[PATCH] kprobes: fix build breakage
[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/string.h>
38 #include <linux/slab.h>
39 #include <linux/preempt.h>
40
41 #include <asm/cacheflush.h>
42 #include <asm/pgtable.h>
43 #include <asm/kdebug.h>
44
45 void jprobe_return_end(void);
46 static void __kprobes arch_copy_kprobe(struct kprobe *p);
47
48 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
49 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
50
51 /*
52  * returns non-zero if opcode modifies the interrupt flag.
53  */
54 static inline int is_IF_modifier(kprobe_opcode_t *insn)
55 {
56         switch (*insn) {
57         case 0xfa:              /* cli */
58         case 0xfb:              /* sti */
59         case 0xcf:              /* iret/iretd */
60         case 0x9d:              /* popf/popfd */
61                 return 1;
62         }
63
64         if (*insn  >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
65                 return 1;
66         return 0;
67 }
68
69 int __kprobes arch_prepare_kprobe(struct kprobe *p)
70 {
71         /* insn: must be on special executable page on x86_64. */
72         p->ainsn.insn = get_insn_slot();
73         if (!p->ainsn.insn) {
74                 return -ENOMEM;
75         }
76         arch_copy_kprobe(p);
77         return 0;
78 }
79
80 /*
81  * Determine if the instruction uses the %rip-relative addressing mode.
82  * If it does, return the address of the 32-bit displacement word.
83  * If not, return null.
84  */
85 static inline s32 *is_riprel(u8 *insn)
86 {
87 #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)                \
88         (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
89           (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
90           (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
91           (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
92          << (row % 64))
93         static const u64 onebyte_has_modrm[256 / 64] = {
94                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
95                 /*      -------------------------------         */
96                 W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
97                 W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
98                 W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
99                 W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
100                 W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
101                 W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
102                 W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
103                 W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
104                 W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
105                 W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
106                 W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
107                 W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
108                 W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
109                 W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
110                 W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
111                 W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1)  /* f0 */
112                 /*      -------------------------------         */
113                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
114         };
115         static const u64 twobyte_has_modrm[256 / 64] = {
116                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
117                 /*      -------------------------------         */
118                 W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
119                 W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
120                 W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
121                 W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
122                 W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
123                 W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
124                 W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
125                 W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
126                 W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
127                 W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
128                 W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
129                 W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
130                 W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
131                 W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
132                 W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
133                 W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0)  /* ff */
134                 /*      -------------------------------         */
135                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
136         };
137 #undef  W
138         int need_modrm;
139
140         /* Skip legacy instruction prefixes.  */
141         while (1) {
142                 switch (*insn) {
143                 case 0x66:
144                 case 0x67:
145                 case 0x2e:
146                 case 0x3e:
147                 case 0x26:
148                 case 0x64:
149                 case 0x65:
150                 case 0x36:
151                 case 0xf0:
152                 case 0xf3:
153                 case 0xf2:
154                         ++insn;
155                         continue;
156                 }
157                 break;
158         }
159
160         /* Skip REX instruction prefix.  */
161         if ((*insn & 0xf0) == 0x40)
162                 ++insn;
163
164         if (*insn == 0x0f) {    /* Two-byte opcode.  */
165                 ++insn;
166                 need_modrm = test_bit(*insn, twobyte_has_modrm);
167         } else {                /* One-byte opcode.  */
168                 need_modrm = test_bit(*insn, onebyte_has_modrm);
169         }
170
171         if (need_modrm) {
172                 u8 modrm = *++insn;
173                 if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
174                         /* Displacement follows ModRM byte.  */
175                         return (s32 *) ++insn;
176                 }
177         }
178
179         /* No %rip-relative addressing mode here.  */
180         return NULL;
181 }
182
183 static void __kprobes arch_copy_kprobe(struct kprobe *p)
184 {
185         s32 *ripdisp;
186         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
187         ripdisp = is_riprel(p->ainsn.insn);
188         if (ripdisp) {
189                 /*
190                  * The copied instruction uses the %rip-relative
191                  * addressing mode.  Adjust the displacement for the
192                  * difference between the original location of this
193                  * instruction and the location of the copy that will
194                  * actually be run.  The tricky bit here is making sure
195                  * that the sign extension happens correctly in this
196                  * calculation, since we need a signed 32-bit result to
197                  * be sign-extended to 64 bits when it's added to the
198                  * %rip value and yield the same 64-bit result that the
199                  * sign-extension of the original signed 32-bit
200                  * displacement would have given.
