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1da177e4 LT |
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 | */ | |
31 | ||
32 | #include <linux/config.h> | |
33 | #include <linux/kprobes.h> | |
34 | #include <linux/ptrace.h> | |
35 | #include <linux/spinlock.h> | |
36 | #include <linux/string.h> | |
37 | #include <linux/slab.h> | |
38 | #include <linux/preempt.h> | |
39 | #include <linux/moduleloader.h> | |
40 | ||
41 | #include <asm/pgtable.h> | |
42 | #include <asm/kdebug.h> | |
43 | ||
44 | static DECLARE_MUTEX(kprobe_mutex); | |
45 | ||
46 | /* kprobe_status settings */ | |
47 | #define KPROBE_HIT_ACTIVE 0x00000001 | |
48 | #define KPROBE_HIT_SS 0x00000002 | |
49 | ||
50 | static struct kprobe *current_kprobe; | |
51 | static unsigned long kprobe_status, kprobe_old_rflags, kprobe_saved_rflags; | |
52 | static struct pt_regs jprobe_saved_regs; | |
53 | static long *jprobe_saved_rsp; | |
54 | static kprobe_opcode_t *get_insn_slot(void); | |
55 | static void free_insn_slot(kprobe_opcode_t *slot); | |
56 | void jprobe_return_end(void); | |
57 | ||
58 | /* copy of the kernel stack at the probe fire time */ | |
59 | static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE]; | |
60 | ||
61 | /* | |
62 | * returns non-zero if opcode modifies the interrupt flag. | |
63 | */ | |
64 | static inline int is_IF_modifier(kprobe_opcode_t *insn) | |
65 | { | |
66 | switch (*insn) { | |
67 | case 0xfa: /* cli */ | |
68 | case 0xfb: /* sti */ | |
69 | case 0xcf: /* iret/iretd */ | |
70 | case 0x9d: /* popf/popfd */ | |
71 | return 1; | |
72 | } | |
73 | ||
74 | if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf) | |
75 | return 1; | |
76 | return 0; | |
77 | } | |
78 | ||
79 | int arch_prepare_kprobe(struct kprobe *p) | |
80 | { | |
81 | /* insn: must be on special executable page on x86_64. */ | |
82 | up(&kprobe_mutex); | |
83 | p->ainsn.insn = get_insn_slot(); | |
84 | down(&kprobe_mutex); | |
85 | if (!p->ainsn.insn) { | |
86 | return -ENOMEM; | |
87 | } | |
88 | return 0; | |
89 | } | |
90 | ||
91 | /* | |
92 | * Determine if the instruction uses the %rip-relative addressing mode. | |
93 | * If it does, return the address of the 32-bit displacement word. | |
94 | * If not, return null. | |
95 | */ | |
96 | static inline s32 *is_riprel(u8 *insn) | |
97 | { | |
98 | #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \ | |
99 | (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \ | |
100 | (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \ | |
101 | (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \ | |
102 | (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \ | |
103 | << (row % 64)) | |
104 | static const u64 onebyte_has_modrm[256 / 64] = { | |
105 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
106 | /* ------------------------------- */ | |
107 | W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */ | |
108 | W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */ | |
109 | W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */ | |
110 | W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */ | |
111 | W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */ | |
112 | W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */ | |
113 | W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */ | |
114 | W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */ | |
115 | W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */ | |
116 | W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */ | |
117 | W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */ | |
118 | W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */ | |
119 | W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */ | |
