- (u8
*) dest
;
395 if ((s64
) (s32
) newdisp
!= newdisp
) {
396 pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp
);
397 pr_err("\tSrc: %p, Dest: %p, old disp: %x\n", src
, dest
, insn
.displacement
.value
);
400 disp
= (u8
*) dest
+ insn_offset_displacement(&insn
);
401 *(s32
*) disp
= (s32
) newdisp
;
407 static int arch_copy_kprobe(struct kprobe
*p
)
411 /* Copy an instruction with recovering if other optprobe modifies it.*/
412 ret
= __copy_instruction(p
->ainsn
.insn
, p
->addr
);
417 * __copy_instruction can modify the displacement of the instruction,
418 * but it doesn't affect boostable check.
420 if (can_boost(p
->ainsn
.insn
, p
->addr
))
421 p
->ainsn
.boostable
= 0;
423 p
->ainsn
.boostable
= -1;
425 /* Check whether the instruction modifies Interrupt Flag or not */
426 p
->ainsn
.if_modifier
= is_IF_modifier(p
->ainsn
.insn
);
428 /* Also, displacement change doesn't affect the first byte */
429 p
->opcode
= p
->ainsn
.insn
[0];
434 int arch_prepare_kprobe(struct kprobe
*p
)
436 if (alternatives_text_reserved(p
->addr
, p
->addr
))
439 if (!can_probe((unsigned long)p
->addr
))
441 /* insn: must be on special executable page on x86. */
442 p
->ainsn
.insn
= get_insn_slot();
446 return arch_copy_kprobe(p
);
449 void arch_arm_kprobe(struct kprobe
*p
)
451 text_poke(p
->addr
, ((unsigned char []){BREAKPOINT_INSTRUCTION
}), 1);
454 void arch_disarm_kprobe(struct kprobe
*p
)
456 text_poke(p
->addr
, &p
->opcode
, 1);
459 void arch_remove_kprobe(struct kprobe
*p
)
462 free_insn_slot(p
->ainsn
.insn
, (p
->ainsn
.boostable
== 1));
463 p
->ainsn
.insn
= NULL
;
467 static nokprobe_inline
void
468 save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
470 kcb
->prev_kprobe
.kp
= kprobe_running();
471 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
472 kcb
->prev_kprobe
.old_flags
= kcb
->kprobe_old_flags
;
473 kcb
->prev_kprobe
.saved_flags
= kcb
->kprobe_saved_flags
;
476 static nokprobe_inline
void
477 restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
479 __this_cpu_write(current_kprobe
, kcb
->prev_kprobe
.kp
);
480 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
481 kcb
->kprobe_old_flags
= kcb
->prev_kprobe
.old_flags
;
482 kcb
->kprobe_saved_flags
= kcb
->prev_kprobe
.saved_flags
;
485 static nokprobe_inline
void
486 set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
487 struct kprobe_ctlblk
*kcb
)
489 __this_cpu_write(current_kprobe
, p
);
490 kcb
->kprobe_saved_flags
= kcb
->kprobe_old_flags
491 = (regs
->flags
& (X86_EFLAGS_TF
| X86_EFLAGS_IF
));
492 if (p
->ainsn
.if_modifier
)
493 kcb
->kprobe_saved_flags
&= ~X86_EFLAGS_IF
;
496 static nokprobe_inline
void clear_btf(void)
498 if (test_thread_flag(TIF_BLOCKSTEP
)) {
499 unsigned long debugctl
= get_debugctlmsr();
501 debugctl
&= ~DEBUGCTLMSR_BTF
;
502 update_debugctlmsr(debugctl
);
506 static nokprobe_inline
void restore_btf(void)
508 if (test_thread_flag(TIF_BLOCKSTEP
)) {
509 unsigned long debugctl
= get_debugctlmsr();
511 debugctl
|= DEBUGCTLMSR_BTF
;
512 update_debugctlmsr(debugctl
);
516 void arch_prepare_kretprobe(struct kretprobe_instance
*ri
, struct pt_regs
*regs
)
518 unsigned long *sara
= stack_addr(regs
);
520 ri
->ret_addr
= (kprobe_opcode_t
*) *sara
;
522 /* Replace the return addr with trampoline addr */
523 *sara
= (unsigned long) &kretprobe_trampoline
;
525 NOKPROBE_SYMBOL(arch_prepare_kretprobe
);
527 static void setup_singlestep(struct kprobe
