kprobes: support kretprobe blacklist
[linux-2.6.git] / arch / x86 / kernel / kprobes_32.c
1 /*
2  *  Kernel Probes (KProbes)
3  *
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.
8  *
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.
13  *
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.
17  *
18  * Copyright (C) IBM Corporation, 2002, 2004
19  *
20  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21  *              Probes initial implementation ( includes contributions from
22  *              Rusty Russell).
23  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24  *              interface to access function arguments.
25  * 2005-May     Hien Nguyen <hien@us.ibm.com>, Jim Keniston
26  *              <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
27  *              <prasanna@in.ibm.com> added function-return probes.
28  */
29
30 #include <linux/kprobes.h>
31 #include <linux/ptrace.h>
32 #include <linux/preempt.h>
33 #include <linux/kdebug.h>
34 #include <asm/cacheflush.h>
35 #include <asm/desc.h>
36 #include <asm/uaccess.h>
37 #include <asm/alternative.h>
38
39 void jprobe_return_end(void);
40
41 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
42 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
43
44 struct kretprobe_blackpoint kretprobe_blacklist[] = {
45         {"__switch_to", }, /* This function switches only current task, but
46                              doesn't switch kernel stack.*/
47         {NULL, NULL}    /* Terminator */
48 };
49 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
50
51 /* insert a jmp code */
52 static __always_inline void set_jmp_op(void *from, void *to)
53 {
54         struct __arch_jmp_op {
55                 char op;
56                 long raddr;
57         } __attribute__((packed)) *jop;
58         jop = (struct __arch_jmp_op *)from;
59         jop->raddr = (long)(to) - ((long)(from) + 5);
60         jop->op = RELATIVEJUMP_INSTRUCTION;
61 }
62
63 /*
64  * returns non-zero if opcodes can be boosted.
65  */
66 static __always_inline int can_boost(kprobe_opcode_t *opcodes)
67 {
68 #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)                \
69         (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
70           (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
71           (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
72           (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
73          << (row % 32))
74         /*
75          * Undefined/reserved opcodes, conditional jump, Opcode Extension
76          * Groups, and some special opcodes can not be boost.
77          */
78         static const unsigned long twobyte_is_boostable[256 / 32] = {
79                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
80                 /*      -------------------------------         */
81                 W(0x00, 0,0,1,1,0,0,1,0,1,1,0,0,0,0,0,0)| /* 00 */
82                 W(0x10, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 10 */
83                 W(0x20, 1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0)| /* 20 */
84                 W(0x30, 0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 30 */
85                 W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 40 */
86                 W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 50 */
87                 W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,0,0,1,1)| /* 60 */
88                 W(0x70, 0,0,0,0,1,1,1,1,0,0,0,0,0,0,1,1), /* 70 */
89                 W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 80 */
90                 W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1), /* 90 */
91                 W(0xa0, 1,1,0,1,1,1,0,0,1,1,0,1,1,1,0,1)| /* a0 */
92                 W(0xb0, 1,1,1,1,1,1,1,1,0,0,0,1,1,1,1,1), /* b0 */
93                 W(0xc0, 1,1,0,0,0,0,0,0,1,1,1,1,1,1,1,1)| /* c0 */
94                 W(0xd0, 0,1,1,1,0,1,0,0,1,1,0,1,1,1,0,1), /* d0 */
95                 W(0xe0, 0,1,1,0,0,1,0,0,1,1,0,1,1,1,0,1)| /* e0 */
96                 W(0xf0, 0,1,1,1,0,1,0,0,1,1,1,0,1,1,1,0)  /* f0 */
97                 /*      -------------------------------         */
98                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
99         };
100 #undef W
101         kprobe_opcode_t opcode;
102         kprobe_opcode_t *orig_opcodes = opcodes;
103 retry:
104         if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
105                 return 0;
106         opcode = *(opcodes++);
107
108         /* 2nd-byte opcode */
109         if (opcode == 0x0f) {
110                 if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
111                         return 0;
112                 return test_bit(*opcodes, twobyte_is_boostable);
113         }
114
115         switch (opcode & 0xf0) {
116         case 0x60:
117                 if (0x63 < opcode && opcode < 0x67)
118                         goto retry; /* prefixes */
119                 /* can't boost Address-size override and bound */
120                 return (opcode != 0x62 && opcode != 0x67);
121         case 0x70:
122                 return 0; /* can't boost conditional jump */
123         case 0xc0:
124                 /* can't boost software-interruptions */
125                 return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
126         case 0xd0:
127                 /* can boost AA* and XLAT */
128                 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
129         case 0xe0:
130                 /* can boost in/out and absolute jmps */
131                 return ((opcode & 0x04) || opcode == 0xea);
132         case 0xf0:
133                 if ((opcode & 0x0c) == 0 && opcode != 0xf1)
134                         goto retry; /* lock/rep(ne) prefix */
135                 /* clear and set flags can be boost */
136                 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
137         default:
138                 if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
139                         goto retry; /* prefixes */
140                 /* can't boost CS override and call */
141                 return (opcode != 0x2e && opcode != 0x9a);
142         }
143 }
144
145 /*
146  * returns non-zero if opcode modifies the interrupt flag.
