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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. | |
73649dab RL |
30 | * 2005-May Rusty Lynch <rusty.lynch@intel.com> |
31 | * Added function return probes functionality | |
1da177e4 LT |
32 | */ |
33 | ||
34 | #include <linux/config.h> | |
35 | #include <linux/kprobes.h> | |
36 | #include <linux/ptrace.h> | |
37 | #include <linux/spinlock.h> | |
38 | #include <linux/string.h> | |
39 | #include <linux/slab.h> | |
40 | #include <linux/preempt.h> | |
41 | #include <linux/moduleloader.h> | |
42 | ||
43 | #include <asm/pgtable.h> | |
44 | #include <asm/kdebug.h> | |
45 | ||
46 | static DECLARE_MUTEX(kprobe_mutex); | |
47 | ||
48 | /* kprobe_status settings */ | |
49 | #define KPROBE_HIT_ACTIVE 0x00000001 | |
50 | #define KPROBE_HIT_SS 0x00000002 | |
51 | ||
52 | static struct kprobe *current_kprobe; | |
53 | static unsigned long kprobe_status, kprobe_old_rflags, kprobe_saved_rflags; | |
54 | static struct pt_regs jprobe_saved_regs; | |
55 | static long *jprobe_saved_rsp; | |
56 | static kprobe_opcode_t *get_insn_slot(void); | |
57 | static void free_insn_slot(kprobe_opcode_t *slot); | |
58 | void jprobe_return_end(void); | |
59 | ||
60 | /* copy of the kernel stack at the probe fire time */ | |
61 | static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE]; | |
62 | ||
63 | /* | |
64 | * returns non-zero if opcode modifies the interrupt flag. | |
65 | */ | |
66 | static inline int is_IF_modifier(kprobe_opcode_t *insn) | |
67 | { | |
68 | switch (*insn) { | |
69 | case 0xfa: /* cli */ | |
70 | case 0xfb: /* sti */ | |
71 | case 0xcf: /* iret/iretd */ | |
72 | case 0x9d: /* popf/popfd */ | |
73 | return 1; | |
74 | } | |
75 | ||
76 | if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf) | |
77 | return 1; | |
78 | return 0; | |
79 | } | |
80 | ||
81 | int arch_prepare_kprobe(struct kprobe *p) | |
82 | { | |
83 | /* insn: must be on special executable page on x86_64. */ | |
84 | up(&kprobe_mutex); | |
85 | p->ainsn.insn = get_insn_slot(); | |
86 | down(&kprobe_mutex); | |
87 | if (!p->ainsn.insn) { | |
88 | return -ENOMEM; | |
89 | } | |
90 | return 0; | |
91 | } | |
92 | ||
93 | /* | |
94 | * Determine if the instruction uses the %rip-relative addressing mode. | |
95 | * If it does, return the address of the 32-bit displacement word. | |
96 | * If not, return null. | |
97 | */ | |
98 | static inline s32 *is_riprel(u8 *insn) | |
99 | { | |
100 | #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \ | |
101 | (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \ | |
102 | (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \ | |
103 | (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \ | |
104 | (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \ | |
105 | << (row % 64)) | |
106 | static const u64 onebyte_has_modrm[256 / 64] = { | |
107 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
108 | /* ------------------------------- */ | |
109 | W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */ | |
110 | W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */ | |
111 | W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */ | |
112 | W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */ | |
113 | W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */ | |
114 | W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */ | |
115 | W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */ | |
116 | W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */ | |
117 | W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */ | |
118 | W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */ | |
119 | W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */ | |
120 | W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */ | |
