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> |
5a0e3ad6 | 10 | #include <linux/slab.h> |
1da177e4 | 11 | #include <asm/signal.h> |
05e14cb3 | 12 | #include <asm/cacheflush.h> |
b6700096 | 13 | #include <asm/uaccess.h> |
1da177e4 LT |
14 | |
15 | /* We do not have hardware single-stepping on sparc64. | |
16 | * So we implement software single-stepping with breakpoint | |
17 | * traps. The top-level scheme is similar to that used | |
18 | * in the x86 kprobes implementation. | |
19 | * | |
20 | * In the kprobe->ainsn.insn[] array we store the original | |
21 | * instruction at index zero and a break instruction at | |
22 | * index one. | |
23 | * | |
24 | * When we hit a kprobe we: | |
25 | * - Run the pre-handler | |
26 | * - Remember "regs->tnpc" and interrupt level stored in | |
27 | * "regs->tstate" so we can restore them later | |
28 | * - Disable PIL interrupts | |
29 | * - Set regs->tpc to point to kprobe->ainsn.insn[0] | |
30 | * - Set regs->tnpc to point to kprobe->ainsn.insn[1] | |
31 | * - Mark that we are actively in a kprobe | |
32 | * | |
33 | * At this point we wait for the second breakpoint at | |
34 | * kprobe->ainsn.insn[1] to hit. When it does we: | |
35 | * - Run the post-handler | |
36 | * - Set regs->tpc to "remembered" regs->tnpc stored above, | |
37 | * restore the PIL interrupt level in "regs->tstate" as well | |
38 | * - Make any adjustments necessary to regs->tnpc in order | |
39 | * to handle relative branches correctly. See below. | |
40 | * - Mark that we are no longer actively in a kprobe. | |
41 | */ | |
42 | ||
f215d985 AM |
43 | DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; |
44 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
45 | ||
f438d914 MH |
46 | struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}}; |
47 | ||
05e14cb3 | 48 | int __kprobes arch_prepare_kprobe(struct kprobe *p) |
1da177e4 | 49 | { |
936cf251 DM |
50 | if ((unsigned long) p->addr & 0x3UL) |
51 | return -EILSEQ; | |
52 | ||
1da177e4 | 53 | p->ainsn.insn[0] = *p->addr; |
f0882589 DM |
54 | flushi(&p->ainsn.insn[0]); |
55 | ||
1da177e4 | 56 | p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2; |
f0882589 DM |
57 | flushi(&p->ainsn.insn[1]); |
58 | ||
7e1048b1 | 59 | p->opcode = *p->addr; |
49a2a1b8 | 60 | return 0; |
7e1048b1 RL |
61 | } |
62 | ||
05e14cb3 | 63 | void __kprobes arch_arm_kprobe(struct kprobe *p) |
7e1048b1 RL |
64 | { |
65 | *p->addr = BREAKPOINT_INSTRUCTION; | |
66 | flushi(p->addr); | |
67 | } | |
68 | ||
05e14cb3 | 69 | void __kprobes arch_disarm_kprobe(struct kprobe *p) |
7e1048b1 RL |
70 | { |
71 | *p->addr = p->opcode; | |
72 | flushi(p->addr); | |
1da177e4 LT |
73 | } |
74 | ||
07fab8da | 75 | static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) |
e539c233 | 76 | { |
f215d985 AM |
77 | kcb->prev_kprobe.kp = kprobe_running(); |
78 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
79 | kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc; | |
80 | kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil; | |
e539c233 PP |
81 | } |
82 | ||
07fab8da | 83 | static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) |
e539c233 | 84 | { |
f215d985 AM |
85 | __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; |
86 | kcb->kprobe_status = kcb->prev_kprobe.status; | |
87 | kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc; | |
88 | kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil; | |
e539c233 PP |
89 | } |
90 | ||
07fab8da | 91 | static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, |
f215d985 | 92 | struct kprobe_ctlblk *kcb) |
1da177e4 | 93 | { |
f215d985 AM |
94 | __get_cpu_var(current_kprobe) = p; |
95 | kcb->kprobe_orig_tnpc = regs->tnpc; | |
96 | kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL); | |
