]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - arch/x86_64/kernel/kprobes.c
Merge branch 'upstream' of git://lost.foo-projects.org/~ahkok/git/netdev-2.6 into...
[mirror_ubuntu-bionic-kernel.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/kprobes.h>
35 #include <linux/ptrace.h>
36 #include <linux/string.h>
37 #include <linux/slab.h>
38 #include <linux/preempt.h>
39 #include <linux/module.h>
40
41 #include <asm/cacheflush.h>
42 #include <asm/pgtable.h>
43 #include <asm/kdebug.h>
44 #include <asm/uaccess.h>
45
46 void jprobe_return_end(void);
47 static void __kprobes arch_copy_kprobe(struct kprobe *p);
48
49 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
50 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
51
52 /*
53 * returns non-zero if opcode modifies the interrupt flag.
54 */
55 static __always_inline int is_IF_modifier(kprobe_opcode_t *insn)
56 {
57 switch (*insn) {
58 case 0xfa: /* cli */
59 case 0xfb: /* sti */
60 case 0xcf: /* iret/iretd */
61 case 0x9d: /* popf/popfd */
62 return 1;
63 }
64
65 if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
66 return 1;
67 return 0;
68 }
69
70 int __kprobes arch_prepare_kprobe(struct kprobe *p)
71 {
72 /* insn: must be on special executable page on x86_64. */
73 p->ainsn.insn = get_insn_slot();
74 if (!p->ainsn.insn) {
75 return -ENOMEM;
76 }
77 arch_copy_kprobe(p);
78 return 0;
79 }
80
81 /*
82 * Determine if the instruction uses the %rip-relative addressing mode.
83 * If it does, return the address of the 32-bit displacement word.
84 * If not, return null.
85 */
86 static s32 __kprobes *is_riprel(u8 *insn)
87 {
88 #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \
89 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
90 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
91 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
92 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
93 << (row % 64))
94 static const u64 onebyte_has_modrm[256 / 64] = {
95 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
96 /* ------------------------------- */
97 W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
98 W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
99 W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
100 W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
101 W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
102 W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
103 W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
104 W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
105 W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
106 W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
107 W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
108 W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
109 W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
110 W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
111 W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
112 W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */
113 /* ------------------------------- */
114 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
115 };
116 static const u64 twobyte_has_modrm[256 / 64] = {
117 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
118 /* ------------------------------- */
119 W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
120 W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
121 W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
122 W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
123 W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
124 W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
125 W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
126 W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
127 W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
128 W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
129 W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
130 W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
131 W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
132 W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
133 W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
134 W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */
135 /* ------------------------------- */
136 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
137 };
138 #undef W
139 int need_modrm;
140
141 /* Skip legacy instruction prefixes. */
142 while (1) {
143 switch (*insn) {
144 case 0x66:
145 case 0x67:
146 case 0x2e:
147 case 0x3e:
148 case 0x26:
149 case 0x64:
150 case 0x65:
151 case 0x36:
152 case 0xf0:
153 case 0xf3:
154 case 0xf2:
155 ++insn;
156 continue;
157 }
158 break;
159 }
160
161 /* Skip REX instruction prefix. */
162 if ((*insn & 0xf0) == 0x40)
163 ++insn;
164
165 if (*insn == 0x0f) { /* Two-byte opcode. */
166 ++insn;
167 need_modrm = test_bit(*insn, twobyte_has_modrm);
168 } else { /* One-byte opcode. */
169 need_modrm = test_bit(*insn, onebyte_has_modrm);
170 }
171
172 if (need_modrm) {
173 u8 modrm = *++insn;
174 if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
175 /* Displacement follows ModRM byte. */
176 return (s32 *) ++insn;
177 }
178 }
179
180 /* No %rip-relative addressing mode here. */
181 return NULL;
182 }
183
184 static void __kprobes arch_copy_kprobe(struct kprobe *p)
185 {
186 s32 *ripdisp;
187 memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
188 ripdisp = is_riprel(p->ainsn.insn);
189 if (ripdisp) {
190 /*
191 * The copied instruction uses the %rip-relative
192 * addressing mode. Adjust the displacement for the
193 * difference between the original location of this
194 * instruction and the location of the copy that will
195 * actually be run. The tricky bit here is making sure
196 * that the sign extension happens correctly in this
197 * calculation, since we need a signed 32-bit result to
198 * be sign-extended to 64 bits when it's added to the
199 * %rip value and yield the same 64-bit result that the
200 * sign-extension of the original signed 32-bit
201 * displacement would have given.