201                  */
202                 s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
203                 BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
204                 *ripdisp = disp;
205         }
206         p->opcode = *p->addr;
207 }
208
209 void __kprobes arch_arm_kprobe(struct kprobe *p)
210 {
211         *p->addr = BREAKPOINT_INSTRUCTION;
212         flush_icache_range((unsigned long) p->addr,
213                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
214 }
215
216 void __kprobes arch_disarm_kprobe(struct kprobe *p)
217 {
218         *p->addr = p->opcode;
219         flush_icache_range((unsigned long) p->addr,
220                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
221 }
222
223 void __kprobes arch_remove_kprobe(struct kprobe *p)
224 {
225         down(&kprobe_mutex);
226         free_insn_slot(p->ainsn.insn);
227         up(&kprobe_mutex);
228 }
229
230 static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
231 {
232         kcb->prev_kprobe.kp = kprobe_running();
233         kcb->prev_kprobe.status = kcb->kprobe_status;
234         kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
235         kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
236 }
237
238 static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
239 {
240         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
241         kcb->kprobe_status = kcb->prev_kprobe.status;
242         kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
243         kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
244 }
245
246 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
247                                 struct kprobe_ctlblk *kcb)
248 {
249         __get_cpu_var(current_kprobe) = p;
250         kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
251                 = (regs->eflags & (TF_MASK | IF_MASK));
252         if (is_IF_modifier(p->ainsn.insn))
253                 kcb->kprobe_saved_rflags &= ~IF_MASK;
254 }
255
256 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
257 {
258         regs->eflags |= TF_MASK;
259         regs->eflags &= ~IF_MASK;
260         /*single step inline if the instruction is an int3*/
261         if (p->opcode == BREAKPOINT_INSTRUCTION)
262                 regs->rip = (unsigned long)p->addr;
263         else
264                 regs->rip = (unsigned long)p->ainsn.insn;
265 }
266
267 /* Called with kretprobe_lock held */
268 void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
269                                       struct pt_regs *regs)
270 {
271         unsigned long *sara = (unsigned long *)regs->rsp;
272         struct kretprobe_instance *ri;
273
274         if ((ri = get_free_rp_inst(rp)) != NULL) {
275                 ri->rp = rp;
276                 ri->task = current;
277                 ri->ret_addr = (kprobe_opcode_t *) *sara;
278
279                 /* Replace the return addr with trampoline addr */
280                 *sara = (unsigned long) &kretprobe_trampoline;
281
282                 add_rp_inst(ri);
283         } else {
284                 rp->nmissed++;
285         }
286 }
287
288 int __kprobes kprobe_handler(struct pt_regs *regs)
289 {
290         struct kprobe *p;
291         int ret = 0;
292         kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
293         struct kprobe_ctlblk *kcb;
294
295         /*
296          * We don't want to be preempted for the entire
297          * duration of kprobe processing
298          */
299         preempt_disable();
300         kcb = get_kprobe_ctlblk();
301
302         /* Check we're not actually recursing */
303         if (kprobe_running()) {
304                 p = get_kprobe(addr);
305                 if (p) {
306                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
307                                 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
308                                 regs->eflags &= ~TF_MASK;
309                                 regs->eflags |= kcb->kprobe_saved_rflags;
310                                 goto no_kprobe;
311                         } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
312                                 /* TODO: Provide re-entrancy from
313                                  * post_kprobes_handler() and avoid exception
314                                  * stack corruption while single-stepping on
315                                  * the instruction of the new probe.
