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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 <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);
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/module.h>
33#include <linux/kdebug.h>
34#include <linux/slab.h>
35#include <asm/cacheflush.h>
36#include <asm/sstep.h>
37#include <asm/uaccess.h>
38
39#ifdef CONFIG_PPC_ADV_DEBUG_REGS
40#define MSR_SINGLESTEP (MSR_DE)
41#else
42#define MSR_SINGLESTEP (MSR_SE)
43#endif
44
45DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
46DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
47
48struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
49
50int __kprobes arch_prepare_kprobe(struct kprobe *p)
51{
52 int ret = 0;
53 kprobe_opcode_t insn = *p->addr;
54
55 if ((unsigned long)p->addr & 0x03) {
56 printk("Attempt to register kprobe at an unaligned address\n");
57 ret = -EINVAL;
58 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
59 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
60 ret = -EINVAL;
61 }
62
63 /* insn must be on a special executable page on ppc64. This is
64 * not explicitly required on ppc32 (right now), but it doesn't hurt */
65 if (!ret) {
66 p->ainsn.insn = get_insn_slot();
67 if (!p->ainsn.insn)
68 ret = -ENOMEM;
69 }
70
71 if (!ret) {
72 memcpy(p->ainsn.insn, p->addr,
73 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
74 p->opcode = *p->addr;
75 flush_icache_range((unsigned long)p->ainsn.insn,
76 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
77 }
78
79 p->ainsn.boostable = 0;
80 return ret;
81}
82
83void __kprobes arch_arm_kprobe(struct kprobe *p)
84{
85 *p->addr = BREAKPOINT_INSTRUCTION;
86 flush_icache_range((unsigned long) p->addr,
87 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
88}
89
90void __kprobes arch_disarm_kprobe(struct kprobe *p)
91{
92 *p->addr = p->opcode;
93 flush_icache_range((unsigned long) p->addr,
94 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
95}
96
97void __kprobes arch_remove_kprobe(struct kprobe *p)
98{
99 if (p->ainsn.insn) {
100 free_insn_slot(p->ainsn.insn, 0);
101 p->ainsn.insn = NULL;
102 }
103}
104
105static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
106{
107 /* We turn off async exceptions to ensure that the single step will
108 * be for the instruction we have the kprobe on, if we dont its
109 * possible we'd get the single step reported for an exception handler
110 * like Decrementer or External Interrupt */
111 regs->msr &= ~MSR_EE;
112 regs->msr |= MSR_SINGLESTEP;
113#ifdef CONFIG_PPC_ADV_DEBUG_REGS
114 regs->msr &= ~MSR_CE;
115 mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
116#ifdef CONFIG_PPC_47x
117 isync();
118#endif
119#endif
120
121 /*
122 * On powerpc we should single step on the original
123 * instruction even if the probed insn is a trap
124 * variant as values in regs could play a part in
125 * if the trap is taken or not
126 */
127 regs->nip = (unsigned long)p->ainsn.insn;
128}
129
130static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
131{
132 kcb->prev_kprobe.kp = kprobe_running();
133 kcb->prev_kprobe.status = kcb->kprobe_status;
134 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
135}
136
137static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
138{
139 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
140 kcb->kprobe_status = kcb->prev_kprobe.status;
141 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
142}
143
144static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
145 struct kprobe_ctlblk *kcb)
146{
147 __get_cpu_var(current_kprobe) = p;
148 kcb->kprobe_saved_msr = regs->msr;
149}
150
151void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
152 struct pt_regs *regs)
153{
154 ri->ret_addr = (kprobe_opcode_t *)regs->link;
155
156 /* Replace the return addr with trampoline addr */
157 regs->link = (unsigned long)kretprobe_trampoline;
158}
159
160static int __kprobes kprobe_handler(struct pt_regs *regs)
161{
162 struct kprobe *p;
163 int ret = 0;
164 unsigned int *addr = (unsigned int *)regs->nip;
165 struct kprobe_ctlblk *kcb;
166
167 /*
168 * We don't want to be preempted for the entire
169 * duration of kprobe processing
170 */
171 preempt_disable();
172 kcb = get_kprobe_ctlblk();
173
174 /* Check we're not actually recursing */
175 if (kprobe_running()) {
176 p = get_kprobe(addr);
177 if (p) {
178 kprobe_opcode_t insn = *p->ainsn.insn;
179 if (kcb->kprobe_status == KPROBE_HIT_SS &&
180 is_trap(insn)) {
181 /* Turn off 'trace' bits */
182 regs->msr &= ~MSR_SINGLESTEP;
183 regs->msr |= kcb->kprobe_saved_msr;
184 goto no_kprobe;
185 }
186 /* We have reentered the kprobe_handler(), since
187 * another probe was hit while within the handler.