147  */
148 static int __kprobes is_IF_modifier(kprobe_opcode_t opcode)
149 {
150         switch (opcode) {
151         case 0xfa:              /* cli */
152         case 0xfb:              /* sti */
153         case 0xcf:              /* iret/iretd */
154         case 0x9d:              /* popf/popfd */
155                 return 1;
156         }
157         return 0;
158 }
159
160 int __kprobes arch_prepare_kprobe(struct kprobe *p)
161 {
162         /* insn: must be on special executable page on i386. */
163         p->ainsn.insn = get_insn_slot();
164         if (!p->ainsn.insn)
165                 return -ENOMEM;
166
167         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
168         p->opcode = *p->addr;
169         if (can_boost(p->addr)) {
170                 p->ainsn.boostable = 0;
171         } else {
172                 p->ainsn.boostable = -1;
173         }
174         return 0;
175 }
176
177 void __kprobes arch_arm_kprobe(struct kprobe *p)
178 {
179         text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
180 }
181
182 void __kprobes arch_disarm_kprobe(struct kprobe *p)
183 {
184         text_poke(p->addr, &p->opcode, 1);
185 }
186
187 void __kprobes arch_remove_kprobe(struct kprobe *p)
188 {
189         mutex_lock(&kprobe_mutex);
190         free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1));
191         mutex_unlock(&kprobe_mutex);
192 }
193
194 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
195 {
196         kcb->prev_kprobe.kp = kprobe_running();
197         kcb->prev_kprobe.status = kcb->kprobe_status;
198         kcb->prev_kprobe.old_eflags = kcb->kprobe_old_eflags;
199         kcb->prev_kprobe.saved_eflags = kcb->kprobe_saved_eflags;
200 }
201
202 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
203 {
204         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
205         kcb->kprobe_status = kcb->prev_kprobe.status;
206         kcb->kprobe_old_eflags = kcb->prev_kprobe.old_eflags;
207         kcb->kprobe_saved_eflags = kcb->prev_kprobe.saved_eflags;
208 }
209
210 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
211                                 struct kprobe_ctlblk *kcb)
212 {
213         __get_cpu_var(current_kprobe) = p;
214         kcb->kprobe_saved_eflags = kcb->kprobe_old_eflags
215                 = (regs->eflags & (TF_MASK | IF_MASK));
216         if (is_IF_modifier(p->opcode))
217                 kcb->kprobe_saved_eflags &= ~IF_MASK;
218 }
219
220 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
221 {
222         regs->eflags |= TF_MASK;
223         regs->eflags &= ~IF_MASK;
224         /*single step inline if the instruction is an int3*/
225         if (p->opcode == BREAKPOINT_INSTRUCTION)
226                 regs->eip = (unsigned long)p->addr;
227         else
228                 regs->eip = (unsigned long)p->ainsn.insn;
229 }
230
231 /* Called with kretprobe_lock held */
232 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
233                                       struct pt_regs *regs)
234 {
235         unsigned long *sara = (unsigned long *)&regs->esp;
236
237         ri->ret_addr = (kprobe_opcode_t *) *sara;
238
239         /* Replace the return addr with trampoline addr */
240         *sara = (unsigned long) &kretprobe_trampoline;
241 }
242
243 /*
244  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
245  * remain disabled thorough out this function.
