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kprobes: support kretprobe blacklist
[deliverable/linux.git] / arch / x86 / kernel / kprobes_64.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 * 2004-Oct Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi
26 * <prasanna@in.ibm.com> adapted for x86_64
27 * 2005-Mar Roland McGrath <roland@redhat.com>
28 * Fixed to handle %rip-relative addressing mode correctly.
29 * 2005-May Rusty Lynch <rusty.lynch@intel.com>
30 * Added function return probes functionality
31 */
32
33 #include <linux/kprobes.h>
34 #include <linux/ptrace.h>
35 #include <linux/string.h>
36 #include <linux/slab.h>
37 #include <linux/preempt.h>
38 #include <linux/module.h>
39 #include <linux/kdebug.h>
40
41 #include <asm/pgtable.h>
42 #include <asm/uaccess.h>
43 #include <asm/alternative.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 struct kretprobe_blackpoint kretprobe_blacklist[] = {
52 {"__switch_to", }, /* This function switches only current task, but
53 doesn't switch kernel stack.*/
54 {NULL, NULL} /* Terminator */
55 };
56 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
57
58 /*
59 * returns non-zero if opcode modifies the interrupt flag.
60 */
61 static __always_inline int is_IF_modifier(kprobe_opcode_t *insn)
62 {
63 switch (*insn) {
64 case 0xfa: /* cli */
65 case 0xfb: /* sti */
66 case 0xcf: /* iret/iretd */
67 case 0x9d: /* popf/popfd */
68 return 1;
69 }
70
71 if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
72 return 1;
73 return 0;
74 }
75
76 int __kprobes arch_prepare_kprobe(struct kprobe *p)
77 {
78 /* insn: must be on special executable page on x86_64. */
79 p->ainsn.insn = get_insn_slot();
80 if (!p->ainsn.insn) {
81 return -ENOMEM;
82 }
83 arch_copy_kprobe(p);
84 return 0;
85 }
86
87 /*
88 * Determine if the instruction uses the %rip-relative addressing mode.
89 * If it does, return the address of the 32-bit displacement word.
90 * If not, return null.
91 */
92 static s32 __kprobes *is_riprel(u8 *insn)
93 {
94 #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \
95 (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
96 (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
97 (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
98 (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
99 << (row % 64))
100 static const u64 onebyte_has_modrm[256 / 64] = {
101 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
102 /* ------------------------------- */
103 W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
104 W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
105 W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
106 W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
107 W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
108 W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
109 W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
110 W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
111 W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
112 W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
113 W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
114 W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
115 W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
116 W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
117 W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
118 W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */
119 /* ------------------------------- */
120 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
121 };
122 static const u64 twobyte_has_modrm[256 / 64] = {
123 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
124 /* ------------------------------- */
125 W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
126 W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
127 W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
128 W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
129 W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
130 W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
131 W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
132 W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
133 W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
134 W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
135 W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
136 W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
137 W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
138 W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
139 W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
140 W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */
141 /* ------------------------------- */
142 /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
143 };
144 #undef W
145 int need_modrm;
146
147 /* Skip legacy instruction prefixes. */
148 while (1) {
149 switch (*insn) {
150 case 0x66:
151 case 0x67:
152 case 0x2e:
153 case 0x3e:
154 case 0x26:
155 case 0x64:
156 case 0x65:
157 case 0x36:
158 case 0xf0:
159 case 0xf3:
160 case 0xf2:
161 ++insn;
162 continue;
163 }
164 break;
165 }
166
167 /* Skip REX instruction prefix. */
168 if ((*insn & 0xf0) == 0x40)
169 ++insn;
170
171 if (*insn == 0x0f) { /* Two-byte opcode. */
172 ++insn;
173 need_modrm = test_bit(*insn, twobyte_has_modrm);
174 } else { /* One-byte opcode. */
175 need_modrm = test_bit(*insn, onebyte_has_modrm);
176 }
177
178 if (need_modrm) {
179 u8 modrm = *++insn;
180 if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
181 /* Displacement follows ModRM byte. */
182 return (s32 *) ++insn;
183 }
184 }
185
186 /* No %rip-relative addressing mode here. */
187 return NULL;
188 }
189
190 static void __kprobes arch_copy_kprobe(struct kprobe *p)
191 {
192 s32 *ripdisp;
193 memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
194 ripdisp = is_riprel(p->ainsn.insn);
195 if (ripdisp) {
196 /*
197 * The copied instruction uses the %rip-relative
198 * addressing mode. Adjust the displacement for the
199 * difference between the original location of this
200 * instruction and the location of the copy that will
201 * actually be run. The tricky bit here is making sure
202 * that the sign extension happens correctly in this
203 * calculation, since we need a signed 32-bit result to
204 * be sign-extended to 64 bits when it's added to the
205 * %rip value and yield the same 64-bit result that the
206 * sign-extension of the original signed 32-bit
207 * displacement would have given.