120 | W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */ | |
121 | W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */ | |
122 | W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */ | |
123 | /* ------------------------------- */ | |
124 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
125 | }; | |
126 | static const u64 twobyte_has_modrm[256 / 64] = { | |
127 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
128 | /* ------------------------------- */ | |
129 | W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */ | |
130 | W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */ | |
131 | W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */ | |
132 | W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */ | |
133 | W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */ | |
134 | W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */ | |
135 | W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */ | |
136 | W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */ | |
137 | W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */ | |
138 | W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */ | |
139 | W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */ | |
140 | W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */ | |
141 | W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */ | |
142 | W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */ | |
143 | W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */ | |
144 | W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */ | |
145 | /* ------------------------------- */ | |
146 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
147 | }; | |
148 | #undef W | |
149 | int need_modrm; | |
150 | ||
151 | /* Skip legacy instruction prefixes. */ | |
152 | while (1) { | |
153 | switch (*insn) { | |
154 | case 0x66: | |
155 | case 0x67: | |
156 | case 0x2e: | |
157 | case 0x3e: | |
158 | case 0x26: | |
159 | case 0x64: | |
160 | case 0x65: | |
161 | case 0x36: | |
162 | case 0xf0: | |
163 | case 0xf3: | |
164 | case 0xf2: | |
165 | ++insn; | |
166 | continue; | |
167 | } | |
168 | break; | |
169 | } | |
170 | ||
171 | /* Skip REX instruction prefix. */ | |
172 | if ((*insn & 0xf0) == 0x40) | |
173 | ++insn; | |
174 | ||
175 | if (*insn == 0x0f) { /* Two-byte opcode. */ | |
176 | ++insn; | |
177 | need_modrm = test_bit(*insn, twobyte_has_modrm); | |
178 | } else { /* One-byte opcode. */ | |
179 | need_modrm = test_bit(*insn, onebyte_has_modrm); | |
180 | } | |
181 | ||
182 | if (need_modrm) { | |
183 | u8 modrm = *++insn; | |
184 | if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */ | |
185 | /* Displacement follows ModRM byte. */ | |
186 | return (s32 *) ++insn; | |
187 | } | |
188 | } | |
189 | ||
190 | /* No %rip-relative addressing mode here. */ | |
191 | return NULL; | |
192 | } | |
193 | ||
194 | void arch_copy_kprobe(struct kprobe *p) | |
195 | { | |
196 | s32 *ripdisp; | |
197 | memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE); | |
198 | ripdisp = is_riprel(p->ainsn.insn); | |
199 | if (ripdisp) { | |
200 | /* | |
201 | * The copied instruction uses the %rip-relative | |
202 | * addressing mode. Adjust the displacement for the | |
203 | * difference between the original location of this | |
204 | * instruction and the location of the copy that will | |
205 | * actually be run. The tricky bit here is making sure | |
206 | * that the sign extension happens correctly in this | |
207 | * calculation, since we need a signed 32-bit result to | |
208 | * be sign-extended to 64 bits when it's added to the | |
209 | * %rip value and yield the same 64-bit result that the | |
210 | * sign-extension of the original signed 32-bit | |
211 | * displacement would have given. | |