246  */
247 static int __kprobes kprobe_handler(struct pt_regs *regs)
248 {
249         struct kprobe *p;
250         int ret = 0;
251         kprobe_opcode_t *addr;
252         struct kprobe_ctlblk *kcb;
253
254         addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
255
256         /*
257          * We don't want to be preempted for the entire
258          * duration of kprobe processing
259          */
260         preempt_disable();
261         kcb = get_kprobe_ctlblk();
262
263         /* Check we're not actually recursing */
264         if (kprobe_running()) {
265                 p = get_kprobe(addr);
266                 if (p) {
267                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
268                                 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
269                                 regs->eflags &= ~TF_MASK;
270                                 regs->eflags |= kcb->kprobe_saved_eflags;
271                                 goto no_kprobe;
272                         }
273                         /* We have reentered the kprobe_handler(), since
274                          * another probe was hit while within the handler.
275                          * We here save the original kprobes variables and
276                          * just single step on the instruction of the new probe
277                          * without calling any user handlers.
278                          */
279                         save_previous_kprobe(kcb);
280                         set_current_kprobe(p, regs, kcb);
281                         kprobes_inc_nmissed_count(p);
282                         prepare_singlestep(p, regs);
283                         kcb->kprobe_status = KPROBE_REENTER;
284                         return 1;
285                 } else {
286                         if (*addr != BREAKPOINT_INSTRUCTION) {
287                         /* The breakpoint instruction was removed by
288                          * another cpu right after we hit, no further
289                          * handling of this interrupt is appropriate
290                          */
291                                 regs->eip -= sizeof(kprobe_opcode_t);
292                                 ret = 1;
293                                 goto no_kprobe;
294                         }
295                         p = __get_cpu_var(current_kprobe);
296                         if (p->break_handler && p->break_handler(p, regs)) {
297                                 goto ss_probe;
298                         }
299                 }
300                 goto no_kprobe;
301         }
302
303         p = get_kprobe(addr);
304         if (!p) {
305                 if (*addr != BREAKPOINT_INSTRUCTION) {
306                         /*
307                          * The breakpoint instruction was removed right
308                          * after we hit it.  Another cpu has removed
309                          * either a probepoint or a debugger breakpoint
310                          * at this address.  In either case, no further
311                          * handling of this interrupt is appropriate.
312                          * Back up over the (now missing) int3 and run
313                          * the original instruction.
314                          */
315                         regs->eip -= sizeof(kprobe_opcode_t);
316                         ret = 1;
317                 }
318                 /* Not one of ours: let kernel handle it */
319                 goto no_kprobe;
320         }
321
322         set_current_kprobe(p, regs, kcb);
323         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
324
325         if (p->pre_handler && p->pre_handler(p, regs))
326                 /* handler has already set things up, so skip ss setup */
327                 return 1;
328
329 ss_probe:
330 #if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)
331         if (p->ainsn.boostable == 1 && !p->post_handler){
332                 /* Boost up -- we can execute copied instructions directly */
333                 reset_current_kprobe();
334                 regs->eip = (unsigned long)p->ainsn.insn;
335                 preempt_enable_no_resched();
336                 return 1;
337         }
338 #endif
339         prepare_singlestep(p, regs);
340         kcb->kprobe_status = KPROBE_HIT_SS;
341         return 1;
342
343 no_kprobe:
344         preempt_enable_no_resched();
345         return ret;
346 }
347
348 /*
349  * For function-return probes, init_kprobes() establishes a probepoint
350  * here. When a retprobed function returns, this probe is hit and
351  * trampoline_probe_handler() runs, calling the kretprobe's handler.