121 | W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */ | |
122 | W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */ | |
123 | W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */ | |
124 | W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */ | |
125 | /* ------------------------------- */ | |
126 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
127 | }; | |
128 | static const u64 twobyte_has_modrm[256 / 64] = { | |
129 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
130 | /* ------------------------------- */ | |
131 | W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */ | |
132 | W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */ | |
133 | W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */ | |
134 | W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */ | |
135 | W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */ | |
136 | W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */ | |
137 | W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */ | |
138 | W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */ | |
139 | W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */ | |
140 | W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */ | |
141 | W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */ | |
142 | W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */ | |
143 | W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */ | |
144 | W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */ | |
145 | W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */ | |
146 | W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */ | |
147 | /* ------------------------------- */ | |
148 | /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ | |
149 | }; | |
150 | #undef W | |
151 | int need_modrm; | |
152 | ||
153 | /* Skip legacy instruction prefixes. */ | |
154 | while (1) { | |
155 | switch (*insn) { | |
156 | case 0x66: | |
157 | case 0x67: | |
158 | case 0x2e: | |
159 | case 0x3e: | |
160 | case 0x26: | |
161 | case 0x64: | |
162 | case 0x65: | |
163 | case 0x36: | |
164 | case 0xf0: | |
165 | case 0xf3: | |
166 | case 0xf2: | |
167 | ++insn; | |
168 | continue; | |
169 | } | |
170 | break; | |
171 | } | |
172 | ||
173 | /* Skip REX instruction prefix. */ | |
174 | if ((*insn & 0xf0) == 0x40) | |
175 | ++insn; | |
176 | ||
177 | if (*insn == 0x0f) { /* Two-byte opcode. */ | |
178 | ++insn; | |
179 | need_modrm = test_bit(*insn, twobyte_has_modrm); | |
180 | } else { /* One-byte opcode. */ | |
181 | need_modrm = test_bit(*insn, onebyte_has_modrm); | |
182 | } | |
183 | ||
184 | if (need_modrm) { | |
185 | u8 modrm = *++insn; | |
186 | if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */ | |
187 | /* Displacement follows ModRM byte. */ | |
188 | return (s32 *) ++insn; | |
189 | } | |
190 | } | |
191 | ||
192 | /* No %rip-relative addressing mode here. */ | |
193 | return NULL; | |
194 | } | |
195 | ||
196 | void arch_copy_kprobe(struct kprobe *p) | |
197 | { | |
198 | s32 *ripdisp; | |
199 | memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE); | |
200 | ripdisp = is_riprel(p->ainsn.insn); | |
201 | if (ripdisp) { | |
202 | /* | |
203 | * The copied instruction uses the %rip-relative | |
204 | * addressing mode. Adjust the displacement for the | |
205 | * difference between the original location of this | |
206 | * instruction and the location of the copy that will | |
207 | * actually be run. The tricky bit here is making sure | |
208 | * that the sign extension happens correctly in this | |
209 | * calculation, since we need a signed 32-bit result to | |
210 | * be sign-extended to 64 bits when it's added to the | |
211 | * %rip value and yield the same 64-bit result that the | |
