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)
428 static void __kprobes restore_btf(void)
433 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
434 struct pt_regs *regs)
436 unsigned long *sara = stack_addr(regs);
438 ri->ret_addr = (kprobe_opcode_t *) *sara;
440 /* Replace the return addr with trampoline addr */
441 *sara = (unsigned long) &kretprobe_trampoline;
444 #ifdef CONFIG_OPTPROBES
445 static int __kprobes setup_detour_execution(struct kprobe *p,
446 struct pt_regs *regs,
449 #define setup_detour_execution(p, regs, reenter) (0)
452 static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
453 struct kprobe_ctlblk *kcb, int reenter)
455 if (setup_detour_execution(p, regs, reenter))
458 #if !defined(CONFIG_PREEMPT)
459 if (p->ainsn.boostable == 1 && !p->post_handler) {
460 /* Boost up -- we can execute copied instructions directly */
462 reset_current_kprobe();
464 * Reentering boosted probe doesn't reset current_kprobe,
465 * nor set current_kprobe, because it doesn't use single
468 regs->ip = (unsigned long)p->ainsn.insn;
469 preempt_enable_no_resched();
474 save_previous_kprobe(kcb);
475 set_current_kprobe(p, regs, kcb);
476 kcb->kprobe_status = KPROBE_REENTER;
478 kcb->kprobe_status = KPROBE_HIT_SS;
479 /* Prepare real single stepping */
481 regs->flags |= X86_EFLAGS_TF;
482 regs->flags &= ~X86_EFLAGS_IF;
483 /* single step inline if the instruction is an int3 */
484 if (p->opcode == BREAKPOINT_INSTRUCTION)
485 regs->ip = (unsigned long)p->addr;
487 regs->ip = (unsigned long)p->ainsn.insn;
491 * We have reentered the kprobe_handler(), since another probe was hit while
492 * within the handler. We save the original kprobes variables and just single
493 * step on the instruction of the new probe without calling any user handlers.
495 static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
496 struct kprobe_ctlblk *kcb)
498 switch (kcb->kprobe_status) {
499 case KPROBE_HIT_SSDONE:
500 case KPROBE_HIT_ACTIVE:
501 kprobes_inc_nmissed_count(p);
502 setup_singlestep(p, regs, kcb, 1);
505 /* A probe has been hit in the codepath leading up to, or just
506 * after, single-stepping of a probed instruction. This entire
507 * codepath should strictly reside in .kprobes.text section.
508 * Raise a BUG or we'll continue in an endless reentering loop
509 * and eventually a stack overflow.
511 printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n",
516 /* impossible cases */
525 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
526 * remain disabled throughout this function.
528 static int __kprobes kprobe_handler(struct pt_regs *regs)
530 kprobe_opcode_t *addr;
532 struct kprobe_ctlblk *kcb;
534 addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
535 if (*addr != BREAKPOINT_INSTRUCTION) {
537 * The breakpoint instruction was removed right
538 * after we hit it. Another cpu has removed
539 * either a probepoint or a debugger breakpoint
540 * at this address. In either case, no further
541 * handling of this interrupt is appropriate.
542 * Back up over the (now missing) int3 and run
543 * the original instruction.
545 regs->ip = (unsigned long)addr;
550 * We don't want to be preempted for the entire
551 * duration of kprobe processing. We conditionally
552 * re-enable preemption at the end of this function,
553 * and also in reenter_kprobe() and setup_singlestep().