212 | */ | |
213 | s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn; | |
214 | BUG_ON((s64) (s32) disp != disp); /* Sanity check. */ | |
215 | *ripdisp = disp; | |
216 | } | |
217 | } | |
218 | ||
219 | void arch_remove_kprobe(struct kprobe *p) | |
220 | { | |
221 | up(&kprobe_mutex); | |
222 | free_insn_slot(p->ainsn.insn); | |
223 | down(&kprobe_mutex); | |
224 | } | |
225 | ||
226 | static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs) | |
227 | { | |
228 | *p->addr = p->opcode; | |
229 | regs->rip = (unsigned long)p->addr; | |
230 | } | |
231 | ||
232 | static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs) | |
233 | { | |
234 | regs->eflags |= TF_MASK; | |
235 | regs->eflags &= ~IF_MASK; | |
236 | /*single step inline if the instruction is an int3*/ | |
237 | if (p->opcode == BREAKPOINT_INSTRUCTION) | |
238 | regs->rip = (unsigned long)p->addr; | |
239 | else | |
240 | regs->rip = (unsigned long)p->ainsn.insn; | |
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 | int kprobe_handler(struct pt_regs *regs) | |
248 | { | |
249 | struct kprobe *p; | |
250 | int ret = 0; | |
251 | kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t)); | |
252 | ||
253 | /* We're in an interrupt, but this is clear and BUG()-safe. */ | |
254 | preempt_disable(); | |
255 | ||
256 | /* Check we're not actually recursing */ | |
257 | if (kprobe_running()) { | |
258 | /* We *are* holding lock here, so this is safe. | |
259 | Disarm the probe we just hit, and ignore it. */ | |
260 | p = get_kprobe(addr); | |
261 | if (p) { | |
262 | if (kprobe_status == KPROBE_HIT_SS) { | |
263 | regs->eflags &= ~TF_MASK; | |
264 | regs->eflags |= kprobe_saved_rflags; | |
265 | unlock_kprobes(); | |
266 | goto no_kprobe; | |
267 | } | |
268 | disarm_kprobe(p, regs); | |
269 | ret = 1; | |
270 | } else { | |
271 | p = current_kprobe; | |
272 | if (p->break_handler && p->break_handler(p, regs)) { | |
273 | goto ss_probe; | |
274 | } | |
275 | } | |
276 | /* If it's not ours, can't be delete race, (we hold lock). */ | |
277 | goto no_kprobe; | |
278 | } | |
279 | ||
280 | lock_kprobes(); | |
281 | p = get_kprobe(addr); | |
282 | if (!p) { | |
283 | unlock_kprobes(); | |
284 | if (*addr != BREAKPOINT_INSTRUCTION) { | |
285 | /* | |
286 | * The breakpoint instruction was removed right | |
287 | * after we hit it. Another cpu has removed | |
288 | * either a probepoint or a debugger breakpoint | |
289 | * at this address. In either case, no further | |
290 | * handling of this interrupt is appropriate. | |
291 | */ | |
292 | ret = 1; | |
293 | } | |
294 | /* Not one of ours: let kernel handle it */ | |
295 | goto no_kprobe; | |
296 | } | |
297 | ||
298 | kprobe_status = KPROBE_HIT_ACTIVE; | |
299 | current_kprobe = p; | |
300 | kprobe_saved_rflags = kprobe_old_rflags | |
301 | = (regs->eflags & (TF_MASK | IF_MASK)); | |
302 | if (is_IF_modifier(p->ainsn.insn)) | |
303 | kprobe_saved_rflags &= ~IF_MASK; | |
304 | ||
305 | if (p->pre_handler && p->pre_handler(p, regs)) | |
306 | /* handler has already set things up, so skip ss setup */ | |
307 | return 1; | |
308 | ||
309 | ss_probe: | |
310 | prepare_singlestep(p, regs); | |
311 | kprobe_status = KPROBE_HIT_SS; | |
312 | return 1; | |
313 | ||
314 | no_kprobe: | |
315 | preempt_enable_no_resched(); | |
316 | return ret; | |
317 | } | |
318 | ||
319 | /* | |
320 | * Called after single-stepping. p->addr is the address of the | |
321 | * instruction whose first byte has been replaced by the "int 3" | |
322 | * instruction. To avoid the SMP problems that can occur when we | |
323 | * temporarily put back the original opcode to single-step, we | |
324 | * single-stepped a copy of the instruction. The address of this | |
