Commit | Line | Data |
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1da177e4 LT |
1 | /* arch/sparc64/kernel/kprobes.c |
2 | * | |
3 | * Copyright (C) 2004 David S. Miller <davem@davemloft.net> | |
4 | */ | |
5 | ||
1da177e4 LT |
6 | #include <linux/kernel.h> |
7 | #include <linux/kprobes.h> | |
b6700096 | 8 | #include <linux/module.h> |
1eeb66a1 | 9 | #include <linux/kdebug.h> |
1da177e4 | 10 | #include <asm/signal.h> |
05e14cb3 | 11 | #include <asm/cacheflush.h> |
b6700096 | 12 | #include <asm/uaccess.h> |
1da177e4 LT |
13 | |
14 | /* We do not have hardware single-stepping on sparc64. | |
15 | * So we implement software single-stepping with breakpoint | |
16 | * traps. The top-level scheme is similar to that used | |
17 | * in the x86 kprobes implementation. | |
18 | * | |
19 | * In the kprobe->ainsn.insn[] array we store the original | |
20 | * instruction at index zero and a break instruction at | |
21 | * index one. | |
22 | * | |
23 | * When we hit a kprobe we: | |
24 | * - Run the pre-handler | |
25 | * - Remember "regs->tnpc" and interrupt level stored in | |
26 | * "regs->tstate" so we can restore them later | |
27 | * - Disable PIL interrupts | |
28 | * - Set regs->tpc to point to kprobe->ainsn.insn[0] | |
29 | * - Set regs->tnpc to point to kprobe->ainsn.insn[1] | |
30 | * - Mark that we are actively in a kprobe | |
31 | * | |
32 | * At this point we wait for the second breakpoint at | |
33 | * kprobe->ainsn.insn[1] to hit. When it does we: | |
34 | * - Run the post-handler | |
35 | * - Set regs->tpc to "remembered" regs->tnpc stored above, | |
36 | * restore the PIL interrupt level in "regs->tstate" as well | |
37 | * - Make any adjustments necessary to regs->tnpc in order | |
38 | * to handle relative branches correctly. See below. | |
39 | * - Mark that we are no longer actively in a kprobe. | |
40 | */ | |
41 | ||
f215d985 AM |
42 | DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; |
43 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
44 | ||
f438d914 MH |
45 | struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}}; |
46 | ||
05e14cb3 | 47 | int __kprobes arch_prepare_kprobe(struct kprobe *p) |
1da177e4 LT |
48 | { |
49 | p->ainsn.insn[0] = *p->addr; | |
f0882589 DM |
50 | flushi(&p->ainsn.insn[0]); |
51 | ||
1da177e4 | 52 | p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2; |
f0882589 DM |
53 | flushi(&p->ainsn.insn[1]); |
54 | ||
7e1048b1 | 55 | p->opcode = *p->addr; |
49a2a1b8 | 56 | return 0; |
7e1048b1 RL |
57 | } |
58 | ||
05e14cb3 | 59 | void __kprobes arch_arm_kprobe(struct kprobe *p) |
7e1048b1 RL |
60 | { |
61 | *p->addr = BREAKPOINT_INSTRUCTION; | |
62 | flushi(p->addr); | |
63 | } | |
64 | ||
05e14cb3 | 65 | void __kprobes arch_disarm_kprobe(struct kprobe *p) |
7e1048b1 RL |
66 | { |
67 | *p->addr = p->opcode; | |
68 | flushi(p->addr); | |
1da177e4 LT |
69 | } |
70 | ||
07fab8da | 71 | static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) |
e539c233 | 72 | { |
f215d985 AM |
73 | kcb->prev_kprobe.kp = kprobe_running(); |
74 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
75 | kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc; | |
76 | kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil; | |
e539c233 PP |
77 | } |
78 | ||
07fab8da | 79 | static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) |
e539c233 | 80 | { |
f215d985 AM |
81 | __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; |
82 | kcb->kprobe_status = kcb->prev_kprobe.status; | |
83 | kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc; | |
84 | kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil; | |
e539c233 PP |
85 | } |
86 | ||
07fab8da | 87 | static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, |
f215d985 | 88 | struct kprobe_ctlblk *kcb) |