557 kcb = get_kprobe_ctlblk();
558 p = get_kprobe(addr);
561 if (kprobe_running()) {
562 if (reenter_kprobe(p, regs, kcb))
565 set_current_kprobe(p, regs, kcb);
566 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
569 * If we have no pre-handler or it returned 0, we
570 * continue with normal processing. If we have a
571 * pre-handler and it returned non-zero, it prepped
572 * for calling the break_handler below on re-entry
573 * for jprobe processing, so get out doing nothing
576 if (!p->pre_handler || !p->pre_handler(p, regs))
577 setup_singlestep(p, regs, kcb, 0);
580 } else if (kprobe_running()) {
581 p = __get_cpu_var(current_kprobe);
582 if (p->break_handler && p->break_handler(p, regs)) {
583 setup_singlestep(p, regs, kcb, 0);
586 } /* else: not a kprobe fault; let the kernel handle it */
588 preempt_enable_no_resched();
593 #define SAVE_REGS_STRING \
594 /* Skip cs, ip, orig_ax. */ \
595 " subq $24, %rsp\n" \
611 #define RESTORE_REGS_STRING \
627 /* Skip orig_ax, ip, cs */ \
630 #define SAVE_REGS_STRING \
631 /* Skip cs, ip, orig_ax and gs. */ \
632 " subl $16, %esp\n" \
643 #define RESTORE_REGS_STRING \
651 /* Skip ds, es, fs, gs, orig_ax, and ip. Note: don't pop cs here*/\
656 * When a retprobed function returns, this code saves registers and
657 * calls trampoline_handler() runs, which calls the kretprobe's handler.
659 static void __used __kprobes kretprobe_trampoline_holder(void)
662 ".global kretprobe_trampoline\n"
663 "kretprobe_trampoline: \n"
665 /* We don't bother saving the ss register */
670 " call trampoline_handler\n"
671 /* Replace saved sp with true return address. */
672 " movq %rax, 152(%rsp)\n"
679 " call trampoline_handler\n"
680 /* Move flags to cs */
681 " movl 56(%esp), %edx\n"
682 " movl %edx, 52(%esp)\n"
683 /* Replace saved flags with true return address. */
684 " movl %eax, 56(%esp)\n"
692 * Called from kretprobe_trampoline
694 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
696 struct kretprobe_instance *ri = NULL;
697 struct hlist_head *head, empty_rp;
698 struct hlist_node *node, *tmp;
699 unsigned long flags, orig_ret_address = 0;
700 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
702 INIT_HLIST_HEAD(&empty_rp);
703 kretprobe_hash_lock(current, &head, &flags);
704 /* fixup registers */
706 regs->cs = __KERNEL_CS;
708 regs->cs = __KERNEL_CS | get_kernel_rpl();
711 regs->ip = trampoline_address;
712 regs->orig_ax = ~0UL;
715 * It is possible to have multiple instances associated with a given
716 * task either because multiple functions in the call path have
717 * return probes installed on them, and/or more than one
718 * return probe was registered for a target function.
720 * We can handle this because:
721 * - instances are always pushed into the head of the list
722 * - when multiple return probes are registered for the same
723 * function, the (chronologically) first instance's ret_addr
724 * will be the real return address, and all the rest will
725 * point to kretprobe_trampoline.
727 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
728 if (ri->task != current)
729 /* another task is sharing our hash bucket */
732 if (ri->rp && ri->rp->handler) {
733 __get_cpu_var(current_kprobe) = &ri->rp->kp;
734 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
735 ri->rp->handler(ri, regs);
736 __get_cpu_var(current_kprobe) = NULL;
739 orig_ret_address = (unsigned long)ri->ret_addr;
740 recycle_rp_inst(ri, &empty_rp);
742 if (orig_ret_address != trampoline_address)
744 * This is the real return address. Any other
745 * instances associated with this task are for
746 * other calls deeper on the call stack
751 kretprobe_assert(ri, orig_ret_address, trampoline_address);
753 kretprobe_hash_unlock(current, &flags);
755 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
756 hlist_del(&ri->hlist);
759 return (void *)orig_ret_address;
763 * Called after single-stepping. p->addr is the address of the
764 * instruction whose first byte has been replaced by the "int 3"
765 * instruction. To avoid the SMP problems that can occur when we
766 * temporarily put back the original opcode to single-step, we
767 * single-stepped a copy of the instruction. The address of this
768 * copy is p->ainsn.insn.
770 * This function prepares to return from the post-single-step
771 * interrupt. We have to fix up the stack as follows:
773 * 0) Except in the case of absolute or indirect jump or call instructions,
774 * the new ip is relative to the copied instruction. We need to make
775 * it relative to the original instruction.
777 * 1) If the single-stepped instruction was pushfl, then the TF and IF
778 * flags are set in the just-pushed flags, and may need to be cleared.
