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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/*
2 * Kernel Probes (KProbes)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2004
19 *
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
22 * Rusty Russell).
23 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24 * interface to access function arguments.
25 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
26 * for PPC64
27 */
28
29#include <linux/kprobes.h>
30#include <linux/ptrace.h>
31#include <linux/preempt.h>
32#include <linux/extable.h>
33#include <linux/kdebug.h>
34#include <linux/slab.h>
35#include <asm/code-patching.h>
36#include <asm/cacheflush.h>
37#include <asm/sstep.h>
38#include <linux/uaccess.h>
39
40DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
41DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
42
43struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
44
45int __kprobes arch_prepare_kprobe(struct kprobe *p)
46{
47 int ret = 0;
48 kprobe_opcode_t insn = *p->addr;
49
50 if ((unsigned long)p->addr & 0x03) {
51 printk("Attempt to register kprobe at an unaligned address\n");
52 ret = -EINVAL;
53 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
54 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
55 ret = -EINVAL;
56 }
57
58 /* insn must be on a special executable page on ppc64. This is
59 * not explicitly required on ppc32 (right now), but it doesn't hurt */
60 if (!ret) {
61 p->ainsn.insn = get_insn_slot();
62 if (!p->ainsn.insn)
63 ret = -ENOMEM;
64 }
65
66 if (!ret) {
67 memcpy(p->ainsn.insn, p->addr,
68 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
69 p->opcode = *p->addr;
70 flush_icache_range((unsigned long)p->ainsn.insn,
71 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
72 }
73
74 p->ainsn.boostable = 0;
75 return ret;
76}
77
78void __kprobes arch_arm_kprobe(struct kprobe *p)
79{
80 *p->addr = BREAKPOINT_INSTRUCTION;
81 flush_icache_range((unsigned long) p->addr,
82 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
83}
84
85void __kprobes arch_disarm_kprobe(struct kprobe *p)
86{
87 *p->addr = p->opcode;
88 flush_icache_range((unsigned long) p->addr,
89 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
90}
91
92void __kprobes arch_remove_kprobe(struct kprobe *p)
93{
94 if (p->ainsn.insn) {
95 free_insn_slot(p->ainsn.insn, 0);
96 p->ainsn.insn = NULL;
97 }
98}
99
100static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
101{
102 enable_single_step(regs);
103
104 /*
105 * On powerpc we should single step on the original
106 * instruction even if the probed insn is a trap
107 * variant as values in regs could play a part in
108 * if the trap is taken or not
109 */
110 regs->nip = (unsigned long)p->ainsn.insn;
111}
112
113static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
114{
115 kcb->prev_kprobe.kp = kprobe_running();
116 kcb->prev_kprobe.status = kcb->kprobe_status;
117 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
118}
119
120static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
121{
122 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
123 kcb->kprobe_status = kcb->prev_kprobe.status;
124 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
125}
126
127static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
128 struct kprobe_ctlblk *kcb)
129{
130 __this_cpu_write(current_kprobe, p);
131 kcb->kprobe_saved_msr = regs->msr;
132}
133
134void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
135 struct pt_regs *regs)
136{
137 ri->ret_addr = (kprobe_opcode_t *)regs->link;
138
139 /* Replace the return addr with trampoline addr */
140 regs->link = (unsigned long)kretprobe_trampoline;
141}
142
143int __kprobes kprobe_handler(struct pt_regs *regs)
144{
145 struct kprobe *p;
146 int ret = 0;
147 unsigned int *addr = (unsigned int *)regs->nip;
148 struct kprobe_ctlblk *kcb;
149
150 if (user_mode(regs))
151 return 0;
152
153 /*
154 * We don't want to be preempted for the entire
155 * duration of kprobe processing
156 */
157 preempt_disable();
158 kcb = get_kprobe_ctlblk();
159
160 /* Check we're not actually recursing */
161 if (kprobe_running()) {
162 p = get_kprobe(addr);
163 if (p) {
164 kprobe_opcode_t insn = *p->ainsn.insn;
165 if (kcb->kprobe_status == KPROBE_HIT_SS &&
166 is_trap(insn)) {
167 /* Turn off 'trace' bits */
168 regs->msr &= ~MSR_SINGLESTEP;
169 regs->msr |= kcb->kprobe_saved_msr;
170 goto no_kprobe;
171 }
172 /* We have reentered the kprobe_handler(), since
173 * another probe was hit while within the handler.
174 * We here save the original kprobes variables and
175 * just single step on the instruction of the new probe
176 * without calling any user handlers.
