[PATCH] kprobes: fix single-step out of line - take2
[linux-2.6.git] / arch / x86_64 / kernel / kprobes.c
1 /*
2  *  Kernel Probes (KProbes)
3  *  arch/x86_64/kernel/kprobes.c
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; either version 2 of the License, or
8  * (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program; if not, write to the Free Software
17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18  *
19  * Copyright (C) IBM Corporation, 2002, 2004
20  *
21  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
22  *              Probes initial implementation ( includes contributions from
23  *              Rusty Russell).
24  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
25  *              interface to access function arguments.
26  * 2004-Oct     Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi
27  *              <prasanna@in.ibm.com> adapted for x86_64
28  * 2005-Mar     Roland McGrath <roland@redhat.com>
29  *              Fixed to handle %rip-relative addressing mode correctly.
30  * 2005-May     Rusty Lynch <rusty.lynch@intel.com>
31  *              Added function return probes functionality
32  */
33
34 #include <linux/config.h>
35 #include <linux/kprobes.h>
36 #include <linux/ptrace.h>
37 #include <linux/spinlock.h>
38 #include <linux/string.h>
39 #include <linux/slab.h>
40 #include <linux/preempt.h>
41
42 #include <asm/cacheflush.h>
43 #include <asm/pgtable.h>
44 #include <asm/kdebug.h>
45
46 static DECLARE_MUTEX(kprobe_mutex);
47
48 static struct kprobe *current_kprobe;
49 static unsigned long kprobe_status, kprobe_old_rflags, kprobe_saved_rflags;
50 static struct kprobe *kprobe_prev;
51 static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev;
52 static struct pt_regs jprobe_saved_regs;
53 static long *jprobe_saved_rsp;
54 void jprobe_return_end(void);
55
56 /* copy of the kernel stack at the probe fire time */
57 static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
58
59 /*
60  * returns non-zero if opcode modifies the interrupt flag.
61  */
62 static inline int is_IF_modifier(kprobe_opcode_t *insn)
63 {
64         switch (*insn) {
65         case 0xfa:              /* cli */
66         case 0xfb:              /* sti */
67         case 0xcf:              /* iret/iretd */
68         case 0x9d:              /* popf/popfd */
69                 return 1;
70         }
71
72         if (*insn  >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
73                 return 1;
74         return 0;
75 }
76
77 int arch_prepare_kprobe(struct kprobe *p)
78 {
79         /* insn: must be on special executable page on x86_64. */
80         up(&kprobe_mutex);
81         p->ainsn.insn = get_insn_slot();
82         down(&kprobe_mutex);
83         if (!p->ainsn.insn) {
84                 return -ENOMEM;
85         }
86         return 0;
87 }
88
89 /*
90  * Determine if the instruction uses the %rip-relative addressing mode.
91  * If it does, return the address of the 32-bit displacement word.
92  * If not, return null.
93  */
94 static inline s32 *is_riprel(u8 *insn)
95 {
96 #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)                \
97         (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
98           (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
99           (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
100           (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
101          << (row % 64))
102         static const u64 onebyte_has_modrm[256 / 64] = {
103                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
104                 /*      -------------------------------         */
105                 W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
106                 W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
107                 W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
108                 W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
109                 W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
110                 W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
111                 W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
112                 W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
113                 W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
114                 W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
115                 W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
116                 W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
117                 W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
118                 W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
119                 W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
120                 W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1)  /* f0 */
121                 /*      -------------------------------         */
122                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
123         };
124         static const u64 twobyte_has_modrm[256 / 64] = {
125                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
126                 /*      -------------------------------         */
127                 W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
128                 W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
129                 W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
130                 W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
131                 W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
132                 W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
133                 W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
134                 W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
135                 W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
136                 W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