325 | * copy is p->ainsn.insn. | |
326 | * | |
327 | * This function prepares to return from the post-single-step | |
328 | * interrupt. We have to fix up the stack as follows: | |
329 | * | |
330 | * 0) Except in the case of absolute or indirect jump or call instructions, | |
331 | * the new rip is relative to the copied instruction. We need to make | |
332 | * it relative to the original instruction. | |
333 | * | |
334 | * 1) If the single-stepped instruction was pushfl, then the TF and IF | |
335 | * flags are set in the just-pushed eflags, and may need to be cleared. | |
336 | * | |
337 | * 2) If the single-stepped instruction was a call, the return address | |
338 | * that is atop the stack is the address following the copied instruction. | |
339 | * We need to make it the address following the original instruction. | |
340 | */ | |
341 | static void resume_execution(struct kprobe *p, struct pt_regs *regs) | |
342 | { | |
343 | unsigned long *tos = (unsigned long *)regs->rsp; | |
344 | unsigned long next_rip = 0; | |
345 | unsigned long copy_rip = (unsigned long)p->ainsn.insn; | |
346 | unsigned long orig_rip = (unsigned long)p->addr; | |
347 | kprobe_opcode_t *insn = p->ainsn.insn; | |
348 | ||
349 | /*skip the REX prefix*/ | |
350 | if (*insn >= 0x40 && *insn <= 0x4f) | |
351 | insn++; | |
352 | ||
353 | switch (*insn) { | |
354 | case 0x9c: /* pushfl */ | |
355 | *tos &= ~(TF_MASK | IF_MASK); | |
356 | *tos |= kprobe_old_rflags; | |
357 | break; | |
358 | case 0xe8: /* call relative - Fix return addr */ | |
359 | *tos = orig_rip + (*tos - copy_rip); | |
360 | break; | |
361 | case 0xff: | |
362 | if ((*insn & 0x30) == 0x10) { | |
363 | /* call absolute, indirect */ | |
364 | /* Fix return addr; rip is correct. */ | |
365 | next_rip = regs->rip; | |
366 | *tos = orig_rip + (*tos - copy_rip); | |
367 | } else if (((*insn & 0x31) == 0x20) || /* jmp near, absolute indirect */ | |
368 | ((*insn & 0x31) == 0x21)) { /* jmp far, absolute indirect */ | |
369 | /* rip is correct. */ | |
370 | next_rip = regs->rip; | |
371 | } | |
372 | break; | |
373 | case 0xea: /* jmp absolute -- rip is correct */ | |
374 | next_rip = regs->rip; | |
375 | break; | |
376 | default: | |
377 | break; | |
378 | } | |
379 | ||
380 | regs->eflags &= ~TF_MASK; | |
381 | if (next_rip) { | |
382 | regs->rip = next_rip; | |
383 | } else { | |
384 | regs->rip = orig_rip + (regs->rip - copy_rip); | |
385 | } | |
386 | } | |
387 | ||
388 | /* | |
389 | * Interrupts are disabled on entry as trap1 is an interrupt gate and they | |
390 | * remain disabled thoroughout this function. And we hold kprobe lock. | |
391 | */ | |
392 | int post_kprobe_handler(struct pt_regs *regs) | |
393 | { | |
394 | if (!kprobe_running()) | |
395 | return 0; | |
396 | ||
397 | if (current_kprobe->post_handler) | |
398 | current_kprobe->post_handler(current_kprobe, regs, 0); | |
399 | ||
400 | resume_execution(current_kprobe, regs); | |
401 | regs->eflags |= kprobe_saved_rflags; | |
402 | ||
403 | unlock_kprobes(); | |
404 | preempt_enable_no_resched(); | |
405 | ||
406 | /* | |
407 | * if somebody else is singlestepping across a probe point, eflags | |
408 | * will have TF set, in which case, continue the remaining processing | |
409 | * of do_debug, as if this is not a probe hit. | |
410 | */ | |
411 | if (regs->eflags & TF_MASK) | |
412 | return 0; | |
413 | ||
414 | return 1; | |
415 | } | |
416 | ||
417 | /* Interrupts disabled, kprobe_lock held. */ | |
418 | int kprobe_fault_handler(struct pt_regs *regs, int trapnr) | |
419 | { | |
420 | if (current_kprobe->fault_handler | |
421 | && current_kprobe->fault_handler(current_kprobe, regs, trapnr)) | |
422 | return 1; | |
423 | ||
424 | if (kprobe_status & KPROBE_HIT_SS) { | |
