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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 <linux/moduleloader.h>
23#include <asm/code-patching.h>
24#include <asm/cacheflush.h>
25#include <asm/sstep.h>
26#include <asm/sections.h>
27#include <asm/inst.h>
28#include <asm/set_memory.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 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(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
108void *alloc_insn_page(void)
109{
110 void *page;
111
112 page = module_alloc(PAGE_SIZE);
113 if (!page)
114 return NULL;
115
116 if (strict_module_rwx_enabled()) {
117 set_memory_ro((unsigned long)page, 1);
118 set_memory_x((unsigned long)page, 1);
119 }
120 return page;
121}
122
123int arch_prepare_kprobe(struct kprobe *p)
124{
125 int ret = 0;
126 struct kprobe *prev;
127 struct ppc_inst insn = ppc_inst_read(p->addr);
128
129 if ((unsigned long)p->addr & 0x03) {
130 printk("Attempt to register kprobe at an unaligned address\n");
131 ret = -EINVAL;
132 } else if (IS_MTMSRD(insn) || IS_RFID(insn)) {
133 printk("Cannot register a kprobe on mtmsr[d]/rfi[d]\n");
134 ret = -EINVAL;
135 } else if ((unsigned long)p->addr & ~PAGE_MASK &&
136 ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) {
137 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
138 ret = -EINVAL;
139 }
140 preempt_disable();
141 prev = get_kprobe(p->addr - 1);
142 preempt_enable_no_resched();
143 if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
144 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
145 ret = -EINVAL;
146 }
147
148 /* insn must be on a special executable page on ppc64. This is
149 * not explicitly required on ppc32 (right now), but it doesn't hurt */
150 if (!ret) {
151 p->ainsn.insn = get_insn_slot();
152 if (!p->ainsn.insn)
153 ret = -ENOMEM;
154 }
155
156 if (!ret) {
157 patch_instruction(p->ainsn.insn, insn);
158 p->opcode = ppc_inst_val(insn);
159 }
160
161 p->ainsn.boostable = 0;
162 return ret;
163}
164NOKPROBE_SYMBOL(arch_prepare_kprobe);
165
166void arch_arm_kprobe(struct kprobe *p)
167{
168 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION)));
169}
170NOKPROBE_SYMBOL(arch_arm_kprobe);
171
172void arch_disarm_kprobe(struct kprobe *p)
173{
174 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode)));
175}
176NOKPROBE_SYMBOL(arch_disarm_kprobe);
177
178void arch_remove_kprobe(struct kprobe *p)
179{
180 if (p->ainsn.insn) {
181 free_insn_slot(p->ainsn.insn, 0);
182 p->ainsn.insn = NULL;
183 }
184}
185NOKPROBE_SYMBOL(arch_remove_kprobe);
186
187static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
188{
189 enable_single_step(regs);
190
191 /*
192 * On powerpc we should single step on the original
193 * instruction even if the probed insn is a trap
194 * variant as values in regs could play a part in
195 * if the trap is taken or not
196 */
197 regs_set_return_ip(regs, (unsigned long)p->ainsn.insn);
198}
199
200static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
201{
202 kcb->prev_kprobe.kp = kprobe_running();
203 kcb->prev_kprobe.status = kcb->kprobe_status;
204 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
205}
206
207static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
208{
209 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
210 kcb->kprobe_status = kcb->prev_kprobe.status;
211 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
212}
213
214static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
215 struct kprobe_ctlblk *kcb)
216{
217 __this_cpu_write(current_kprobe, p);
218 kcb->kprobe_saved_msr = regs->msr;
219}
220
221bool arch_kprobe_on_func_entry(unsigned long offset)
222{
223#ifdef PPC64_ELF_ABI_v2
224#ifdef CONFIG_KPROBES_ON_FTRACE
225 return offset <= 16;
226#else
227 return offset <= 8;
228#endif
229#else
230 return !offset;
231#endif
232}
233
234void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
235{
236 ri->ret_addr = (kprobe_opcode_t *)regs->link;
237 ri->fp = NULL;
238
239 /* Replace the return addr with trampoline addr */
240 regs->link = (unsigned long)kretprobe_trampoline;
241}
242NOKPROBE_SYMBOL(arch_prepare_kretprobe);
243
244static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
245{
246 int ret;
247 struct ppc_inst insn = ppc_inst_read(p->ainsn.insn);
248
249 /* regs->nip is also adjusted if emulate_step returns 1 */
250 ret = emulate_step(regs, insn);
251 if (ret > 0) {
252 /*
253 * Once this instruction has been boosted
254 * successfully, set the boostable flag
255 */
256 if (unlikely(p->ainsn.boostable == 0))
257 p->ainsn.boostable = 1;
258 } else if (ret < 0) {
259 /*
260 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
261 * So, we should never get here... but, its still
262 * good to catch them, just in case...