352  */
353  void __kprobes kretprobe_trampoline_holder(void)
354  {
355         asm volatile ( ".global kretprobe_trampoline\n"
356                         "kretprobe_trampoline: \n"
357                         "       pushf\n"
358                         /* skip cs, eip, orig_eax */
359                         "       subl $12, %esp\n"
360                         "       pushl %fs\n"
361                         "       pushl %ds\n"
362                         "       pushl %es\n"
363                         "       pushl %eax\n"
364                         "       pushl %ebp\n"
365                         "       pushl %edi\n"
366                         "       pushl %esi\n"
367                         "       pushl %edx\n"
368                         "       pushl %ecx\n"
369                         "       pushl %ebx\n"
370                         "       movl %esp, %eax\n"
371                         "       call trampoline_handler\n"
372                         /* move eflags to cs */
373                         "       movl 52(%esp), %edx\n"
374                         "       movl %edx, 48(%esp)\n"
375                         /* save true return address on eflags */
376                         "       movl %eax, 52(%esp)\n"
377                         "       popl %ebx\n"
378                         "       popl %ecx\n"
379                         "       popl %edx\n"
380                         "       popl %esi\n"
381                         "       popl %edi\n"
382                         "       popl %ebp\n"
383                         "       popl %eax\n"
384                         /* skip eip, orig_eax, es, ds, fs */
385                         "       addl $20, %esp\n"
386                         "       popf\n"
387                         "       ret\n");
388 }
389
390 /*
391  * Called from kretprobe_trampoline
392  */
393 fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
394 {
395         struct kretprobe_instance *ri = NULL;
396         struct hlist_head *head, empty_rp;
397         struct hlist_node *node, *tmp;
398         unsigned long flags, orig_ret_address = 0;
399         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
400
401         INIT_HLIST_HEAD(&empty_rp);
402         spin_lock_irqsave(&kretprobe_lock, flags);
403         head = kretprobe_inst_table_head(current);
404         /* fixup registers */
405         regs->xcs = __KERNEL_CS | get_kernel_rpl();
406         regs->eip = trampoline_address;
407         regs->orig_eax = 0xffffffff;
408
409         /*
410          * It is possible to have multiple instances associated with a given
411          * task either because an multiple functions in the call path
412          * have a return probe installed on them, and/or more then one return
413          * return probe was registered for a target function.
414          *
415          * We can handle this because:
416          *     - instances are always inserted at the head of the list
417          *     - when multiple return probes are registered for the same
418          *       function, the first instance's ret_addr will point to the
419          *       real return address, and all the rest will point to
420          *       kretprobe_trampoline
421          */
422         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
423                 if (ri->task != current)
424                         /* another task is sharing our hash bucket */
425                         continue;
426
427                 if (ri->rp && ri->rp->handler){
428                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
429                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
430                         ri->rp->handler(ri, regs);
431                         __get_cpu_var(current_kprobe) = NULL;
432                 }
433
434                 orig_ret_address = (unsigned long)ri->ret_addr;
435                 recycle_rp_inst(ri, &empty_rp);
436
437                 if (orig_ret_address != trampoline_address)
438                         /*
439                          * This is the real return address. Any other
440                          * instances associated with this task are for
441                          * other calls deeper on the call stack
442                          */
443                         break;
444         }
445
446         kretprobe_assert(ri, orig_ret_address, trampoline_address);
447         spin_unlock_irqrestore(&kretprobe_lock, flags);
448
449         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
450                 hlist_del(&ri->hlist);
451                 kfree(ri);
452         }
453         return (void*)orig_ret_address;
454 }
455
456 /*
457  * Called after single-stepping.  p->addr is the address of the
458  * instruction whose first byte has been replaced by the "int 3"
459  * instruction.  To avoid the SMP problems that can occur when we
460  * temporarily put back the original opcode to single-step, we
461  * single-stepped a copy of the instruction.  The address of this
462  * copy is p->ainsn.insn.
463  *
464  * This function prepares to return from the post-single-step
465  * interrupt.  We have to fix up the stack as follows:
466  *
467  * 0) Except in the case of absolute or indirect jump or call instructions,
468  * the new eip is relative to the copied instruction.  We need to make
469  * it relative to the original instruction.
470  *
471  * 1) If the single-stepped instruction was pushfl, then the TF and IF
472  * flags are set in the just-pushed eflags, and may need to be cleared.
473  *
474  * 2) If the single-stepped instruction was a call, the return address
475  * that is atop the stack is the address following the copied instruction.
476  * We need to make it the address following the original instruction.
477  *
478  * This function also checks instruction size for preparing direct execution.