137                 W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
138                 W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
139                 W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
140                 W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
141                 W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
142                 W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0)  /* ff */
143                 /*      -------------------------------         */
144                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
145         };
146 #undef  W
147         int need_modrm;
148
149         /* Skip legacy instruction prefixes.  */
150         while (1) {
151                 switch (*insn) {
152                 case 0x66:
153                 case 0x67:
154                 case 0x2e:
155                 case 0x3e:
156                 case 0x26:
157                 case 0x64:
158                 case 0x65:
159                 case 0x36:
160                 case 0xf0:
161                 case 0xf3:
162                 case 0xf2:
163                         ++insn;
164                         continue;
165                 }
166                 break;
167         }
168
169         /* Skip REX instruction prefix.  */
170         if ((*insn & 0xf0) == 0x40)
171                 ++insn;
172
173         if (*insn == 0x0f) {    /* Two-byte opcode.  */
174                 ++insn;
175                 need_modrm = test_bit(*insn, twobyte_has_modrm);
176         } else {                /* One-byte opcode.  */
177                 need_modrm = test_bit(*insn, onebyte_has_modrm);
178         }
179
180         if (need_modrm) {
181                 u8 modrm = *++insn;
182                 if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
183                         /* Displacement follows ModRM byte.  */
184                         return (s32 *) ++insn;
185                 }
186         }
187
188         /* No %rip-relative addressing mode here.  */
189         return NULL;
190 }
191
192 void arch_copy_kprobe(struct kprobe *p)
193 {
194         s32 *ripdisp;
195         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
196         ripdisp = is_riprel(p->ainsn.insn);
197         if (ripdisp) {
198                 /*
199                  * The copied instruction uses the %rip-relative
200                  * addressing mode.  Adjust the displacement for the
201                  * difference between the original location of this
202                  * instruction and the location of the copy that will
203                  * actually be run.  The tricky bit here is making sure
204                  * that the sign extension happens correctly in this
205                  * calculation, since we need a signed 32-bit result to
206                  * be sign-extended to 64 bits when it's added to the
207                  * %rip value and yield the same 64-bit result that the
208                  * sign-extension of the original signed 32-bit
209                  * displacement would have given.
210                  */
211                 s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
212                 BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
213                 *ripdisp = disp;
214         }
215         p->opcode = *p->addr;
216 }
217
218 void arch_arm_kprobe(struct kprobe *p)
219 {
220         *p->addr = BREAKPOINT_INSTRUCTION;
221         flush_icache_range((unsigned long) p->addr,
222                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
223 }
224
225 void arch_disarm_kprobe(struct kprobe *p)
226 {
227         *p->addr = p->opcode;
228         flush_icache_range((unsigned long) p->addr,
229                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
230 }
231
232 void arch_remove_kprobe(struct kprobe *p)
233 {
234         up(&kprobe_mutex);
235         free_insn_slot(p->ainsn.insn);
236         down(&kprobe_mutex);
237 }
238
239 static inline void save_previous_kprobe(void)
240 {
241         kprobe_prev = current_kprobe;
242         kprobe_status_prev = kprobe_status;
243         kprobe_old_rflags_prev = kprobe_old_rflags;
244         kprobe_saved_rflags_prev = kprobe_saved_rflags;
245 }
246
247 static inline void restore_previous_kprobe(void)
248 {
249         current_kprobe = kprobe_prev;
250         kprobe_status = kprobe_status_prev;
251         kprobe_old_rflags = kprobe_old_rflags_prev;
252         kprobe_saved_rflags = kprobe_saved_rflags_prev;
253 }
254
255 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
256 {
257         current_kprobe = p;
258         kprobe_saved_rflags = kprobe_old_rflags
259                 = (regs->eflags & (TF_MASK | IF_MASK));
260         if (is_IF_modifier(p->ainsn.insn))
261                 kprobe_saved_rflags &= ~IF_MASK;
262 }
263
264 static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
265 {
266         regs->eflags |= TF_MASK;
267         regs->eflags &= ~IF_MASK;
268         /*single step inline if the instruction is an int3*/
269         if (p->opcode == BREAKPOINT_INSTRUCTION)
270                 regs->rip = (unsigned long)p->addr;
271         else
272                 regs->rip = (unsigned long)p->ainsn.insn;
273 }
274
275 struct task_struct  *arch_get_kprobe_task(void *ptr)
276 {
277         return ((struct thread_info *) (((unsigned long) ptr) &
278                                         (~(THREAD_SIZE -1))))->task;
279 }
280
281 void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
282 {
283         unsigned long *sara = (unsigned long *)regs->rsp;
284         struct kretprobe_instance *ri;
285         static void *orig_ret_addr;
286
287         /*
288          * Save the return address when the return probe hits
289          * the first time, and use it to populate the (krprobe
290          * instance)->ret_addr for subsequent return probes at
291          * the same addrress since stack address would have
292          * the kretprobe_trampoline by then.