e539c233 PP |
97 | } |
98 | ||
07fab8da | 99 | static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs, |
f215d985 | 100 | struct kprobe_ctlblk *kcb) |
e539c233 | 101 | { |
1da177e4 LT |
102 | regs->tstate |= TSTATE_PIL; |
103 | ||
104 | /*single step inline, if it a breakpoint instruction*/ | |
105 | if (p->opcode == BREAKPOINT_INSTRUCTION) { | |
106 | regs->tpc = (unsigned long) p->addr; | |
f215d985 | 107 | regs->tnpc = kcb->kprobe_orig_tnpc; |
1da177e4 LT |
108 | } else { |
109 | regs->tpc = (unsigned long) &p->ainsn.insn[0]; | |
110 | regs->tnpc = (unsigned long) &p->ainsn.insn[1]; | |
111 | } | |
112 | } | |
113 | ||
05e14cb3 | 114 | static int __kprobes kprobe_handler(struct pt_regs *regs) |
1da177e4 LT |
115 | { |
116 | struct kprobe *p; | |
117 | void *addr = (void *) regs->tpc; | |
118 | int ret = 0; | |
d217d545 AM |
119 | struct kprobe_ctlblk *kcb; |
120 | ||
121 | /* | |
122 | * We don't want to be preempted for the entire | |
123 | * duration of kprobe processing | |
124 | */ | |
125 | preempt_disable(); | |
126 | kcb = get_kprobe_ctlblk(); | |
1da177e4 | 127 | |
1da177e4 | 128 | if (kprobe_running()) { |
1da177e4 LT |
129 | p = get_kprobe(addr); |
130 | if (p) { | |
f215d985 | 131 | if (kcb->kprobe_status == KPROBE_HIT_SS) { |
1da177e4 | 132 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | |
f215d985 | 133 | kcb->kprobe_orig_tstate_pil); |
1da177e4 LT |
134 | goto no_kprobe; |
135 | } | |
e539c233 PP |
136 | /* We have reentered the kprobe_handler(), since |
137 | * another probe was hit while within the handler. | |
138 | * We here save the original kprobes variables and | |
139 | * just single step on the instruction of the new probe | |
140 | * without calling any user handlers. | |
141 | */ | |
f215d985 AM |
142 | save_previous_kprobe(kcb); |
143 | set_current_kprobe(p, regs, kcb); | |
bf8d5c52 | 144 | kprobes_inc_nmissed_count(p); |
f215d985 AM |
145 | kcb->kprobe_status = KPROBE_REENTER; |
146 | prepare_singlestep(p, regs, kcb); | |
e539c233 | 147 | return 1; |
1da177e4 | 148 | } else { |
eb3a7292 KA |
149 | if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { |
150 | /* The breakpoint instruction was removed by | |
151 | * another cpu right after we hit, no further | |
152 | * handling of this interrupt is appropriate | |
153 | */ | |
154 | ret = 1; | |
155 | goto no_kprobe; | |
156 | } | |
f215d985 | 157 | p = __get_cpu_var(current_kprobe); |
1da177e4 LT |
158 | if (p->break_handler && p->break_handler(p, regs)) |
159 | goto ss_probe; | |
160 | } | |
1da177e4 LT |
161 | goto no_kprobe; |
162 | } | |
163 | ||
1da177e4 LT |
164 | p = get_kprobe(addr); |
165 | if (!p) { | |
1da177e4 LT |
166 | if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { |
167 | /* | |
168 | * The breakpoint instruction was removed right | |
169 | * after we hit it. Another cpu has removed | |
170 | * either a probepoint or a debugger breakpoint | |
171 | * at this address. In either case, no further | |
172 | * handling of this interrupt is appropriate. | |
173 | */ | |
174 | ret = 1; | |
175 | } | |
176 | /* Not one of ours: let kernel handle it */ | |
177 | goto no_kprobe; | |
178 | } | |
179 | ||
f215d985 AM |
180 | set_current_kprobe(p, regs, kcb); |
181 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
1da177e4 LT |
182 | if (p->pre_handler && p->pre_handler(p, regs)) |
183 | return 1; | |
184 | ||
185 | ss_probe: | |
f215d985 AM |
186 | prepare_singlestep(p, regs, kcb); |
187 | kcb->kprobe_status = KPROBE_HIT_SS; | |
1da177e4 LT |
188 | return 1; |
189 | ||
190 | no_kprobe: | |
d217d545 | 191 | preempt_enable_no_resched(); |
1da177e4 LT |
192 | return ret; |
193 | } | |
194 | ||
195 | /* If INSN is a relative control transfer instruction, | |