479  */
480 static void __kprobes resume_execution(struct kprobe *p,
481                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
482 {
483         unsigned long *tos = (unsigned long *)&regs->esp;
484         unsigned long copy_eip = (unsigned long)p->ainsn.insn;
485         unsigned long orig_eip = (unsigned long)p->addr;
486
487         regs->eflags &= ~TF_MASK;
488         switch (p->ainsn.insn[0]) {
489         case 0x9c:              /* pushfl */
490                 *tos &= ~(TF_MASK | IF_MASK);
491                 *tos |= kcb->kprobe_old_eflags;
492                 break;
493         case 0xc2:              /* iret/ret/lret */
494         case 0xc3:
495         case 0xca:
496         case 0xcb:
497         case 0xcf:
498         case 0xea:              /* jmp absolute -- eip is correct */
499                 /* eip is already adjusted, no more changes required */
500                 p->ainsn.boostable = 1;
501                 goto no_change;
502         case 0xe8:              /* call relative - Fix return addr */
503                 *tos = orig_eip + (*tos - copy_eip);
504                 break;
505         case 0x9a:              /* call absolute -- same as call absolute, indirect */
506                 *tos = orig_eip + (*tos - copy_eip);
507                 goto no_change;
508         case 0xff:
509                 if ((p->ainsn.insn[1] & 0x30) == 0x10) {
510                         /*
511                          * call absolute, indirect
512                          * Fix return addr; eip is correct.
513                          * But this is not boostable
514                          */
515                         *tos = orig_eip + (*tos - copy_eip);
516                         goto no_change;
517                 } else if (((p->ainsn.insn[1] & 0x31) == 0x20) ||       /* jmp near, absolute indirect */
518                            ((p->ainsn.insn[1] & 0x31) == 0x21)) {       /* jmp far, absolute indirect */
519                         /* eip is correct. And this is boostable */
520                         p->ainsn.boostable = 1;
521                         goto no_change;
522                 }
523         default:
524                 break;
525         }
526
527         if (p->ainsn.boostable == 0) {
528                 if ((regs->eip > copy_eip) &&
529                     (regs->eip - copy_eip) + 5 < MAX_INSN_SIZE) {
530                         /*
531                          * These instructions can be executed directly if it
532                          * jumps back to correct address.
533                          */
534                         set_jmp_op((void *)regs->eip,
535                                    (void *)orig_eip + (regs->eip - copy_eip));
536                         p->ainsn.boostable = 1;
537                 } else {
538                         p->ainsn.boostable = -1;
539                 }
540         }
541
542         regs->eip = orig_eip + (regs->eip - copy_eip);
543
544 no_change:
545         return;
546 }
547
548 /*
549  * Interrupts are disabled on entry as trap1 is an interrupt gate and they
550  * remain disabled thoroughout this function.
551  */
552 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
553 {
554         struct kprobe *cur = kprobe_running();
555         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
556
557         if (!cur)
558                 return 0;
559
560         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
561                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
562                 cur->post_handler(cur, regs, 0);
563         }
564
565         resume_execution(cur, regs, kcb);
566         regs->eflags |= kcb->kprobe_saved_eflags;
567 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
568         if (raw_irqs_disabled_flags(regs->eflags))
569                 trace_hardirqs_off();
570         else
571                 trace_hardirqs_on();
572 #endif
573
574         /*Restore back the original saved kprobes variables and continue. */
575         if (kcb->kprobe_status == KPROBE_REENTER) {
576                 restore_previous_kprobe(kcb);
577                 goto out;
578         }
579         reset_current_kprobe();
580 out:
581         preempt_enable_no_resched();
582
583         /*
584          * if somebody else is singlestepping across a probe point, eflags
585          * will have TF set, in which case, continue the remaining processing
586          * of do_debug, as if this is not a probe hit.
587          */
588         if (regs->eflags & TF_MASK)
589                 return 0;
590
591         return 1;
592 }
593
594 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
595 {
596         struct kprobe *cur = kprobe_running();
597         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
598
599         switch(kcb->kprobe_status) {
600         case KPROBE_HIT_SS:
601         case KPROBE_REENTER:
602                 /*
603                  * We are here because the instruction being single
604                  * stepped caused a page fault. We reset the current
605                  * kprobe and the eip points back to the probe address
606                  * and allow the page fault handler to continue as a
607                  * normal page fault.
608                  */
609                 regs->eip = (unsigned long)cur->addr;
610                 regs->eflags |= kcb->kprobe_old_eflags;
611                 if (kcb->kprobe_status == KPROBE_REENTER)
612                         restore_previous_kprobe(kcb);
613                 else
614                         reset_current_kprobe();
615                 preempt_enable_no_resched();
616                 break;
617         case KPROBE_HIT_ACTIVE:
618         case KPROBE_HIT_SSDONE:
619                 /*
620                  * We increment the nmissed count for accounting,
621                  * we can also use npre/npostfault count for accouting
622                  * these specific fault cases.