212 | * sign-extension of the original signed 32-bit | |
213 | * displacement would have given. | |
214 | */ | |
215 | s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn; | |
216 | BUG_ON((s64) (s32) disp != disp); /* Sanity check. */ | |
217 | *ripdisp = disp; | |
218 | } | |
219 | } | |
220 | ||
221 | void arch_remove_kprobe(struct kprobe *p) | |
222 | { | |
223 | up(&kprobe_mutex); | |
224 | free_insn_slot(p->ainsn.insn); | |
225 | down(&kprobe_mutex); | |
226 | } | |
227 | ||
228 | static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs) | |
229 | { | |
230 | *p->addr = p->opcode; | |
231 | regs->rip = (unsigned long)p->addr; | |
232 | } | |
233 | ||
234 | static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs) | |
235 | { | |
236 | regs->eflags |= TF_MASK; | |
237 | regs->eflags &= ~IF_MASK; | |
238 | /*single step inline if the instruction is an int3*/ | |
239 | if (p->opcode == BREAKPOINT_INSTRUCTION) | |
240 | regs->rip = (unsigned long)p->addr; | |
241 | else | |
242 | regs->rip = (unsigned long)p->ainsn.insn; | |
243 | } | |
244 | ||
73649dab RL |
245 | struct task_struct *arch_get_kprobe_task(void *ptr) |
246 | { | |
247 | return ((struct thread_info *) (((unsigned long) ptr) & | |
248 | (~(THREAD_SIZE -1))))->task; | |
249 | } | |
250 | ||
251 | void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs) | |
252 | { | |
253 | unsigned long *sara = (unsigned long *)regs->rsp; | |
254 | struct kretprobe_instance *ri; | |
255 | static void *orig_ret_addr; | |
256 | ||
257 | /* | |
258 | * Save the return address when the return probe hits | |
259 | * the first time, and use it to populate the (krprobe | |
260 | * instance)->ret_addr for subsequent return probes at | |
261 | * the same addrress since stack address would have | |
262 | * the kretprobe_trampoline by then. | |
263 | */ | |
264 | if (((void*) *sara) != kretprobe_trampoline) | |
265 | orig_ret_addr = (void*) *sara; | |
266 | ||
267 | if ((ri = get_free_rp_inst(rp)) != NULL) { | |
268 | ri->rp = rp; | |
269 | ri->stack_addr = sara; | |
270 | ri->ret_addr = orig_ret_addr; | |
271 | add_rp_inst(ri); | |
272 | /* Replace the return addr with trampoline addr */ | |
273 | *sara = (unsigned long) &kretprobe_trampoline; | |
274 | } else { | |
275 | rp->nmissed++; | |
276 | } | |
277 | } | |
278 | ||
279 | void arch_kprobe_flush_task(struct task_struct *tk) | |
280 | { | |
281 | struct kretprobe_instance *ri; | |
282 | while ((ri = get_rp_inst_tsk(tk)) != NULL) { | |
283 | *((unsigned long *)(ri->stack_addr)) = | |
284 | (unsigned long) ri->ret_addr; | |
285 | recycle_rp_inst(ri); | |
286 | } | |
287 | } | |
288 | ||
1da177e4 LT |
289 | /* |
290 | * Interrupts are disabled on entry as trap3 is an interrupt gate and they | |
291 | * remain disabled thorough out this function. | |
292 | */ | |
293 | int kprobe_handler(struct pt_regs *regs) | |
294 | { | |
295 | struct kprobe *p; | |
296 | int ret = 0; | |
297 | kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t)); | |
298 | ||
299 | /* We're in an interrupt, but this is clear and BUG()-safe. */ | |
300 | preempt_disable(); | |
301 | ||
302 | /* Check we're not actually recursing */ | |
303 | if (kprobe_running()) { | |
304 | /* We *are* holding lock here, so this is safe. | |
305 | Disarm the probe we just hit, and ignore it. */ | |
306 | p = get_kprobe(addr); | |
307 | if (p) { | |
308 | if (kprobe_status == KPROBE_HIT_SS) { | |
309 | regs->eflags &= ~TF_MASK; | |
310 | regs->eflags |= kprobe_saved_rflags; | |
311 | unlock_kprobes(); | |
312 | goto no_kprobe; | |
313 | } | |
314 | disarm_kprobe(p, regs); | |
315 | ret = 1; | |
316 | } else { | |
317 | p = current_kprobe; | |
318 | if (p->break_handler && p->break_handler(p, regs)) { | |