1da177e4 | 89 | { |
f215d985 AM |
90 | __get_cpu_var(current_kprobe) = p; |
91 | kcb->kprobe_orig_tnpc = regs->tnpc; | |
92 | kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL); | |
e539c233 PP |
93 | } |
94 | ||
07fab8da | 95 | static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs, |
f215d985 | 96 | struct kprobe_ctlblk *kcb) |
e539c233 | 97 | { |
1da177e4 LT |
98 | regs->tstate |= TSTATE_PIL; |
99 | ||
100 | /*single step inline, if it a breakpoint instruction*/ | |
101 | if (p->opcode == BREAKPOINT_INSTRUCTION) { | |
102 | regs->tpc = (unsigned long) p->addr; | |
f215d985 | 103 | regs->tnpc = kcb->kprobe_orig_tnpc; |
1da177e4 LT |
104 | } else { |
105 | regs->tpc = (unsigned long) &p->ainsn.insn[0]; | |
106 | regs->tnpc = (unsigned long) &p->ainsn.insn[1]; | |
107 | } | |
108 | } | |
109 | ||
05e14cb3 | 110 | static int __kprobes kprobe_handler(struct pt_regs *regs) |
1da177e4 LT |
111 | { |
112 | struct kprobe *p; | |
113 | void *addr = (void *) regs->tpc; | |
114 | int ret = 0; | |
d217d545 AM |
115 | struct kprobe_ctlblk *kcb; |
116 | ||
117 | /* | |
118 | * We don't want to be preempted for the entire | |
119 | * duration of kprobe processing | |
120 | */ | |
121 | preempt_disable(); | |
122 | kcb = get_kprobe_ctlblk(); | |
1da177e4 | 123 | |
1da177e4 | 124 | if (kprobe_running()) { |
1da177e4 LT |
125 | p = get_kprobe(addr); |
126 | if (p) { | |
f215d985 | 127 | if (kcb->kprobe_status == KPROBE_HIT_SS) { |
1da177e4 | 128 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | |
f215d985 | 129 | kcb->kprobe_orig_tstate_pil); |
1da177e4 LT |
130 | goto no_kprobe; |
131 | } | |
e539c233 PP |
132 | /* We have reentered the kprobe_handler(), since |
133 | * another probe was hit while within the handler. | |
134 | * We here save the original kprobes variables and | |
135 | * just single step on the instruction of the new probe | |
136 | * without calling any user handlers. | |
137 | */ | |
f215d985 AM |
138 | save_previous_kprobe(kcb); |
139 | set_current_kprobe(p, regs, kcb); | |
bf8d5c52 | 140 | kprobes_inc_nmissed_count(p); |
f215d985 AM |
141 | kcb->kprobe_status = KPROBE_REENTER; |
142 | prepare_singlestep(p, regs, kcb); | |
e539c233 | 143 | return 1; |
1da177e4 | 144 | } else { |
eb3a7292 KA |
145 | if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { |
146 | /* The breakpoint instruction was removed by | |
147 | * another cpu right after we hit, no further | |
148 | * handling of this interrupt is appropriate | |
149 | */ | |
150 | ret = 1; | |
151 | goto no_kprobe; | |
152 | } | |
f215d985 | 153 | p = __get_cpu_var(current_kprobe); |
1da177e4 LT |
154 | if (p->break_handler && p->break_handler(p, regs)) |
155 | goto ss_probe; | |
156 | } | |
1da177e4 LT |
157 | goto no_kprobe; |
158 | } | |
159 | ||
1da177e4 LT |
160 | p = get_kprobe(addr); |
161 | if (!p) { | |
1da177e4 LT |
162 | if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { |
163 | /* | |
164 | * The breakpoint instruction was removed right | |
165 | * after we hit it. Another cpu has removed | |
166 | * either a probepoint or a debugger breakpoint | |
167 | * at this address. In either case, no further | |
168 | * handling of this interrupt is appropriate. | |
169 | */ | |
170 | ret = 1; | |
171 | } | |
172 | /* Not one of ours: let kernel handle it */ | |
173 | goto no_kprobe; | |
174 | } | |
175 | ||
f215d985 AM |
176 | set_current_kprobe(p, regs, kcb); |
177 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
1da177e4 LT |
178 | if (p->pre_handler && p->pre_handler(p, regs)) |
179 | return 1; | |
180 | ||
181 | ss_probe: | |
f215d985 AM |
182 | prepare_singlestep(p, regs, kcb); |
183 | kcb->kprobe_status = KPROBE_HIT_SS; | |
1da177e4 LT |
184 | return 1; |
185 | ||
186 | no_kprobe: | |
d217d545 | 187 | preempt_enable_no_resched(); |