293          */
294         if (((void*) *sara) != kretprobe_trampoline)
295                 orig_ret_addr = (void*) *sara;
296
297         if ((ri = get_free_rp_inst(rp)) != NULL) {
298                 ri->rp = rp;
299                 ri->stack_addr = sara;
300                 ri->ret_addr = orig_ret_addr;
301                 add_rp_inst(ri);
302                 /* Replace the return addr with trampoline addr */
303                 *sara = (unsigned long) &kretprobe_trampoline;
304         } else {
305                 rp->nmissed++;
306         }
307 }
308
309 void arch_kprobe_flush_task(struct task_struct *tk)
310 {
311         struct kretprobe_instance *ri;
312         while ((ri = get_rp_inst_tsk(tk)) != NULL) {
313                 *((unsigned long *)(ri->stack_addr)) =
314                                         (unsigned long) ri->ret_addr;
315                 recycle_rp_inst(ri);
316         }
317 }
318
319 /*
320  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
321  * remain disabled thorough out this function.
322  */
323 int kprobe_handler(struct pt_regs *regs)
324 {
325         struct kprobe *p;
326         int ret = 0;
327         kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
328
329         /* We're in an interrupt, but this is clear and BUG()-safe. */
330         preempt_disable();
331
332         /* Check we're not actually recursing */
333         if (kprobe_running()) {
334                 /* We *are* holding lock here, so this is safe.
335                    Disarm the probe we just hit, and ignore it. */
336                 p = get_kprobe(addr);
337                 if (p) {
338                         if (kprobe_status == KPROBE_HIT_SS) {
339                                 regs->eflags &= ~TF_MASK;
340                                 regs->eflags |= kprobe_saved_rflags;
341                                 unlock_kprobes();
342                                 goto no_kprobe;
343                         } else if (kprobe_status == KPROBE_HIT_SSDONE) {
344                                 /* TODO: Provide re-entrancy from
345                                  * post_kprobes_handler() and avoid exception
346                                  * stack corruption while single-stepping on
347                                  * the instruction of the new probe.
348                                  */
349                                 arch_disarm_kprobe(p);
350                                 regs->rip = (unsigned long)p->addr;
351                                 ret = 1;
352                         } else {
353                                 /* We have reentered the kprobe_handler(), since
354                                  * another probe was hit while within the
355                                  * handler. We here save the original kprobe
356                                  * variables and just single step on instruction
357                                  * of the new probe without calling any user
358                                  * handlers.
359                                  */
360                                 save_previous_kprobe();
361                                 set_current_kprobe(p, regs);
362                                 p->nmissed++;
363                                 prepare_singlestep(p, regs);
364                                 kprobe_status = KPROBE_REENTER;
365                                 return 1;
366                         }
367                 } else {
368                         p = current_kprobe;
369                         if (p->break_handler && p->break_handler(p, regs)) {
370                                 goto ss_probe;
371                         }
372                 }
373                 /* If it's not ours, can't be delete race, (we hold lock). */
374                 goto no_kprobe;
375         }
376
377         lock_kprobes();
378         p = get_kprobe(addr);
379         if (!p) {
380                 unlock_kprobes();
381                 if (*addr != BREAKPOINT_INSTRUCTION) {
382                         /*
383                          * The breakpoint instruction was removed right
384                          * after we hit it.  Another cpu has removed
385                          * either a probepoint or a debugger breakpoint
386                          * at this address.  In either case, no further
387                          * handling of this interrupt is appropriate.
388                          */
389                         ret = 1;
390                 }
391                 /* Not one of ours: let kernel handle it */
392                 goto no_kprobe;
393         }
394
395         kprobe_status = KPROBE_HIT_ACTIVE;
396         set_current_kprobe(p, regs);
397
398         if (p->pre_handler && p->pre_handler(p, regs))
399                 /* handler has already set things up, so skip ss setup */
400                 return 1;
401
402 ss_probe:
403         prepare_singlestep(p, regs);
404         kprobe_status = KPROBE_HIT_SS;
405         return 1;
406
407 no_kprobe:
408         preempt_enable_no_resched();
409         return ret;
410 }
411
412 /*
413  * For function-return probes, init_kprobes() establishes a probepoint
414  * here. When a retprobed function returns, this probe is hit and
415  * trampoline_probe_handler() runs, calling the kretprobe's handler.