*p
, struct pt_regs
*regs
,
528 struct kprobe_ctlblk
*kcb
, int reenter
)
530 if (setup_detour_execution(p
, regs
, reenter
))
533 #if !defined(CONFIG_PREEMPT)
534 if (p
->ainsn
.boostable
== 1 && !p
->post_handler
) {
535 /* Boost up -- we can execute copied instructions directly */
537 reset_current_kprobe();
539 * Reentering boosted probe doesn't reset current_kprobe,
540 * nor set current_kprobe, because it doesn't use single
543 regs
->ip
= (unsigned long)p
->ainsn
.insn
;
544 preempt_enable_no_resched();
549 save_previous_kprobe(kcb
);
550 set_current_kprobe(p
, regs
, kcb
);
551 kcb
->kprobe_status
= KPROBE_REENTER
;
553 kcb
->kprobe_status
= KPROBE_HIT_SS
;
554 /* Prepare real single stepping */
556 regs
->flags
|= X86_EFLAGS_TF
;
557 regs
->flags
&= ~X86_EFLAGS_IF
;
558 /* single step inline if the instruction is an int3 */
559 if (p
->opcode
== BREAKPOINT_INSTRUCTION
)
560 regs
->ip
= (unsigned long)p
->addr
;
562 regs
->ip
= (unsigned long)p
->ainsn
.insn
;
564 NOKPROBE_SYMBOL(setup_singlestep
);
567 * We have reentered the kprobe_handler(), since another probe was hit while
568 * within the handler. We save the original kprobes variables and just single
569 * step on the instruction of the new probe without calling any user handlers.
571 static int reenter_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
572 struct kprobe_ctlblk
*kcb
)
574 switch (kcb
->kprobe_status
) {
575 case KPROBE_HIT_SSDONE
:
576 case KPROBE_HIT_ACTIVE
:
578 kprobes_inc_nmissed_count(p
);
579 setup_singlestep(p
, regs
, kcb
, 1);
582 /* A probe has been hit in the codepath leading up to, or just
583 * after, single-stepping of a probed instruction. This entire
584 * codepath should strictly reside in .kprobes.text section.
585 * Raise a BUG or we'll continue in an endless reentering loop
586 * and eventually a stack overflow.
588 printk(KERN_WARNING
"Unrecoverable kprobe detected at %p.\n",
593 /* impossible cases */
600 NOKPROBE_SYMBOL(reenter_kprobe
);
603 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
604 * remain disabled throughout this function.
606 int kprobe_int3_handler(struct pt_regs
*regs
)
608 kprobe_opcode_t
*addr
;
610 struct kprobe_ctlblk
*kcb
;
615 addr
= (kprobe_opcode_t
*)(regs
->ip
- sizeof(kprobe_opcode_t
));
617 * We don't want to be preempted for the entire
618 * duration of kprobe processing. We conditionally
619 * re-enable preemption at the end of this function,
620 * and also in reenter_kprobe() and setup_singlestep().
624 kcb
= get_kprobe_ctlblk();
625 p
= get_kprobe(addr
);
628 if (kprobe_running()) {
629 if (reenter_kprobe(p
, regs
, kcb
))
632 set_current_kprobe(p
, regs
, kcb
);
633 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
636 * If we have no pre-handler or it returned 0, we
637 * continue with normal processing. If we have a
638 * pre-handler and it returned non-zero, it prepped
639 * for calling the break_handler below on re-entry
640 * for jprobe processing, so get out doing nothing
643 if (!p
->pre_handler
|| !p
->pre_handler(p
, regs
))
644 setup_singlestep(p
, regs
, kcb
, 0);
647 } else if (*addr
!= BREAKPOINT_INSTRUCTION
) {
649 * The breakpoint instruction was removed right
650 * after we hit it. Another cpu has removed
651 * either a probepoint or a debugger breakpoint
652 * at this address. In either case, no further
653 * handling of this interrupt is appropriate.