1da177e4 LT |
188 | return ret; |
189 | } | |
190 | ||
191 | /* If INSN is a relative control transfer instruction, | |
192 | * return the corrected branch destination value. | |
193 | * | |
f0882589 DM |
194 | * regs->tpc and regs->tnpc still hold the values of the |
195 | * program counters at the time of trap due to the execution | |
196 | * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1] | |
197 | * | |
1da177e4 | 198 | */ |
f0882589 DM |
199 | static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p, |
200 | struct pt_regs *regs) | |
1da177e4 | 201 | { |
f0882589 DM |
202 | unsigned long real_pc = (unsigned long) p->addr; |
203 | ||
1da177e4 | 204 | /* Branch not taken, no mods necessary. */ |
f0882589 DM |
205 | if (regs->tnpc == regs->tpc + 0x4UL) |
206 | return real_pc + 0x8UL; | |
1da177e4 LT |
207 | |
208 | /* The three cases are call, branch w/prediction, | |
209 | * and traditional branch. | |
210 | */ | |
211 | if ((insn & 0xc0000000) == 0x40000000 || | |
212 | (insn & 0xc1c00000) == 0x00400000 || | |
213 | (insn & 0xc1c00000) == 0x00800000) { | |
f0882589 DM |
214 | unsigned long ainsn_addr; |
215 | ||
216 | ainsn_addr = (unsigned long) &p->ainsn.insn[0]; | |
217 | ||
1da177e4 LT |
218 | /* The instruction did all the work for us |
219 | * already, just apply the offset to the correct | |
220 | * instruction location. | |
221 | */ | |
f0882589 | 222 | return (real_pc + (regs->tnpc - ainsn_addr)); |
1da177e4 LT |
223 | } |
224 | ||
f0882589 DM |
225 | /* It is jmpl or some other absolute PC modification instruction, |
226 | * leave NPC as-is. | |
227 | */ | |
228 | return regs->tnpc; | |
1da177e4 LT |
229 | } |
230 | ||
231 | /* If INSN is an instruction which writes it's PC location | |
232 | * into a destination register, fix that up. | |
233 | */ | |
05e14cb3 PP |
234 | static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn, |
235 | unsigned long real_pc) | |
1da177e4 LT |
236 | { |
237 | unsigned long *slot = NULL; | |
238 | ||
f0882589 | 239 | /* Simplest case is 'call', which always uses %o7 */ |
1da177e4 LT |
240 | if ((insn & 0xc0000000) == 0x40000000) { |
241 | slot = ®s->u_regs[UREG_I7]; | |
242 | } | |
243 | ||
f0882589 | 244 | /* 'jmpl' encodes the register inside of the opcode */ |
1da177e4 LT |
245 | if ((insn & 0xc1f80000) == 0x81c00000) { |
246 | unsigned long rd = ((insn >> 25) & 0x1f); | |
247 | ||
248 | if (rd <= 15) { | |
249 | slot = ®s->u_regs[rd]; | |
250 | } else { | |
251 | /* Hard case, it goes onto the stack. */ | |
252 | flushw_all(); | |
253 | ||
254 | rd -= 16; | |
255 | slot = (unsigned long *) | |
256 | (regs->u_regs[UREG_FP] + STACK_BIAS); | |
257 | slot += rd; | |
258 | } | |
259 | } | |
260 | if (slot != NULL) | |
261 | *slot = real_pc; | |
262 | } | |
263 | ||
264 | /* | |
265 | * Called after single-stepping. p->addr is the address of the | |
f0882589 | 266 | * instruction which has been replaced by the breakpoint |
1da177e4 LT |
267 | * instruction. To avoid the SMP problems that can occur when we |
268 | * temporarily put back the original opcode to single-step, we | |
269 | * single-stepped a copy of the instruction. The address of this | |
f0882589 | 270 | * copy is &p->ainsn.insn[0]. |
1da177e4 LT |
271 | * |
272 | * This function prepares to return from the post-single-step | |
273 | * breakpoint trap. | |
274 | */ | |
f215d985 AM |
275 | static void __kprobes resume_execution(struct kprobe *p, |
276 | struct pt_regs *regs, struct kprobe_ctlblk *kcb) | |
1da177e4 LT |
277 | { |
278 | u32 insn = p->ainsn.insn[0]; | |
279 | ||
f0882589 DM |
280 | regs->tnpc = relbranch_fixup(insn, p, regs); |
281 | ||
282 | /* This assignment must occur after relbranch_fixup() */ | |
f215d985 | 283 | regs->tpc = kcb->kprobe_orig_tnpc; |