263 */
264 printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
265 BUG();
266 } else {
267 /*
268 * If we haven't previously emulated this instruction, then it
269 * can't be boosted. Note it down so we don't try to do so again.
270 *
271 * If, however, we had emulated this instruction in the past,
272 * then this is just an error with the current run (for
273 * instance, exceptions due to a load/store). We return 0 so
274 * that this is now single-stepped, but continue to try
275 * emulating it in subsequent probe hits.
276 */
277 if (unlikely(p->ainsn.boostable != 1))
278 p->ainsn.boostable = -1;
279 }
280
281 return ret;
282}
283NOKPROBE_SYMBOL(try_to_emulate);
284
285int kprobe_handler(struct pt_regs *regs)
286{
287 struct kprobe *p;
288 int ret = 0;
289 unsigned int *addr = (unsigned int *)regs->nip;
290 struct kprobe_ctlblk *kcb;
291
292 if (user_mode(regs))
293 return 0;
294
295 if (!IS_ENABLED(CONFIG_BOOKE) &&
296 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
297 return 0;
298
299 /*
300 * We don't want to be preempted for the entire
301 * duration of kprobe processing
302 */
303 preempt_disable();
304 kcb = get_kprobe_ctlblk();
305
306 p = get_kprobe(addr);
307 if (!p) {
308 unsigned int instr;
309
310 if (get_kernel_nofault(instr, addr))
311 goto no_kprobe;
312
313 if (instr != BREAKPOINT_INSTRUCTION) {
314 /*
315 * PowerPC has multiple variants of the "trap"
316 * instruction. If the current instruction is a
317 * trap variant, it could belong to someone else
318 */
319 if (is_trap(instr))
320 goto no_kprobe;
321 /*
322 * The breakpoint instruction was removed right
323 * after we hit it. Another cpu has removed
324 * either a probepoint or a debugger breakpoint
325 * at this address. In either case, no further
326 * handling of this interrupt is appropriate.
327 */
328 ret = 1;
329 }
330 /* Not one of ours: let kernel handle it */
331 goto no_kprobe;
332 }
333
334 /* Check we're not actually recursing */
335 if (kprobe_running()) {
336 kprobe_opcode_t insn = *p->ainsn.insn;
337 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
338 /* Turn off 'trace' bits */
339 regs_set_return_msr(regs,
340 (regs->msr & ~MSR_SINGLESTEP) |
341 kcb->kprobe_saved_msr);
342 goto no_kprobe;
343 }
344
345 /*
346 * We have reentered the kprobe_handler(), since another probe
347 * was hit while within the handler. We here save the original
348 * kprobes variables and just single step on the instruction of
349 * the new probe without calling any user handlers.
350 */
351 save_previous_kprobe(kcb);
352 set_current_kprobe(p, regs, kcb);
353 kprobes_inc_nmissed_count(p);
354 kcb->kprobe_status = KPROBE_REENTER;
355 if (p->ainsn.boostable >= 0) {
356 ret = try_to_emulate(p, regs);
357
358 if (ret > 0) {
359 restore_previous_kprobe(kcb);
360 preempt_enable_no_resched();
361 return 1;
362 }
363 }
364 prepare_singlestep(p, regs);
365 return 1;
366 }
367
368 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
369 set_current_kprobe(p, regs, kcb);
370 if (p->pre_handler && p->pre_handler(p, regs)) {
371 /* handler changed execution path, so skip ss setup */
372 reset_current_kprobe();
373 preempt_enable_no_resched();
374 return 1;
375 }
376
377 if (p->ainsn.boostable >= 0) {
378 ret = try_to_emulate(p, regs);
379
380 if (ret > 0) {
381 if (p->post_handler)
382 p->post_handler(p, regs, 0);
383
384 kcb->kprobe_status = KPROBE_HIT_SSDONE;
385 reset_current_kprobe();
386 preempt_enable_no_resched();
387 return 1;
388 }
389 }
390 prepare_singlestep(p, regs);
391 kcb->kprobe_status = KPROBE_HIT_SS;
392 return 1;
393
394no_kprobe:
395 preempt_enable_no_resched();
396 return ret;
397}
398NOKPROBE_SYMBOL(kprobe_handler);
399
400/*
401 * Function return probe trampoline:
402 * - init_kprobes() establishes a probepoint here
403 * - When the probed function returns, this probe
404 * causes the handlers to fire
405 */
406asm(".global kretprobe_trampoline\n"
407 ".type kretprobe_trampoline, @function\n"
408 "kretprobe_trampoline:\n"
409 "nop\n"
410 "blr\n"
411 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
412
413/*
414 * Called when the probe at kretprobe trampoline is hit
415 */
416static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
417{
418 unsigned long orig_ret_address;
419
420 orig_ret_address = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
421 /*
422 * We get here through one of two paths:
423 * 1. by taking a trap -> kprobe_handler() -> here
424 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
425 *
426 * When going back through (1), we need regs->nip to be setup properly
427 * as it is used to determine the return address from the trap.