780 * 2) If the single-stepped instruction was a call, the return address
781 * that is atop the stack is the address following the copied instruction.
782 * We need to make it the address following the original instruction.
784 * If this is the first time we've single-stepped the instruction at
785 * this probepoint, and the instruction is boostable, boost it: add a
786 * jump instruction after the copied instruction, that jumps to the next
787 * instruction after the probepoint.
789 static void __kprobes resume_execution(struct kprobe *p,
790 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
792 unsigned long *tos = stack_addr(regs);
793 unsigned long copy_ip = (unsigned long)p->ainsn.insn;
794 unsigned long orig_ip = (unsigned long)p->addr;
795 kprobe_opcode_t *insn = p->ainsn.insn;
797 /*skip the REX prefix*/
798 if (is_REX_prefix(insn))
801 regs->flags &= ~X86_EFLAGS_TF;
803 case 0x9c: /* pushfl */
804 *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
805 *tos |= kcb->kprobe_old_flags;
807 case 0xc2: /* iret/ret/lret */
812 case 0xea: /* jmp absolute -- ip is correct */
813 /* ip is already adjusted, no more changes required */
814 p->ainsn.boostable = 1;
816 case 0xe8: /* call relative - Fix return addr */
817 *tos = orig_ip + (*tos - copy_ip);
820 case 0x9a: /* call absolute -- same as call absolute, indirect */
821 *tos = orig_ip + (*tos - copy_ip);
825 if ((insn[1] & 0x30) == 0x10) {
827 * call absolute, indirect
828 * Fix return addr; ip is correct.
829 * But this is not boostable
831 *tos = orig_ip + (*tos - copy_ip);
833 } else if (((insn[1] & 0x31) == 0x20) ||
834 ((insn[1] & 0x31) == 0x21)) {
836 * jmp near and far, absolute indirect
837 * ip is correct. And this is boostable
839 p->ainsn.boostable = 1;
846 if (p->ainsn.boostable == 0) {
847 if ((regs->ip > copy_ip) &&
848 (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
850 * These instructions can be executed directly if it
851 * jumps back to correct address.
853 synthesize_reljump((void *)regs->ip,
854 (void *)orig_ip + (regs->ip - copy_ip));
855 p->ainsn.boostable = 1;
857 p->ainsn.boostable = -1;
861 regs->ip += orig_ip - copy_ip;
868 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
869 * remain disabled throughout this function.
871 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
873 struct kprobe *cur = kprobe_running();
874 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
879 resume_execution(cur, regs, kcb);
880 regs->flags |= kcb->kprobe_saved_flags;
882 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
883 kcb->kprobe_status = KPROBE_HIT_SSDONE;
884 cur->post_handler(cur, regs, 0);
887 /* Restore back the original saved kprobes variables and continue. */
888 if (kcb->kprobe_status == KPROBE_REENTER) {
889 restore_previous_kprobe(kcb);
892 reset_current_kprobe();
894 preempt_enable_no_resched();
897 * if somebody else is singlestepping across a probe point, flags
898 * will have TF set, in which case, continue the remaining processing
899 * of do_debug, as if this is not a probe hit.
901 if (regs->flags & X86_EFLAGS_TF)
907 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
909 struct kprobe *cur = kprobe_running();
910 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
912 switch (kcb->kprobe_status) {
916 * We are here because the instruction being single
917 * stepped caused a page fault. We reset the current
918 * kprobe and the ip points back to the probe address
919 * and allow the page fault handler to continue as a
922 regs->ip = (unsigned long)cur->addr;
923 regs->flags |= kcb->kprobe_old_flags;
924 if (kcb->kprobe_status == KPROBE_REENTER)
925 restore_previous_kprobe(kcb);
927 reset_current_kprobe();
928 preempt_enable_no_resched();
930 case KPROBE_HIT_ACTIVE:
931 case KPROBE_HIT_SSDONE:
933 * We increment the nmissed count for accounting,
934 * we can also use npre/npostfault count for accounting
935 * these specific fault cases.
937 kprobes_inc_nmissed_count(cur);
940 * We come here because instructions in the pre/post
941 * handler caused the page_fault, this could happen
942 * if handler tries to access user space by
943 * copy_from_user(), get_user() etc. Let the
944 * user-specified handler try to fix it first.
