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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#include <linux/kdebug.h>
41
42#include <asm/pgtable.h>
43#include <asm/uaccess.h>
44#include <asm/alternative.h>
45
46void jprobe_return_end(void);
47static void __kprobes arch_copy_kprobe(struct kprobe *p);
48
49DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
50DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
51
52/*
53 * returns non-zero if opcode modifies the interrupt flag.
54 */
55static __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
70int __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 */
86static 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
184static 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
210void __kprobes arch_arm_kprobe(struct kprobe *p)
211{
212 text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
213}
214
215void __kprobes arch_disarm_kprobe(struct kprobe *p)
216{
217 text_poke(p->addr, &p->opcode, 1);
218}
219
220void __kprobes arch_remove_kprobe(struct kprobe *p)
221{
222 mutex_lock(&kprobe_mutex);
223 free_insn_slot(p->ainsn.insn, 0);
224 mutex_unlock(&kprobe_mutex);
225}
226
227static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
228{
229 kcb->prev_kprobe.kp = kprobe_running();
230 kcb->prev_kprobe.status = kcb->kprobe_status;
231 kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
232 kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
233}
234
235static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
236{
237 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
238 kcb->kprobe_status = kcb->prev_kprobe.status;
239 kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
240 kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
241}
242
243static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
244 struct kprobe_ctlblk *kcb)
245{
246 __get_cpu_var(current_kprobe) = p;
247 kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
248 = (regs->eflags & (TF_MASK | IF_MASK));
249 if (is_IF_modifier(p->ainsn.insn))
250 kcb->kprobe_saved_rflags &= ~IF_MASK;
251}
252
253static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
254{
255 regs->eflags |= TF_MASK;
256 regs->eflags &= ~IF_MASK;
257 /*single step inline if the instruction is an int3*/
258 if (p->opcode == BREAKPOINT_INSTRUCTION)
259 regs->rip = (unsigned long)p->addr;
260 else
261 regs->rip = (unsigned long)p->ainsn.insn;
262}
263
264/* Called with kretprobe_lock held */
265void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
266 struct pt_regs *regs)
267{
268 unsigned long *sara = (unsigned long *)regs->rsp;
269
270 ri->ret_addr = (kprobe_opcode_t *) *sara;
271 /* Replace the return addr with trampoline addr */
272 *sara = (unsigned long) &kretprobe_trampoline;
273}
274
275int __kprobes kprobe_handler(struct pt_regs *regs)
276{
277 struct kprobe *p;
278 int ret = 0;
279 kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
280 struct kprobe_ctlblk *kcb;
281
282 /*
283 * We don't want to be preempted for the entire
284 * duration of kprobe processing
285 */
286 preempt_disable();
287 kcb = get_kprobe_ctlblk();
288
289 /* Check we're not actually recursing */
290 if (kprobe_running()) {
291 p = get_kprobe(addr);
292 if (p) {
293 if (kcb->kprobe_status == KPROBE_HIT_SS &&
294 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
295 regs->eflags &= ~TF_MASK;
296 regs->eflags |= kcb->kprobe_saved_rflags;
297 goto no_kprobe;
298 } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
299 /* TODO: Provide re-entrancy from
300 * post_kprobes_handler() and avoid exception
301 * stack corruption while single-stepping on
302 * the instruction of the new probe.
303 */
304 arch_disarm_kprobe(p);
305 regs->rip = (unsigned long)p->addr;
306 reset_current_kprobe();
307 ret = 1;
308 } else {
309 /* We have reentered the kprobe_handler(), since
310 * another probe was hit while within the
311 * handler. We here save the original kprobe
312 * variables and just single step on instruction
313 * of the new probe without calling any user
314 * handlers.