188 * We here save the original kprobes variables and
189 * just single step on the instruction of the new probe
190 * without calling any user handlers.
191 */
192 save_previous_kprobe(kcb);
193 set_current_kprobe(p, regs, kcb);
194 kcb->kprobe_saved_msr = regs->msr;
195 kprobes_inc_nmissed_count(p);
196 prepare_singlestep(p, regs);
197 kcb->kprobe_status = KPROBE_REENTER;
198 return 1;
199 } else {
200 if (*addr != BREAKPOINT_INSTRUCTION) {
201 /* If trap variant, then it belongs not to us */
202 kprobe_opcode_t cur_insn = *addr;
203 if (is_trap(cur_insn))
204 goto no_kprobe;
205 /* The breakpoint instruction was removed by
206 * another cpu right after we hit, no further
207 * handling of this interrupt is appropriate
208 */
209 ret = 1;
210 goto no_kprobe;
211 }
212 p = __get_cpu_var(current_kprobe);
213 if (p->break_handler && p->break_handler(p, regs)) {
214 goto ss_probe;
215 }
216 }
217 goto no_kprobe;
218 }
219
220 p = get_kprobe(addr);
221 if (!p) {
222 if (*addr != BREAKPOINT_INSTRUCTION) {
223 /*
224 * PowerPC has multiple variants of the "trap"
225 * instruction. If the current instruction is a
226 * trap variant, it could belong to someone else
227 */
228 kprobe_opcode_t cur_insn = *addr;
229 if (is_trap(cur_insn))
230 goto no_kprobe;
231 /*
232 * The breakpoint instruction was removed right
233 * after we hit it. Another cpu has removed
234 * either a probepoint or a debugger breakpoint
235 * at this address. In either case, no further
236 * handling of this interrupt is appropriate.
237 */
238 ret = 1;
239 }
240 /* Not one of ours: let kernel handle it */
241 goto no_kprobe;
242 }
243
244 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
245 set_current_kprobe(p, regs, kcb);
246 if (p->pre_handler && p->pre_handler(p, regs))
247 /* handler has already set things up, so skip ss setup */
248 return 1;
249
250ss_probe:
251 if (p->ainsn.boostable >= 0) {
252 unsigned int insn = *p->ainsn.insn;
253
254 /* regs->nip is also adjusted if emulate_step returns 1 */
255 ret = emulate_step(regs, insn);
256 if (ret > 0) {
257 /*
258 * Once this instruction has been boosted
259 * successfully, set the boostable flag
260 */
261 if (unlikely(p->ainsn.boostable == 0))
262 p->ainsn.boostable = 1;
263
264 if (p->post_handler)
265 p->post_handler(p, regs, 0);
266
267 kcb->kprobe_status = KPROBE_HIT_SSDONE;
268 reset_current_kprobe();
269 preempt_enable_no_resched();
270 return 1;
271 } else if (ret < 0) {
272 /*
273 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
274 * So, we should never get here... but, its still
275 * good to catch them, just in case...