654 * Back up over the (now missing) int3 and run
655 * the original instruction.
657 regs
->ip
= (unsigned long)addr
;
658 preempt_enable_no_resched();
660 } else if (kprobe_running()) {
661 p
= __this_cpu_read(current_kprobe
);
662 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
663 if (!skip_singlestep(p
, regs
, kcb
))
664 setup_singlestep(p
, regs
, kcb
, 0);
667 } /* else: not a kprobe fault; let the kernel handle it */
669 preempt_enable_no_resched();
672 NOKPROBE_SYMBOL(kprobe_int3_handler
);
675 * When a retprobed function returns, this code saves registers and
676 * calls trampoline_handler() runs, which calls the kretprobe's handler.
679 ".global kretprobe_trampoline\n"
680 ".type kretprobe_trampoline, @function\n"
681 "kretprobe_trampoline:\n"
683 /* We don't bother saving the ss register */
688 " call trampoline_handler\n"
689 /* Replace saved sp with true return address. */
690 " movq %rax, 152(%rsp)\n"
697 " call trampoline_handler\n"
698 /* Move flags to cs */
699 " movl 56(%esp), %edx\n"
700 " movl %edx, 52(%esp)\n"
701 /* Replace saved flags with true return address. */
702 " movl %eax, 56(%esp)\n"
707 ".size kretprobe_trampoline, .-kretprobe_trampoline\n"
709 NOKPROBE_SYMBOL(kretprobe_trampoline
);
710 STACK_FRAME_NON_STANDARD(kretprobe_trampoline
);
713 * Called from kretprobe_trampoline
715 __visible __used
void *trampoline_handler(struct pt_regs
*regs
)
717 struct kretprobe_instance
*ri
= NULL
;
718 struct hlist_head
*head
, empty_rp
;
719 struct hlist_node
*tmp
;
720 unsigned long flags
, orig_ret_address
= 0;
721 unsigned long trampoline_address
= (unsigned long)&kretprobe_trampoline
;
722 kprobe_opcode_t
*correct_ret_addr
= NULL
;
724 INIT_HLIST_HEAD(&empty_rp
);
725 kretprobe_hash_lock(current
, &head
, &flags
);
726 /* fixup registers */
728 regs
->cs
= __KERNEL_CS
;
730 regs
->cs
= __KERNEL_CS
| get_kernel_rpl();
733 regs
->ip
= trampoline_address
;
734 regs
->orig_ax
= ~0UL;
737 * It is possible to have multiple instances associated with a given
738 * task either because multiple functions in the call path have
739 * return probes installed on them, and/or more than one
740 * return probe was registered for a target function.
742 * We can handle this because:
743 * - instances are always pushed into the head of the list
744 * - when multiple return probes are registered for the same
745 * function, the (chronologically) first instance's ret_addr
746 * will be the real return address, and all the rest will
747 * point to kretprobe_trampoline.