f0882589 | 284 | |
1da177e4 LT |
285 | retpc_fixup(regs, insn, (unsigned long) p->addr); |
286 | ||
287 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | | |
f215d985 | 288 | kcb->kprobe_orig_tstate_pil); |
1da177e4 LT |
289 | } |
290 | ||
07fab8da | 291 | static int __kprobes post_kprobe_handler(struct pt_regs *regs) |
1da177e4 | 292 | { |
f215d985 AM |
293 | struct kprobe *cur = kprobe_running(); |
294 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
295 | ||
296 | if (!cur) | |
1da177e4 LT |
297 | return 0; |
298 | ||
f215d985 AM |
299 | if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { |
300 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
301 | cur->post_handler(cur, regs, 0); | |
e539c233 | 302 | } |
1da177e4 | 303 | |
f215d985 | 304 | resume_execution(cur, regs, kcb); |
1da177e4 | 305 | |
e539c233 | 306 | /*Restore back the original saved kprobes variables and continue. */ |
f215d985 AM |
307 | if (kcb->kprobe_status == KPROBE_REENTER) { |
308 | restore_previous_kprobe(kcb); | |
e539c233 PP |
309 | goto out; |
310 | } | |
f215d985 | 311 | reset_current_kprobe(); |
e539c233 | 312 | out: |
1da177e4 LT |
313 | preempt_enable_no_resched(); |
314 | ||
315 | return 1; | |
316 | } | |
317 | ||
127cda1e | 318 | int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) |
1da177e4 | 319 | { |
f215d985 AM |
320 | struct kprobe *cur = kprobe_running(); |
321 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
b6700096 PP |
322 | const struct exception_table_entry *entry; |
323 | ||
324 | switch(kcb->kprobe_status) { | |
325 | case KPROBE_HIT_SS: | |
326 | case KPROBE_REENTER: | |
327 | /* | |
328 | * We are here because the instruction being single | |
329 | * stepped caused a page fault. We reset the current | |
330 | * kprobe and the tpc points back to the probe address | |
331 | * and allow the page fault handler to continue as a | |
332 | * normal page fault. | |
333 | */ | |
334 | regs->tpc = (unsigned long)cur->addr; | |
335 | regs->tnpc = kcb->kprobe_orig_tnpc; | |
336 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | | |
337 | kcb->kprobe_orig_tstate_pil); | |
338 | if (kcb->kprobe_status == KPROBE_REENTER) | |
339 | restore_previous_kprobe(kcb); | |
340 | else | |
341 | reset_current_kprobe(); | |
342 | preempt_enable_no_resched(); | |
343 | break; | |
344 | case KPROBE_HIT_ACTIVE: | |
345 | case KPROBE_HIT_SSDONE: | |
346 | /* | |
347 | * We increment the nmissed count for accounting, | |
348 | * we can also use npre/npostfault count for accouting | |
349 | * these specific fault cases. | |
350 | */ | |
351 | kprobes_inc_nmissed_count(cur); | |
352 | ||
353 | /* | |
354 | * We come here because instructions in the pre/post | |
355 | * handler caused the page_fault, this could happen | |
356 | * if handler tries to access user space by | |
357 | * copy_from_user(), get_user() etc. Let the | |
358 | * user-specified handler try to fix it first. | |
359 | */ | |
360 | if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) | |
361 | return 1; | |
f215d985 | 362 | |
b6700096 PP |
363 | /* |
364 | * In case the user-specified fault handler returned | |
365 | * zero, try to fix up. | |
366 | */ | |
1da177e4 | 367 | |
b6700096 PP |
368 | entry = search_exception_tables(regs->tpc); |
369 | if (entry) { | |
370 | regs->tpc = entry->fixup; | |
371 | regs->tnpc = regs->tpc + 4; | |
372 | return 1; | |
373 | } | |
1da177e4 | 374 | |
b6700096 PP |
375 | /* |
376 | * fixup_exception() could not handle it, | |
377 | * Let do_page_fault() fix it. | |
378 | */ | |
379 | break; | |
380 | default: | |
381 | break; | |
1da177e4 | 382 | } |
b6700096 | 383 | |
1da177e4 LT |
384 | return 0; |
385 | } | |
386 | ||
387 | /* | |
388 | * Wrapper routine to for handling exceptions. | |
389 | */ | |
05e14cb3 PP |