316                                  */
317                                 arch_disarm_kprobe(p);
318                                 regs->rip = (unsigned long)p->addr;
319                                 reset_current_kprobe();
320                                 ret = 1;
321                         } else {
322                                 /* We have reentered the kprobe_handler(), since
323                                  * another probe was hit while within the
324                                  * handler. We here save the original kprobe
325                                  * variables and just single step on instruction
326                                  * of the new probe without calling any user
327                                  * handlers.
328                                  */
329                                 save_previous_kprobe(kcb);
330                                 set_current_kprobe(p, regs, kcb);
331                                 kprobes_inc_nmissed_count(p);
332                                 prepare_singlestep(p, regs);
333                                 kcb->kprobe_status = KPROBE_REENTER;
334                                 return 1;
335                         }
336                 } else {
337                         p = __get_cpu_var(current_kprobe);
338                         if (p->break_handler && p->break_handler(p, regs)) {
339                                 goto ss_probe;
340                         }
341                 }
342                 goto no_kprobe;
343         }
344
345         p = get_kprobe(addr);
346         if (!p) {
347                 if (*addr != BREAKPOINT_INSTRUCTION) {
348                         /*
349                          * The breakpoint instruction was removed right
350                          * after we hit it.  Another cpu has removed
351                          * either a probepoint or a debugger breakpoint
352                          * at this address.  In either case, no further
353                          * handling of this interrupt is appropriate.
354                          * Back up over the (now missing) int3 and run
355                          * the original instruction.
356                          */
357                         regs->rip = (unsigned long)addr;
358                         ret = 1;
359                 }
360                 /* Not one of ours: let kernel handle it */
361                 goto no_kprobe;
362         }
363
364         set_current_kprobe(p, regs, kcb);
365         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
366
367         if (p->pre_handler && p->pre_handler(p, regs))
368                 /* handler has already set things up, so skip ss setup */
369                 return 1;
370
371 ss_probe:
372         prepare_singlestep(p, regs);
373         kcb->kprobe_status = KPROBE_HIT_SS;
374         return 1;
375
376 no_kprobe:
377         preempt_enable_no_resched();
378         return ret;
379 }
380
381 /*
382  * For function-return probes, init_kprobes() establishes a probepoint
383  * here. When a retprobed function returns, this probe is hit and
384  * trampoline_probe_handler() runs, calling the kretprobe's handler.
385  */
386  void kretprobe_trampoline_holder(void)
387  {
388         asm volatile (  ".global kretprobe_trampoline\n"
389                         "kretprobe_trampoline: \n"
390                         "nop\n");
391  }
392
393 /*
394  * Called when we hit the probe point at kretprobe_trampoline
395  */
396 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
397 {
398         struct kretprobe_instance *ri = NULL;
399         struct hlist_head *head;
400         struct hlist_node *node, *tmp;
401         unsigned long flags, orig_ret_address = 0;
402         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
403
404         spin_lock_irqsave(&kretprobe_lock, flags);
405         head = kretprobe_inst_table_head(current);
406
407         /*
408          * It is possible to have multiple instances associated with a given
409          * task either because an multiple functions in the call path
410          * have a return probe installed on them, and/or more then one return
411          * return probe was registered for a target function.
412          *
413          * We can handle this because:
414          *     - instances are always inserted at the head of the list
415          *     - when multiple return probes are registered for the same
416          *       function, the first instance's ret_addr will point to the
417          *       real return address, and all the rest will point to
418          *       kretprobe_trampoline
419          */
420         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
421                 if (ri->task != current)
422                         /* another task is sharing our hash bucket */
423                         continue;
424
425                 if (ri->rp && ri->rp->handler)
426                         ri->rp->handler(ri, regs);
427
428                 orig_ret_address = (unsigned long)ri->ret_addr;
429                 recycle_rp_inst(ri);
430
431                 if (orig_ret_address != trampoline_address)
432                         /*
433                          * This is the real return address. Any other
434                          * instances associated with this task are for
435                          * other calls deeper on the call stack
436                          */
437                         break;
438         }
439
440         BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
441         regs->rip = orig_ret_address;
442
443         reset_current_kprobe();
444         spin_unlock_irqrestore(&kretprobe_lock, flags);
445         preempt_enable_no_resched();
446
447         /*
448          * By returning a non-zero value, we are telling
449          * kprobe_handler() that we don't want the post_handler
450          * to run (and have re-enabled preemption)
451          */
452         return 1;
453 }
454
455 /*
456  * Called after single-stepping.  p->addr is the address of the
457  * instruction whose first byte has been replaced by the "int 3"
458  * instruction.  To avoid the SMP problems that can occur when we
459  * temporarily put back the original opcode to single-step, we
460  * single-stepped a copy of the instruction.  The address of this
461  * copy is p->ainsn.insn.