946 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
950 * In case the user-specified fault handler returned
951 * zero, try to fix up.
953 if (fixup_exception(regs))
957 * fixup routine could not handle it,
958 * Let do_page_fault() fix it.
968 * Wrapper routine for handling exceptions.
970 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
971 unsigned long val, void *data)
973 struct die_args *args = data;
974 int ret = NOTIFY_DONE;
976 if (args->regs && user_mode_vm(args->regs))
981 if (kprobe_handler(args->regs))
985 if (post_kprobe_handler(args->regs)) {
987 * Reset the BS bit in dr6 (pointed by args->err) to
988 * denote completion of processing
990 (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
996 * To be potentially processing a kprobe fault and to
997 * trust the result from kprobe_running(), we have
998 * be non-preemptible.
1000 if (!preemptible() && kprobe_running() &&
1001 kprobe_fault_handler(args->regs, args->trapnr))
1010 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
1012 struct jprobe *jp = container_of(p, struct jprobe, kp);
1014 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1016 kcb->jprobe_saved_regs = *regs;
1017 kcb->jprobe_saved_sp = stack_addr(regs);
1018 addr = (unsigned long)(kcb->jprobe_saved_sp);
1021 * As Linus pointed out, gcc assumes that the callee
1022 * owns the argument space and could overwrite it, e.g.
1023 * tailcall optimization. So, to be absolutely safe
1024 * we also save and restore enough stack bytes to cover
1025 * the argument area.
1027 memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
1028 MIN_STACK_SIZE(addr));
1029 regs->flags &= ~X86_EFLAGS_IF;
1030 trace_hardirqs_off();
1031 regs->ip = (unsigned long)(jp->entry);
1035 void __kprobes jprobe_return(void)
1037 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1040 #ifdef CONFIG_X86_64
1041 " xchg %%rbx,%%rsp \n"
1043 " xchgl %%ebx,%%esp \n"
1046 " .globl jprobe_return_end\n"
1047 " jprobe_return_end: \n"
1049 (kcb->jprobe_saved_sp):"memory");
1052 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
1054 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1055 u8 *addr = (u8 *) (regs->ip - 1);
1056 struct jprobe *jp = container_of(p, struct jprobe, kp);
1058 if ((addr > (u8 *) jprobe_return) &&
1059 (addr < (u8 *) jprobe_return_end)) {
1060 if (stack_addr(regs) != kcb->jprobe_saved_sp) {
1061 struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
1063 "current sp %p does not match saved sp %p\n",
1064 stack_addr(regs), kcb->jprobe_saved_sp);
1065 printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
1066 show_registers(saved_regs);
1067 printk(KERN_ERR "Current registers\n");
1068 show_registers(regs);
1071 *regs = kcb->jprobe_saved_regs;
1072 memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp),
1074 MIN_STACK_SIZE(kcb->jprobe_saved_sp));
1075 preempt_enable_no_resched();
1082 #ifdef CONFIG_OPTPROBES
1084 /* Insert a call instruction at address 'from', which calls address 'to'.*/
1085 static void __kprobes synthesize_relcall(void *from, void *to)
1087 __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE);
1090 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
1091 static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr,
1094 #ifdef CONFIG_X86_64
1100 *(unsigned long *)addr = val;
1103 void __kprobes kprobes_optinsn_template_holder(void)
1106 ".global optprobe_template_entry\n"
1107 "optprobe_template_entry: \n"
1108 #ifdef CONFIG_X86_64
1109 /* We don't bother saving the ss register */
1113 " movq %rsp, %rsi\n"
1114 ".global optprobe_template_val\n"
1115 "optprobe_template_val: \n"
1118 ".global optprobe_template_call\n"