177 */
178 save_previous_kprobe(kcb);
179 set_current_kprobe(p, regs, kcb);
180 kcb->kprobe_saved_msr = regs->msr;
181 kprobes_inc_nmissed_count(p);
182 prepare_singlestep(p, regs);
183 kcb->kprobe_status = KPROBE_REENTER;
184 return 1;
185 } else {
186 if (*addr != BREAKPOINT_INSTRUCTION) {
187 /* If trap variant, then it belongs not to us */
188 kprobe_opcode_t cur_insn = *addr;
189 if (is_trap(cur_insn))
190 goto no_kprobe;
191 /* The breakpoint instruction was removed by
192 * another cpu right after we hit, no further
193 * handling of this interrupt is appropriate
194 */
195 ret = 1;
196 goto no_kprobe;
197 }
198 p = __this_cpu_read(current_kprobe);
199 if (p->break_handler && p->break_handler(p, regs)) {
200 goto ss_probe;
201 }
202 }
203 goto no_kprobe;
204 }
205
206 p = get_kprobe(addr);
207 if (!p) {
208 if (*addr != BREAKPOINT_INSTRUCTION) {
209 /*
210 * PowerPC has multiple variants of the "trap"
211 * instruction. If the current instruction is a
212 * trap variant, it could belong to someone else
213 */
214 kprobe_opcode_t cur_insn = *addr;
215 if (is_trap(cur_insn))
216 goto no_kprobe;
217 /*
218 * The breakpoint instruction was removed right
219 * after we hit it. Another cpu has removed
220 * either a probepoint or a debugger breakpoint
221 * at this address. In either case, no further
222 * handling of this interrupt is appropriate.
223 */
224 ret = 1;
225 }
226 /* Not one of ours: let kernel handle it */
227 goto no_kprobe;
228 }
229
230 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
231 set_current_kprobe(p, regs, kcb);
232 if (p->pre_handler && p->pre_handler(p, regs))
233 /* handler has already set things up, so skip ss setup */
234 return 1;
235
236ss_probe:
237 if (p->ainsn.boostable >= 0) {
238 unsigned int insn = *p->ainsn.insn;
239
240 /* regs->nip is also adjusted if emulate_step returns 1 */
241 ret = emulate_step(regs, insn);
242 if (ret > 0) {
243 /*
244 * Once this instruction has been boosted
245 * successfully, set the boostable flag
246 */
247 if (unlikely(p->ainsn.boostable == 0))
248 p->ainsn.boostable = 1;
249
250 if (p->post_handler)
251 p->post_handler(p, regs, 0);
252
253 kcb->kprobe_status = KPROBE_HIT_SSDONE;
254 reset_current_kprobe();
255 preempt_enable_no_resched();
256 return 1;
257 } else if (ret < 0) {
258 /*
259 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
260 * So, we should never get here... but, its still
261 * good to catch them, just in case...
262 */
263 printk("Can't step on instruction %x\n", insn);
264 BUG();
265 } else if (ret == 0)
266 /* This instruction can't be boosted */
267 p->ainsn.boostable = -1;
268 }
269 prepare_singlestep(p, regs);
270 kcb->kprobe_status = KPROBE_HIT_SS;
271 return 1;
272
273no_kprobe:
274 preempt_enable_no_resched();
275 return ret;
276}
277
278/*
279 * Function return probe trampoline:
280 * - init_kprobes() establishes a probepoint here
281 * - When the probed function returns, this probe
282 * causes the handlers to fire
283 */
284asm(".global kretprobe_trampoline\n"
285 ".type kretprobe_trampoline, @function\n"
286 "kretprobe_trampoline:\n"
287 "nop\n"
288 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
289
290/*
291 * Called when the probe at kretprobe trampoline is hit
292 */
293static int __kprobes trampoline_probe_handler(struct kprobe *p,
294 struct pt_regs *regs)
295{
296 struct kretprobe_instance *ri = NULL;
297 struct hlist_head *head, empty_rp;
298 struct hlist_node *tmp;
299 unsigned long flags, orig_ret_address = 0;
300 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
301
302 INIT_HLIST_HEAD(&empty_rp);
303 kretprobe_hash_lock(current, &head, &flags);
304
305 /*
306 * It is possible to have multiple instances associated with a given
307 * task either because an multiple functions in the call path
308 * have a return probe installed on them, and/or more than one return
309 * return probe was registered for a target function.
310 *
311 * We can handle this because:
312 * - instances are always inserted at the head of the list
313 * - when multiple return probes are registered for the same
314 * function, the first instance's ret_addr will point to the
315 * real return address, and all the rest will point to
316 * kretprobe_trampoline
317 */
318 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
319 if (ri->task != current)
320 /* another task is sharing our hash bucket */
321 continue;
322
323 if (ri->rp && ri->rp->handler)
324 ri->rp->handler(ri, regs);
325
326 orig_ret_address = (unsigned long)ri->ret_addr;
327 recycle_rp_inst(ri, &empty_rp);
328
329 if (orig_ret_address != trampoline_address)
330 /*
331 * This is the real return address. Any other
332 * instances associated with this task are for
333 * other calls deeper on the call stack
334 */
335 break;
336 }
337
338 kretprobe_assert(ri, orig_ret_address, trampoline_address);
339 regs->nip = orig_ret_address;
340
341 reset_current_kprobe();
342 kretprobe_hash_unlock(current, &flags);
343 preempt_enable_no_resched();
344
345 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
346 hlist_del(&ri->hlist);
347 kfree(ri);
348 }
349 /*
350 * By returning a non-zero value, we are telling
351 * kprobe_handler() that we don't want the post_handler
352 * to run (and have re-enabled preemption)
353 */
354 return 1;
355}
356
357/*
358 * Called after single-stepping. p->addr is the address of the
359 * instruction whose first byte has been replaced by the "breakpoint"
360 * instruction. To avoid the SMP problems that can occur when we
361 * temporarily put back the original opcode to single-step, we
362 * single-stepped a copy of the instruction. The address of this
363 * copy is p->ainsn.insn.