196 | * return the corrected branch destination value. | |
197 | * | |
f0882589 DM |
198 | * regs->tpc and regs->tnpc still hold the values of the |
199 | * program counters at the time of trap due to the execution | |
200 | * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1] | |
201 | * | |
1da177e4 | 202 | */ |
f0882589 DM |
203 | static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p, |
204 | struct pt_regs *regs) | |
1da177e4 | 205 | { |
f0882589 DM |
206 | unsigned long real_pc = (unsigned long) p->addr; |
207 | ||
1da177e4 | 208 | /* Branch not taken, no mods necessary. */ |
f0882589 DM |
209 | if (regs->tnpc == regs->tpc + 0x4UL) |
210 | return real_pc + 0x8UL; | |
1da177e4 LT |
211 | |
212 | /* The three cases are call, branch w/prediction, | |
213 | * and traditional branch. | |
214 | */ | |
215 | if ((insn & 0xc0000000) == 0x40000000 || | |
216 | (insn & 0xc1c00000) == 0x00400000 || | |
217 | (insn & 0xc1c00000) == 0x00800000) { | |
f0882589 DM |
218 | unsigned long ainsn_addr; |
219 | ||
220 | ainsn_addr = (unsigned long) &p->ainsn.insn[0]; | |
221 | ||
1da177e4 LT |
222 | /* The instruction did all the work for us |
223 | * already, just apply the offset to the correct | |
224 | * instruction location. | |
225 | */ | |
f0882589 | 226 | return (real_pc + (regs->tnpc - ainsn_addr)); |
1da177e4 LT |
227 | } |
228 | ||
f0882589 DM |
229 | /* It is jmpl or some other absolute PC modification instruction, |
230 | * leave NPC as-is. | |
231 | */ | |
232 | return regs->tnpc; | |
1da177e4 LT |
233 | } |
234 | ||
235 | /* If INSN is an instruction which writes it's PC location | |
236 | * into a destination register, fix that up. | |
237 | */ | |
05e14cb3 PP |
238 | static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn, |
239 | unsigned long real_pc) | |
1da177e4 LT |
240 | { |
241 | unsigned long *slot = NULL; | |
242 | ||
f0882589 | 243 | /* Simplest case is 'call', which always uses %o7 */ |
1da177e4 LT |
244 | if ((insn & 0xc0000000) == 0x40000000) { |
245 | slot = ®s->u_regs[UREG_I7]; | |
246 | } | |
247 | ||
f0882589 | 248 | /* 'jmpl' encodes the register inside of the opcode */ |
1da177e4 LT |
249 | if ((insn & 0xc1f80000) == 0x81c00000) { |
250 | unsigned long rd = ((insn >> 25) & 0x1f); | |
251 | ||
252 | if (rd <= 15) { | |
253 | slot = ®s->u_regs[rd]; | |
254 | } else { | |
255 | /* Hard case, it goes onto the stack. */ | |
256 | flushw_all(); | |
257 | ||
258 | rd -= 16; | |
259 | slot = (unsigned long *) | |
260 | (regs->u_regs[UREG_FP] + STACK_BIAS); | |
261 | slot += rd; | |
262 | } | |
263 | } | |
264 | if (slot != NULL) | |
265 | *slot = real_pc; | |
266 | } | |
267 | ||
268 | /* | |
269 | * Called after single-stepping. p->addr is the address of the | |
f0882589 | 270 | * instruction which has been replaced by the breakpoint |
1da177e4 LT |
271 | * instruction. To avoid the SMP problems that can occur when we |
272 | * temporarily put back the original opcode to single-step, we | |
273 | * single-stepped a copy of the instruction. The address of this | |
f0882589 | 274 | * copy is &p->ainsn.insn[0]. |
1da177e4 LT |
275 | * |
276 | * This function prepares to return from the post-single-step | |
277 | * breakpoint trap. | |
278 | */ | |
f215d985 AM |
279 | static void __kprobes resume_execution(struct kprobe *p, |
280 | struct pt_regs *regs, struct kprobe_ctlblk *kcb) | |
1da177e4 LT |
281 | { |
282 | u32 insn = p->ainsn.insn[0]; | |
283 | ||
f0882589 DM |
284 | regs->tnpc = relbranch_fixup(insn, p, regs); |
285 | ||
286 | /* This assignment must occur after relbranch_fixup() */ | |
f215d985 | 287 | regs->tpc = kcb->kprobe_orig_tnpc; |
f0882589 | 288 | |
1da177e4 LT |
289 | retpc_fixup(regs, insn, (unsigned long) p->addr); |
290 | ||
