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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright (C) IBM Corporation, 2002, 2004
6 *
7 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8 * Probes initial implementation ( includes contributions from
9 * Rusty Russell).
10 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
11 * interface to access function arguments.
12 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
13 * for PPC64
14 */
15
16#include <linux/kprobes.h>
17#include <linux/ptrace.h>
18#include <linux/preempt.h>
19#include <linux/extable.h>
20#include <linux/kdebug.h>
21#include <linux/slab.h>
22#include <asm/code-patching.h>
23#include <asm/cacheflush.h>
24#include <asm/sstep.h>
25#include <asm/sections.h>
26#include <asm/inst.h>
27#include <linux/uaccess.h>
28
29DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
30DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
31
32struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
33
34bool arch_within_kprobe_blacklist(unsigned long addr)
35{
36 return (addr >= (unsigned long)__kprobes_text_start &&
37 addr < (unsigned long)__kprobes_text_end) ||
38 (addr >= (unsigned long)_stext &&
39 addr < (unsigned long)__head_end);
40}
41
42kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
43{
44 kprobe_opcode_t *addr = NULL;
45
46#ifdef PPC64_ELF_ABI_v2
47 /* PPC64 ABIv2 needs local entry point */
48 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
49 if (addr && !offset) {
50#ifdef CONFIG_KPROBES_ON_FTRACE
51 unsigned long faddr;
52 /*
53 * Per livepatch.h, ftrace location is always within the first
54 * 16 bytes of a function on powerpc with -mprofile-kernel.
55 */
56 faddr = ftrace_location_range((unsigned long)addr,
57 (unsigned long)addr + 16);
58 if (faddr)
59 addr = (kprobe_opcode_t *)faddr;
60 else
61#endif
62 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
63 }
64#elif defined(PPC64_ELF_ABI_v1)
65 /*
66 * 64bit powerpc ABIv1 uses function descriptors:
67 * - Check for the dot variant of the symbol first.
68 * - If that fails, try looking up the symbol provided.
69 *
70 * This ensures we always get to the actual symbol and not
71 * the descriptor.
72 *
73 * Also handle <module:symbol> format.
74 */
75 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
76 bool dot_appended = false;
77 const char *c;
78 ssize_t ret = 0;
79 int len = 0;
80
81 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
82 c++;
83 len = c - name;
84 memcpy(dot_name, name, len);
85 } else
86 c = name;
87
88 if (*c != '\0' && *c != '.') {
89 dot_name[len++] = '.';
90 dot_appended = true;
91 }
92 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
93 if (ret > 0)
94 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
95
96 /* Fallback to the original non-dot symbol lookup */
97 if (!addr && dot_appended)
98 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
99#else
100 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
101#endif
102
103 return addr;
104}
105
106int arch_prepare_kprobe(struct kprobe *p)
107{
108 int ret = 0;
109 struct kprobe *prev;
110 struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr);
111 struct ppc_inst prefix = ppc_inst_read((struct ppc_inst *)(p->addr - 1));
112
113 if ((unsigned long)p->addr & 0x03) {
114 printk("Attempt to register kprobe at an unaligned address\n");
115 ret = -EINVAL;
116 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
117 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
118 ret = -EINVAL;
119 } else if (ppc_inst_prefixed(prefix)) {
120 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
121 ret = -EINVAL;
122 }
123 preempt_disable();
124 prev = get_kprobe(p->addr - 1);
125 preempt_enable_no_resched();
126 if (prev &&
127 ppc_inst_prefixed(ppc_inst_read((struct ppc_inst *)prev->ainsn.insn))) {
128 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
129 ret = -EINVAL;
130 }
131
132 /* insn must be on a special executable page on ppc64. This is
133 * not explicitly required on ppc32 (right now), but it doesn't hurt */
134 if (!ret) {
135 p->ainsn.insn = get_insn_slot();
136 if (!p->ainsn.insn)
137 ret = -ENOMEM;
138 }
139
140 if (!ret) {
141 patch_instruction((struct ppc_inst *)p->ainsn.insn, insn);
142 p->opcode = ppc_inst_val(insn);
143 }
144
145 p->ainsn.boostable = 0;
146 return ret;
147}
148NOKPROBE_SYMBOL(arch_prepare_kprobe);
149
150void arch_arm_kprobe(struct kprobe *p)
151{