276 */
277 printk("Can't step on instruction %x\n", insn);
278 BUG();
279 } else if (ret == 0)
280 /* This instruction can't be boosted */
281 p->ainsn.boostable = -1;
282 }
283 prepare_singlestep(p, regs);
284 kcb->kprobe_status = KPROBE_HIT_SS;
285 return 1;
286
287no_kprobe:
288 preempt_enable_no_resched();
289 return ret;
290}
291
292/*
293 * Function return probe trampoline:
294 * - init_kprobes() establishes a probepoint here
295 * - When the probed function returns, this probe
296 * causes the handlers to fire
297 */
298static void __used kretprobe_trampoline_holder(void)
299{
300 asm volatile(".global kretprobe_trampoline\n"
301 "kretprobe_trampoline:\n"
302 "nop\n");
303}
304
305/*
306 * Called when the probe at kretprobe trampoline is hit
307 */
308static int __kprobes trampoline_probe_handler(struct kprobe *p,
309 struct pt_regs *regs)
310{
311 struct kretprobe_instance *ri = NULL;
312 struct hlist_head *head, empty_rp;
313 struct hlist_node *node, *tmp;
314 unsigned long flags, orig_ret_address = 0;
315 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
316
317 INIT_HLIST_HEAD(&empty_rp);
318 kretprobe_hash_lock(current, &head, &flags);
319
320 /*
321 * It is possible to have multiple instances associated with a given
322 * task either because an multiple functions in the call path
323 * have a return probe installed on them, and/or more than one return
324 * return probe was registered for a target function.
325 *
326 * We can handle this because:
327 * - instances are always inserted at the head of the list
328 * - when multiple return probes are registered for the same
329 * function, the first instance's ret_addr will point to the
330 * real return address, and all the rest will point to
331 * kretprobe_trampoline
332 */
333 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
334 if (ri->task != current)
335 /* another task is sharing our hash bucket */
336 continue;
337
338 if (ri->rp && ri->rp->handler)
339 ri->rp->handler(ri, regs);
340
341 orig_ret_address = (unsigned long)ri->ret_addr;
342 recycle_rp_inst(ri, &empty_rp);
343
344 if (orig_ret_address != trampoline_address)
345 /*
346 * This is the real return address. Any other
347 * instances associated with this task are for
348 * other calls deeper on the call stack
349 */
350 break;
351 }
352
353 kretprobe_assert(ri, orig_ret_address, trampoline_address);
354 regs->nip = orig_ret_address;
355
356 reset_current_kprobe();
357 kretprobe_hash_unlock(current, &flags);
358 preempt_enable_no_resched();
359
360 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
361 hlist_del(&ri->hlist);
362 kfree(ri);
363 }
364 /*
365 * By returning a non-zero value, we are telling
366 * kprobe_handler() that we don't want the post_handler
367 * to run (and have re-enabled preemption)
368 */
369 return 1;
370}
371
372/*
373 * Called after single-stepping. p->addr is the address of the
374 * instruction whose first byte has been replaced by the "breakpoint"
375 * instruction. To avoid the SMP problems that can occur when we
376 * temporarily put back the original opcode to single-step, we
377 * single-stepped a copy of the instruction. The address of this
378 * copy is p->ainsn.insn.
379 */
380static int __kprobes post_kprobe_handler(struct pt_regs *regs)
381{
382 struct kprobe *cur = kprobe_running();
383 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
384
385 if (!cur)
386 return 0;
387
388 /* make sure we got here for instruction we have a kprobe on */
389 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
390 return 0;
391
392 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
393 kcb->kprobe_status = KPROBE_HIT_SSDONE;
394 cur->post_handler(cur, regs, 0);
395 }
396
397 /* Adjust nip to after the single-stepped instruction */
398 regs->nip = (unsigned long)cur->addr + 4;
399 regs->msr |= kcb->kprobe_saved_msr;
400
401 /*Restore back the original saved kprobes variables and continue. */
402 if (kcb->kprobe_status == KPROBE_REENTER) {
403 restore_previous_kprobe(kcb);
404 goto out;
405 }
406 reset_current_kprobe();
407out:
408 preempt_enable_no_resched();
409
410 /*
411 * if somebody else is singlestepping across a probe point, msr
412 * will have DE/SE set, in which case, continue the remaining processing
413 * of do_debug, as if this is not a probe hit.