425 | resume_execution(current_kprobe, regs); | |
426 | regs->eflags |= kprobe_old_rflags; | |
427 | ||
428 | unlock_kprobes(); | |
429 | preempt_enable_no_resched(); | |
430 | } | |
431 | return 0; | |
432 | } | |
433 | ||
434 | /* | |
435 | * Wrapper routine for handling exceptions. | |
436 | */ | |
437 | int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, | |
438 | void *data) | |
439 | { | |
440 | struct die_args *args = (struct die_args *)data; | |
441 | switch (val) { | |
442 | case DIE_INT3: | |
443 | if (kprobe_handler(args->regs)) | |
444 | return NOTIFY_STOP; | |
445 | break; | |
446 | case DIE_DEBUG: | |
447 | if (post_kprobe_handler(args->regs)) | |
448 | return NOTIFY_STOP; | |
449 | break; | |
450 | case DIE_GPF: | |
451 | if (kprobe_running() && | |
452 | kprobe_fault_handler(args->regs, args->trapnr)) | |
453 | return NOTIFY_STOP; | |
454 | break; | |
455 | case DIE_PAGE_FAULT: | |
456 | if (kprobe_running() && | |
457 | kprobe_fault_handler(args->regs, args->trapnr)) | |
458 | return NOTIFY_STOP; | |
459 | break; | |
460 | default: | |
461 | break; | |
462 | } | |
463 | return NOTIFY_DONE; | |
464 | } | |
465 | ||
466 | int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
467 | { | |
468 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
469 | unsigned long addr; | |
470 | ||
471 | jprobe_saved_regs = *regs; | |
472 | jprobe_saved_rsp = (long *) regs->rsp; | |
473 | addr = (unsigned long)jprobe_saved_rsp; | |
474 | /* | |
475 | * As Linus pointed out, gcc assumes that the callee | |
476 | * owns the argument space and could overwrite it, e.g. | |
477 | * tailcall optimization. So, to be absolutely safe | |
478 | * we also save and restore enough stack bytes to cover | |
479 | * the argument area. | |
480 | */ | |
481 | memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr)); | |
482 | regs->eflags &= ~IF_MASK; | |
483 | regs->rip = (unsigned long)(jp->entry); | |
484 | return 1; | |
485 | } | |
486 | ||
487 | void jprobe_return(void) | |
488 | { | |
489 | preempt_enable_no_resched(); | |
490 | asm volatile (" xchg %%rbx,%%rsp \n" | |
491 | " int3 \n" | |
492 | " .globl jprobe_return_end \n" | |
493 | " jprobe_return_end: \n" | |
494 | " nop \n"::"b" | |
495 | (jprobe_saved_rsp):"memory"); | |
496 | } | |
497 | ||
498 | int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) | |
499 | { | |
500 | u8 *addr = (u8 *) (regs->rip - 1); | |
501 | unsigned long stack_addr = (unsigned long)jprobe_saved_rsp; | |
502 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
503 | ||
504 | if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) { | |
505 | if ((long *)regs->rsp != jprobe_saved_rsp) { | |
506 | struct pt_regs *saved_regs = | |
507 | container_of(jprobe_saved_rsp, struct pt_regs, rsp); | |
508 | printk("current rsp %p does not match saved rsp %p\n", | |
509 | (long *)regs->rsp, jprobe_saved_rsp); | |
510 | printk("Saved registers for jprobe %p\n", jp); | |
511 | show_registers(saved_regs); | |
512 | printk("Current registers\n"); | |
513 | show_registers(regs); | |
514 | BUG(); | |
515 | } | |
516 | *regs = jprobe_saved_regs; | |
517 | memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack, | |
518 | MIN_STACK_SIZE(stack_addr)); | |
519 | return 1; | |
520 | } | |
521 | return 0; | |
522 | } | |
523 | ||
524 | /* | |
525 | * kprobe->ainsn.insn points to the copy of the instruction to be single-stepped. | |
526 | * By default on x86_64, pages we get from kmalloc or vmalloc are not | |
527 | * executable. Single-stepping an instruction on such a page yields an | |
528 | * oops. So instead of storing the instruction copies in their respective | |
529 | * kprobe objects, we allocate a page, map it executable, and store all the | |