152 patch_instruction((struct ppc_inst *)p->addr, ppc_inst(BREAKPOINT_INSTRUCTION));
153}
154NOKPROBE_SYMBOL(arch_arm_kprobe);
155
156void arch_disarm_kprobe(struct kprobe *p)
157{
158 patch_instruction((struct ppc_inst *)p->addr, ppc_inst(p->opcode));
159}
160NOKPROBE_SYMBOL(arch_disarm_kprobe);
161
162void arch_remove_kprobe(struct kprobe *p)
163{
164 if (p->ainsn.insn) {
165 free_insn_slot(p->ainsn.insn, 0);
166 p->ainsn.insn = NULL;
167 }
168}
169NOKPROBE_SYMBOL(arch_remove_kprobe);
170
171static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
172{
173 enable_single_step(regs);
174
175 /*
176 * On powerpc we should single step on the original
177 * instruction even if the probed insn is a trap
178 * variant as values in regs could play a part in
179 * if the trap is taken or not
180 */
181 regs->nip = (unsigned long)p->ainsn.insn;
182}
183
184static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
185{
186 kcb->prev_kprobe.kp = kprobe_running();
187 kcb->prev_kprobe.status = kcb->kprobe_status;
188 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
189}
190
191static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
192{
193 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
194 kcb->kprobe_status = kcb->prev_kprobe.status;
195 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
196}
197
198static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
199 struct kprobe_ctlblk *kcb)
200{
201 __this_cpu_write(current_kprobe, p);
202 kcb->kprobe_saved_msr = regs->msr;
203}
204
205bool arch_kprobe_on_func_entry(unsigned long offset)
206{
207#ifdef PPC64_ELF_ABI_v2
208#ifdef CONFIG_KPROBES_ON_FTRACE
209 return offset <= 16;
210#else
211 return offset <= 8;
212#endif
213#else
214 return !offset;
215#endif
216}
217
218void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
219{
220 ri->ret_addr = (kprobe_opcode_t *)regs->link;
221
222 /* Replace the return addr with trampoline addr */
223 regs->link = (unsigned long)kretprobe_trampoline;
224}
225NOKPROBE_SYMBOL(arch_prepare_kretprobe);
226
227static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
228{
229 int ret;
230 struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
231
232 /* regs->nip is also adjusted if emulate_step returns 1 */
233 ret = emulate_step(regs, insn);
234 if (ret > 0) {
235 /*
236 * Once this instruction has been boosted
237 * successfully, set the boostable flag
238 */
239 if (unlikely(p->ainsn.boostable == 0))
240 p->ainsn.boostable = 1;
241 } else if (ret < 0) {
242 /*
243 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
244 * So, we should never get here... but, its still
245 * good to catch them, just in case...
246 */
247 printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
248 BUG();
249 } else {
250 /*
251 * If we haven't previously emulated this instruction, then it
252 * can't be boosted. Note it down so we don't try to do so again.
253 *
254 * If, however, we had emulated this instruction in the past,
255 * then this is just an error with the current run (for
256 * instance, exceptions due to a load/store). We return 0 so
257 * that this is now single-stepped, but continue to try
258 * emulating it in subsequent probe hits.
259 */
260 if (unlikely(p->ainsn.boostable != 1))
261 p->ainsn.boostable = -1;
262 }
263
264 return ret;
265}
266NOKPROBE_SYMBOL(try_to_emulate);
267
268int kprobe_handler(struct pt_regs *regs)
269{
270 struct kprobe *p;
271 int ret = 0;
272 unsigned int *addr = (unsigned int *)regs->nip;
273 struct kprobe_ctlblk *kcb;
274
275 if (user_mode(regs))
276 return 0;
277
278 if (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR))
279 return 0;
280
281 /*
282 * We don't want to be preempted for the entire
283 * duration of kprobe processing
284 */
285 preempt_disable();
286 kcb = get_kprobe_ctlblk();
287
288 p = get_kprobe(addr);
289 if (!p) {
290 unsigned int instr;
291
292 if (get_kernel_nofault(instr, addr))
293 goto no_kprobe;
294
295 if (instr != BREAKPOINT_INSTRUCTION) {
296 /*
297 * PowerPC has multiple variants of the "trap"
298 * instruction. If the current instruction is a
299 * trap variant, it could belong to someone else
300 */
301 if (is_trap(instr))
302 goto no_kprobe;
303 /*
304 * The breakpoint instruction was removed right
305 * after we hit it. Another cpu has removed
306 * either a probepoint or a debugger breakpoint
307 * at this address. In either case, no further
308 * handling of this interrupt is appropriate.