462  *
463  * This function prepares to return from the post-single-step
464  * interrupt.  We have to fix up the stack as follows:
465  *
466  * 0) Except in the case of absolute or indirect jump or call instructions,
467  * the new rip is relative to the copied instruction.  We need to make
468  * it relative to the original instruction.
469  *
470  * 1) If the single-stepped instruction was pushfl, then the TF and IF
471  * flags are set in the just-pushed eflags, and may need to be cleared.
472  *
473  * 2) If the single-stepped instruction was a call, the return address
474  * that is atop the stack is the address following the copied instruction.
475  * We need to make it the address following the original instruction.
476  */
477 static void __kprobes resume_execution(struct kprobe *p,
478                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
479 {
480         unsigned long *tos = (unsigned long *)regs->rsp;
481         unsigned long next_rip = 0;
482         unsigned long copy_rip = (unsigned long)p->ainsn.insn;
483         unsigned long orig_rip = (unsigned long)p->addr;
484         kprobe_opcode_t *insn = p->ainsn.insn;
485
486         /*skip the REX prefix*/
487         if (*insn >= 0x40 && *insn <= 0x4f)
488                 insn++;
489
490         switch (*insn) {
491         case 0x9c:              /* pushfl */
492                 *tos &= ~(TF_MASK | IF_MASK);
493                 *tos |= kcb->kprobe_old_rflags;
494                 break;
495         case 0xc3:              /* ret/lret */
496         case 0xcb:
497         case 0xc2:
498         case 0xca:
499                 regs->eflags &= ~TF_MASK;
500                 /* rip is already adjusted, no more changes required*/
501                 return;
502         case 0xe8:              /* call relative - Fix return addr */
503                 *tos = orig_rip + (*tos - copy_rip);
504                 break;
505         case 0xff:
506                 if ((*insn & 0x30) == 0x10) {
507                         /* call absolute, indirect */
508                         /* Fix return addr; rip is correct. */
509                         next_rip = regs->rip;
510                         *tos = orig_rip + (*tos - copy_rip);
511                 } else if (((*insn & 0x31) == 0x20) ||  /* jmp near, absolute indirect */
512                            ((*insn & 0x31) == 0x21)) {  /* jmp far, absolute indirect */
513                         /* rip is correct. */
514                         next_rip = regs->rip;
515                 }
516                 break;
517         case 0xea:              /* jmp absolute -- rip is correct */
518                 next_rip = regs->rip;
519                 break;
520         default:
521                 break;
522         }
523
524         regs->eflags &= ~TF_MASK;
525         if (next_rip) {
526                 regs->rip = next_rip;
527         } else {
528                 regs->rip = orig_rip + (regs->rip - copy_rip);
529         }
530 }
531
532 int __kprobes post_kprobe_handler(struct pt_regs *regs)
533 {
534         struct kprobe *cur = kprobe_running();
535         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
536
537         if (!cur)
538                 return 0;
539
540         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
541                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
542                 cur->post_handler(cur, regs, 0);
543         }
544
545         resume_execution(cur, regs, kcb);
546         regs->eflags |= kcb->kprobe_saved_rflags;
547
548         /* Restore the original saved kprobes variables and continue. */
549         if (kcb->kprobe_status == KPROBE_REENTER) {
550                 restore_previous_kprobe(kcb);
551                 goto out;
552         }
553         reset_current_kprobe();
554 out:
555         preempt_enable_no_resched();
556
557         /*
558          * if somebody else is singlestepping across a probe point, eflags
559          * will have TF set, in which case, continue the remaining processing
560          * of do_debug, as if this is not a probe hit.
