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