416  */
417  void kretprobe_trampoline_holder(void)
418  {
419         asm volatile (  ".global kretprobe_trampoline\n"
420                         "kretprobe_trampoline: \n"
421                         "nop\n");
422  }
423
424 /*
425  * Called when we hit the probe point at kretprobe_trampoline
426  */
427 int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
428 {
429         struct task_struct *tsk;
430         struct kretprobe_instance *ri;
431         struct hlist_head *head;
432         struct hlist_node *node;
433         unsigned long *sara = (unsigned long *)regs->rsp - 1;
434
435         tsk = arch_get_kprobe_task(sara);
436         head = kretprobe_inst_table_head(tsk);
437
438         hlist_for_each_entry(ri, node, head, hlist) {
439                 if (ri->stack_addr == sara && ri->rp) {
440                         if (ri->rp->handler)
441                                 ri->rp->handler(ri, regs);
442                 }
443         }
444         return 0;
445 }
446
447 void trampoline_post_handler(struct kprobe *p, struct pt_regs *regs,
448                                                 unsigned long flags)
449 {
450         struct kretprobe_instance *ri;
451         /* RA already popped */
452         unsigned long *sara = ((unsigned long *)regs->rsp) - 1;
453
454         while ((ri = get_rp_inst(sara))) {
455                 regs->rip = (unsigned long)ri->ret_addr;
456                 recycle_rp_inst(ri);
457         }
458         regs->eflags &= ~TF_MASK;
459 }
460
461 /*
462  * Called after single-stepping.  p->addr is the address of the
463  * instruction whose first byte has been replaced by the "int 3"
464  * instruction.  To avoid the SMP problems that can occur when we
465  * temporarily put back the original opcode to single-step, we
466  * single-stepped a copy of the instruction.  The address of this
467  * copy is p->ainsn.insn.
468  *
469  * This function prepares to return from the post-single-step
470  * interrupt.  We have to fix up the stack as follows:
471  *
472  * 0) Except in the case of absolute or indirect jump or call instructions,
473  * the new rip is relative to the copied instruction.  We need to make
474  * it relative to the original instruction.
475  *
476  * 1) If the single-stepped instruction was pushfl, then the TF and IF
477  * flags are set in the just-pushed eflags, and may need to be cleared.
478  *
479  * 2) If the single-stepped instruction was a call, the return address
480  * that is atop the stack is the address following the copied instruction.
481  * We need to make it the address following the original instruction.
482  */
483 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
484 {
485         unsigned long *tos = (unsigned long *)regs->rsp;
486         unsigned long next_rip = 0;
487         unsigned long copy_rip = (unsigned long)p->ainsn.insn;
488         unsigned long orig_rip = (unsigned long)p->addr;
489         kprobe_opcode_t *insn = p->ainsn.insn;
490
491         /*skip the REX prefix*/
492         if (*insn >= 0x40 && *insn <= 0x4f)
493                 insn++;
494
495         switch (*insn) {
496         case 0x9c:              /* pushfl */
497                 *tos &= ~(TF_MASK | IF_MASK);
498                 *tos |= kprobe_old_rflags;
499                 break;
500         case 0xc3:              /* ret/lret */
501         case 0xcb:
502         case 0xc2:
503         case 0xca:
504                 regs->eflags &= ~TF_MASK;
505                 /* rip is already adjusted, no more changes required*/
506                 return;
507         case 0xe8:              /* call relative - Fix return addr */
508                 *tos = orig_rip + (*tos - copy_rip);
509                 break;
510         case 0xff:
511                 if ((*insn & 0x30) == 0x10) {
512                         /* call absolute, indirect */
513                         /* Fix return addr; rip is correct. */
514                         next_rip = regs->rip;
515                         *tos = orig_rip + (*tos - copy_rip);
516                 } else if (((*insn & 0x31) == 0x20) ||  /* jmp near, absolute indirect */
517                            ((*insn & 0x31) == 0x21)) {  /* jmp far, absolute indirect */
518                         /* rip is correct. */
519                         next_rip = regs->rip;
520                 }
521                 break;
522         case 0xea:              /* jmp absolute -- rip is correct */
523                 next_rip = regs->rip;
524                 break;
525         default:
526                 break;
527         }
528
529         regs->eflags &= ~TF_MASK;
530         if (next_rip) {
531                 regs->rip = next_rip;
532         } else {
533                 regs->rip = orig_rip + (regs->rip - copy_rip);
534         }
535 }
536
537 /*
538  * Interrupts are disabled on entry as trap1 is an interrupt gate and they
539  * remain disabled thoroughout this function.  And we hold kprobe lock.