561          */
562         if (regs->eflags & TF_MASK)
563                 return 0;
564
565         return 1;
566 }
567
568 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
569 {
570         struct kprobe *cur = kprobe_running();
571         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
572
573         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
574                 return 1;
575
576         if (kcb->kprobe_status & KPROBE_HIT_SS) {
577                 resume_execution(cur, regs, kcb);
578                 regs->eflags |= kcb->kprobe_old_rflags;
579
580                 reset_current_kprobe();
581                 preempt_enable_no_resched();
582         }
583         return 0;
584 }
585
586 /*
587  * Wrapper routine for handling exceptions.
588  */
589 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
590                                        unsigned long val, void *data)
591 {
592         struct die_args *args = (struct die_args *)data;
593         int ret = NOTIFY_DONE;
594
595         switch (val) {
596         case DIE_INT3:
597                 if (kprobe_handler(args->regs))
598                         ret = NOTIFY_STOP;
599                 break;
600         case DIE_DEBUG:
601                 if (post_kprobe_handler(args->regs))
602                         ret = NOTIFY_STOP;
603                 break;
604         case DIE_GPF:
605         case DIE_PAGE_FAULT:
606                 /* kprobe_running() needs smp_processor_id() */
607                 preempt_disable();
608                 if (kprobe_running() &&
609                     kprobe_fault_handler(args->regs, args->trapnr))
610                         ret = NOTIFY_STOP;
611                 preempt_enable();
612                 break;
613         default:
614                 break;
615         }
616         return ret;
617 }
618
619 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
620 {
621         struct jprobe *jp = container_of(p, struct jprobe, kp);
622         unsigned long addr;
623         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
624
625         kcb->jprobe_saved_regs = *regs;
626         kcb->jprobe_saved_rsp = (long *) regs->rsp;
627         addr = (unsigned long)(kcb->jprobe_saved_rsp);
628         /*
629          * As Linus pointed out, gcc assumes that the callee
630          * owns the argument space and could overwrite it, e.g.
631          * tailcall optimization. So, to be absolutely safe
632          * we also save and restore enough stack bytes to cover
633          * the argument area.
634          */
635         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
636                         MIN_STACK_SIZE(addr));
637         regs->eflags &= ~IF_MASK;
638         regs->rip = (unsigned long)(jp->entry);
639         return 1;
640 }
641
642 void __kprobes jprobe_return(void)
643 {
644         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
645
646         asm volatile ("       xchg   %%rbx,%%rsp     \n"
647                       "       int3                      \n"
648                       "       .globl jprobe_return_end  \n"
649                       "       jprobe_return_end:        \n"
650                       "       nop                       \n"::"b"
651                       (kcb->jprobe_saved_rsp):"memory");
652 }
653
654 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
655 {
656         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
657         u8 *addr = (u8 *) (regs->rip - 1);
658         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
659         struct jprobe *jp = container_of(p, struct jprobe, kp);
660
661         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
662                 if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
663                         struct pt_regs *saved_regs =
664                             container_of(kcb->jprobe_saved_rsp,
665                                             struct pt_regs, rsp);
666                         printk("current rsp %p does not match saved rsp %p\n",
667                                (long *)regs->rsp, kcb->jprobe_saved_rsp);
668                         printk("Saved registers for jprobe %p\n", jp);
669                         show_registers(saved_regs);
670                         printk("Current registers\n");
671                         show_registers(regs);
672                         BUG();
673                 }
674                 *regs = kcb->jprobe_saved_regs;
675                 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
676                        MIN_STACK_SIZE(stack_addr));
677                 preempt_enable_no_resched();
678                 return 1;
679         }
680         return 0;
681 }
682
683 static struct kprobe trampoline_p = {
684         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
685         .pre_handler = trampoline_probe_handler
686 };
687
688 int __init arch_init_kprobes(void)
689 {
690         return register_kprobe(&trampoline_p);
691 }