291 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | | |
f215d985 | 292 | kcb->kprobe_orig_tstate_pil); |
1da177e4 LT |
293 | } |
294 | ||
07fab8da | 295 | static int __kprobes post_kprobe_handler(struct pt_regs *regs) |
1da177e4 | 296 | { |
f215d985 AM |
297 | struct kprobe *cur = kprobe_running(); |
298 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
299 | ||
300 | if (!cur) | |
1da177e4 LT |
301 | return 0; |
302 | ||
f215d985 AM |
303 | if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { |
304 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
305 | cur->post_handler(cur, regs, 0); | |
e539c233 | 306 | } |
1da177e4 | 307 | |
f215d985 | 308 | resume_execution(cur, regs, kcb); |
1da177e4 | 309 | |
e539c233 | 310 | /*Restore back the original saved kprobes variables and continue. */ |
f215d985 AM |
311 | if (kcb->kprobe_status == KPROBE_REENTER) { |
312 | restore_previous_kprobe(kcb); | |
e539c233 PP |
313 | goto out; |
314 | } | |
f215d985 | 315 | reset_current_kprobe(); |
e539c233 | 316 | out: |
1da177e4 LT |
317 | preempt_enable_no_resched(); |
318 | ||
319 | return 1; | |
320 | } | |
321 | ||
127cda1e | 322 | int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) |
1da177e4 | 323 | { |
f215d985 AM |
324 | struct kprobe *cur = kprobe_running(); |
325 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
b6700096 PP |
326 | const struct exception_table_entry *entry; |
327 | ||
328 | switch(kcb->kprobe_status) { | |
329 | case KPROBE_HIT_SS: | |
330 | case KPROBE_REENTER: | |
331 | /* | |
332 | * We are here because the instruction being single | |
333 | * stepped caused a page fault. We reset the current | |
334 | * kprobe and the tpc points back to the probe address | |
335 | * and allow the page fault handler to continue as a | |
336 | * normal page fault. | |
337 | */ | |
338 | regs->tpc = (unsigned long)cur->addr; | |
339 | regs->tnpc = kcb->kprobe_orig_tnpc; | |
340 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | | |
341 | kcb->kprobe_orig_tstate_pil); | |
342 | if (kcb->kprobe_status == KPROBE_REENTER) | |
343 | restore_previous_kprobe(kcb); | |
344 | else | |
345 | reset_current_kprobe(); | |
346 | preempt_enable_no_resched(); | |
347 | break; | |
348 | case KPROBE_HIT_ACTIVE: | |
349 | case KPROBE_HIT_SSDONE: | |
350 | /* | |
351 | * We increment the nmissed count for accounting, | |
352 | * we can also use npre/npostfault count for accouting | |
353 | * these specific fault cases. | |
354 | */ | |
355 | kprobes_inc_nmissed_count(cur); | |
356 | ||
357 | /* | |
358 | * We come here because instructions in the pre/post | |
359 | * handler caused the page_fault, this could happen | |
360 | * if handler tries to access user space by | |
361 | * copy_from_user(), get_user() etc. Let the | |
362 | * user-specified handler try to fix it first. | |
363 | */ | |
364 | if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) | |
365 | return 1; | |
f215d985 | 366 | |
b6700096 PP |
367 | /* |
368 | * In case the user-specified fault handler returned | |
369 | * zero, try to fix up. | |
370 | */ | |
1da177e4 | 371 | |
b6700096 PP |
372 | entry = search_exception_tables(regs->tpc); |
373 | if (entry) { | |
374 | regs->tpc = entry->fixup; | |
375 | regs->tnpc = regs->tpc + 4; | |
376 | return 1; | |
377 | } | |
1da177e4 | 378 | |
b6700096 PP |
379 | /* |
380 | * fixup_exception() could not handle it, | |
381 | * Let do_page_fault() fix it. | |
382 | */ | |
383 | break; | |
384 | default: | |
385 | break; | |
1da177e4 | 386 | } |
b6700096 | 387 | |
1da177e4 LT |
388 | return 0; |
389 | } | |
390 | ||
391 | /* | |
392 | * Wrapper routine to for handling exceptions. | |
393 | */ | |
05e14cb3 PP |
394 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, |
