Commit | Line | Data |
---|---|---|
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> |
812cb83a | 11 | #include <linux/context_tracking.h> |
1da177e4 | 12 | #include <asm/signal.h> |
05e14cb3 | 13 | #include <asm/cacheflush.h> |
b6700096 | 14 | #include <asm/uaccess.h> |
1da177e4 LT |
15 | |
16 | /* We do not have hardware single-stepping on sparc64. | |
17 | * So we implement software single-stepping with breakpoint | |
18 | * traps. The top-level scheme is similar to that used | |
19 | * in the x86 kprobes implementation. | |
20 | * | |
21 | * In the kprobe->ainsn.insn[] array we store the original | |
22 | * instruction at index zero and a break instruction at | |
23 | * index one. | |
24 | * | |
25 | * When we hit a kprobe we: | |
26 | * - Run the pre-handler | |
27 | * - Remember "regs->tnpc" and interrupt level stored in | |
28 | * "regs->tstate" so we can restore them later | |
29 | * - Disable PIL interrupts | |
30 | * - Set regs->tpc to point to kprobe->ainsn.insn[0] | |
31 | * - Set regs->tnpc to point to kprobe->ainsn.insn[1] | |
32 | * - Mark that we are actively in a kprobe | |
33 | * | |
34 | * At this point we wait for the second breakpoint at | |
35 | * kprobe->ainsn.insn[1] to hit. When it does we: | |
36 | * - Run the post-handler | |
37 | * - Set regs->tpc to "remembered" regs->tnpc stored above, | |
38 | * restore the PIL interrupt level in "regs->tstate" as well | |
39 | * - Make any adjustments necessary to regs->tnpc in order | |
40 | * to handle relative branches correctly. See below. | |
41 | * - Mark that we are no longer actively in a kprobe. | |
42 | */ | |
43 | ||
f215d985 AM |
44 | DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; |
45 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
46 | ||
f438d914 MH |
47 | struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}}; |
48 | ||
05e14cb3 | 49 | int __kprobes arch_prepare_kprobe(struct kprobe *p) |
1da177e4 | 50 | { |
936cf251 DM |
51 | if ((unsigned long) p->addr & 0x3UL) |
52 | return -EILSEQ; | |
53 | ||
1da177e4 | 54 | p->ainsn.insn[0] = *p->addr; |
f0882589 DM |
55 | flushi(&p->ainsn.insn[0]); |
56 | ||
1da177e4 | 57 | p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2; |
f0882589 DM |
58 | flushi(&p->ainsn.insn[1]); |
59 | ||
7e1048b1 | 60 | p->opcode = *p->addr; |
49a2a1b8 | 61 | return 0; |
7e1048b1 RL |
62 | } |
63 | ||
05e14cb3 | 64 | void __kprobes arch_arm_kprobe(struct kprobe *p) |
7e1048b1 RL |
65 | { |
66 | *p->addr = BREAKPOINT_INSTRUCTION; | |
67 | flushi(p->addr); | |
68 | } | |
69 | ||
05e14cb3 | 70 | void __kprobes arch_disarm_kprobe(struct kprobe *p) |
7e1048b1 RL |
71 | { |
72 | *p->addr = p->opcode; | |
73 | flushi(p->addr); | |
1da177e4 LT |
74 | } |
75 | ||
07fab8da | 76 | static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) |
e539c233 | 77 | { |
f215d985 AM |
78 | kcb->prev_kprobe.kp = kprobe_running(); |
79 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
80 | kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc; | |
81 | kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil; | |
e539c233 PP |
82 | } |
83 | ||
07fab8da | 84 | static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) |
e539c233 | 85 | { |
494fc421 | 86 | __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); |
f215d985 AM |
87 | kcb->kprobe_status = kcb->prev_kprobe.status; |
88 | kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc; | |
89 | kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil; | |
e539c233 PP |
90 | } |
91 | ||
07fab8da | 92 | static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, |
f215d985 | 93 | struct kprobe_ctlblk *kcb) |
1da177e4 | 94 | { |
494fc421 | 95 | __this_cpu_write(current_kprobe, p); |
f215d985 AM |
96 | kcb->kprobe_orig_tnpc = regs->tnpc; |
97 | kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL); | |