315 */
316 save_previous_kprobe(kcb);
317 set_current_kprobe(p, regs, kcb);
318 kprobes_inc_nmissed_count(p);
319 prepare_singlestep(p, regs);
320 kcb->kprobe_status = KPROBE_REENTER;
321 return 1;
322 }
323 } else {
324 if (*addr != BREAKPOINT_INSTRUCTION) {
325 /* The breakpoint instruction was removed by
326 * another cpu right after we hit, no further
327 * handling of this interrupt is appropriate
328 */
329 regs->rip = (unsigned long)addr;
330 ret = 1;
331 goto no_kprobe;
332 }
333 p = __get_cpu_var(current_kprobe);
334 if (p->break_handler && p->break_handler(p, regs)) {
335 goto ss_probe;
336 }
337 }
338 goto no_kprobe;
339 }
340
341 p = get_kprobe(addr);
342 if (!p) {
343 if (*addr != BREAKPOINT_INSTRUCTION) {
344 /*
345 * The breakpoint instruction was removed right
346 * after we hit it. Another cpu has removed
347 * either a probepoint or a debugger breakpoint
348 * at this address. In either case, no further
349 * handling of this interrupt is appropriate.
350 * Back up over the (now missing) int3 and run
351 * the original instruction.
352 */
353 regs->rip = (unsigned long)addr;
354 ret = 1;
355 }
356 /* Not one of ours: let kernel handle it */
357 goto no_kprobe;
358 }
359
360 set_current_kprobe(p, regs, kcb);
361 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
362
363 if (p->pre_handler && p->pre_handler(p, regs))
364 /* handler has already set things up, so skip ss setup */
365 return 1;
366
367ss_probe:
368 prepare_singlestep(p, regs);
369 kcb->kprobe_status = KPROBE_HIT_SS;
370 return 1;
371
372no_kprobe:
373 preempt_enable_no_resched();
374 return ret;
375}
376
377/*
378 * For function-return probes, init_kprobes() establishes a probepoint
379 * here. When a retprobed function returns, this probe is hit and
380 * trampoline_probe_handler() runs, calling the kretprobe's handler.
381 */
382 void kretprobe_trampoline_holder(void)
383 {
384 asm volatile ( ".global kretprobe_trampoline\n"
385 "kretprobe_trampoline: \n"
386 "nop\n");
387 }
388
389/*
390 * Called when we hit the probe point at kretprobe_trampoline
391 */
392int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
393{
394 struct kretprobe_instance *ri = NULL;
395 struct hlist_head *head, empty_rp;
396 struct hlist_node *node, *tmp;
397 unsigned long flags, orig_ret_address = 0;
398 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
399
400 INIT_HLIST_HEAD(&empty_rp);
401 spin_lock_irqsave(&kretprobe_lock, flags);
402 head = kretprobe_inst_table_head(current);
403
404 /*
405 * It is possible to have multiple instances associated with a given
406 * task either because an multiple functions in the call path
407 * have a return probe installed on them, and/or more then one return
408 * return probe was registered for a target function.
409 *
410 * We can handle this because:
411 * - instances are always inserted at the head of the list
412 * - when multiple return probes are registered for the same
413 * function, the first instance's ret_addr will point to the
414 * real return address, and all the rest will point to
415 * kretprobe_trampoline
416 */
417 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
418 if (ri->task != current)
419 /* another task is sharing our hash bucket */
420 continue;
421
422 if (ri->rp && ri->rp->handler)
423 ri->rp->handler(ri, regs);
424
425 orig_ret_address = (unsigned long)ri->ret_addr;
426 recycle_rp_inst(ri, &empty_rp);
427
428 if (orig_ret_address != trampoline_address)
429 /*
430 * This is the real return address. Any other
431 * instances associated with this task are for
432 * other calls deeper on the call stack
433 */
434 break;
435 }
436
437 kretprobe_assert(ri, orig_ret_address, trampoline_address);
438 regs->rip = orig_ret_address;
439
440 reset_current_kprobe();
441 spin_unlock_irqrestore(&kretprobe_lock, flags);
442 preempt_enable_no_resched();
443
444 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