202 */
203 s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
204 BUG_ON((s64) (s32) disp != disp); /* Sanity check. */
205 *ripdisp = disp;
206 }
207 p->opcode = *p->addr;
208 }
209
210 void __kprobes arch_arm_kprobe(struct kprobe *p)
211 {
212 *p->addr = BREAKPOINT_INSTRUCTION;
213 flush_icache_range((unsigned long) p->addr,
214 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
215 }
216
217 void __kprobes arch_disarm_kprobe(struct kprobe *p)
218 {
219 *p->addr = p->opcode;
220 flush_icache_range((unsigned long) p->addr,
221 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
222 }
223
224 void __kprobes arch_remove_kprobe(struct kprobe *p)
225 {
226 mutex_lock(&kprobe_mutex);
227 free_insn_slot(p->ainsn.insn);
228 mutex_unlock(&kprobe_mutex);
229 }
230
231 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
232 {
233 kcb->prev_kprobe.kp = kprobe_running();
234 kcb->prev_kprobe.status = kcb->kprobe_status;
235 kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
236 kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
237 }
238
239 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
240 {
241 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
242 kcb->kprobe_status = kcb->prev_kprobe.status;
243 kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
244 kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
245 }
246
247 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
248 struct kprobe_ctlblk *kcb)
249 {
250 __get_cpu_var(current_kprobe) = p;
251 kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
252 = (regs->eflags & (TF_MASK | IF_MASK));
253 if (is_IF_modifier(p->ainsn.insn))
254 kcb->kprobe_saved_rflags &= ~IF_MASK;
255 }
256
257 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
258 {
259 regs->eflags |= TF_MASK;
260 regs->eflags &= ~IF_MASK;
261 /*single step inline if the instruction is an int3*/
262 if (p->opcode == BREAKPOINT_INSTRUCTION)
263 regs->rip = (unsigned long)p->addr;
264 else
265 regs->rip = (unsigned long)p->ainsn.insn;
266 }
267
268 /* Called with kretprobe_lock held */
269 void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
270 struct pt_regs *regs)
271 {
272 unsigned long *sara = (unsigned long *)regs->rsp;
273 struct kretprobe_instance *ri;
274
275 if ((ri = get_free_rp_inst(rp)) != NULL) {
276 ri->rp = rp;
277 ri->task = current;
278 ri->ret_addr = (kprobe_opcode_t *) *sara;
279
280 /* Replace the return addr with trampoline addr */
281 *sara = (unsigned long) &kretprobe_trampoline;
282
283 add_rp_inst(ri);
284 } else {
285 rp->nmissed++;
286 }
287 }
288
289 int __kprobes kprobe_handler(struct pt_regs *regs)
290 {
291 struct kprobe *p;
292 int ret = 0;
293 kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
294 struct kprobe_ctlblk *kcb;
295
296 /*
297 * We don't want to be preempted for the entire
298 * duration of kprobe processing
299 */
300 preempt_disable();
301 kcb = get_kprobe_ctlblk();
302
303 /* Check we're not actually recursing */
304 if (kprobe_running()) {
305 p = get_kprobe(addr);
306 if (p) {
307 if (kcb->kprobe_status == KPROBE_HIT_SS &&
308 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
309 regs->eflags &= ~TF_MASK;
310 regs->eflags |= kcb->kprobe_saved_rflags;
311 goto no_kprobe;
312 } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
313 /* TODO: Provide re-entrancy from
314 * post_kprobes_handler() and avoid exception
315 * stack corruption while single-stepping on
316 * the instruction of the new probe.
317 */
318 arch_disarm_kprobe(p);
319 regs->rip = (unsigned long)p->addr;
320 reset_current_kprobe();
321 ret = 1;
322 } else {
323 /* We have reentered the kprobe_handler(), since
324 * another probe was hit while within the
325 * handler. We here save the original kprobe
326 * variables and just single step on instruction
327 * of the new probe without calling any user
328 * handlers.