319 | goto ss_probe; | |
320 | } | |
321 | } | |
322 | /* If it's not ours, can't be delete race, (we hold lock). */ | |
323 | goto no_kprobe; | |
324 | } | |
325 | ||
326 | lock_kprobes(); | |
327 | p = get_kprobe(addr); | |
328 | if (!p) { | |
329 | unlock_kprobes(); | |
330 | if (*addr != BREAKPOINT_INSTRUCTION) { | |
331 | /* | |
332 | * The breakpoint instruction was removed right | |
333 | * after we hit it. Another cpu has removed | |
334 | * either a probepoint or a debugger breakpoint | |
335 | * at this address. In either case, no further | |
336 | * handling of this interrupt is appropriate. | |
337 | */ | |
338 | ret = 1; | |
339 | } | |
340 | /* Not one of ours: let kernel handle it */ | |
341 | goto no_kprobe; | |
342 | } | |
343 | ||
344 | kprobe_status = KPROBE_HIT_ACTIVE; | |
345 | current_kprobe = p; | |
346 | kprobe_saved_rflags = kprobe_old_rflags | |
347 | = (regs->eflags & (TF_MASK | IF_MASK)); | |
348 | if (is_IF_modifier(p->ainsn.insn)) | |
349 | kprobe_saved_rflags &= ~IF_MASK; | |
350 | ||
351 | if (p->pre_handler && p->pre_handler(p, regs)) | |
352 | /* handler has already set things up, so skip ss setup */ | |
353 | return 1; | |
354 | ||
355 | ss_probe: | |
356 | prepare_singlestep(p, regs); | |
357 | kprobe_status = KPROBE_HIT_SS; | |
358 | return 1; | |
359 | ||
360 | no_kprobe: | |
361 | preempt_enable_no_resched(); | |
362 | return ret; | |
363 | } | |
364 | ||
73649dab RL |
365 | /* |
366 | * For function-return probes, init_kprobes() establishes a probepoint | |
367 | * here. When a retprobed function returns, this probe is hit and | |
368 | * trampoline_probe_handler() runs, calling the kretprobe's handler. | |
369 | */ | |
370 | void kretprobe_trampoline_holder(void) | |
371 | { | |
372 | asm volatile ( ".global kretprobe_trampoline\n" | |
373 | "kretprobe_trampoline: \n" | |
374 | "nop\n"); | |
375 | } | |
376 | ||
377 | /* | |
378 | * Called when we hit the probe point at kretprobe_trampoline | |
379 | */ | |
380 | int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) | |
381 | { | |
382 | struct task_struct *tsk; | |
383 | struct kretprobe_instance *ri; | |
384 | struct hlist_head *head; | |
385 | struct hlist_node *node; | |
386 | unsigned long *sara = (unsigned long *)regs->rsp - 1; | |
387 | ||
388 | tsk = arch_get_kprobe_task(sara); | |
389 | head = kretprobe_inst_table_head(tsk); | |
390 | ||
391 | hlist_for_each_entry(ri, node, head, hlist) { | |
392 | if (ri->stack_addr == sara && ri->rp) { | |
393 | if (ri->rp->handler) | |
394 | ri->rp->handler(ri, regs); | |
395 | } | |
396 | } | |
397 | return 0; | |
398 | } | |
399 | ||
400 | void trampoline_post_handler(struct kprobe *p, struct pt_regs *regs, | |
401 | unsigned long flags) | |
402 | { | |
403 | struct kretprobe_instance *ri; | |
404 | /* RA already popped */ | |
405 | unsigned long *sara = ((unsigned long *)regs->rsp) - 1; | |
406 | ||
407 | while ((ri = get_rp_inst(sara))) { | |
408 | regs->rip = (unsigned long)ri->ret_addr; | |
409 | recycle_rp_inst(ri); | |
410 | } | |
411 | regs->eflags &= ~TF_MASK; | |
412 | } | |
413 | ||
1da177e4 LT |
414 | /* |
415 | * Called after single-stepping. p->addr is the address of the | |
416 | * instruction whose first byte has been replaced by the "int 3" | |
417 | * instruction. To avoid the SMP problems that can occur when we | |
418 | * temporarily put back the original opcode to single-step, we | |
419 | * single-stepped a copy of the instruction. The address of this | |
420 | * copy is p->ainsn.insn. | |
421 | * | |
422 | * This function prepares to return from the post-single-step | |
423 | * interrupt. We have to fix up the stack as follows: | |
424 | * | |
425 | * 0) Except in the case of absolute or indirect jump or call instructions, | |