208 */
209 s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
210 BUG_ON((s64) (s32) disp != disp); /* Sanity check. */
211 *ripdisp = disp;
212 }
213 p->opcode = *p->addr;
214 }
215
216 void __kprobes arch_arm_kprobe(struct kprobe *p)
217 {
218 text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
219 }
220
221 void __kprobes arch_disarm_kprobe(struct kprobe *p)
222 {
223 text_poke(p->addr, &p->opcode, 1);
224 }
225
226 void __kprobes arch_remove_kprobe(struct kprobe *p)
227 {
228 mutex_lock(&kprobe_mutex);
229 free_insn_slot(p->ainsn.insn, 0);
230 mutex_unlock(&kprobe_mutex);
231 }
232
233 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
234 {
235 kcb->prev_kprobe.kp = kprobe_running();
236 kcb->prev_kprobe.status = kcb->kprobe_status;
237 kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
238 kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
239 }
240
241 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
242 {
243 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
244 kcb->kprobe_status = kcb->prev_kprobe.status;
245 kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
246 kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
247 }
248
249 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
250 struct kprobe_ctlblk *kcb)
251 {
252 __get_cpu_var(current_kprobe) = p;
253 kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
254 = (regs->eflags & (TF_MASK | IF_MASK));
255 if (is_IF_modifier(p->ainsn.insn))
256 kcb->kprobe_saved_rflags &= ~IF_MASK;
257 }
258
259 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
260 {
261 regs->eflags |= TF_MASK;
262 regs->eflags &= ~IF_MASK;
263 /*single step inline if the instruction is an int3*/
264 if (p->opcode == BREAKPOINT_INSTRUCTION)
265 regs->rip = (unsigned long)p->addr;
266 else
267 regs->rip = (unsigned long)p->ainsn.insn;
268 }
269
270 /* Called with kretprobe_lock held */
271 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
272 struct pt_regs *regs)
273 {
274 unsigned long *sara = (unsigned long *)regs->rsp;
275
276 ri->ret_addr = (kprobe_opcode_t *) *sara;
277 /* Replace the return addr with trampoline addr */
278 *sara = (unsigned long) &kretprobe_trampoline;
279 }
280
281 int __kprobes kprobe_handler(struct pt_regs *regs)
282 {
283 struct kprobe *p;
284 int ret = 0;
285 kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
286 struct kprobe_ctlblk *kcb;
287
288 /*
289 * We don't want to be preempted for the entire
290 * duration of kprobe processing
291 */
292 preempt_disable();
293 kcb = get_kprobe_ctlblk();
294
295 /* Check we're not actually recursing */
296 if (kprobe_running()) {
297 p = get_kprobe(addr);
298 if (p) {
299 if (kcb->kprobe_status == KPROBE_HIT_SS &&
300 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
301 regs->eflags &= ~TF_MASK;
302 regs->eflags |= kcb->kprobe_saved_rflags;
303 goto no_kprobe;
304 } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
305 /* TODO: Provide re-entrancy from
306 * post_kprobes_handler() and avoid exception
307 * stack corruption while single-stepping on
308 * the instruction of the new probe.
309 */
310 arch_disarm_kprobe(p);
311 regs->rip = (unsigned long)p->addr;
312 reset_current_kprobe();
313 ret = 1;
314 } else {
315 /* We have reentered the kprobe_handler(), since
316 * another probe was hit while within the
317 * handler. We here save the original kprobe
318 * variables and just single step on instruction
319 * of the new probe without calling any user
320 * handlers.