395 | unsigned long val, void *data) | |
1da177e4 LT |
396 | { |
397 | struct die_args *args = (struct die_args *)data; | |
66ff2d06 AM |
398 | int ret = NOTIFY_DONE; |
399 | ||
2326c770 | 400 | if (args->regs && user_mode(args->regs)) |
401 | return ret; | |
402 | ||
1da177e4 LT |
403 | switch (val) { |
404 | case DIE_DEBUG: | |
405 | if (kprobe_handler(args->regs)) | |
66ff2d06 | 406 | ret = NOTIFY_STOP; |
1da177e4 LT |
407 | break; |
408 | case DIE_DEBUG_2: | |
409 | if (post_kprobe_handler(args->regs)) | |
66ff2d06 | 410 | ret = NOTIFY_STOP; |
1da177e4 | 411 | break; |
1da177e4 LT |
412 | default: |
413 | break; | |
414 | } | |
66ff2d06 | 415 | return ret; |
1da177e4 LT |
416 | } |
417 | ||
05e14cb3 PP |
418 | asmlinkage void __kprobes kprobe_trap(unsigned long trap_level, |
419 | struct pt_regs *regs) | |
1da177e4 LT |
420 | { |
421 | BUG_ON(trap_level != 0x170 && trap_level != 0x171); | |
422 | ||
423 | if (user_mode(regs)) { | |
424 | local_irq_enable(); | |
425 | bad_trap(regs, trap_level); | |
426 | return; | |
427 | } | |
428 | ||
429 | /* trap_level == 0x170 --> ta 0x70 | |
430 | * trap_level == 0x171 --> ta 0x71 | |
431 | */ | |
432 | if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2, | |
433 | (trap_level == 0x170) ? "debug" : "debug_2", | |
434 | regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP) | |
435 | bad_trap(regs, trap_level); | |
436 | } | |
437 | ||
438 | /* Jprobes support. */ | |
05e14cb3 | 439 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) |
1da177e4 LT |
440 | { |
441 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
f215d985 | 442 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
1da177e4 | 443 | |
f215d985 | 444 | memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs)); |
1da177e4 | 445 | |
1da177e4 LT |
446 | regs->tpc = (unsigned long) jp->entry; |
447 | regs->tnpc = ((unsigned long) jp->entry) + 0x4UL; | |
448 | regs->tstate |= TSTATE_PIL; | |
449 | ||
450 | return 1; | |
451 | } | |
452 | ||
05e14cb3 | 453 | void __kprobes jprobe_return(void) |
1da177e4 | 454 | { |
f0882589 DM |
455 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
456 | register unsigned long orig_fp asm("g1"); | |
457 | ||
458 | orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP]; | |
459 | __asm__ __volatile__("\n" | |
460 | "1: cmp %%sp, %0\n\t" | |
461 | "blu,a,pt %%xcc, 1b\n\t" | |
462 | " restore\n\t" | |
463 | ".globl jprobe_return_trap_instruction\n" | |
1da177e4 | 464 | "jprobe_return_trap_instruction:\n\t" |
f0882589 DM |
465 | "ta 0x70" |
466 | : /* no outputs */ | |
467 | : "r" (orig_fp)); | |
1da177e4 LT |
468 | } |
469 | ||
470 | extern void jprobe_return_trap_instruction(void); | |
471 | ||
05e14cb3 | 472 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) |
1da177e4 LT |
473 | { |
474 | u32 *addr = (u32 *) regs->tpc; | |
f215d985 | 475 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
1da177e4 LT |
476 | |
477 | if (addr == (u32 *) jprobe_return_trap_instruction) { | |
f215d985 | 478 | memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs)); |
d217d545 | 479 | preempt_enable_no_resched(); |
1da177e4 LT |
480 | return 1; |
481 | } | |
482 | return 0; | |
483 | } | |
e539c233 | 484 | |
ef53d9c5 S |
485 | /* The value stored in the return address register is actually 2 |
486 | * instructions before where the callee will return to. | |
487 | * Sequences usually look something like this | |
d38f1220 DM |
488 | * |
489 | * call some_function <--- return register points here | |
490 | * nop <--- call delay slot | |
491 | * whatever <--- where callee returns to | |
492 | * | |
493 | * To keep trampoline_probe_handler logic simpler, we normalize the | |
494 | * value kept in ri->ret_addr so we don't need to keep adjusting it | |