445 hlist_del(&ri->hlist);
446 kfree(ri);
447 }
448 /*
449 * By returning a non-zero value, we are telling
450 * kprobe_handler() that we don't want the post_handler
451 * to run (and have re-enabled preemption)
452 */
453 return 1;
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 rip 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 */
478static void __kprobes resume_execution(struct kprobe *p,
479 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
480{
481 unsigned long *tos = (unsigned long *)regs->rsp;
482 unsigned long next_rip = 0;
483 unsigned long copy_rip = (unsigned long)p->ainsn.insn;
484 unsigned long orig_rip = (unsigned long)p->addr;
485 kprobe_opcode_t *insn = p->ainsn.insn;
486
487 /*skip the REX prefix*/
488 if (*insn >= 0x40 && *insn <= 0x4f)
489 insn++;
490
491 switch (*insn) {
492 case 0x9c: /* pushfl */
493 *tos &= ~(TF_MASK | IF_MASK);
494 *tos |= kcb->kprobe_old_rflags;
495 break;
496 case 0xc3: /* ret/lret */
497 case 0xcb:
498 case 0xc2:
499 case 0xca:
500 regs->eflags &= ~TF_MASK;
501 /* rip is already adjusted, no more changes required*/
502 return;
503 case 0xe8: /* call relative - Fix return addr */
504 *tos = orig_rip + (*tos - copy_rip);
505 break;
506 case 0xff:
507 if ((insn[1] & 0x30) == 0x10) {
508 /* call absolute, indirect */
509 /* Fix return addr; rip is correct. */
510 next_rip = regs->rip;
511 *tos = orig_rip + (*tos - copy_rip);
512 } else if (((insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
513 ((insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
514 /* rip is correct. */
515 next_rip = regs->rip;
516 }
517 break;
518 case 0xea: /* jmp absolute -- rip is correct */
519 next_rip = regs->rip;
520 break;
521 default:
522 break;
523 }
524
525 regs->eflags &= ~TF_MASK;
526 if (next_rip) {
527 regs->rip = next_rip;
528 } else {
529 regs->rip = orig_rip + (regs->rip - copy_rip);
530 }
531}
532
533int __kprobes post_kprobe_handler(struct pt_regs *regs)
534{
535 struct kprobe *cur = kprobe_running();
536 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
537
538 if (!cur)
539 return 0;
540
541 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
542 kcb->kprobe_status = KPROBE_HIT_SSDONE;
543 cur->post_handler(cur, regs, 0);
544 }
545
546 resume_execution(cur, regs, kcb);
547 regs->eflags |= kcb->kprobe_saved_rflags;
548
549 /* Restore the original saved kprobes variables and continue. */
550 if (kcb->kprobe_status == KPROBE_REENTER) {
551 restore_previous_kprobe(kcb);
552 goto out;
553 }
554 reset_current_kprobe();
555out:
556 preempt_enable_no_resched();
557
558 /*
559 * if somebody else is singlestepping across a probe point, eflags
560 * will have TF set, in which case, continue the remaining processing
561 * of do_debug, as if this is not a probe hit.
562 */
563 if (regs->eflags & TF_MASK)
564 return 0;
565
566 return 1;
567}
568
569int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
570{
571 struct kprobe *cur = kprobe_running();
572 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
573 const struct exception_table_entry *fixup;
574
575 switch(kcb->kprobe_status) {
576 case KPROBE_HIT_SS:
577 case KPROBE_REENTER:
578 /*
579 * We are here because the instruction being single
580 * stepped caused a page fault. We reset the current
581 * kprobe and the rip points back to the probe address
582 * and allow the page fault handler to continue as a
583 * normal page fault.
584 */
585 regs->rip = (unsigned long)cur->addr;
586 regs->eflags |= kcb->kprobe_old_rflags;
587 if (kcb->kprobe_status == KPROBE_REENTER)
588 restore_previous_kprobe(kcb);
589 else
590 reset_current_kprobe();
591 preempt_enable_no_resched();
592 break;
593 case KPROBE_HIT_ACTIVE:
594 case KPROBE_HIT_SSDONE:
595 /*
596 * We increment the nmissed count for accounting,
597 * we can also use npre/npostfault count for accouting
598 * these specific fault cases.