e539c233 PP |
98 | } |
99 | ||
07fab8da | 100 | static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs, |
f215d985 | 101 | struct kprobe_ctlblk *kcb) |
e539c233 | 102 | { |
1da177e4 LT |
103 | regs->tstate |= TSTATE_PIL; |
104 | ||
105 | /*single step inline, if it a breakpoint instruction*/ | |
106 | if (p->opcode == BREAKPOINT_INSTRUCTION) { | |
107 | regs->tpc = (unsigned long) p->addr; | |
f215d985 | 108 | regs->tnpc = kcb->kprobe_orig_tnpc; |
1da177e4 LT |
109 | } else { |
110 | regs->tpc = (unsigned long) &p->ainsn.insn[0]; | |
111 | regs->tnpc = (unsigned long) &p->ainsn.insn[1]; | |
112 | } | |
113 | } | |
114 | ||
05e14cb3 | 115 | static int __kprobes kprobe_handler(struct pt_regs *regs) |
1da177e4 LT |
116 | { |
117 | struct kprobe *p; | |
118 | void *addr = (void *) regs->tpc; | |
119 | int ret = 0; | |
d217d545 AM |
120 | struct kprobe_ctlblk *kcb; |
121 | ||
122 | /* | |
123 | * We don't want to be preempted for the entire | |
124 | * duration of kprobe processing | |
125 | */ | |
126 | preempt_disable(); | |
127 | kcb = get_kprobe_ctlblk(); | |
1da177e4 | 128 | |
1da177e4 | 129 | if (kprobe_running()) { |
1da177e4 LT |
130 | p = get_kprobe(addr); |
131 | if (p) { | |
f215d985 | 132 | if (kcb->kprobe_status == KPROBE_HIT_SS) { |
1da177e4 | 133 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | |
f215d985 | 134 | kcb->kprobe_orig_tstate_pil); |
1da177e4 LT |
135 | goto no_kprobe; |
136 | } | |
e539c233 PP |
137 | /* We have reentered the kprobe_handler(), since |
138 | * another probe was hit while within the handler. | |
139 | * We here save the original kprobes variables and | |
140 | * just single step on the instruction of the new probe | |
141 | * without calling any user handlers. | |
142 | */ | |
f215d985 AM |
143 | save_previous_kprobe(kcb); |
144 | set_current_kprobe(p, regs, kcb); | |
bf8d5c52 | 145 | kprobes_inc_nmissed_count(p); |
f215d985 AM |
146 | kcb->kprobe_status = KPROBE_REENTER; |
147 | prepare_singlestep(p, regs, kcb); | |
e539c233 | 148 | return 1; |
1da177e4 | 149 | } else { |
eb3a7292 KA |
150 | if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { |
151 | /* The breakpoint instruction was removed by | |
152 | * another cpu right after we hit, no further | |
153 | * handling of this interrupt is appropriate | |
154 | */ | |
155 | ret = 1; | |
156 | goto no_kprobe; | |
157 | } | |
494fc421 | 158 | p = __this_cpu_read(current_kprobe); |
1da177e4 LT |
159 | if (p->break_handler && p->break_handler(p, regs)) |
160 | goto ss_probe; | |
161 | } | |
1da177e4 LT |
162 | goto no_kprobe; |
163 | } | |
164 | ||
1da177e4 LT |
165 | p = get_kprobe(addr); |
166 | if (!p) { | |
1da177e4 LT |
167 | if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { |
168 | /* | |
169 | * The breakpoint instruction was removed right | |
170 | * after we hit it. Another cpu has removed | |
171 | * either a probepoint or a debugger breakpoint | |
172 | * at this address. In either case, no further | |
173 | * handling of this interrupt is appropriate. | |
174 | */ | |
175 | ret = 1; | |
176 | } | |
177 | /* Not one of ours: let kernel handle it */ | |
178 | goto no_kprobe; | |
179 | } | |
180 | ||
f215d985 AM |
181 | set_current_kprobe(p, regs, kcb); |
182 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
1da177e4 LT |
183 | if (p->pre_handler && p->pre_handler(p, regs)) |
184 | return 1; | |
185 | ||
186 | ss_probe: | |
f215d985 AM |
187 | prepare_singlestep(p, regs, kcb); |
188 | kcb->kprobe_status = KPROBE_HIT_SS; | |
1da177e4 LT |
189 | return 1; |
190 | ||
191 | no_kprobe: | |
d217d545 | 192 | preempt_enable_no_resched(); |
1da177e4 LT |
193 | return ret; |
194 | } | |
195 | ||
196 | /* If INSN is a relative control transfer instruction, | |
197 | * return the corrected branch destination value. | |