1119 "optprobe_template_call: \n"
1121 /* Move flags to rsp */
1122 " movq 144(%rsp), %rdx\n"
1123 " movq %rdx, 152(%rsp)\n"
1125 /* Skip flags entry */
1128 #else /* CONFIG_X86_32 */
1131 " movl %esp, %edx\n"
1132 ".global optprobe_template_val\n"
1133 "optprobe_template_val: \n"
1135 ".global optprobe_template_call\n"
1136 "optprobe_template_call: \n"
1139 " addl $4, %esp\n" /* skip cs */
1142 ".global optprobe_template_end\n"
1143 "optprobe_template_end: \n");
1146 #define TMPL_MOVE_IDX \
1147 ((long)&optprobe_template_val - (long)&optprobe_template_entry)
1148 #define TMPL_CALL_IDX \
1149 ((long)&optprobe_template_call - (long)&optprobe_template_entry)
1150 #define TMPL_END_IDX \
1151 ((long)&optprobe_template_end - (long)&optprobe_template_entry)
1153 #define INT3_SIZE sizeof(kprobe_opcode_t)
1155 /* Optimized kprobe call back function: called from optinsn */
1156 static void __kprobes optimized_callback(struct optimized_kprobe *op,
1157 struct pt_regs *regs)
1159 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1162 if (kprobe_running()) {
1163 kprobes_inc_nmissed_count(&op->kp);
1165 /* Save skipped registers */
1166 #ifdef CONFIG_X86_64
1167 regs->cs = __KERNEL_CS;
1169 regs->cs = __KERNEL_CS | get_kernel_rpl();
1172 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
1173 regs->orig_ax = ~0UL;
1175 __get_cpu_var(current_kprobe) = &op->kp;
1176 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
1177 opt_pre_handler(&op->kp, regs);
1178 __get_cpu_var(current_kprobe) = NULL;
1180 preempt_enable_no_resched();
1183 static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
1187 while (len < RELATIVEJUMP_SIZE) {
1188 ret = __copy_instruction(dest + len, src + len, 1);
1189 if (!ret || !can_boost(dest + len))
1193 /* Check whether the address range is reserved */
1194 if (ftrace_text_reserved(src, src + len - 1) ||
1195 alternatives_text_reserved(src, src + len - 1))
1201 /* Check whether insn is indirect jump */
1202 static int __kprobes insn_is_indirect_jump(struct insn *insn)
1204 return ((insn->opcode.bytes[0] == 0xff &&
1205 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
1206 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
1209 /* Check whether insn jumps into specified address range */
1210 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
1212 unsigned long target = 0;
1214 switch (insn->opcode.bytes[0]) {
1215 case 0xe0: /* loopne */
1216 case 0xe1: /* loope */
1217 case 0xe2: /* loop */
1218 case 0xe3: /* jcxz */
1219 case 0xe9: /* near relative jump */
1220 case 0xeb: /* short relative jump */
1223 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
1227 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
1231 target = (unsigned long)insn->next_byte + insn->immediate.value;
1233 return (start <= target && target <= start + len);
1236 /* Decode whole function to ensure any instructions don't jump into target */
1237 static int __kprobes can_optimize(unsigned long paddr)
1240 unsigned long addr, size = 0, offset = 0;
1242 kprobe_opcode_t buf[MAX_INSN_SIZE];
1243 /* Dummy buffers for lookup_symbol_attrs */
1244 static char __dummy_buf[KSYM_NAME_LEN];
1246 /* Lookup symbol including addr */
1247 if (!kallsyms_lookup(paddr, &size, &offset, NULL, __dummy_buf))
1250 /* Check there is enough space for a relative jump. */
1251 if (size - offset < RELATIVEJUMP_SIZE)
1254 /* Decode instructions */
1255 addr = paddr - offset;
1256 while (addr < paddr - offset + size) { /* Decode until function end */
1257 if (search_exception_tables(addr))
1259 * Since some fixup code will jumps into this function,
1260 * we can't optimize kprobe in this function.