749 hlist_for_each_entry(ri
, head
, hlist
) {
750 if (ri
->task
!= current
)
751 /* another task is sharing our hash bucket */
754 orig_ret_address
= (unsigned long)ri
->ret_addr
;
756 if (orig_ret_address
!= trampoline_address
)
758 * This is the real return address. Any other
759 * instances associated with this task are for
760 * other calls deeper on the call stack
765 kretprobe_assert(ri
, orig_ret_address
, trampoline_address
);
767 correct_ret_addr
= ri
->ret_addr
;
768 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
769 if (ri
->task
!= current
)
770 /* another task is sharing our hash bucket */
773 orig_ret_address
= (unsigned long)ri
->ret_addr
;
774 if (ri
->rp
&& ri
->rp
->handler
) {
775 __this_cpu_write(current_kprobe
, &ri
->rp
->kp
);
776 get_kprobe_ctlblk()->kprobe_status
= KPROBE_HIT_ACTIVE
;
777 ri
->ret_addr
= correct_ret_addr
;
778 ri
->rp
->handler(ri
, regs
);
779 __this_cpu_write(current_kprobe
, NULL
);
782 recycle_rp_inst(ri
, &empty_rp
);
784 if (orig_ret_address
!= trampoline_address
)
786 * This is the real return address. Any other
787 * instances associated with this task are for
788 * other calls deeper on the call stack
793 kretprobe_hash_unlock(current
, &flags
);
795 hlist_for_each_entry_safe(ri
, tmp
, &empty_rp
, hlist
) {
796 hlist_del(&ri
->hlist
);
799 return (void *)orig_ret_address
;
801 NOKPROBE_SYMBOL(trampoline_handler
);
804 * Called after single-stepping. p->addr is the address of the
805 * instruction whose first byte has been replaced by the "int 3"
806 * instruction. To avoid the SMP problems that can occur when we
807 * temporarily put back the original opcode to single-step, we
808 * single-stepped a copy of the instruction. The address of this
809 * copy is p->ainsn.insn.
811 * This function prepares to return from the post-single-step
812 * interrupt. We have to fix up the stack as follows:
814 * 0) Except in the case of absolute or indirect jump or call instructions,
815 * the new ip is relative to the copied instruction. We need to make
816 * it relative to the original instruction.
818 * 1) If the single-stepped instruction was pushfl, then the TF and IF
819 * flags are set in the just-pushed flags, and may need to be cleared.
821 * 2) If the single-stepped instruction was a call, the return address
822 * that is atop the stack is the address following the copied instruction.
823 * We need to make it the address following the original instruction.
825 * If this is the first time we've single-stepped the instruction at
826 * this probepoint, and the instruction is boostable, boost it: add a
827 * jump instruction after the copied instruction, that jumps to the next
828 * instruction after the probepoint.
830 static void resume_execution(struct kprobe
*p
, struct pt_regs
*regs
,
831 struct kprobe_ctlblk
*kcb
)
833 unsigned long *tos
= stack_addr(regs
);
834 unsigned long copy_ip
= (unsigned long)p
->ainsn
.insn
;
835 unsigned long orig_ip
= (unsigned long)p
->addr
;
836 kprobe_opcode_t
*insn
= p
->ainsn
.insn
;
839 insn
= skip_prefixes(insn
);
841 regs
->flags
&= ~X86_EFLAGS_TF
;
843 case 0x9c: /* pushfl */
844 *tos
&= ~(X86_EFLAGS_TF
| X86_EFLAGS_IF
);
845 *tos
|= kcb
->kprobe_old_flags
;
847 case 0xc2: /* iret/ret/lret */
852 case 0xea: /* jmp absolute -- ip is correct */
853 /* ip is already adjusted, no more changes required */
854 p
->ainsn
.boostable
= 1;
856 case 0xe8: /* call relative - Fix return addr */
857 *tos
= orig_ip
+ (*tos
- copy_ip
);
860 case 0x9a: /* call absolute -- same as call absolute, indirect */
861 *tos
= orig_ip
+ (*tos
- copy_ip
);
865 if ((insn
[1] & 0x30) == 0x10) {
867 * call absolute, indirect
868 * Fix return addr; ip is correct.
869 * But this is not boostable
871 *tos
= orig_ip
+ (*tos
- copy_ip
);
873 } else if (((insn
[1] & 0x31) == 0x20) ||
874 ((insn
[1] & 0x31) == 0x21)) {
876 * jmp near and far, absolute indirect
877 * ip is correct. And this is boostable
879 p
->ainsn
.boostable
= 1;
886 if (p
->ainsn
.boostable
== 0) {
887 if ((regs
->ip
> copy_ip
) &&
888 (regs
->ip
- copy_ip
) + 5 < MAX_INSN_SIZE
) {
890 * These instructions can be executed directly if it
891 * jumps back to correct address.