198 | * | |
f0882589 DM |
199 | * regs->tpc and regs->tnpc still hold the values of the |
200 | * program counters at the time of trap due to the execution | |
201 | * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1] | |
202 | * | |
1da177e4 | 203 | */ |
f0882589 DM |
204 | static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p, |
205 | struct pt_regs *regs) | |
1da177e4 | 206 | { |
f0882589 DM |
207 | unsigned long real_pc = (unsigned long) p->addr; |
208 | ||
1da177e4 | 209 | /* Branch not taken, no mods necessary. */ |
f0882589 DM |
210 | if (regs->tnpc == regs->tpc + 0x4UL) |
211 | return real_pc + 0x8UL; | |
1da177e4 LT |
212 | |
213 | /* The three cases are call, branch w/prediction, | |
214 | * and traditional branch. | |
215 | */ | |
216 | if ((insn & 0xc0000000) == 0x40000000 || | |
217 | (insn & 0xc1c00000) == 0x00400000 || | |
218 | (insn & 0xc1c00000) == 0x00800000) { | |
f0882589 DM |
219 | unsigned long ainsn_addr; |
220 | ||
221 | ainsn_addr = (unsigned long) &p->ainsn.insn[0]; | |
222 | ||
1da177e4 LT |
223 | /* The instruction did all the work for us |
224 | * already, just apply the offset to the correct | |
225 | * instruction location. | |
226 | */ | |
f0882589 | 227 | return (real_pc + (regs->tnpc - ainsn_addr)); |
1da177e4 LT |
228 | } |
229 | ||
f0882589 DM |
230 | /* It is jmpl or some other absolute PC modification instruction, |
231 | * leave NPC as-is. | |
232 | */ | |
233 | return regs->tnpc; | |
1da177e4 LT |
234 | } |
235 | ||
236 | /* If INSN is an instruction which writes it's PC location | |
237 | * into a destination register, fix that up. | |
238 | */ | |
05e14cb3 PP |
239 | static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn, |
240 | unsigned long real_pc) | |
1da177e4 LT |
241 | { |
242 | unsigned long *slot = NULL; | |
243 | ||
f0882589 | 244 | /* Simplest case is 'call', which always uses %o7 */ |
1da177e4 LT |
245 | if ((insn & 0xc0000000) == 0x40000000) { |
246 | slot = ®s->u_regs[UREG_I7]; | |
247 | } | |
248 | ||
f0882589 | 249 | /* 'jmpl' encodes the register inside of the opcode */ |
1da177e4 LT |
250 | if ((insn & 0xc1f80000) == 0x81c00000) { |
251 | unsigned long rd = ((insn >> 25) & 0x1f); | |
252 | ||
253 | if (rd <= 15) { | |
254 | slot = ®s->u_regs[rd]; | |
255 | } else { | |
256 | /* Hard case, it goes onto the stack. */ | |
257 | flushw_all(); | |
258 | ||
259 | rd -= 16; | |
260 | slot = (unsigned long *) | |
261 | (regs->u_regs[UREG_FP] + STACK_BIAS); | |
262 | slot += rd; | |
263 | } | |
264 | } | |
265 | if (slot != NULL) | |
266 | *slot = real_pc; | |
267 | } | |
268 | ||
269 | /* | |
270 | * Called after single-stepping. p->addr is the address of the | |
f0882589 | 271 | * instruction which has been replaced by the breakpoint |
1da177e4 LT |
272 | * instruction. To avoid the SMP problems that can occur when we |
273 | * temporarily put back the original opcode to single-step, we | |
274 | * single-stepped a copy of the instruction. The address of this | |
f0882589 | 275 | * copy is &p->ainsn.insn[0]. |
1da177e4 LT |
276 | * |
277 | * This function prepares to return from the post-single-step | |
278 | * breakpoint trap. | |
279 | */ | |
f215d985 AM |
280 | static void __kprobes resume_execution(struct kprobe *p, |
281 | struct pt_regs *regs, struct kprobe_ctlblk *kcb) | |
1da177e4 LT |
282 | { |
283 | u32 insn = p->ainsn.insn[0]; | |
284 | ||
f0882589 DM |
285 | regs->tnpc = relbranch_fixup(insn, p, regs); |
286 | ||
287 | /* This assignment must occur after relbranch_fixup() */ | |
f215d985 | 288 | regs->tpc = kcb->kprobe_orig_tnpc; |
f0882589 | 289 | |
1da177e4 LT |
290 | retpc_fixup(regs, insn, (unsigned long) p->addr); |
291 | ||
292 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | | |
f215d985 | 293 | kcb->kprobe_orig_tstate_pil); |
1da177e4 LT |
294 | } |