623                  */
624                 kprobes_inc_nmissed_count(cur);
625
626                 /*
627                  * We come here because instructions in the pre/post
628                  * handler caused the page_fault, this could happen
629                  * if handler tries to access user space by
630                  * copy_from_user(), get_user() etc. Let the
631                  * user-specified handler try to fix it first.
632                  */
633                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
634                         return 1;
635
636                 /*
637                  * In case the user-specified fault handler returned
638                  * zero, try to fix up.
639                  */
640                 if (fixup_exception(regs))
641                         return 1;
642
643                 /*
644                  * fixup_exception() could not handle it,
645                  * Let do_page_fault() fix it.
646                  */
647                 break;
648         default:
649                 break;
650         }
651         return 0;
652 }
653
654 /*
655  * Wrapper routine to for handling exceptions.
656  */
657 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
658                                        unsigned long val, void *data)
659 {
660         struct die_args *args = (struct die_args *)data;
661         int ret = NOTIFY_DONE;
662
663         if (args->regs && user_mode_vm(args->regs))
664                 return ret;
665
666         switch (val) {
667         case DIE_INT3:
668                 if (kprobe_handler(args->regs))
669                         ret = NOTIFY_STOP;
670                 break;
671         case DIE_DEBUG:
672                 if (post_kprobe_handler(args->regs))
673                         ret = NOTIFY_STOP;
674                 break;
675         case DIE_GPF:
676                 /* kprobe_running() needs smp_processor_id() */
677                 preempt_disable();
678                 if (kprobe_running() &&
679                     kprobe_fault_handler(args->regs, args->trapnr))
680                         ret = NOTIFY_STOP;
681                 preempt_enable();
682                 break;
683         default:
684                 break;
685         }
686         return ret;
687 }
688
689 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
690 {
691         struct jprobe *jp = container_of(p, struct jprobe, kp);
692         unsigned long addr;
693         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
694
695         kcb->jprobe_saved_regs = *regs;
696         kcb->jprobe_saved_esp = &regs->esp;
697         addr = (unsigned long)(kcb->jprobe_saved_esp);
698
699         /*
700          * TBD: As Linus pointed out, gcc assumes that the callee
701          * owns the argument space and could overwrite it, e.g.
702          * tailcall optimization. So, to be absolutely safe
703          * we also save and restore enough stack bytes to cover
704          * the argument area.
705          */
706         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
707                         MIN_STACK_SIZE(addr));
708         regs->eflags &= ~IF_MASK;
709         trace_hardirqs_off();
710         regs->eip = (unsigned long)(jp->entry);
711         return 1;
712 }
713
714 void __kprobes jprobe_return(void)
715 {
716         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
717
718         asm volatile ("       xchgl   %%ebx,%%esp     \n"
719                       "       int3                      \n"
720                       "       .globl jprobe_return_end  \n"
721                       "       jprobe_return_end:        \n"
722                       "       nop                       \n"::"b"
723                       (kcb->jprobe_saved_esp):"memory");
724 }
725
726 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
727 {
728         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
729         u8 *addr = (u8 *) (regs->eip - 1);
730         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_esp);
731         struct jprobe *jp = container_of(p, struct jprobe, kp);
732
733         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
734                 if (&regs->esp != kcb->jprobe_saved_esp) {
735                         struct pt_regs *saved_regs =
736                             container_of(kcb->jprobe_saved_esp,
737                                             struct pt_regs, esp);
738                         printk("current esp %p does not match saved esp %p\n",
739                                &regs->esp, kcb->jprobe_saved_esp);
740                         printk("Saved registers for jprobe %p\n", jp);
741                         show_registers(saved_regs);
742                         printk("Current registers\n");
743                         show_registers(regs);
744                         BUG();
745                 }
746                 *regs = kcb->jprobe_saved_regs;
747                 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
748                        MIN_STACK_SIZE(stack_addr));
749                 preempt_enable_no_resched();
750                 return 1;
751         }
752         return 0;
753 }
754
755 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
756 {
757         return 0;
758 }
759
760 int __init arch_init_kprobes(void)
761 {
762         return 0;
763 }