893 synthesize_reljump((void *)regs
->ip
,
894 (void *)orig_ip
+ (regs
->ip
- copy_ip
));
895 p
->ainsn
.boostable
= 1;
897 p
->ainsn
.boostable
= -1;
901 regs
->ip
+= orig_ip
- copy_ip
;
906 NOKPROBE_SYMBOL(resume_execution
);
909 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
910 * remain disabled throughout this function.
912 int kprobe_debug_handler(struct pt_regs
*regs
)
914 struct kprobe
*cur
= kprobe_running();
915 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
920 resume_execution(cur
, regs
, kcb
);
921 regs
->flags
|= kcb
->kprobe_saved_flags
;
923 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
924 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
925 cur
->post_handler(cur
, regs
, 0);
928 /* Restore back the original saved kprobes variables and continue. */
929 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
930 restore_previous_kprobe(kcb
);
933 reset_current_kprobe();
935 preempt_enable_no_resched();
938 * if somebody else is singlestepping across a probe point, flags
939 * will have TF set, in which case, continue the remaining processing
940 * of do_debug, as if this is not a probe hit.
942 if (regs
->flags
& X86_EFLAGS_TF
)
947 NOKPROBE_SYMBOL(kprobe_debug_handler
);
949 int kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
951 struct kprobe
*cur
= kprobe_running();
952 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
954 if (unlikely(regs
->ip
== (unsigned long)cur
->ainsn
.insn
)) {
955 /* This must happen on single-stepping */
956 WARN_ON(kcb
->kprobe_status
!= KPROBE_HIT_SS
&&
957 kcb
->kprobe_status
!= KPROBE_REENTER
);
959 * We are here because the instruction being single
960 * stepped caused a page fault. We reset the current
961 * kprobe and the ip points back to the probe address
962 * and allow the page fault handler to continue as a
965 regs
->ip
= (unsigned long)cur
->addr
;
967 * Trap flag (TF) has been set here because this fault
968 * happened where the single stepping will be done.
969 * So clear it by resetting the current kprobe:
971 regs
->flags
&= ~X86_EFLAGS_TF
;
974 * If the TF flag was set before the kprobe hit,
977 regs
->flags
|= kcb
->kprobe_old_flags
;
979 if (kcb
->kprobe_status
== KPROBE_REENTER
)
980 restore_previous_kprobe(kcb
);
982 reset_current_kprobe();
983 preempt_enable_no_resched();
984 } else if (kcb
->kprobe_status
== KPROBE_HIT_ACTIVE
||
985 kcb
->kprobe_status
== KPROBE_HIT_SSDONE
) {
987 * We increment the nmissed count for accounting,
988 * we can also use npre/npostfault count for accounting
989 * these specific fault cases.
991 kprobes_inc_nmissed_count(cur
);
994 * We come here because instructions in the pre/post
995 * handler caused the page_fault, this could happen
996 * if handler tries to access user space by
997 * copy_from_user(), get_user() etc. Let the
998 * user-specified handler try to fix it first.
1000 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
1004 * In case the user-specified fault handler returned
1005 * zero, try to fix up.
1007 if (fixup_exception(regs
, trapnr
))
1011 * fixup routine could not handle it,
1012 * Let do_page_fault() fix it.
1018 NOKPROBE_SYMBOL(kprobe_fault_handler
);
1021 * Wrapper routine for handling exceptions.
1023 int kprobe_exceptions_notify(struct notifier_block
*self
, unsigned long val
,
1026 struct die_args
*args
= data
;
1027 int ret
= NOTIFY_DONE
;
1029 if (args
->regs
&& user_mode(args
->regs
))
1032 if (val
== DIE_GPF
) {
1034 * To be potentially processing a kprobe fault and to
1035 * trust the result from kprobe_running(), we have
1036 * be non-preemptible.