321 */
322 save_previous_kprobe(kcb);
323 set_current_kprobe(p, regs, kcb);
324 kprobes_inc_nmissed_count(p);
325 prepare_singlestep(p, regs);
326 kcb->kprobe_status = KPROBE_REENTER;
327 return 1;
328 }
329 } else {
330 if (*addr != BREAKPOINT_INSTRUCTION) {
331 /* The breakpoint instruction was removed by
332 * another cpu right after we hit, no further
333 * handling of this interrupt is appropriate
334 */
335 regs->rip = (unsigned long)addr;
336 ret = 1;
337 goto no_kprobe;
338 }
339 p = __get_cpu_var(current_kprobe);
340 if (p->break_handler && p->break_handler(p, regs)) {
341 goto ss_probe;
342 }
343 }
344 goto no_kprobe;
345 }
346
347 p = get_kprobe(addr);
348 if (!p) {
349 if (*addr != BREAKPOINT_INSTRUCTION) {
350 /*
351 * The breakpoint instruction was removed right
352 * after we hit it. Another cpu has removed
353 * either a probepoint or a debugger breakpoint
354 * at this address. In either case, no further
355 * handling of this interrupt is appropriate.
356 * Back up over the (now missing) int3 and run
357 * the original instruction.
358 */
359 regs->rip = (unsigned long)addr;
360 ret = 1;
361 }
362 /* Not one of ours: let kernel handle it */
363 goto no_kprobe;
364 }
365
366 set_current_kprobe(p, regs, kcb);
367 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
368
369 if (p->pre_handler && p->pre_handler(p, regs))
370 /* handler has already set things up, so skip ss setup */
371 return 1;
372
373 ss_probe:
374 prepare_singlestep(p, regs);
375 kcb->kprobe_status = KPROBE_HIT_SS;
376 return 1;
377
378 no_kprobe:
379 preempt_enable_no_resched();
380 return ret;
381 }
382
383 /*
384 * For function-return probes, init_kprobes() establishes a probepoint
385 * here. When a retprobed function returns, this probe is hit and
386 * trampoline_probe_handler() runs, calling the kretprobe's handler.
387 */
388 void kretprobe_trampoline_holder(void)
389 {
390 asm volatile ( ".global kretprobe_trampoline\n"
391 "kretprobe_trampoline: \n"
392 "nop\n");
393 }
394
395 /*
396 * Called when we hit the probe point at kretprobe_trampoline
397 */
398 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
399 {
400 struct kretprobe_instance *ri = NULL;
401 struct hlist_head *head, empty_rp;
402 struct hlist_node *node, *tmp;
403 unsigned long flags, orig_ret_address = 0;
404 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
405
406 INIT_HLIST_HEAD(&empty_rp);
407 spin_lock_irqsave(&kretprobe_lock, flags);
408 head = kretprobe_inst_table_head(current);
409
410 /*
411 * It is possible to have multiple instances associated with a given
412 * task either because an multiple functions in the call path
413 * have a return probe installed on them, and/or more then one return
414 * return probe was registered for a target function.
415 *
416 * We can handle this because:
417 * - instances are always inserted at the head of the list
418 * - when multiple return probes are registered for the same
419 * function, the first instance's ret_addr will point to the
420 * real return address, and all the rest will point to
421 * kretprobe_trampoline
422 */
423 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
424 if (ri->task != current)
425 /* another task is sharing our hash bucket */
426 continue;
427
428 if (ri->rp && ri->rp->handler)
429 ri->rp->handler(ri, regs);
430
431 orig_ret_address = (unsigned long)ri->ret_addr;
432 recycle_rp_inst(ri, &empty_rp);
433
434 if (orig_ret_address != trampoline_address)
435 /*
436 * This is the real return address. Any other
437 * instances associated with this task are for
438 * other calls deeper on the call stack
439 */
440 break;
441 }
442
443 kretprobe_assert(ri, orig_ret_address, trampoline_address);
444 regs->rip = orig_ret_address;
445
446 reset_current_kprobe();
447 spin_unlock_irqrestore(&kretprobe_lock, flags);
448 preempt_enable_no_resched();
449
450 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
451 hlist_del(&ri->hlist);
452 kfree(ri);
453 }
454 /*
455 * By returning a non-zero value, we are telling
456 * kprobe_handler() that we don't want the post_handler
457 * to run (and have re-enabled preemption)
458 */
459 return 1;
460 }
461
462 /*
463 * Called after single-stepping. p->addr is the address of the
464 * instruction whose first byte has been replaced by the "int 3"
465 * instruction. To avoid the SMP problems that can occur when we
466 * temporarily put back the original opcode to single-step, we
467 * single-stepped a copy of the instruction. The address of this
468 * copy is p->ainsn.insn.