495 | * back and forth. | |
496 | */ | |
497 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, | |
498 | struct pt_regs *regs) | |
499 | { | |
500 | ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8); | |
501 | ||
502 | /* Replace the return addr with trampoline addr */ | |
503 | regs->u_regs[UREG_RETPC] = | |
504 | ((unsigned long)kretprobe_trampoline) - 8; | |
505 | } | |
506 | ||
507 | /* | |
508 | * Called when the probe at kretprobe trampoline is hit | |
509 | */ | |
510 | int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) | |
511 | { | |
512 | struct kretprobe_instance *ri = NULL; | |
513 | struct hlist_head *head, empty_rp; | |
514 | struct hlist_node *node, *tmp; | |
515 | unsigned long flags, orig_ret_address = 0; | |
516 | unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; | |
517 | ||
518 | INIT_HLIST_HEAD(&empty_rp); | |
ef53d9c5 | 519 | kretprobe_hash_lock(current, &head, &flags); |
d38f1220 DM |
520 | |
521 | /* | |
522 | * It is possible to have multiple instances associated with a given | |
523 | * task either because an multiple functions in the call path | |
025dfdaf | 524 | * have a return probe installed on them, and/or more than one return |
d38f1220 DM |
525 | * return probe was registered for a target function. |
526 | * | |
527 | * We can handle this because: | |
528 | * - instances are always inserted at the head of the list | |
529 | * - when multiple return probes are registered for the same | |
530 | * function, the first instance's ret_addr will point to the | |
531 | * real return address, and all the rest will point to | |
532 | * kretprobe_trampoline | |
533 | */ | |
534 | hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { | |
535 | if (ri->task != current) | |
536 | /* another task is sharing our hash bucket */ | |
537 | continue; | |
538 | ||
539 | if (ri->rp && ri->rp->handler) | |
540 | ri->rp->handler(ri, regs); | |
541 | ||
542 | orig_ret_address = (unsigned long)ri->ret_addr; | |
543 | recycle_rp_inst(ri, &empty_rp); | |
544 | ||
545 | if (orig_ret_address != trampoline_address) | |
546 | /* | |
547 | * This is the real return address. Any other | |
548 | * instances associated with this task are for | |
549 | * other calls deeper on the call stack | |
550 | */ | |
551 | break; | |
552 | } | |
553 | ||
554 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
555 | regs->tpc = orig_ret_address; | |
556 | regs->tnpc = orig_ret_address + 4; | |
557 | ||
558 | reset_current_kprobe(); | |
ef53d9c5 | 559 | kretprobe_hash_unlock(current, &flags); |
d38f1220 DM |
560 | preempt_enable_no_resched(); |
561 | ||
562 | hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { | |
563 | hlist_del(&ri->hlist); | |
564 | kfree(ri); | |
565 | } | |
566 | /* | |
567 | * By returning a non-zero value, we are telling | |
568 | * kprobe_handler() that we don't want the post_handler | |
569 | * to run (and have re-enabled preemption) | |
570 | */ | |
571 | return 1; | |
572 | } | |
573 | ||
574 | void kretprobe_trampoline_holder(void) | |
575 | { | |
576 | asm volatile(".global kretprobe_trampoline\n" | |
577 | "kretprobe_trampoline:\n" | |
578 | "\tnop\n" | |
579 | "\tnop\n"); | |
580 | } | |
581 | static struct kprobe trampoline_p = { | |
582 | .addr = (kprobe_opcode_t *) &kretprobe_trampoline, | |
583 | .pre_handler = trampoline_probe_handler | |
584 | }; | |
585 | ||
586 | int __init arch_init_kprobes(void) | |
6772926b | 587 | { |
d38f1220 DM |
588 | return register_kprobe(&trampoline_p); |
589 | } | |
590 | ||
591 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) | |
592 | { | |
593 | if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) | |
594 | return 1; | |
595 | ||
6772926b RL |
596 | return 0; |
597 | } |