364 */
365int __kprobes kprobe_post_handler(struct pt_regs *regs)
366{
367 struct kprobe *cur = kprobe_running();
368 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
369
370 if (!cur || user_mode(regs))
371 return 0;
372
373 /* make sure we got here for instruction we have a kprobe on */
374 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
375 return 0;
376
377 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
378 kcb->kprobe_status = KPROBE_HIT_SSDONE;
379 cur->post_handler(cur, regs, 0);
380 }
381
382 /* Adjust nip to after the single-stepped instruction */
383 regs->nip = (unsigned long)cur->addr + 4;
384 regs->msr |= kcb->kprobe_saved_msr;
385
386 /*Restore back the original saved kprobes variables and continue. */
387 if (kcb->kprobe_status == KPROBE_REENTER) {
388 restore_previous_kprobe(kcb);
389 goto out;
390 }
391 reset_current_kprobe();
392out:
393 preempt_enable_no_resched();
394
395 /*
396 * if somebody else is singlestepping across a probe point, msr
397 * will have DE/SE set, in which case, continue the remaining processing
398 * of do_debug, as if this is not a probe hit.
399 */
400 if (regs->msr & MSR_SINGLESTEP)
401 return 0;
402
403 return 1;
404}
405
406int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
407{
408 struct kprobe *cur = kprobe_running();
409 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
410 const struct exception_table_entry *entry;
411
412 switch(kcb->kprobe_status) {
413 case KPROBE_HIT_SS:
414 case KPROBE_REENTER:
415 /*
416 * We are here because the instruction being single
417 * stepped caused a page fault. We reset the current
418 * kprobe and the nip points back to the probe address
419 * and allow the page fault handler to continue as a
420 * normal page fault.
421 */
422 regs->nip = (unsigned long)cur->addr;
423 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
424 regs->msr |= kcb->kprobe_saved_msr;
425 if (kcb->kprobe_status == KPROBE_REENTER)
426 restore_previous_kprobe(kcb);
427 else
428 reset_current_kprobe();
429 preempt_enable_no_resched();
430 break;
431 case KPROBE_HIT_ACTIVE:
432 case KPROBE_HIT_SSDONE:
433 /*
434 * We increment the nmissed count for accounting,
435 * we can also use npre/npostfault count for accounting
436 * these specific fault cases.
437 */
438 kprobes_inc_nmissed_count(cur);
439
440 /*
441 * We come here because instructions in the pre/post
442 * handler caused the page_fault, this could happen
443 * if handler tries to access user space by
444 * copy_from_user(), get_user() etc. Let the
445 * user-specified handler try to fix it first.
446 */
447 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
448 return 1;
449
450 /*
451 * In case the user-specified fault handler returned
452 * zero, try to fix up.
453 */
454 if ((entry = search_exception_tables(regs->nip)) != NULL) {
455 regs->nip = extable_fixup(entry);
456 return 1;
457 }
458
459 /*
460 * fixup_exception() could not handle it,
461 * Let do_page_fault() fix it.
462 */
463 break;
464 default:
465 break;
466 }
467 return 0;
468}
469
470/*
471 * Wrapper routine to for handling exceptions.
472 */
473int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
474 unsigned long val, void *data)
475{
476 return NOTIFY_DONE;
477}
478
479unsigned long arch_deref_entry_point(void *entry)
480{
481 return ppc_global_function_entry(entry);
482}
483
484int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
485{
486 struct jprobe *jp = container_of(p, struct jprobe, kp);
487 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
488
489 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
490
491 /* setup return addr to the jprobe handler routine */
492 regs->nip = arch_deref_entry_point(jp->entry);
493#ifdef PPC64_ELF_ABI_v2
494 regs->gpr[12] = (unsigned long)jp->entry;
495#elif defined(PPC64_ELF_ABI_v1)
496 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
497#endif
498
499 return 1;
500}
501
502void __used __kprobes jprobe_return(void)
503{
504 asm volatile("trap" ::: "memory");
505}
506
507static void __used __kprobes jprobe_return_end(void)
508{
509};
510
511int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
512{
513 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
514
515 /*
516 * FIXME - we should ideally be validating that we got here 'cos
517 * of the "trap" in jprobe_return() above, before restoring the
518 * saved regs...
519 */
520 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
521 preempt_enable_no_resched();
522 return 1;
523}
524
525static struct kprobe trampoline_p = {
526 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
527 .pre_handler = trampoline_probe_handler
528};
529
530int __init arch_init_kprobes(void)
531{
532 return register_kprobe(&trampoline_p);
533}
534
535int __kprobes arch_trampoline_kprobe(struct kprobe *p)
536{
537 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
538 return 1;
539
540 return 0;
541}