309 */
310 ret = 1;
311 }
312 /* Not one of ours: let kernel handle it */
313 goto no_kprobe;
314 }
315
316 /* Check we're not actually recursing */
317 if (kprobe_running()) {
318 kprobe_opcode_t insn = *p->ainsn.insn;
319 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
320 /* Turn off 'trace' bits */
321 regs->msr &= ~MSR_SINGLESTEP;
322 regs->msr |= kcb->kprobe_saved_msr;
323 goto no_kprobe;
324 }
325
326 /*
327 * We have reentered the kprobe_handler(), since another probe
328 * was hit while within the handler. We here save the original
329 * kprobes variables and just single step on the instruction of
330 * the new probe without calling any user handlers.
331 */
332 save_previous_kprobe(kcb);
333 set_current_kprobe(p, regs, kcb);
334 kprobes_inc_nmissed_count(p);
335 kcb->kprobe_status = KPROBE_REENTER;
336 if (p->ainsn.boostable >= 0) {
337 ret = try_to_emulate(p, regs);
338
339 if (ret > 0) {
340 restore_previous_kprobe(kcb);
341 preempt_enable_no_resched();
342 return 1;
343 }
344 }
345 prepare_singlestep(p, regs);
346 return 1;
347 }
348
349 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
350 set_current_kprobe(p, regs, kcb);
351 if (p->pre_handler && p->pre_handler(p, regs)) {
352 /* handler changed execution path, so skip ss setup */
353 reset_current_kprobe();
354 preempt_enable_no_resched();
355 return 1;
356 }
357
358 if (p->ainsn.boostable >= 0) {
359 ret = try_to_emulate(p, regs);
360
361 if (ret > 0) {
362 if (p->post_handler)
363 p->post_handler(p, regs, 0);
364
365 kcb->kprobe_status = KPROBE_HIT_SSDONE;
366 reset_current_kprobe();
367 preempt_enable_no_resched();
368 return 1;
369 }
370 }
371 prepare_singlestep(p, regs);
372 kcb->kprobe_status = KPROBE_HIT_SS;
373 return 1;
374
375no_kprobe:
376 preempt_enable_no_resched();
377 return ret;
378}
379NOKPROBE_SYMBOL(kprobe_handler);
380
381/*
382 * Function return probe trampoline:
383 * - init_kprobes() establishes a probepoint here
384 * - When the probed function returns, this probe
385 * causes the handlers to fire
386 */
387asm(".global kretprobe_trampoline\n"
388 ".type kretprobe_trampoline, @function\n"
389 "kretprobe_trampoline:\n"
390 "nop\n"
391 "blr\n"
392 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
393
394/*
395 * Called when the probe at kretprobe trampoline is hit
396 */
397static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
398{
399 struct kretprobe_instance *ri = NULL;
400 struct hlist_head *head, empty_rp;
401 struct hlist_node *tmp;
402 unsigned long flags, orig_ret_address = 0;
403 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
404
405 INIT_HLIST_HEAD(&empty_rp);
406 kretprobe_hash_lock(current, &head, &flags);
407
408 /*
409 * It is possible to have multiple instances associated with a given
410 * task either because an multiple functions in the call path
411 * have a return probe installed on them, and/or more than one return
412 * return probe was registered for a target function.