530 | * instruction copies there. (We can allocate additional pages if somebody | |
531 | * inserts a huge number of probes.) Each page can hold up to INSNS_PER_PAGE | |
532 | * instruction slots, each of which is MAX_INSN_SIZE*sizeof(kprobe_opcode_t) | |
533 | * bytes. | |
534 | */ | |
535 | #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE*sizeof(kprobe_opcode_t))) | |
536 | struct kprobe_insn_page { | |
537 | struct hlist_node hlist; | |
538 | kprobe_opcode_t *insns; /* page of instruction slots */ | |
539 | char slot_used[INSNS_PER_PAGE]; | |
540 | int nused; | |
541 | }; | |
542 | ||
543 | static struct hlist_head kprobe_insn_pages; | |
544 | ||
545 | /** | |
546 | * get_insn_slot() - Find a slot on an executable page for an instruction. | |
547 | * We allocate an executable page if there's no room on existing ones. | |
548 | */ | |
549 | static kprobe_opcode_t *get_insn_slot(void) | |
550 | { | |
551 | struct kprobe_insn_page *kip; | |
552 | struct hlist_node *pos; | |
553 | ||
554 | hlist_for_each(pos, &kprobe_insn_pages) { | |
555 | kip = hlist_entry(pos, struct kprobe_insn_page, hlist); | |
556 | if (kip->nused < INSNS_PER_PAGE) { | |
557 | int i; | |
558 | for (i = 0; i < INSNS_PER_PAGE; i++) { | |
559 | if (!kip->slot_used[i]) { | |
560 | kip->slot_used[i] = 1; | |
561 | kip->nused++; | |
562 | return kip->insns + (i*MAX_INSN_SIZE); | |
563 | } | |
564 | } | |
565 | /* Surprise! No unused slots. Fix kip->nused. */ | |
566 | kip->nused = INSNS_PER_PAGE; | |
567 | } | |
568 | } | |
569 | ||
570 | /* All out of space. Need to allocate a new page. Use slot 0.*/ | |
571 | kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); | |
572 | if (!kip) { | |
573 | return NULL; | |
574 | } | |
575 | ||
576 | /* | |
577 | * For the %rip-relative displacement fixups to be doable, we | |
578 | * need our instruction copy to be within +/- 2GB of any data it | |
579 | * might access via %rip. That is, within 2GB of where the | |
580 | * kernel image and loaded module images reside. So we allocate | |
581 | * a page in the module loading area. | |
582 | */ | |
583 | kip->insns = module_alloc(PAGE_SIZE); | |
584 | if (!kip->insns) { | |
585 | kfree(kip); | |
586 | return NULL; | |
587 | } | |
588 | INIT_HLIST_NODE(&kip->hlist); | |
589 | hlist_add_head(&kip->hlist, &kprobe_insn_pages); | |
590 | memset(kip->slot_used, 0, INSNS_PER_PAGE); | |
591 | kip->slot_used[0] = 1; | |
592 | kip->nused = 1; | |
593 | return kip->insns; | |
594 | } | |
595 | ||
596 | /** | |
597 | * free_insn_slot() - Free instruction slot obtained from get_insn_slot(). | |
598 | */ | |
599 | static void free_insn_slot(kprobe_opcode_t *slot) | |
600 | { | |
601 | struct kprobe_insn_page *kip; | |
602 | struct hlist_node *pos; | |
603 | ||
604 | hlist_for_each(pos, &kprobe_insn_pages) { | |
605 | kip = hlist_entry(pos, struct kprobe_insn_page, hlist); | |
606 | if (kip->insns <= slot | |
607 | && slot < kip->insns+(INSNS_PER_PAGE*MAX_INSN_SIZE)) { | |
608 | int i = (slot - kip->insns) / MAX_INSN_SIZE; | |
609 | kip->slot_used[i] = 0; | |
610 | kip->nused--; | |
611 | if (kip->nused == 0) { | |
612 | /* | |
613 | * Page is no longer in use. Free it unless | |
614 | * it's the last one. We keep the last one | |
615 | * so as not to have to set it up again the | |
616 | * next time somebody inserts a probe. | |
617 | */ | |
618 | hlist_del(&kip->hlist); | |
619 | if (hlist_empty(&kprobe_insn_pages)) { | |
620 | INIT_HLIST_NODE(&kip->hlist); | |
621 | hlist_add_head(&kip->hlist, | |
622 | &kprobe_insn_pages); | |
623 | } else { | |
624 | module_free(NULL, kip->insns); | |
625 | kfree(kip); | |
626 | } | |
627 | } | |
628 | return; | |
629 | } | |
630 | } | |
631 | } |