1038 if (!preemptible() && kprobe_running() &&
1039 kprobe_fault_handler(args
->regs
, args
->trapnr
))
1044 NOKPROBE_SYMBOL(kprobe_exceptions_notify
);
1046 int setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
1048 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
1050 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
1052 kcb
->jprobe_saved_regs
= *regs
;
1053 kcb
->jprobe_saved_sp
= stack_addr(regs
);
1054 addr
= (unsigned long)(kcb
->jprobe_saved_sp
);
1057 * As Linus pointed out, gcc assumes that the callee
1058 * owns the argument space and could overwrite it, e.g.
1059 * tailcall optimization. So, to be absolutely safe
1060 * we also save and restore enough stack bytes to cover
1061 * the argument area.
1062 * Use __memcpy() to avoid KASAN stack out-of-bounds reports as we copy
1063 * raw stack chunk with redzones:
1065 __memcpy(kcb
->jprobes_stack
, (kprobe_opcode_t
*)addr
, MIN_STACK_SIZE(addr
));
1066 regs
->flags
&= ~X86_EFLAGS_IF
;
1067 trace_hardirqs_off();
1068 regs
->ip
= (unsigned long)(jp
->entry
);
1071 * jprobes use jprobe_return() which skips the normal return
1072 * path of the function, and this messes up the accounting of the
1073 * function graph tracer to get messed up.
1075 * Pause function graph tracing while performing the jprobe function.
1077 pause_graph_tracing();
1080 NOKPROBE_SYMBOL(setjmp_pre_handler
);
1082 void jprobe_return(void)
1084 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
1086 /* Unpoison stack redzones in the frames we are going to jump over. */
1087 kasan_unpoison_stack_above_sp_to(kcb
->jprobe_saved_sp
);
1090 #ifdef CONFIG_X86_64
1091 " xchg %%rbx,%%rsp \n"
1093 " xchgl %%ebx,%%esp \n"
1096 " .globl jprobe_return_end\n"
1097 " jprobe_return_end: \n"
1099 (kcb
->jprobe_saved_sp
):"memory");
1101 NOKPROBE_SYMBOL(jprobe_return
);
1102 NOKPROBE_SYMBOL(jprobe_return_end
);
1104 int longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
1106 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
1107 u8
*addr
= (u8
*) (regs
->ip
- 1);
1108 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
1109 void *saved_sp
= kcb
->jprobe_saved_sp
;
1111 if ((addr
> (u8
*) jprobe_return
) &&
1112 (addr
< (u8
*) jprobe_return_end
)) {
1113 if (stack_addr(regs
) != saved_sp
) {
1114 struct pt_regs
*saved_regs
= &kcb
->jprobe_saved_regs
;
1116 "current sp %p does not match saved sp %p\n",
1117 stack_addr(regs
), saved_sp
);
1118 printk(KERN_ERR
"Saved registers for jprobe %p\n", jp
);
1119 show_regs(saved_regs
);
1120 printk(KERN_ERR
"Current registers\n");
1124 /* It's OK to start function graph tracing again */
1125 unpause_graph_tracing();
1126 *regs
= kcb
->jprobe_saved_regs
;
1127 __memcpy(saved_sp
, kcb
->jprobes_stack
, MIN_STACK_SIZE(saved_sp
));
1128 preempt_enable_no_resched();
1133 NOKPROBE_SYMBOL(longjmp_break_handler
);
1135 bool arch_within_kprobe_blacklist(unsigned long addr
)
1137 return (addr
>= (unsigned long)__kprobes_text_start
&&
1138 addr
< (unsigned long)__kprobes_text_end
) ||
1139 (addr
>= (unsigned long)__entry_text_start
&&
1140 addr
< (unsigned long)__entry_text_end
);
1143 int __init
arch_init_kprobes(void)
1148 int arch_trampoline_kprobe(struct kprobe
*p
)