426 | * the new rip is relative to the copied instruction. We need to make | |
427 | * it relative to the original instruction. | |
428 | * | |
429 | * 1) If the single-stepped instruction was pushfl, then the TF and IF | |
430 | * flags are set in the just-pushed eflags, and may need to be cleared. | |
431 | * | |
432 | * 2) If the single-stepped instruction was a call, the return address | |
433 | * that is atop the stack is the address following the copied instruction. | |
434 | * We need to make it the address following the original instruction. | |
435 | */ | |
436 | static void resume_execution(struct kprobe *p, struct pt_regs *regs) | |
437 | { | |
438 | unsigned long *tos = (unsigned long *)regs->rsp; | |
439 | unsigned long next_rip = 0; | |
440 | unsigned long copy_rip = (unsigned long)p->ainsn.insn; | |
441 | unsigned long orig_rip = (unsigned long)p->addr; | |
442 | kprobe_opcode_t *insn = p->ainsn.insn; | |
443 | ||
444 | /*skip the REX prefix*/ | |
445 | if (*insn >= 0x40 && *insn <= 0x4f) | |
446 | insn++; | |
447 | ||
448 | switch (*insn) { | |
449 | case 0x9c: /* pushfl */ | |
450 | *tos &= ~(TF_MASK | IF_MASK); | |
451 | *tos |= kprobe_old_rflags; | |
452 | break; | |
0b9e2cac PP |
453 | case 0xc3: /* ret/lret */ |
454 | case 0xcb: | |
455 | case 0xc2: | |
456 | case 0xca: | |
457 | regs->eflags &= ~TF_MASK; | |
458 | /* rip is already adjusted, no more changes required*/ | |
459 | return; | |
1da177e4 LT |
460 | case 0xe8: /* call relative - Fix return addr */ |
461 | *tos = orig_rip + (*tos - copy_rip); | |
462 | break; | |
463 | case 0xff: | |
464 | if ((*insn & 0x30) == 0x10) { | |
465 | /* call absolute, indirect */ | |
466 | /* Fix return addr; rip is correct. */ | |
467 | next_rip = regs->rip; | |
468 | *tos = orig_rip + (*tos - copy_rip); | |
469 | } else if (((*insn & 0x31) == 0x20) || /* jmp near, absolute indirect */ | |
470 | ((*insn & 0x31) == 0x21)) { /* jmp far, absolute indirect */ | |
471 | /* rip is correct. */ | |
472 | next_rip = regs->rip; | |
473 | } | |
474 | break; | |
475 | case 0xea: /* jmp absolute -- rip is correct */ | |
476 | next_rip = regs->rip; | |
477 | break; | |
478 | default: | |
479 | break; | |
480 | } | |
481 | ||
482 | regs->eflags &= ~TF_MASK; | |
483 | if (next_rip) { | |
484 | regs->rip = next_rip; | |
485 | } else { | |
486 | regs->rip = orig_rip + (regs->rip - copy_rip); | |
487 | } | |
488 | } | |
489 | ||
490 | /* | |
491 | * Interrupts are disabled on entry as trap1 is an interrupt gate and they | |
492 | * remain disabled thoroughout this function. And we hold kprobe lock. | |
493 | */ | |
494 | int post_kprobe_handler(struct pt_regs *regs) | |
495 | { | |
496 | if (!kprobe_running()) | |
497 | return 0; | |
498 | ||
499 | if (current_kprobe->post_handler) | |
500 | current_kprobe->post_handler(current_kprobe, regs, 0); | |
501 | ||
73649dab RL |
502 | if (current_kprobe->post_handler != trampoline_post_handler) |
503 | resume_execution(current_kprobe, regs); | |
1da177e4 LT |
504 | regs->eflags |= kprobe_saved_rflags; |
505 | ||
506 | unlock_kprobes(); | |
507 | preempt_enable_no_resched(); | |
508 | ||
509 | /* | |
510 | * if somebody else is singlestepping across a probe point, eflags | |
511 | * will have TF set, in which case, continue the remaining processing | |
512 | * of do_debug, as if this is not a probe hit. | |
513 | */ | |
514 | if (regs->eflags & TF_MASK) | |
515 | return 0; | |
516 | ||
517 | return 1; | |
518 | } | |
519 | ||
520 | /* Interrupts disabled, kprobe_lock held. */ | |
521 | int kprobe_fault_handler(struct pt_regs *regs, int trapnr) | |
522 | { | |
523 | if (current_kprobe->fault_handler | |
524 | && current_kprobe->fault_handler(current_kprobe, regs, trapnr)) | |
525 | return 1; | |