413 *
414 * We can handle this because:
415 * - instances are always inserted at the head of the list
416 * - when multiple return probes are registered for the same
417 * function, the first instance's ret_addr will point to the
418 * real return address, and all the rest will point to
419 * kretprobe_trampoline
420 */
421 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
422 if (ri->task != current)
423 /* another task is sharing our hash bucket */
424 continue;
425
426 if (ri->rp && ri->rp->handler)
427 ri->rp->handler(ri, regs);
428
429 orig_ret_address = (unsigned long)ri->ret_addr;
430 recycle_rp_inst(ri, &empty_rp);
431
432 if (orig_ret_address != trampoline_address)
433 /*
434 * This is the real return address. Any other
435 * instances associated with this task are for
436 * other calls deeper on the call stack
437 */
438 break;
439 }
440
441 kretprobe_assert(ri, orig_ret_address, trampoline_address);
442
443 /*
444 * We get here through one of two paths:
445 * 1. by taking a trap -> kprobe_handler() -> here
446 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
447 *
448 * When going back through (1), we need regs->nip to be setup properly
449 * as it is used to determine the return address from the trap.
450 * For (2), since nip is not honoured with optprobes, we instead setup
451 * the link register properly so that the subsequent 'blr' in
452 * kretprobe_trampoline jumps back to the right instruction.
453 *
454 * For nip, we should set the address to the previous instruction since
455 * we end up emulating it in kprobe_handler(), which increments the nip
456 * again.
457 */
458 regs->nip = orig_ret_address - 4;
459 regs->link = orig_ret_address;
460
461 kretprobe_hash_unlock(current, &flags);
462
463 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
464 hlist_del(&ri->hlist);
465 kfree(ri);
466 }
467
468 return 0;
469}
470NOKPROBE_SYMBOL(trampoline_probe_handler);
471
472/*
473 * Called after single-stepping. p->addr is the address of the
474 * instruction whose first byte has been replaced by the "breakpoint"
475 * instruction. To avoid the SMP problems that can occur when we
476 * temporarily put back the original opcode to single-step, we
477 * single-stepped a copy of the instruction. The address of this
478 * copy is p->ainsn.insn.
479 */
480int kprobe_post_handler(struct pt_regs *regs)
481{
482 int len;
483 struct kprobe *cur = kprobe_running();
484 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
485
486 if (!cur || user_mode(regs))
487 return 0;
488
489 len = ppc_inst_len(ppc_inst_read((struct ppc_inst *)cur->ainsn.insn));
490 /* make sure we got here for instruction we have a kprobe on */
491 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
492 return 0;
493
494 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
495 kcb->kprobe_status = KPROBE_HIT_SSDONE;
496 cur->post_handler(cur, regs, 0);
497 }
498
499 /* Adjust nip to after the single-stepped instruction */
500 regs->nip = (unsigned long)cur->addr + len;
501 regs->msr |= kcb->kprobe_saved_msr;
502
503 /*Restore back the original saved kprobes variables and continue. */
504 if (kcb->kprobe_status == KPROBE_REENTER) {
505 restore_previous_kprobe(kcb);
506 goto out;
507 }
508 reset_current_kprobe();
509out:
510 preempt_enable_no_resched();
511
512 /*
513 * if somebody else is singlestepping across a probe point, msr
514 * will have DE/SE set, in which case, continue the remaining processing
515 * of do_debug, as if this is not a probe hit.
516 */
517 if (regs->msr & MSR_SINGLESTEP)
518 return 0;
519
520 return 1;
521}
522NOKPROBE_SYMBOL(kprobe_post_handler);
523
524int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
525{
526 struct kprobe *cur = kprobe_running();
527 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
528 const struct exception_table_entry *entry;
529
530 switch(kcb->kprobe_status) {
531 case KPROBE_HIT_SS:
532 case KPROBE_REENTER:
533 /*
534 * We are here because the instruction being single
535 * stepped caused a page fault. We reset the current
536 * kprobe and the nip points back to the probe address
537 * and allow the page fault handler to continue as a
538 * normal page fault.
539 */
540 regs->nip = (unsigned long)cur->addr;
541 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
542 regs->msr |= kcb->kprobe_saved_msr;
543 if (kcb->kprobe_status == KPROBE_REENTER)
544 restore_previous_kprobe(kcb);
545 else
546 reset_current_kprobe();
547 preempt_enable_no_resched();
548 break;
549 case KPROBE_HIT_ACTIVE:
550 case KPROBE_HIT_SSDONE:
551 /*
552 * We increment the nmissed count for accounting,
553 * we can also use npre/npostfault count for accounting
554 * these specific fault cases.