390 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, |
391 | unsigned long val, void *data) | |
1da177e4 LT |
392 | { |
393 | struct die_args *args = (struct die_args *)data; | |
66ff2d06 AM |
394 | int ret = NOTIFY_DONE; |
395 | ||
2326c770 | 396 | if (args->regs && user_mode(args->regs)) |
397 | return ret; | |
398 | ||
1da177e4 LT |
399 | switch (val) { |
400 | case DIE_DEBUG: | |
401 | if (kprobe_handler(args->regs)) | |
66ff2d06 | 402 | ret = NOTIFY_STOP; |
1da177e4 LT |
403 | break; |
404 | case DIE_DEBUG_2: | |
405 | if (post_kprobe_handler(args->regs)) | |
66ff2d06 | 406 | ret = NOTIFY_STOP; |
1da177e4 | 407 | break; |
1da177e4 LT |
408 | default: |
409 | break; | |
410 | } | |
66ff2d06 | 411 | return ret; |
1da177e4 LT |
412 | } |
413 | ||
05e14cb3 PP |
414 | asmlinkage void __kprobes kprobe_trap(unsigned long trap_level, |
415 | struct pt_regs *regs) | |
1da177e4 LT |
416 | { |
417 | BUG_ON(trap_level != 0x170 && trap_level != 0x171); | |
418 | ||
419 | if (user_mode(regs)) { | |
420 | local_irq_enable(); | |
421 | bad_trap(regs, trap_level); | |
422 | return; | |
423 | } | |
424 | ||
425 | /* trap_level == 0x170 --> ta 0x70 | |
426 | * trap_level == 0x171 --> ta 0x71 | |
427 | */ | |
428 | if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2, | |
429 | (trap_level == 0x170) ? "debug" : "debug_2", | |
430 | regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP) | |
431 | bad_trap(regs, trap_level); | |
432 | } | |
433 | ||
434 | /* Jprobes support. */ | |
05e14cb3 | 435 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) |
1da177e4 LT |
436 | { |
437 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
f215d985 | 438 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
1da177e4 | 439 | |
f215d985 | 440 | memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs)); |
1da177e4 | 441 | |
1da177e4 LT |
442 | regs->tpc = (unsigned long) jp->entry; |
443 | regs->tnpc = ((unsigned long) jp->entry) + 0x4UL; | |
444 | regs->tstate |= TSTATE_PIL; | |
445 | ||
446 | return 1; | |
447 | } | |
448 | ||
05e14cb3 | 449 | void __kprobes jprobe_return(void) |
1da177e4 | 450 | { |
f0882589 DM |
451 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
452 | register unsigned long orig_fp asm("g1"); | |
453 | ||
454 | orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP]; | |
455 | __asm__ __volatile__("\n" | |
456 | "1: cmp %%sp, %0\n\t" | |
457 | "blu,a,pt %%xcc, 1b\n\t" | |
458 | " restore\n\t" | |
459 | ".globl jprobe_return_trap_instruction\n" | |
1da177e4 | 460 | "jprobe_return_trap_instruction:\n\t" |
f0882589 DM |
461 | "ta 0x70" |
462 | : /* no outputs */ | |
463 | : "r" (orig_fp)); | |
1da177e4 LT |
464 | } |
465 | ||
466 | extern void jprobe_return_trap_instruction(void); | |
467 | ||
05e14cb3 | 468 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) |
1da177e4 LT |
469 | { |
470 | u32 *addr = (u32 *) regs->tpc; | |
f215d985 | 471 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
1da177e4 LT |
472 | |
473 | if (addr == (u32 *) jprobe_return_trap_instruction) { | |
f215d985 | 474 | memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs)); |
d217d545 | 475 | preempt_enable_no_resched(); |
1da177e4 LT |
476 | return 1; |
477 | } | |
478 | return 0; | |
479 | } | |
e539c233 | 480 | |
ef53d9c5 S |
481 | /* The value stored in the return address register is actually 2 |
482 | * instructions before where the callee will return to. | |
483 | * Sequences usually look something like this | |
d38f1220 DM |
484 | * |
485 | * call some_function <--- return register points here | |
486 | * nop <--- call delay slot | |
487 | * whatever <--- where callee returns to | |
488 | * | |
489 | * To keep trampoline_probe_handler logic simpler, we normalize the | |