599 */
600 kprobes_inc_nmissed_count(cur);
601
602 /*
603 * We come here because instructions in the pre/post
604 * handler caused the page_fault, this could happen
605 * if handler tries to access user space by
606 * copy_from_user(), get_user() etc. Let the
607 * user-specified handler try to fix it first.
608 */
609 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
610 return 1;
611
612 /*
613 * In case the user-specified fault handler returned
614 * zero, try to fix up.
615 */
616 fixup = search_exception_tables(regs->rip);
617 if (fixup) {
618 regs->rip = fixup->fixup;
619 return 1;
620 }
621
622 /*
623 * fixup() could not handle it,
624 * Let do_page_fault() fix it.
625 */
626 break;
627 default:
628 break;
629 }
630 return 0;
631}
632
633/*
634 * Wrapper routine for handling exceptions.
635 */
636int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
637 unsigned long val, void *data)
638{
639 struct die_args *args = (struct die_args *)data;
640 int ret = NOTIFY_DONE;
641
642 if (args->regs && user_mode(args->regs))
643 return ret;
644
645 switch (val) {
646 case DIE_INT3:
647 if (kprobe_handler(args->regs))
648 ret = NOTIFY_STOP;
649 break;
650 case DIE_DEBUG:
651 if (post_kprobe_handler(args->regs))
652 ret = NOTIFY_STOP;
653 break;
654 case DIE_GPF:
655 case DIE_PAGE_FAULT:
656 /* kprobe_running() needs smp_processor_id() */
657 preempt_disable();
658 if (kprobe_running() &&
659 kprobe_fault_handler(args->regs, args->trapnr))
660 ret = NOTIFY_STOP;
661 preempt_enable();
662 break;
663 default:
664 break;
665 }
666 return ret;
667}
668
669int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
670{
671 struct jprobe *jp = container_of(p, struct jprobe, kp);
672 unsigned long addr;
673 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
674
675 kcb->jprobe_saved_regs = *regs;
676 kcb->jprobe_saved_rsp = (long *) regs->rsp;
677 addr = (unsigned long)(kcb->jprobe_saved_rsp);
678 /*
679 * As Linus pointed out, gcc assumes that the callee
680 * owns the argument space and could overwrite it, e.g.
681 * tailcall optimization. So, to be absolutely safe
682 * we also save and restore enough stack bytes to cover
683 * the argument area.
684 */
685 memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
686 MIN_STACK_SIZE(addr));
687 regs->eflags &= ~IF_MASK;
688 regs->rip = (unsigned long)(jp->entry);
689 return 1;
690}
691
692void __kprobes jprobe_return(void)
693{
694 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
695
696 asm volatile (" xchg %%rbx,%%rsp \n"
697 " int3 \n"
698 " .globl jprobe_return_end \n"
699 " jprobe_return_end: \n"
700 " nop \n"::"b"
701 (kcb->jprobe_saved_rsp):"memory");
702}
703
704int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
705{
706 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
707 u8 *addr = (u8 *) (regs->rip - 1);
708 unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
709 struct jprobe *jp = container_of(p, struct jprobe, kp);
710
711 if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
712 if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
713 struct pt_regs *saved_regs =
714 container_of(kcb->jprobe_saved_rsp,
715 struct pt_regs, rsp);
716 printk("current rsp %p does not match saved rsp %p\n",
717 (long *)regs->rsp, kcb->jprobe_saved_rsp);
718 printk("Saved registers for jprobe %p\n", jp);
719 show_registers(saved_regs);
720 printk("Current registers\n");
721 show_registers(regs);
722 BUG();
723 }
724 *regs = kcb->jprobe_saved_regs;
725 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
726 MIN_STACK_SIZE(stack_addr));
727 preempt_enable_no_resched();
728 return 1;
729 }
730 return 0;
731}
732
733static struct kprobe trampoline_p = {
734 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
735 .pre_handler = trampoline_probe_handler
736};
737
738int __init arch_init_kprobes(void)
739{
740 return register_kprobe(&trampoline_p);
741}
742
743int __kprobes arch_trampoline_kprobe(struct kprobe *p)
744{
745 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
746 return 1;
747
748 return 0;
749}
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-27 15:25:57 -0500