555 */
556 kprobes_inc_nmissed_count(cur);
557
558 /*
559 * We come here because instructions in the pre/post
560 * handler caused the page_fault, this could happen
561 * if handler tries to access user space by
562 * copy_from_user(), get_user() etc. Let the
563 * user-specified handler try to fix it first.
564 */
565 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
566 return 1;
567
568 /*
569 * In case the user-specified fault handler returned
570 * zero, try to fix up.
571 */
572 if ((entry = search_exception_tables(regs->nip)) != NULL) {
573 regs->nip = extable_fixup(entry);
574 return 1;
575 }
576
577 /*
578 * fixup_exception() could not handle it,
579 * Let do_page_fault() fix it.
580 */
581 break;
582 default:
583 break;
584 }
585 return 0;
586}
587NOKPROBE_SYMBOL(kprobe_fault_handler);
588
589unsigned long arch_deref_entry_point(void *entry)
590{
591#ifdef PPC64_ELF_ABI_v1
592 if (!kernel_text_address((unsigned long)entry))
593 return ppc_global_function_entry(entry);
594 else
595#endif
596 return (unsigned long)entry;
597}
598NOKPROBE_SYMBOL(arch_deref_entry_point);
599
600static struct kprobe trampoline_p = {
601 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
602 .pre_handler = trampoline_probe_handler
603};
604
605int __init arch_init_kprobes(void)
606{
607 return register_kprobe(&trampoline_p);
608}
609
610int arch_trampoline_kprobe(struct kprobe *p)
611{
612 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
613 return 1;
614
615 return 0;
616}
617NOKPROBE_SYMBOL(arch_trampoline_kprobe);
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright (C) IBM Corporation, 2002, 2004
6 *
7 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8 * Probes initial implementation ( includes contributions from
9 * Rusty Russell).
10 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
11 * interface to access function arguments.
12 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
13 * for PPC64
14 */
15
16#include <linux/kprobes.h>
17#include <linux/ptrace.h>
18#include <linux/preempt.h>
19#include <linux/extable.h>
20#include <linux/kdebug.h>
21#include <linux/slab.h>
22#include <linux/set_memory.h>
23#include <linux/execmem.h>
24#include <asm/text-patching.h>
25#include <asm/cacheflush.h>
26#include <asm/sstep.h>
27#include <asm/sections.h>
28#include <asm/inst.h>
29#include <linux/uaccess.h>
30
31DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
32DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
33
34struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
35
36bool arch_within_kprobe_blacklist(unsigned long addr)
37{
38 return (addr >= (unsigned long)__kprobes_text_start &&
39 addr < (unsigned long)__kprobes_text_end) ||
40 (addr >= (unsigned long)_stext &&
41 addr < (unsigned long)__head_end);
42}
43
44kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
45{
46 kprobe_opcode_t *addr = NULL;
47
48#ifdef CONFIG_PPC64_ELF_ABI_V2
49 /* PPC64 ABIv2 needs local entry point */
50 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
51 if (addr && !offset) {
52#ifdef CONFIG_KPROBES_ON_FTRACE
53 unsigned long faddr;
54 /*
55 * Per livepatch.h, ftrace location is always within the first
56 * 16 bytes of a function on powerpc with -mprofile-kernel.
57 */
58 faddr = ftrace_location_range((unsigned long)addr,
59 (unsigned long)addr + 16);
60 if (faddr)
61 addr = (kprobe_opcode_t *)faddr;
62 else
63#endif
64 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
65 }
66#elif defined(CONFIG_PPC64_ELF_ABI_V1)
67 /*
68 * 64bit powerpc ABIv1 uses function descriptors:
69 * - Check for the dot variant of the symbol first.
70 * - If that fails, try looking up the symbol provided.
71 *
72 * This ensures we always get to the actual symbol and not
73 * the descriptor.
74 *
75 * Also handle <module:symbol> format.