1263 kernel_insn_init(&insn, (void *)addr);
1264 insn_get_opcode(&insn);
1265 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) {
1266 ret = recover_probed_instruction(buf, addr);
1269 kernel_insn_init(&insn, buf);
1271 insn_get_length(&insn);
1272 /* Recover address */
1273 insn.kaddr = (void *)addr;
1274 insn.next_byte = (void *)(addr + insn.length);
1275 /* Check any instructions don't jump into target */
1276 if (insn_is_indirect_jump(&insn) ||
1277 insn_jump_into_range(&insn, paddr + INT3_SIZE,
1278 RELATIVE_ADDR_SIZE))
1280 addr += insn.length;
1286 /* Check optimized_kprobe can actually be optimized. */
1287 int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
1292 for (i = 1; i < op->optinsn.size; i++) {
1293 p = get_kprobe(op->kp.addr + i);
1294 if (p && !kprobe_disabled(p))
1301 /* Check the addr is within the optimized instructions. */
1302 int __kprobes arch_within_optimized_kprobe(struct optimized_kprobe *op,
1305 return ((unsigned long)op->kp.addr <= addr &&
1306 (unsigned long)op->kp.addr + op->optinsn.size > addr);
1309 /* Free optimized instruction slot */
1311 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
1313 if (op->optinsn.insn) {
1314 free_optinsn_slot(op->optinsn.insn, dirty);
1315 op->optinsn.insn = NULL;
1316 op->optinsn.size = 0;
1320 void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)
1322 __arch_remove_optimized_kprobe(op, 1);
1326 * Copy replacing target instructions
1327 * Target instructions MUST be relocatable (checked inside)
1329 int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
1335 if (!can_optimize((unsigned long)op->kp.addr))
1338 op->optinsn.insn = get_optinsn_slot();
1339 if (!op->optinsn.insn)
1343 * Verify if the address gap is in 2GB range, because this uses
1346 rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
1347 if (abs(rel) > 0x7fffffff)
1350 buf = (u8 *)op->optinsn.insn;
1352 /* Copy instructions into the out-of-line buffer */
1353 ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
1355 __arch_remove_optimized_kprobe(op, 0);
1358 op->optinsn.size = ret;
1360 /* Copy arch-dep-instance from template */
1361 memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
1363 /* Set probe information */
1364 synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
1366 /* Set probe function call */
1367 synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
1369 /* Set returning jmp instruction at the tail of out-of-line buffer */
1370 synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
1371 (u8 *)op->kp.addr + op->optinsn.size);
1373 flush_icache_range((unsigned long) buf,
1374 (unsigned long) buf + TMPL_END_IDX +
1375 op->optinsn.size + RELATIVEJUMP_SIZE);
1379 /* Replace a breakpoint (int3) with a relative jump. */
1380 int __kprobes arch_optimize_kprobe(struct optimized_kprobe *op)
1382 unsigned char jmp_code[RELATIVEJUMP_SIZE];
1383 s32 rel = (s32)((long)op->optinsn.insn -
1384 ((long)op->kp.addr + RELATIVEJUMP_SIZE));
1386 /* Backup instructions which will be replaced by jump address */
1387 memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
1388 RELATIVE_ADDR_SIZE);
1390 jmp_code[0] = RELATIVEJUMP_OPCODE;
1391 *(s32 *)(&jmp_code[1]) = rel;
1394 * text_poke_smp doesn't support NMI/MCE code modifying.
1395 * However, since kprobes itself also doesn't support NMI/MCE
1396 * code probing, it's not a problem.
1398 text_poke_smp(op->kp.addr, jmp_code, RELATIVEJUMP_SIZE);
1402 /* Replace a relative jump with a breakpoint (int3). */
1403 void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
1405 u8 buf[RELATIVEJUMP_SIZE];
1407 /* Set int3 to first byte for kprobes */
1408 buf[0] = BREAKPOINT_INSTRUCTION;
1409 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
1410 text_poke_smp(op->kp.addr, buf, RELATIVEJUMP_SIZE);
1413 static int __kprobes setup_detour_execution(struct kprobe *p,
1414 struct pt_regs *regs,
1417 struct optimized_kprobe *op;
1419 if (p->flags & KPROBE_FLAG_OPTIMIZED) {
1420 /* This kprobe is really able to run optimized path. */
1421 op = container_of(p, struct optimized_kprobe, kp);
1422 /* Detour through copied instructions */
1423 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
1425 reset_current_kprobe();
1426 preempt_enable_no_resched();
1433 int __init arch_init_kprobes(void)
1438 int __kprobes arch_trampoline_kprobe(struct kprobe *p)