428 * For (2), since nip is not honoured with optprobes, we instead setup
429 * the link register properly so that the subsequent 'blr' in
430 * kretprobe_trampoline jumps back to the right instruction.
431 *
432 * For nip, we should set the address to the previous instruction since
433 * we end up emulating it in kprobe_handler(), which increments the nip
434 * again.
435 */
436 regs_set_return_ip(regs, orig_ret_address - 4);
437 regs->link = orig_ret_address;
438
439 return 0;
440}
441NOKPROBE_SYMBOL(trampoline_probe_handler);
442
443/*
444 * Called after single-stepping. p->addr is the address of the
445 * instruction whose first byte has been replaced by the "breakpoint"
446 * instruction. To avoid the SMP problems that can occur when we
447 * temporarily put back the original opcode to single-step, we
448 * single-stepped a copy of the instruction. The address of this
449 * copy is p->ainsn.insn.
450 */
451int kprobe_post_handler(struct pt_regs *regs)
452{
453 int len;
454 struct kprobe *cur = kprobe_running();
455 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
456
457 if (!cur || user_mode(regs))
458 return 0;
459
460 len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn));
461 /* make sure we got here for instruction we have a kprobe on */
462 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
463 return 0;
464
465 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
466 kcb->kprobe_status = KPROBE_HIT_SSDONE;
467 cur->post_handler(cur, regs, 0);
468 }
469
470 /* Adjust nip to after the single-stepped instruction */
471 regs_set_return_ip(regs, (unsigned long)cur->addr + len);
472 regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr);
473
474 /*Restore back the original saved kprobes variables and continue. */
475 if (kcb->kprobe_status == KPROBE_REENTER) {
476 restore_previous_kprobe(kcb);
477 goto out;
478 }
479 reset_current_kprobe();
480out:
481 preempt_enable_no_resched();
482
483 /*
484 * if somebody else is singlestepping across a probe point, msr
485 * will have DE/SE set, in which case, continue the remaining processing
486 * of do_debug, as if this is not a probe hit.
487 */
488 if (regs->msr & MSR_SINGLESTEP)
489 return 0;
490
491 return 1;
492}
493NOKPROBE_SYMBOL(kprobe_post_handler);
494
495int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
496{
497 struct kprobe *cur = kprobe_running();
498 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
499 const struct exception_table_entry *entry;
500
501 switch(kcb->kprobe_status) {
502 case KPROBE_HIT_SS:
503 case KPROBE_REENTER:
504 /*
505 * We are here because the instruction being single
506 * stepped caused a page fault. We reset the current
507 * kprobe and the nip points back to the probe address
508 * and allow the page fault handler to continue as a
509 * normal page fault.
510 */
511 regs_set_return_ip(regs, (unsigned long)cur->addr);
512 /* Turn off 'trace' bits */
513 regs_set_return_msr(regs,
514 (regs->msr & ~MSR_SINGLESTEP) |
515 kcb->kprobe_saved_msr);
516 if (kcb->kprobe_status == KPROBE_REENTER)
517 restore_previous_kprobe(kcb);
518 else
519 reset_current_kprobe();
520 preempt_enable_no_resched();
521 break;
522 case KPROBE_HIT_ACTIVE:
523 case KPROBE_HIT_SSDONE:
524 /*
525 * In case the user-specified fault handler returned
526 * zero, try to fix up.
527 */
528 if ((entry = search_exception_tables(regs->nip)) != NULL) {
529 regs_set_return_ip(regs, extable_fixup(entry));
530 return 1;
531 }
532
533 /*
534 * fixup_exception() could not handle it,
535 * Let do_page_fault() fix it.
536 */
537 break;
538 default:
539 break;
540 }
541 return 0;
542}
543NOKPROBE_SYMBOL(kprobe_fault_handler);
544
545unsigned long arch_deref_entry_point(void *entry)
546{
547#ifdef PPC64_ELF_ABI_v1
548 if (!kernel_text_address((unsigned long)entry))
549 return ppc_global_function_entry(entry);
550 else
551#endif
552 return (unsigned long)entry;
553}
554NOKPROBE_SYMBOL(arch_deref_entry_point);
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);