490 | * value kept in ri->ret_addr so we don't need to keep adjusting it | |
491 | * back and forth. | |
492 | */ | |
493 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, | |
494 | struct pt_regs *regs) | |
495 | { | |
496 | ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8); | |
497 | ||
498 | /* Replace the return addr with trampoline addr */ | |
499 | regs->u_regs[UREG_RETPC] = | |
500 | ((unsigned long)kretprobe_trampoline) - 8; | |
501 | } | |
502 | ||
503 | /* | |
504 | * Called when the probe at kretprobe trampoline is hit | |
505 | */ | |
506 | int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) | |
507 | { | |
508 | struct kretprobe_instance *ri = NULL; | |
509 | struct hlist_head *head, empty_rp; | |
510 | struct hlist_node *node, *tmp; | |
511 | unsigned long flags, orig_ret_address = 0; | |
512 | unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; | |
513 | ||
514 | INIT_HLIST_HEAD(&empty_rp); | |
ef53d9c5 | 515 | kretprobe_hash_lock(current, &head, &flags); |
d38f1220 DM |
516 | |
517 | /* | |
518 | * It is possible to have multiple instances associated with a given | |
519 | * task either because an multiple functions in the call path | |
025dfdaf | 520 | * have a return probe installed on them, and/or more than one return |
d38f1220 DM |
521 | * return probe was registered for a target function. |
522 | * | |
523 | * We can handle this because: | |
524 | * - instances are always inserted at the head of the list | |
525 | * - when multiple return probes are registered for the same | |
526 | * function, the first instance's ret_addr will point to the | |
527 | * real return address, and all the rest will point to | |
528 | * kretprobe_trampoline | |
529 | */ | |
530 | hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { | |
531 | if (ri->task != current) | |
532 | /* another task is sharing our hash bucket */ | |
533 | continue; | |
534 | ||
535 | if (ri->rp && ri->rp->handler) | |
536 | ri->rp->handler(ri, regs); | |
537 | ||
538 | orig_ret_address = (unsigned long)ri->ret_addr; | |
539 | recycle_rp_inst(ri, &empty_rp); | |
540 | ||
541 | if (orig_ret_address != trampoline_address) | |
542 | /* | |
543 | * This is the real return address. Any other | |
544 | * instances associated with this task are for | |
545 | * other calls deeper on the call stack | |
546 | */ | |
547 | break; | |
548 | } | |
549 | ||
550 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
551 | regs->tpc = orig_ret_address; | |
552 | regs->tnpc = orig_ret_address + 4; | |
553 | ||
554 | reset_current_kprobe(); | |
ef53d9c5 | 555 | kretprobe_hash_unlock(current, &flags); |
d38f1220 DM |
556 | preempt_enable_no_resched(); |
557 | ||
558 | hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { | |
559 | hlist_del(&ri->hlist); | |
560 | kfree(ri); | |
561 | } | |
562 | /* | |
563 | * By returning a non-zero value, we are telling | |
564 | * kprobe_handler() that we don't want the post_handler | |
565 | * to run (and have re-enabled preemption) | |
566 | */ | |
567 | return 1; | |
568 | } | |
569 | ||
570 | void kretprobe_trampoline_holder(void) | |
571 | { | |
572 | asm volatile(".global kretprobe_trampoline\n" | |
573 | "kretprobe_trampoline:\n" | |
574 | "\tnop\n" | |
575 | "\tnop\n"); | |
576 | } | |
577 | static struct kprobe trampoline_p = { | |
578 | .addr = (kprobe_opcode_t *) &kretprobe_trampoline, | |
579 | .pre_handler = trampoline_probe_handler | |
580 | }; | |
581 | ||
582 | int __init arch_init_kprobes(void) | |
6772926b | 583 | { |
d38f1220 DM |
584 | return register_kprobe(&trampoline_p); |
585 | } | |
586 | ||
587 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) | |
588 | { | |
589 | if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) | |
590 | return 1; | |
591 | ||
6772926b RL |
592 | return 0; |
593 | } |