526 | ||
527 | if (kprobe_status & KPROBE_HIT_SS) { | |
528 | resume_execution(current_kprobe, regs); | |
529 | regs->eflags |= kprobe_old_rflags; | |
530 | ||
531 | unlock_kprobes(); | |
532 | preempt_enable_no_resched(); | |
533 | } | |
534 | return 0; | |
535 | } | |
536 | ||
537 | /* | |
538 | * Wrapper routine for handling exceptions. | |
539 | */ | |
540 | int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, | |
541 | void *data) | |
542 | { | |
543 | struct die_args *args = (struct die_args *)data; | |
544 | switch (val) { | |
545 | case DIE_INT3: | |
546 | if (kprobe_handler(args->regs)) | |
547 | return NOTIFY_STOP; | |
548 | break; | |
549 | case DIE_DEBUG: | |
550 | if (post_kprobe_handler(args->regs)) | |
551 | return NOTIFY_STOP; | |
552 | break; | |
553 | case DIE_GPF: | |
554 | if (kprobe_running() && | |
555 | kprobe_fault_handler(args->regs, args->trapnr)) | |
556 | return NOTIFY_STOP; | |
557 | break; | |
558 | case DIE_PAGE_FAULT: | |
559 | if (kprobe_running() && | |
560 | kprobe_fault_handler(args->regs, args->trapnr)) | |
561 | return NOTIFY_STOP; | |
562 | break; | |
563 | default: | |
564 | break; | |
565 | } | |
566 | return NOTIFY_DONE; | |
567 | } | |
568 | ||
569 | int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
570 | { | |
571 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
572 | unsigned long addr; | |
573 | ||
574 | jprobe_saved_regs = *regs; | |
575 | jprobe_saved_rsp = (long *) regs->rsp; | |
576 | addr = (unsigned long)jprobe_saved_rsp; | |
577 | /* | |
578 | * As Linus pointed out, gcc assumes that the callee | |
579 | * owns the argument space and could overwrite it, e.g. | |
580 | * tailcall optimization. So, to be absolutely safe | |
581 | * we also save and restore enough stack bytes to cover | |
582 | * the argument area. | |
583 | */ | |
584 | memcpy(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr)); | |
585 | regs->eflags &= ~IF_MASK; | |
586 | regs->rip = (unsigned long)(jp->entry); | |
587 | return 1; | |
588 | } | |
589 | ||
590 | void jprobe_return(void) | |
591 | { | |
592 | preempt_enable_no_resched(); | |
593 | asm volatile (" xchg %%rbx,%%rsp \n" | |
594 | " int3 \n" | |
595 | " .globl jprobe_return_end \n" | |
596 | " jprobe_return_end: \n" | |
597 | " nop \n"::"b" | |
598 | (jprobe_saved_rsp):"memory"); | |
599 | } | |
600 | ||
601 | int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) | |
602 | { | |
603 | u8 *addr = (u8 *) (regs->rip - 1); | |
604 | unsigned long stack_addr = (unsigned long)jprobe_saved_rsp; | |
605 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
606 | ||
607 | if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) { | |
608 | if ((long *)regs->rsp != jprobe_saved_rsp) { | |
609 | struct pt_regs *saved_regs = | |
610 | container_of(jprobe_saved_rsp, struct pt_regs, rsp); | |
611 | printk("current rsp %p does not match saved rsp %p\n", | |
612 | (long *)regs->rsp, jprobe_saved_rsp); | |
613 | printk("Saved registers for jprobe %p\n", jp); | |
614 | show_registers(saved_regs); | |
615 | printk("Current registers\n"); | |
616 | show_registers(regs); | |
617 | BUG(); | |
618 | } | |
619 | *regs = jprobe_saved_regs; | |
620 | memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack, | |
621 | MIN_STACK_SIZE(stack_addr)); | |
622 | return 1; | |
623 | } | |
624 | return 0; | |
625 | } | |
626 | ||
627 | /* | |
628 | * kprobe->ainsn.insn points to the copy of the instruction to be single-stepped. | |
629 | * By default on x86_64, pages we get from kmalloc or vmalloc are not | |
630 | * executable. Single-stepping an instruction on such a page yields an | |
631 | * oops. So instead of storing the instruction copies in their respective | |