414 */
415 if (regs->msr & MSR_SINGLESTEP)
416 return 0;
417
418 return 1;
419}
420
421int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
422{
423 struct kprobe *cur = kprobe_running();
424 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
425 const struct exception_table_entry *entry;
426
427 switch(kcb->kprobe_status) {
428 case KPROBE_HIT_SS:
429 case KPROBE_REENTER:
430 /*
431 * We are here because the instruction being single
432 * stepped caused a page fault. We reset the current
433 * kprobe and the nip points back to the probe address
434 * and allow the page fault handler to continue as a
435 * normal page fault.
436 */
437 regs->nip = (unsigned long)cur->addr;
438 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
439 regs->msr |= kcb->kprobe_saved_msr;
440 if (kcb->kprobe_status == KPROBE_REENTER)
441 restore_previous_kprobe(kcb);
442 else
443 reset_current_kprobe();
444 preempt_enable_no_resched();
445 break;
446 case KPROBE_HIT_ACTIVE:
447 case KPROBE_HIT_SSDONE:
448 /*
449 * We increment the nmissed count for accounting,
450 * we can also use npre/npostfault count for accouting
451 * these specific fault cases.
452 */
453 kprobes_inc_nmissed_count(cur);
454
455 /*
456 * We come here because instructions in the pre/post
457 * handler caused the page_fault, this could happen
458 * if handler tries to access user space by
459 * copy_from_user(), get_user() etc. Let the
460 * user-specified handler try to fix it first.
461 */
462 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
463 return 1;
464
465 /*
466 * In case the user-specified fault handler returned
467 * zero, try to fix up.
468 */
469 if ((entry = search_exception_tables(regs->nip)) != NULL) {
470 regs->nip = entry->fixup;
471 return 1;
472 }
473
474 /*
475 * fixup_exception() could not handle it,
476 * Let do_page_fault() fix it.
477 */
478 break;
479 default:
480 break;
481 }
482 return 0;
483}
484
485/*
486 * Wrapper routine to for handling exceptions.
487 */
488int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
489 unsigned long val, void *data)
490{
491 struct die_args *args = (struct die_args *)data;
492 int ret = NOTIFY_DONE;
493
494 if (args->regs && user_mode(args->regs))
495 return ret;
496
497 switch (val) {
498 case DIE_BPT:
499 if (kprobe_handler(args->regs))
500 ret = NOTIFY_STOP;
501 break;
502 case DIE_SSTEP:
503 if (post_kprobe_handler(args->regs))
504 ret = NOTIFY_STOP;
505 break;
506 default:
507 break;
508 }
509 return ret;
510}
511
512#ifdef CONFIG_PPC64
513unsigned long arch_deref_entry_point(void *entry)
514{
515 return ((func_descr_t *)entry)->entry;
516}
517#endif
518
519int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
520{
521 struct jprobe *jp = container_of(p, struct jprobe, kp);
522 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
523
524 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
525
526 /* setup return addr to the jprobe handler routine */
527 regs->nip = arch_deref_entry_point(jp->entry);
528#ifdef CONFIG_PPC64
529 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
530#endif
531
532 return 1;
533}
534
535void __used __kprobes jprobe_return(void)
536{
537 asm volatile("trap" ::: "memory");
538}
539
540static void __used __kprobes jprobe_return_end(void)
541{
542};
543
544int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
545{
546 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
547
548 /*
549 * FIXME - we should ideally be validating that we got here 'cos
550 * of the "trap" in jprobe_return() above, before restoring the
551 * saved regs...
552 */
553 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
554 preempt_enable_no_resched();
555 return 1;
556}
557
558static struct kprobe trampoline_p = {
559 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
560 .pre_handler = trampoline_probe_handler
561};
562
563int __init arch_init_kprobes(void)
564{
565 return register_kprobe(&trampoline_p);
566}
567
568int __kprobes arch_trampoline_kprobe(struct kprobe *p)
569{
570 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
571 return 1;
572
573 return 0;
574}