76 */
77 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
78 bool dot_appended = false;
79 const char *c;
80 ssize_t ret = 0;
81 int len = 0;
82
83 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
84 c++;
85 len = c - name;
86 memcpy(dot_name, name, len);
87 } else
88 c = name;
89
90 if (*c != '\0' && *c != '.') {
91 dot_name[len++] = '.';
92 dot_appended = true;
93 }
94 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
95 if (ret > 0)
96 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
97
98 /* Fallback to the original non-dot symbol lookup */
99 if (!addr && dot_appended)
100 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
101#else
102 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
103#endif
104
105 return addr;
106}
107
108static bool arch_kprobe_on_func_entry(unsigned long addr, unsigned long offset)
109{
110 unsigned long ip = ftrace_location(addr);
111
112 if (ip)
113 return offset <= (ip - addr);
114 if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
115 return offset <= 8;
116 return !offset;
117}
118
119/* XXX try and fold the magic of kprobe_lookup_name() in this */
120kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
121 bool *on_func_entry)
122{
123 *on_func_entry = arch_kprobe_on_func_entry(addr, offset);
124 return (kprobe_opcode_t *)(addr + offset);
125}
126
127int arch_prepare_kprobe(struct kprobe *p)
128{
129 int ret = 0;
130 struct kprobe *prev;
131 ppc_inst_t insn = ppc_inst_read(p->addr);
132
133 if ((unsigned long)p->addr & 0x03) {
134 printk("Attempt to register kprobe at an unaligned address\n");
135 ret = -EINVAL;
136 } else if (!can_single_step(ppc_inst_val(insn))) {
137 printk("Cannot register a kprobe on instructions that can't be single stepped\n");
138 ret = -EINVAL;
139 } else if ((unsigned long)p->addr & ~PAGE_MASK &&
140 ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) {
141 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
142 ret = -EINVAL;
143 }
144 prev = get_kprobe(p->addr - 1);
145
146 /*
147 * When prev is a ftrace-based kprobe, we don't have an insn, and it
148 * doesn't probe for prefixed instruction.
149 */
150 if (prev && !kprobe_ftrace(prev) &&
151 ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
152 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
153 ret = -EINVAL;
154 }
155
156 /* insn must be on a special executable page on ppc64. This is
157 * not explicitly required on ppc32 (right now), but it doesn't hurt */
158 if (!ret) {
159 p->ainsn.insn = get_insn_slot();
160 if (!p->ainsn.insn)
161 ret = -ENOMEM;
162 }
163
164 if (!ret) {
165 patch_instruction(p->ainsn.insn, insn);
166 p->opcode = ppc_inst_val(insn);
167 }
168
169 p->ainsn.boostable = 0;
170 return ret;
171}
172NOKPROBE_SYMBOL(arch_prepare_kprobe);
173
174void arch_arm_kprobe(struct kprobe *p)
175{
176 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION)));
177}
178NOKPROBE_SYMBOL(arch_arm_kprobe);
179
180void arch_disarm_kprobe(struct kprobe *p)
181{
182 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode)));
183}
184NOKPROBE_SYMBOL(arch_disarm_kprobe);
185
186void arch_remove_kprobe(struct kprobe *p)
187{
188 if (p->ainsn.insn) {
189 free_insn_slot(p->ainsn.insn, 0);
190 p->ainsn.insn = NULL;
191 }
192}
193NOKPROBE_SYMBOL(arch_remove_kprobe);
194
195static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
196{
197 enable_single_step(regs);
198
199 /*
200 * On powerpc we should single step on the original
201 * instruction even if the probed insn is a trap
202 * variant as values in regs could play a part in
203 * if the trap is taken or not
204 */
205 regs_set_return_ip(regs, (unsigned long)p->ainsn.insn);
206}
207
208static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
209{
210 kcb->prev_kprobe.kp = kprobe_running();
211 kcb->prev_kprobe.status = kcb->kprobe_status;
212 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
213}
214
215static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
216{
217 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
218 kcb->kprobe_status = kcb->prev_kprobe.status;
219 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
220}
221
222static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
223 struct kprobe_ctlblk *kcb)
224{
225 __this_cpu_write(current_kprobe, p);
226 kcb->kprobe_saved_msr = regs->msr;
227}
228
229static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
230{
231 int ret;
232 ppc_inst_t insn = ppc_inst_read(p->ainsn.insn);
233
234 /* regs->nip is also adjusted if emulate_step returns 1 */
235 ret = emulate_step(regs, insn);
236 if (ret > 0) {
237 /*
238 * Once this instruction has been boosted
239 * successfully, set the boostable flag
240 */
241 if (unlikely(p->ainsn.boostable == 0))
242 p->ainsn.boostable = 1;
243 } else if (ret < 0) {
244 /*
245 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
246 * So, we should never get here... but, its still
247 * good to catch them, just in case...