632 | * kprobe objects, we allocate a page, map it executable, and store all the | |
633 | * instruction copies there. (We can allocate additional pages if somebody | |
634 | * inserts a huge number of probes.) Each page can hold up to INSNS_PER_PAGE | |
635 | * instruction slots, each of which is MAX_INSN_SIZE*sizeof(kprobe_opcode_t) | |
636 | * bytes. | |
637 | */ | |
638 | #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE*sizeof(kprobe_opcode_t))) | |
639 | struct kprobe_insn_page { | |
640 | struct hlist_node hlist; | |
641 | kprobe_opcode_t *insns; /* page of instruction slots */ | |
642 | char slot_used[INSNS_PER_PAGE]; | |
643 | int nused; | |
644 | }; | |
645 | ||
646 | static struct hlist_head kprobe_insn_pages; | |
647 | ||
648 | /** | |
649 | * get_insn_slot() - Find a slot on an executable page for an instruction. | |
650 | * We allocate an executable page if there's no room on existing ones. | |
651 | */ | |
652 | static kprobe_opcode_t *get_insn_slot(void) | |
653 | { | |
654 | struct kprobe_insn_page *kip; | |
655 | struct hlist_node *pos; | |
656 | ||
657 | hlist_for_each(pos, &kprobe_insn_pages) { | |
658 | kip = hlist_entry(pos, struct kprobe_insn_page, hlist); | |
659 | if (kip->nused < INSNS_PER_PAGE) { | |
660 | int i; | |
661 | for (i = 0; i < INSNS_PER_PAGE; i++) { | |
662 | if (!kip->slot_used[i]) { | |
663 | kip->slot_used[i] = 1; | |
664 | kip->nused++; | |
665 | return kip->insns + (i*MAX_INSN_SIZE); | |
666 | } | |
667 | } | |
668 | /* Surprise! No unused slots. Fix kip->nused. */ | |
669 | kip->nused = INSNS_PER_PAGE; | |
670 | } | |
671 | } | |
672 | ||
673 | /* All out of space. Need to allocate a new page. Use slot 0.*/ | |
674 | kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); | |
675 | if (!kip) { | |
676 | return NULL; | |
677 | } | |
678 | ||
679 | /* | |
680 | * For the %rip-relative displacement fixups to be doable, we | |
681 | * need our instruction copy to be within +/- 2GB of any data it | |
682 | * might access via %rip. That is, within 2GB of where the | |
683 | * kernel image and loaded module images reside. So we allocate | |
684 | * a page in the module loading area. | |
685 | */ | |
686 | kip->insns = module_alloc(PAGE_SIZE); | |
687 | if (!kip->insns) { | |
688 | kfree(kip); | |
689 | return NULL; | |
690 | } | |
691 | INIT_HLIST_NODE(&kip->hlist); | |
692 | hlist_add_head(&kip->hlist, &kprobe_insn_pages); | |
693 | memset(kip->slot_used, 0, INSNS_PER_PAGE); | |
694 | kip->slot_used[0] = 1; | |
695 | kip->nused = 1; | |
696 | return kip->insns; | |
697 | } | |
698 | ||
699 | /** | |
700 | * free_insn_slot() - Free instruction slot obtained from get_insn_slot(). | |
701 | */ | |
702 | static void free_insn_slot(kprobe_opcode_t *slot) | |
703 | { | |
704 | struct kprobe_insn_page *kip; | |
705 | struct hlist_node *pos; | |
706 | ||
707 | hlist_for_each(pos, &kprobe_insn_pages) { | |
708 | kip = hlist_entry(pos, struct kprobe_insn_page, hlist); | |
709 | if (kip->insns <= slot | |
710 | && slot < kip->insns+(INSNS_PER_PAGE*MAX_INSN_SIZE)) { | |
711 | int i = (slot - kip->insns) / MAX_INSN_SIZE; | |
712 | kip->slot_used[i] = 0; | |
713 | kip->nused--; | |
714 | if (kip->nused == 0) { | |
715 | /* | |
716 | * Page is no longer in use. Free it unless | |
717 | * it's the last one. We keep the last one | |
718 | * so as not to have to set it up again the | |
719 | * next time somebody inserts a probe. | |
720 | */ | |
721 | hlist_del(&kip->hlist); | |
722 | if (hlist_empty(&kprobe_insn_pages)) { | |
723 | INIT_HLIST_NODE(&kip->hlist); | |
724 | hlist_add_head(&kip->hlist, | |
725 | &kprobe_insn_pages); | |
726 | } else { | |
727 | module_free(NULL, kip->insns); | |
728 | kfree(kip); | |
729 | } | |
730 | } | |
731 | return; | |
732 | } | |
733 | } | |
734 | } |