540  */
541 int post_kprobe_handler(struct pt_regs *regs)
542 {
543         if (!kprobe_running())
544                 return 0;
545
546         if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
547                 kprobe_status = KPROBE_HIT_SSDONE;
548                 current_kprobe->post_handler(current_kprobe, regs, 0);
549         }
550
551         if (current_kprobe->post_handler != trampoline_post_handler)
552                 resume_execution(current_kprobe, regs);
553         regs->eflags |= kprobe_saved_rflags;
554
555         /* Restore the original saved kprobes variables and continue. */
556         if (kprobe_status == KPROBE_REENTER) {
557                 restore_previous_kprobe();
558                 goto out;
559         } else {
560                 unlock_kprobes();
561         }
562 out:
563         preempt_enable_no_resched();
564
565         /*
566          * if somebody else is singlestepping across a probe point, eflags
567          * will have TF set, in which case, continue the remaining processing
568          * of do_debug, as if this is not a probe hit.
569          */
570         if (regs->eflags & TF_MASK)
571                 return 0;
572
573         return 1;
574 }
575
576 /* Interrupts disabled, kprobe_lock held. */
577 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
578 {
579         if (current_kprobe->fault_handler
580             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
581                 return 1;
582
583         if (kprobe_status & KPROBE_HIT_SS) {
584                 resume_execution(current_kprobe, regs);
585                 regs->eflags |= kprobe_old_rflags;
586
587                 unlock_kprobes();
588                 preempt_enable_no_resched();
589         }
590         return 0;
591 }
592
593 /*
594  * Wrapper routine for handling exceptions.
595  */
596 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
597                              void *data)
598 {
599         struct die_args *args = (struct die_args *)data;
600         switch (val) {
601         case DIE_INT3:
602                 if (kprobe_handler(args->regs))
603                         return NOTIFY_STOP;
604                 break;
605         case DIE_DEBUG:
606                 if (post_kprobe_handler(args->regs))
607                         return NOTIFY_STOP;
608                 break;
609         case DIE_GPF:
610                 if (kprobe_running() &&
611                     kprobe_fault_handler(args->regs, args->trapnr))
612                         return NOTIFY_STOP;
613                 break;
614         case DIE_PAGE_FAULT:
615                 if (kprobe_running() &&
616                     kprobe_fault_handler(args->regs, args->trapnr))
617                         return NOTIFY_STOP;
618                 break;
619         default:
620                 break;
621         }
622         return NOTIFY_DONE;
623 }
624
625 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
626 {
627         struct jprobe *jp = container_of(p, struct jprobe, kp);
628         unsigned long addr;
629
630         jprobe_saved_regs = *regs;
631         jprobe_saved_rsp = (long *) regs->rsp;
632         addr = (unsigned long)jprobe_saved_rsp;
633         /*
634          * As Linus pointed out, gcc assumes that the callee
635          * owns the argument space and could overwrite it, e.g.
636          * tailcall optimization. So, to be absolutely safe
637          * we also save and restore enough stack bytes to cover
638          * the argument area.
639          */
640         memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr));
641         regs->eflags &= ~IF_MASK;
642         regs->rip = (unsigned long)(jp->entry);
643         return 1;
644 }
645
646 void jprobe_return(void)
647 {
648         preempt_enable_no_resched();
649         asm volatile ("       xchg   %%rbx,%%rsp     \n"
650                       "       int3                      \n"
651                       "       .globl jprobe_return_end  \n"
652                       "       jprobe_return_end:        \n"
653                       "       nop                       \n"::"b"
654                       (jprobe_saved_rsp):"memory");
655 }
656
657 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
658 {
659         u8 *addr = (u8 *) (regs->rip - 1);
660         unsigned long stack_addr = (unsigned long)jprobe_saved_rsp;
661         struct jprobe *jp = container_of(p, struct jprobe, kp);
662
663         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
664                 if ((long *)regs->rsp != jprobe_saved_rsp) {
665                         struct pt_regs *saved_regs =
666                             container_of(jprobe_saved_rsp, struct pt_regs, rsp);
667                         printk("current rsp %p does not match saved rsp %p\n",
668                                (long *)regs->rsp, jprobe_saved_rsp);
669                         printk("Saved registers for jprobe %p\n", jp);
670                         show_registers(saved_regs);
671                         printk("Current registers\n");
672                         show_registers(regs);
673                         BUG();
674                 }
675                 *regs = jprobe_saved_regs;
676                 memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,
677                        MIN_STACK_SIZE(stack_addr));
678                 return 1;
679         }
680         return 0;
681 }