329 */
330 save_previous_kprobe(kcb);
331 set_current_kprobe(p, regs, kcb);
332 kprobes_inc_nmissed_count(p);
333 prepare_singlestep(p, regs);
334 kcb->kprobe_status = KPROBE_REENTER;
335 return 1;
336 }
337 } else {
338 if (*addr != BREAKPOINT_INSTRUCTION) {
339 /* The breakpoint instruction was removed by
340 * another cpu right after we hit, no further
341 * handling of this interrupt is appropriate
342 */
343 regs->rip = (unsigned long)addr;
344 ret = 1;
345 goto no_kprobe;
346 }
347 p = __get_cpu_var(current_kprobe);
348 if (p->break_handler && p->break_handler(p, regs)) {
349 goto ss_probe;
350 }
351 }
352 goto no_kprobe;
353 }
354
355 p = get_kprobe(addr);
356 if (!p) {
357 if (*addr != BREAKPOINT_INSTRUCTION) {
358 /*
359 * The breakpoint instruction was removed right
360 * after we hit it. Another cpu has removed
361 * either a probepoint or a debugger breakpoint
362 * at this address. In either case, no further
363 * handling of this interrupt is appropriate.
364 * Back up over the (now missing) int3 and run
365 * the original instruction.
366 */
367 regs->rip = (unsigned long)addr;
368 ret = 1;
369 }
370 /* Not one of ours: let kernel handle it */
371 goto no_kprobe;
372 }
373
374 set_current_kprobe(p, regs, kcb);
375 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
376
377 if (p->pre_handler && p->pre_handler(p, regs))
378 /* handler has already set things up, so skip ss setup */
379 return 1;
380
381 ss_probe:
382 prepare_singlestep(p, regs);
383 kcb->kprobe_status = KPROBE_HIT_SS;
384 return 1;
385
386 no_kprobe:
387 preempt_enable_no_resched();
388 return ret;
389 }
390
391 /*
392 * For function-return probes, init_kprobes() establishes a probepoint
393 * here. When a retprobed function returns, this probe is hit and
394 * trampoline_probe_handler() runs, calling the kretprobe's handler.
395 */
396 void kretprobe_trampoline_holder(void)
397 {
398 asm volatile ( ".global kretprobe_trampoline\n"
399 "kretprobe_trampoline: \n"
400 "nop\n");
401 }
402
403 /*
404 * Called when we hit the probe point at kretprobe_trampoline
405 */
406 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
407 {
408 struct kretprobe_instance *ri = NULL;
409 struct hlist_head *head;
410 struct hlist_node *node, *tmp;
411 unsigned long flags, orig_ret_address = 0;
412 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
413
414 spin_lock_irqsave(&kretprobe_lock, flags);
415 head = kretprobe_inst_table_head(current);
416
417 /*
418 * It is possible to have multiple instances associated with a given
419 * task either because an multiple functions in the call path
420 * have a return probe installed on them, and/or more then one return
421 * return probe was registered for a target function.
422 *
423 * We can handle this because:
424 * - instances are always inserted at the head of the list
425 * - when multiple return probes are registered for the same
426 * function, the first instance's ret_addr will point to the
427 * real return address, and all the rest will point to
428 * kretprobe_trampoline
429 */
430 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
431 if (ri->task != current)
432 /* another task is sharing our hash bucket */
433 continue;
434
435 if (ri->rp && ri->rp->handler)
436 ri->rp->handler(ri, regs);
437
438 orig_ret_address = (unsigned long)ri->ret_addr;
439 recycle_rp_inst(ri);
440
441 if (orig_ret_address != trampoline_address)
442 /*
443 * This is the real return address. Any other
444 * instances associated with this task are for
445 * other calls deeper on the call stack
446 */
447 break;
448 }
449
450 BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
451 regs->rip = orig_ret_address;
452
453 reset_current_kprobe();
454 spin_unlock_irqrestore(&kretprobe_lock, flags);
455 preempt_enable_no_resched();
456
457 /*
458 * By returning a non-zero value, we are telling
459 * kprobe_handler() that we don't want the post_handler
460 * to run (and have re-enabled preemption)
461 */
462 return 1;
463 }
464
465 /*
466 * Called after single-stepping. p->addr is the address of the
467 * instruction whose first byte has been replaced by the "int 3"
468 * instruction. To avoid the SMP problems that can occur when we
469 * temporarily put back the original opcode to single-step, we
470 * single-stepped a copy of the instruction. The address of this
471 * copy is p->ainsn.insn.