248 */
249 printk("Can't step on instruction %08lx\n", ppc_inst_as_ulong(insn));
250 BUG();
251 } else {
252 /*
253 * If we haven't previously emulated this instruction, then it
254 * can't be boosted. Note it down so we don't try to do so again.
255 *
256 * If, however, we had emulated this instruction in the past,
257 * then this is just an error with the current run (for
258 * instance, exceptions due to a load/store). We return 0 so
259 * that this is now single-stepped, but continue to try
260 * emulating it in subsequent probe hits.
261 */
262 if (unlikely(p->ainsn.boostable != 1))
263 p->ainsn.boostable = -1;
264 }
265
266 return ret;
267}
268NOKPROBE_SYMBOL(try_to_emulate);
269
270int kprobe_handler(struct pt_regs *regs)
271{
272 struct kprobe *p;
273 int ret = 0;
274 unsigned int *addr = (unsigned int *)regs->nip;
275 struct kprobe_ctlblk *kcb;
276
277 if (user_mode(regs))
278 return 0;
279
280 if (!IS_ENABLED(CONFIG_BOOKE) &&
281 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
282 return 0;
283
284 /*
285 * We don't want to be preempted for the entire
286 * duration of kprobe processing
287 */
288 preempt_disable();
289 kcb = get_kprobe_ctlblk();
290
291 p = get_kprobe(addr);
292 if (!p) {
293 unsigned int instr;
294
295 if (get_kernel_nofault(instr, addr))
296 goto no_kprobe;
297
298 if (instr != BREAKPOINT_INSTRUCTION) {
299 /*
300 * PowerPC has multiple variants of the "trap"
301 * instruction. If the current instruction is a
302 * trap variant, it could belong to someone else
303 */
304 if (is_trap(instr))
305 goto no_kprobe;
306 /*
307 * The breakpoint instruction was removed right
308 * after we hit it. Another cpu has removed
309 * either a probepoint or a debugger breakpoint
310 * at this address. In either case, no further
311 * handling of this interrupt is appropriate.
312 */
313 ret = 1;
314 }
315 /* Not one of ours: let kernel handle it */
316 goto no_kprobe;
317 }
318
319 /* Check we're not actually recursing */
320 if (kprobe_running()) {
321 kprobe_opcode_t insn = *p->ainsn.insn;
322 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
323 /* Turn off 'trace' bits */
324 regs_set_return_msr(regs,
325 (regs->msr & ~MSR_SINGLESTEP) |
326 kcb->kprobe_saved_msr);
327 goto no_kprobe;
328 }
329
330 /*
331 * We have reentered the kprobe_handler(), since another probe
332 * was hit while within the handler. We here save the original
333 * kprobes variables and just single step on the instruction of
334 * the new probe without calling any user handlers.