469 *
470 * This function prepares to return from the post-single-step
471 * interrupt. We have to fix up the stack as follows:
472 *
473 * 0) Except in the case of absolute or indirect jump or call instructions,
474 * the new rip is relative to the copied instruction. We need to make
475 * it relative to the original instruction.
476 *
477 * 1) If the single-stepped instruction was pushfl, then the TF and IF
478 * flags are set in the just-pushed eflags, and may need to be cleared.
479 *
480 * 2) If the single-stepped instruction was a call, the return address
481 * that is atop the stack is the address following the copied instruction.
482 * We need to make it the address following the original instruction.
483 */
484 static void __kprobes resume_execution(struct kprobe *p,
485 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
486 {
487 unsigned long *tos = (unsigned long *)regs->rsp;
488 unsigned long next_rip = 0;
489 unsigned long copy_rip = (unsigned long)p->ainsn.insn;
490 unsigned long orig_rip = (unsigned long)p->addr;
491 kprobe_opcode_t *insn = p->ainsn.insn;
492
493 /*skip the REX prefix*/
494 if (*insn >= 0x40 && *insn <= 0x4f)
495 insn++;
496
497 switch (*insn) {
498 case 0x9c: /* pushfl */
499 *tos &= ~(TF_MASK | IF_MASK);
500 *tos |= kcb->kprobe_old_rflags;
501 break;
502 case 0xc3: /* ret/lret */
503 case 0xcb:
504 case 0xc2:
505 case 0xca:
506 regs->eflags &= ~TF_MASK;
507 /* rip is already adjusted, no more changes required*/
508 return;
509 case 0xe8: /* call relative - Fix return addr */
510 *tos = orig_rip + (*tos - copy_rip);
511 break;
512 case 0xff:
513 if ((insn[1] & 0x30) == 0x10) {
514 /* call absolute, indirect */
515 /* Fix return addr; rip is correct. */
516 next_rip = regs->rip;
517 *tos = orig_rip + (*tos - copy_rip);
518 } else if (((insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
519 ((insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
520 /* rip is correct. */
521 next_rip = regs->rip;
522 }
523 break;
524 case 0xea: /* jmp absolute -- rip is correct */
525 next_rip = regs->rip;
526 break;
527 default:
528 break;
529 }
530
531 regs->eflags &= ~TF_MASK;
532 if (next_rip) {
533 regs->rip = next_rip;
534 } else {
535 regs->rip = orig_rip + (regs->rip - copy_rip);
536 }
537 }
538
539 int __kprobes post_kprobe_handler(struct pt_regs *regs)
540 {
541 struct kprobe *cur = kprobe_running();
542 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
543
544 if (!cur)
545 return 0;
546
547 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
548 kcb->kprobe_status = KPROBE_HIT_SSDONE;
549 cur->post_handler(cur, regs, 0);
550 }
551
552 resume_execution(cur, regs, kcb);
553 regs->eflags |= kcb->kprobe_saved_rflags;
554 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
555 if (raw_irqs_disabled_flags(regs->eflags))
556 trace_hardirqs_off();
557 else
558 trace_hardirqs_on();
559 #endif
560
561 /* Restore the original saved kprobes variables and continue. */
562 if (kcb->kprobe_status == KPROBE_REENTER) {
563 restore_previous_kprobe(kcb);
564 goto out;
565 }
566 reset_current_kprobe();
567 out:
568 preempt_enable_no_resched();
569
570 /*
571 * if somebody else is singlestepping across a probe point, eflags
572 * will have TF set, in which case, continue the remaining processing
573 * of do_debug, as if this is not a probe hit.
574 */
575 if (regs->eflags & TF_MASK)
576 return 0;
577
578 return 1;
579 }
580
581 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
582 {
583 struct kprobe *cur = kprobe_running();
584 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
585 const struct exception_table_entry *fixup;
586
587 switch(kcb->kprobe_status) {
588 case KPROBE_HIT_SS:
589 case KPROBE_REENTER:
590 /*
591 * We are here because the instruction being single
592 * stepped caused a page fault. We reset the current
593 * kprobe and the rip points back to the probe address
594 * and allow the page fault handler to continue as a
595 * normal page fault.
596 */
597 regs->rip = (unsigned long)cur->addr;
598 regs->eflags |= kcb->kprobe_old_rflags;
599 if (kcb->kprobe_status == KPROBE_REENTER)
600 restore_previous_kprobe(kcb);
601 else
602 reset_current_kprobe();
603 preempt_enable_no_resched();
604 break;
605 case KPROBE_HIT_ACTIVE:
606 case KPROBE_HIT_SSDONE:
607 /*
608 * We increment the nmissed count for accounting,
609 * we can also use npre/npostfault count for accouting
610 * these specific fault cases.