472 *
473 * This function prepares to return from the post-single-step
474 * interrupt. We have to fix up the stack as follows:
475 *
476 * 0) Except in the case of absolute or indirect jump or call instructions,
477 * the new rip is relative to the copied instruction. We need to make
478 * it relative to the original instruction.
479 *
480 * 1) If the single-stepped instruction was pushfl, then the TF and IF
481 * flags are set in the just-pushed eflags, and may need to be cleared.
482 *
483 * 2) If the single-stepped instruction was a call, the return address
484 * that is atop the stack is the address following the copied instruction.
485 * We need to make it the address following the original instruction.
486 */
487 static void __kprobes resume_execution(struct kprobe *p,
488 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
489 {
490 unsigned long *tos = (unsigned long *)regs->rsp;
491 unsigned long next_rip = 0;
492 unsigned long copy_rip = (unsigned long)p->ainsn.insn;
493 unsigned long orig_rip = (unsigned long)p->addr;
494 kprobe_opcode_t *insn = p->ainsn.insn;
495
496 /*skip the REX prefix*/
497 if (*insn >= 0x40 && *insn <= 0x4f)
498 insn++;
499
500 switch (*insn) {
501 case 0x9c: /* pushfl */
502 *tos &= ~(TF_MASK | IF_MASK);
503 *tos |= kcb->kprobe_old_rflags;
504 break;
505 case 0xc3: /* ret/lret */
506 case 0xcb:
507 case 0xc2:
508 case 0xca:
509 regs->eflags &= ~TF_MASK;
510 /* rip is already adjusted, no more changes required*/
511 return;
512 case 0xe8: /* call relative - Fix return addr */
513 *tos = orig_rip + (*tos - copy_rip);
514 break;
515 case 0xff:
516 if ((insn[1] & 0x30) == 0x10) {
517 /* call absolute, indirect */
518 /* Fix return addr; rip is correct. */
519 next_rip = regs->rip;
520 *tos = orig_rip + (*tos - copy_rip);
521 } else if (((insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
522 ((insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
523 /* rip is correct. */
524 next_rip = regs->rip;
525 }
526 break;
527 case 0xea: /* jmp absolute -- rip is correct */
528 next_rip = regs->rip;
529 break;
530 default:
531 break;
532 }
533
534 regs->eflags &= ~TF_MASK;
535 if (next_rip) {
536 regs->rip = next_rip;
537 } else {
538 regs->rip = orig_rip + (regs->rip - copy_rip);
539 }
540 }
541
542 int __kprobes post_kprobe_handler(struct pt_regs *regs)
543 {
544 struct kprobe *cur = kprobe_running();
545 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
546
547 if (!cur)
548 return 0;
549
550 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
551 kcb->kprobe_status = KPROBE_HIT_SSDONE;
552 cur->post_handler(cur, regs, 0);
553 }
554
555 resume_execution(cur, regs, kcb);
556 regs->eflags |= kcb->kprobe_saved_rflags;
557
558 /* Restore the original saved kprobes variables and continue. */
559 if (kcb->kprobe_status == KPROBE_REENTER) {
560 restore_previous_kprobe(kcb);
561 goto out;
562 }
563 reset_current_kprobe();
564 out:
565 preempt_enable_no_resched();
566
567 /*
568 * if somebody else is singlestepping across a probe point, eflags
569 * will have TF set, in which case, continue the remaining processing
570 * of do_debug, as if this is not a probe hit.
571 */
572 if (regs->eflags & TF_MASK)
573 return 0;
574
575 return 1;
576 }
577
578 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
579 {
580 struct kprobe *cur = kprobe_running();
581 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
582 const struct exception_table_entry *fixup;
583
584 switch(kcb->kprobe_status) {
585 case KPROBE_HIT_SS:
586 case KPROBE_REENTER:
587 /*
588 * We are here because the instruction being single
589 * stepped caused a page fault. We reset the current
590 * kprobe and the rip points back to the probe address
591 * and allow the page fault handler to continue as a
592 * normal page fault.
593 */
594 regs->rip = (unsigned long)cur->addr;
595 regs->eflags |= kcb->kprobe_old_rflags;
596 if (kcb->kprobe_status == KPROBE_REENTER)
597 restore_previous_kprobe(kcb);
598 else
599 reset_current_kprobe();
600 preempt_enable_no_resched();
601 break;
602 case KPROBE_HIT_ACTIVE:
603 case KPROBE_HIT_SSDONE:
604 /*
605 * We increment the nmissed count for accounting,
606 * we can also use npre/npostfault count for accouting
607 * these specific fault cases.