295 | ||
07fab8da | 296 | static int __kprobes post_kprobe_handler(struct pt_regs *regs) |
1da177e4 | 297 | { |
f215d985 AM |
298 | struct kprobe *cur = kprobe_running(); |
299 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
300 | ||
301 | if (!cur) | |
1da177e4 LT |
302 | return 0; |
303 | ||
f215d985 AM |
304 | if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { |
305 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
306 | cur->post_handler(cur, regs, 0); | |
e539c233 | 307 | } |
1da177e4 | 308 | |
f215d985 | 309 | resume_execution(cur, regs, kcb); |
1da177e4 | 310 | |
e539c233 | 311 | /*Restore back the original saved kprobes variables and continue. */ |
f215d985 AM |
312 | if (kcb->kprobe_status == KPROBE_REENTER) { |
313 | restore_previous_kprobe(kcb); | |
e539c233 PP |
314 | goto out; |
315 | } | |
f215d985 | 316 | reset_current_kprobe(); |
e539c233 | 317 | out: |
1da177e4 LT |
318 | preempt_enable_no_resched(); |
319 | ||
320 | return 1; | |
321 | } | |
322 | ||
127cda1e | 323 | int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) |
1da177e4 | 324 | { |
f215d985 AM |
325 | struct kprobe *cur = kprobe_running(); |
326 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
b6700096 PP |
327 | const struct exception_table_entry *entry; |
328 | ||
329 | switch(kcb->kprobe_status) { | |
330 | case KPROBE_HIT_SS: | |
331 | case KPROBE_REENTER: | |
332 | /* | |
333 | * We are here because the instruction being single | |
334 | * stepped caused a page fault. We reset the current | |
335 | * kprobe and the tpc points back to the probe address | |
336 | * and allow the page fault handler to continue as a | |
337 | * normal page fault. | |
338 | */ | |
339 | regs->tpc = (unsigned long)cur->addr; | |
340 | regs->tnpc = kcb->kprobe_orig_tnpc; | |
341 | regs->tstate = ((regs->tstate & ~TSTATE_PIL) | | |
342 | kcb->kprobe_orig_tstate_pil); | |
343 | if (kcb->kprobe_status == KPROBE_REENTER) | |
344 | restore_previous_kprobe(kcb); | |
345 | else | |
346 | reset_current_kprobe(); | |
347 | preempt_enable_no_resched(); | |
348 | break; | |
349 | case KPROBE_HIT_ACTIVE: | |
350 | case KPROBE_HIT_SSDONE: | |
351 | /* | |
352 | * We increment the nmissed count for accounting, | |
23d6d3db | 353 | * we can also use npre/npostfault count for accounting |
b6700096 PP |
354 | * these specific fault cases. |
355 | */ | |
356 | kprobes_inc_nmissed_count(cur); | |
357 | ||
358 | /* | |
359 | * We come here because instructions in the pre/post | |
360 | * handler caused the page_fault, this could happen | |
361 | * if handler tries to access user space by | |
362 | * copy_from_user(), get_user() etc. Let the | |
363 | * user-specified handler try to fix it first. | |
364 | */ | |
365 | if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) | |
366 | return 1; | |
f215d985 | 367 | |
b6700096 PP |
368 | /* |
369 | * In case the user-specified fault handler returned | |
370 | * zero, try to fix up. | |
371 | */ | |
1da177e4 | 372 | |
b6700096 PP |
373 | entry = search_exception_tables(regs->tpc); |
374 | if (entry) { | |
375 | regs->tpc = entry->fixup; | |
376 | regs->tnpc = regs->tpc + 4; | |
377 | return 1; | |
378 | } | |
1da177e4 | 379 | |
b6700096 PP |
380 | /* |
381 | * fixup_exception() could not handle it, | |
382 | * Let do_page_fault() fix it. | |
383 | */ | |
384 | break; | |
385 | default: | |
386 | break; | |
1da177e4 | 387 | } |
b6700096 | 388 | |
1da177e4 LT |
389 | return 0; |
390 | } | |
391 | ||
392 | /* | |
393 | * Wrapper routine to for handling exceptions. | |
394 | */ | |
05e14cb3 PP |
395 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, |
396 | unsigned long val, void *data) | |
1da177e4 LT |
397 | { |
398 | struct die_args *args = (struct die_args *)data; | |
66ff2d06 AM |
399 | int ret = NOTIFY_DONE; |
400 | ||