335 */
336 save_previous_kprobe(kcb);
337 set_current_kprobe(p, regs, kcb);
338 kprobes_inc_nmissed_count(p);
339 kcb->kprobe_status = KPROBE_REENTER;
340 if (p->ainsn.boostable >= 0) {
341 ret = try_to_emulate(p, regs);
342
343 if (ret > 0) {
344 restore_previous_kprobe(kcb);
345 preempt_enable();
346 return 1;
347 }
348 }
349 prepare_singlestep(p, regs);
350 return 1;
351 }
352
353 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
354 set_current_kprobe(p, regs, kcb);
355 if (p->pre_handler && p->pre_handler(p, regs)) {
356 /* handler changed execution path, so skip ss setup */
357 reset_current_kprobe();
358 preempt_enable();
359 return 1;
360 }
361
362 if (p->ainsn.boostable >= 0) {
363 ret = try_to_emulate(p, regs);
364
365 if (ret > 0) {
366 if (p->post_handler)
367 p->post_handler(p, regs, 0);
368
369 kcb->kprobe_status = KPROBE_HIT_SSDONE;
370 reset_current_kprobe();
371 preempt_enable();
372 return 1;
373 }
374 }
375 prepare_singlestep(p, regs);
376 kcb->kprobe_status = KPROBE_HIT_SS;
377 return 1;
378
379no_kprobe:
380 preempt_enable();
381 return ret;
382}
383NOKPROBE_SYMBOL(kprobe_handler);
384
385/*
386 * Called after single-stepping. p->addr is the address of the
387 * instruction whose first byte has been replaced by the "breakpoint"
388 * instruction. To avoid the SMP problems that can occur when we
389 * temporarily put back the original opcode to single-step, we
390 * single-stepped a copy of the instruction. The address of this
391 * copy is p->ainsn.insn.
392 */
393int kprobe_post_handler(struct pt_regs *regs)
394{
395 int len;
396 struct kprobe *cur = kprobe_running();
397 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
398
399 if (!cur || user_mode(regs))
400 return 0;
401
402 len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn));
403 /* make sure we got here for instruction we have a kprobe on */
404 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
405 return 0;
406
407 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
408 kcb->kprobe_status = KPROBE_HIT_SSDONE;
409 cur->post_handler(cur, regs, 0);
410 }
411
412 /* Adjust nip to after the single-stepped instruction */
413 regs_set_return_ip(regs, (unsigned long)cur->addr + len);
414 regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr);
415
416 /*Restore back the original saved kprobes variables and continue. */
417 if (kcb->kprobe_status == KPROBE_REENTER) {
418 restore_previous_kprobe(kcb);
419 goto out;
420 }
421 reset_current_kprobe();
422out:
423 preempt_enable();
424
425 /*
426 * if somebody else is singlestepping across a probe point, msr
427 * will have DE/SE set, in which case, continue the remaining processing
428 * of do_debug, as if this is not a probe hit.
429 */
430 if (regs->msr & MSR_SINGLESTEP)
431 return 0;
432
433 return 1;
434}
435NOKPROBE_SYMBOL(kprobe_post_handler);
436
437int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
438{
439 struct kprobe *cur = kprobe_running();
440 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
441 const struct exception_table_entry *entry;
442
443 switch(kcb->kprobe_status) {
444 case KPROBE_HIT_SS:
445 case KPROBE_REENTER:
446 /*
447 * We are here because the instruction being single
448 * stepped caused a page fault. We reset the current
449 * kprobe and the nip points back to the probe address
450 * and allow the page fault handler to continue as a
451 * normal page fault.
452 */
453 regs_set_return_ip(regs, (unsigned long)cur->addr);
454 /* Turn off 'trace' bits */
455 regs_set_return_msr(regs,
456 (regs->msr & ~MSR_SINGLESTEP) |
457 kcb->kprobe_saved_msr);
458 if (kcb->kprobe_status == KPROBE_REENTER)
459 restore_previous_kprobe(kcb);
460 else
461 reset_current_kprobe();
462 preempt_enable();
463 break;
464 case KPROBE_HIT_ACTIVE:
465 case KPROBE_HIT_SSDONE:
466 /*
467 * In case the user-specified fault handler returned
468 * zero, try to fix up.
469 */
470 if ((entry = search_exception_tables(regs->nip)) != NULL) {
471 regs_set_return_ip(regs, extable_fixup(entry));
472 return 1;
473 }
474
475 /*
476 * fixup_exception() could not handle it,
477 * Let do_page_fault() fix it.
478 */
479 break;
480 default:
481 break;
482 }
483 return 0;
484}
485NOKPROBE_SYMBOL(kprobe_fault_handler);
486
487int arch_trampoline_kprobe(struct kprobe *p)
488{
489 if (p->addr == (kprobe_opcode_t *)&arch_rethook_trampoline)
490 return 1;
491
492 return 0;
493}
494NOKPROBE_SYMBOL(arch_trampoline_kprobe);