608 */
609 kprobes_inc_nmissed_count(cur);
610
611 /*
612 * We come here because instructions in the pre/post
613 * handler caused the page_fault, this could happen
614 * if handler tries to access user space by
615 * copy_from_user(), get_user() etc. Let the
616 * user-specified handler try to fix it first.
617 */
618 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
619 return 1;
620
621 /*
622 * In case the user-specified fault handler returned
623 * zero, try to fix up.
624 */
625 fixup = search_exception_tables(regs->rip);
626 if (fixup) {
627 regs->rip = fixup->fixup;
628 return 1;
629 }
630
631 /*
632 * fixup() could not handle it,
633 * Let do_page_fault() fix it.
634 */
635 break;
636 default:
637 break;
638 }
639 return 0;
640 }
641
642 /*
643 * Wrapper routine for handling exceptions.
644 */
645 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
646 unsigned long val, void *data)
647 {
648 struct die_args *args = (struct die_args *)data;
649 int ret = NOTIFY_DONE;
650
651 if (args->regs && user_mode(args->regs))
652 return ret;
653
654 switch (val) {
655 case DIE_INT3:
656 if (kprobe_handler(args->regs))
657 ret = NOTIFY_STOP;
658 break;
659 case DIE_DEBUG:
660 if (post_kprobe_handler(args->regs))
661 ret = NOTIFY_STOP;
662 break;
663 case DIE_GPF:
664 case DIE_PAGE_FAULT:
665 /* kprobe_running() needs smp_processor_id() */
666 preempt_disable();
667 if (kprobe_running() &&
668 kprobe_fault_handler(args->regs, args->trapnr))
669 ret = NOTIFY_STOP;
670 preempt_enable();
671 break;
672 default:
673 break;
674 }
675 return ret;
676 }
677
678 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
679 {
680 struct jprobe *jp = container_of(p, struct jprobe, kp);
681 unsigned long addr;
682 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
683
684 kcb->jprobe_saved_regs = *regs;
685 kcb->jprobe_saved_rsp = (long *) regs->rsp;
686 addr = (unsigned long)(kcb->jprobe_saved_rsp);
687 /*
688 * As Linus pointed out, gcc assumes that the callee
689 * owns the argument space and could overwrite it, e.g.
690 * tailcall optimization. So, to be absolutely safe
691 * we also save and restore enough stack bytes to cover
692 * the argument area.
693 */
694 memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
695 MIN_STACK_SIZE(addr));
696 regs->eflags &= ~IF_MASK;
697 regs->rip = (unsigned long)(jp->entry);
698 return 1;
699 }
700
701 void __kprobes jprobe_return(void)
702 {
703 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
704
705 asm volatile (" xchg %%rbx,%%rsp \n"
706 " int3 \n"
707 " .globl jprobe_return_end \n"
708 " jprobe_return_end: \n"
709 " nop \n"::"b"
710 (kcb->jprobe_saved_rsp):"memory");
711 }
712
713 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
714 {
715 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
716 u8 *addr = (u8 *) (regs->rip - 1);
717 unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
718 struct jprobe *jp = container_of(p, struct jprobe, kp);
719
720 if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
721 if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
722 struct pt_regs *saved_regs =
723 container_of(kcb->jprobe_saved_rsp,
724 struct pt_regs, rsp);
725 printk("current rsp %p does not match saved rsp %p\n",
726 (long *)regs->rsp, kcb->jprobe_saved_rsp);
727 printk("Saved registers for jprobe %p\n", jp);
728 show_registers(saved_regs);
729 printk("Current registers\n");
730 show_registers(regs);
731 BUG();
732 }
733 *regs = kcb->jprobe_saved_regs;
734 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
735 MIN_STACK_SIZE(stack_addr));
736 preempt_enable_no_resched();
737 return 1;
738 }
739 return 0;
740 }
741
742 static struct kprobe trampoline_p = {
743 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
744 .pre_handler = trampoline_probe_handler
745 };
746
747 int __init arch_init_kprobes(void)
748 {
749 return register_kprobe(&trampoline_p);
750 }