611 */
612 kprobes_inc_nmissed_count(cur);
613
614 /*
615 * We come here because instructions in the pre/post
616 * handler caused the page_fault, this could happen
617 * if handler tries to access user space by
618 * copy_from_user(), get_user() etc. Let the
619 * user-specified handler try to fix it first.
620 */
621 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
622 return 1;
623
624 /*
625 * In case the user-specified fault handler returned
626 * zero, try to fix up.
627 */
628 fixup = search_exception_tables(regs->rip);
629 if (fixup) {
630 regs->rip = fixup->fixup;
631 return 1;
632 }
633
634 /*
635 * fixup() could not handle it,
636 * Let do_page_fault() fix it.
637 */
638 break;
639 default:
640 break;
641 }
642 return 0;
643 }
644
645 /*
646 * Wrapper routine for handling exceptions.
647 */
648 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
649 unsigned long val, void *data)
650 {
651 struct die_args *args = (struct die_args *)data;
652 int ret = NOTIFY_DONE;
653
654 if (args->regs && user_mode(args->regs))
655 return ret;
656
657 switch (val) {
658 case DIE_INT3:
659 if (kprobe_handler(args->regs))
660 ret = NOTIFY_STOP;
661 break;
662 case DIE_DEBUG:
663 if (post_kprobe_handler(args->regs))
664 ret = NOTIFY_STOP;
665 break;
666 case DIE_GPF:
667 /* kprobe_running() needs smp_processor_id() */
668 preempt_disable();
669 if (kprobe_running() &&
670 kprobe_fault_handler(args->regs, args->trapnr))
671 ret = NOTIFY_STOP;
672 preempt_enable();
673 break;
674 default:
675 break;
676 }
677 return ret;
678 }
679
680 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
681 {
682 struct jprobe *jp = container_of(p, struct jprobe, kp);
683 unsigned long addr;
684 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
685
686 kcb->jprobe_saved_regs = *regs;
687 kcb->jprobe_saved_rsp = (long *) regs->rsp;
688 addr = (unsigned long)(kcb->jprobe_saved_rsp);
689 /*
690 * As Linus pointed out, gcc assumes that the callee
691 * owns the argument space and could overwrite it, e.g.
692 * tailcall optimization. So, to be absolutely safe
693 * we also save and restore enough stack bytes to cover
694 * the argument area.
695 */
696 memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
697 MIN_STACK_SIZE(addr));
698 regs->eflags &= ~IF_MASK;
699 trace_hardirqs_off();
700 regs->rip = (unsigned long)(jp->entry);
701 return 1;
702 }
703
704 void __kprobes jprobe_return(void)
705 {
706 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
707
708 asm volatile (" xchg %%rbx,%%rsp \n"
709 " int3 \n"
710 " .globl jprobe_return_end \n"
711 " jprobe_return_end: \n"
712 " nop \n"::"b"
713 (kcb->jprobe_saved_rsp):"memory");
714 }
715
716 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
717 {
718 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
719 u8 *addr = (u8 *) (regs->rip - 1);
720 unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
721 struct jprobe *jp = container_of(p, struct jprobe, kp);
722
723 if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
724 if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
725 struct pt_regs *saved_regs =
726 container_of(kcb->jprobe_saved_rsp,
727 struct pt_regs, rsp);
728 printk("current rsp %p does not match saved rsp %p\n",
729 (long *)regs->rsp, kcb->jprobe_saved_rsp);
730 printk("Saved registers for jprobe %p\n", jp);
731 show_registers(saved_regs);
732 printk("Current registers\n");
733 show_registers(regs);
734 BUG();
735 }
736 *regs = kcb->jprobe_saved_regs;
737 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
738 MIN_STACK_SIZE(stack_addr));
739 preempt_enable_no_resched();
740 return 1;
741 }
742 return 0;
743 }
744
745 static struct kprobe trampoline_p = {
746 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
747 .pre_handler = trampoline_probe_handler
748 };
749
750 int __init arch_init_kprobes(void)
751 {
752 return register_kprobe(&trampoline_p);
753 }
754
755 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
756 {
757 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
758 return 1;
759
760 return 0;
761 }
Linux kernel - Deliverables
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