2326c770 | 401 | if (args->regs && user_mode(args->regs)) |
402 | return ret; | |
403 | ||
1da177e4 LT |
404 | switch (val) { |
405 | case DIE_DEBUG: | |
406 | if (kprobe_handler(args->regs)) | |
66ff2d06 | 407 | ret = NOTIFY_STOP; |
1da177e4 LT |
408 | break; |
409 | case DIE_DEBUG_2: | |
410 | if (post_kprobe_handler(args->regs)) | |
66ff2d06 | 411 | ret = NOTIFY_STOP; |
1da177e4 | 412 | break; |
1da177e4 LT |
413 | default: |
414 | break; | |
415 | } | |
66ff2d06 | 416 | return ret; |
1da177e4 LT |
417 | } |
418 | ||
05e14cb3 PP |
419 | asmlinkage void __kprobes kprobe_trap(unsigned long trap_level, |
420 | struct pt_regs *regs) | |
1da177e4 | 421 | { |
812cb83a KT |
422 | enum ctx_state prev_state = exception_enter(); |
423 | ||
1da177e4 LT |
424 | BUG_ON(trap_level != 0x170 && trap_level != 0x171); |
425 | ||
426 | if (user_mode(regs)) { | |
427 | local_irq_enable(); | |
428 | bad_trap(regs, trap_level); | |
812cb83a | 429 | goto out; |
1da177e4 LT |
430 | } |
431 | ||
432 | /* trap_level == 0x170 --> ta 0x70 | |
433 | * trap_level == 0x171 --> ta 0x71 | |
434 | */ | |
435 | if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2, | |
436 | (trap_level == 0x170) ? "debug" : "debug_2", | |
437 | regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP) | |
438 | bad_trap(regs, trap_level); | |
812cb83a KT |
439 | out: |
440 | exception_exit(prev_state); | |
1da177e4 LT |
441 | } |
442 | ||
443 | /* Jprobes support. */ | |
05e14cb3 | 444 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) |
1da177e4 LT |
445 | { |
446 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
f215d985 | 447 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
1da177e4 | 448 | |
f215d985 | 449 | memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs)); |
1da177e4 | 450 | |
1da177e4 LT |
451 | regs->tpc = (unsigned long) jp->entry; |
452 | regs->tnpc = ((unsigned long) jp->entry) + 0x4UL; | |
453 | regs->tstate |= TSTATE_PIL; | |
454 | ||
455 | return 1; | |
456 | } | |
457 | ||
05e14cb3 | 458 | void __kprobes jprobe_return(void) |
1da177e4 | 459 | { |
f0882589 DM |
460 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
461 | register unsigned long orig_fp asm("g1"); | |
462 | ||
463 | orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP]; | |
464 | __asm__ __volatile__("\n" | |
465 | "1: cmp %%sp, %0\n\t" | |
466 | "blu,a,pt %%xcc, 1b\n\t" | |
467 | " restore\n\t" | |
468 | ".globl jprobe_return_trap_instruction\n" | |
1da177e4 | 469 | "jprobe_return_trap_instruction:\n\t" |
f0882589 DM |
470 | "ta 0x70" |
471 | : /* no outputs */ | |
472 | : "r" (orig_fp)); | |
1da177e4 LT |
473 | } |
474 | ||
475 | extern void jprobe_return_trap_instruction(void); | |
476 | ||
05e14cb3 | 477 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) |
1da177e4 LT |
478 | { |
479 | u32 *addr = (u32 *) regs->tpc; | |
f215d985 | 480 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); |
1da177e4 LT |
481 | |
482 | if (addr == (u32 *) jprobe_return_trap_instruction) { | |
f215d985 | 483 | memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs)); |
d217d545 | 484 | preempt_enable_no_resched(); |
1da177e4 LT |
485 | return 1; |
486 | } | |
487 | return 0; | |
488 | } | |
e539c233 | 489 | |
ef53d9c5 S |
490 | /* The value stored in the return address register is actually 2 |
491 | * instructions before where the callee will return to. | |
492 | * Sequences usually look something like this | |
d38f1220 DM |
493 | * |
494 | * call some_function <--- return register points here | |
495 | * nop <--- call delay slot | |
496 | * whatever <--- where callee returns to | |
497 | * | |
498 | * To keep trampoline_probe_handler logic simpler, we normalize the | |
499 | * value kept in ri->ret_addr so we don't need to keep adjusting it | |
500 | * back and forth. | |
501 | */ | |
502 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, | |
503 | struct pt_regs *regs) | |
504 | { | |
505 | ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8); | |
506 | ||
507 | /* Replace the return addr with trampoline addr */ | |
508 | regs->u_regs[UREG_RETPC] = | |
509 | ((unsigned long)kretprobe_trampoline) - 8; | |
510 | } | |
511 | ||
512 | /* | |
513 | * Called when the probe at kretprobe trampoline is hit | |
514 | */ | |
2f827ea7 SR |
515 | static int __kprobes trampoline_probe_handler(struct kprobe *p, |
516 | struct pt_regs *regs) | |
d38f1220 DM |
517 | { |
518 | struct kretprobe_instance *ri = NULL; | |
519 | struct hlist_head *head, empty_rp; | |
b67bfe0d | 520 | struct hlist_node *tmp; |
d38f1220 DM |
521 | unsigned long flags, orig_ret_address = 0; |
522 | unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; | |
523 | ||
524 | INIT_HLIST_HEAD(&empty_rp); | |
ef53d9c5 | 525 | kretprobe_hash_lock(current, &head, &flags); |
d38f1220 DM |
526 | |
527 | /* | |
528 | * It is possible to have multiple instances associated with a given | |
529 | * task either because an multiple functions in the call path | |
025dfdaf | 530 | * have a return probe installed on them, and/or more than one return |
d38f1220 DM |
531 | * return probe was registered for a target function. |
532 | * | |
533 | * We can handle this because: | |
534 | * - instances are always inserted at the head of the list | |
535 | * - when multiple return probes are registered for the same | |
536 | * function, the first instance's ret_addr will point to the | |
537 | * real return address, and all the rest will point to | |
538 | * kretprobe_trampoline | |
539 | */ | |
b67bfe0d | 540 | hlist_for_each_entry_safe(ri, tmp, head, hlist) { |
d38f1220 DM |
541 | if (ri->task != current) |
542 | /* another task is sharing our hash bucket */ | |
543 | continue; | |
544 | ||
545 | if (ri->rp && ri->rp->handler) | |
546 | ri->rp->handler(ri, regs); | |
547 | ||
548 | orig_ret_address = (unsigned long)ri->ret_addr; | |
549 | recycle_rp_inst(ri, &empty_rp); | |
550 | ||
551 | if (orig_ret_address != trampoline_address) | |
552 | /* | |
553 | * This is the real return address. Any other | |
554 | * instances associated with this task are for | |
555 | * other calls deeper on the call stack | |
556 | */ | |
557 | break; | |
558 | } | |
559 | ||
560 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
561 | regs->tpc = orig_ret_address; | |
562 | regs->tnpc = orig_ret_address + 4; | |
563 | ||
564 | reset_current_kprobe(); | |
ef53d9c5 | 565 | kretprobe_hash_unlock(current, &flags); |
d38f1220 DM |
566 | preempt_enable_no_resched(); |
567 | ||
b67bfe0d | 568 | hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { |
d38f1220 DM |
569 | hlist_del(&ri->hlist); |
570 | kfree(ri); | |
571 | } | |
572 | /* | |
573 | * By returning a non-zero value, we are telling | |
574 | * kprobe_handler() that we don't want the post_handler | |
575 | * to run (and have re-enabled preemption) | |
576 | */ | |
577 | return 1; | |
578 | } | |
579 | ||
2f827ea7 | 580 | static void __used kretprobe_trampoline_holder(void) |
d38f1220 DM |
581 | { |
582 | asm volatile(".global kretprobe_trampoline\n" | |
583 | "kretprobe_trampoline:\n" | |
584 | "\tnop\n" | |
585 | "\tnop\n"); | |
586 | } | |
587 | static struct kprobe trampoline_p = { | |
588 | .addr = (kprobe_opcode_t *) &kretprobe_trampoline, | |
589 | .pre_handler = trampoline_probe_handler | |
590 | }; | |
591 | ||
592 | int __init arch_init_kprobes(void) | |
6772926b | 593 | { |
d38f1220 DM |
594 | return register_kprobe(&trampoline_p); |
595 | } | |
596 | ||
597 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) | |
598 | { | |
599 | if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) | |
600 | return 1; | |
601 | ||
6772926b RL |
602 | return 0; |
603 | } |