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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Dynamic function tracing support.
4 *
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6 *
7 * Thanks goes to Ingo Molnar, for suggesting the idea.
8 * Mathieu Desnoyers, for suggesting postponing the modifications.
9 * Arjan van de Ven, for keeping me straight, and explaining to me
10 * the dangers of modifying code on the run.
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/spinlock.h>
16#include <linux/hardirq.h>
17#include <linux/uaccess.h>
18#include <linux/ftrace.h>
19#include <linux/percpu.h>
20#include <linux/sched.h>
21#include <linux/slab.h>
22#include <linux/init.h>
23#include <linux/list.h>
24#include <linux/module.h>
25#include <linux/memory.h>
26
27#include <trace/syscall.h>
28
29#include <asm/set_memory.h>
30#include <asm/kprobes.h>
31#include <asm/ftrace.h>
32#include <asm/nops.h>
33#include <asm/text-patching.h>
34
35#ifdef CONFIG_DYNAMIC_FTRACE
36
37int ftrace_arch_code_modify_prepare(void)
38 __acquires(&text_mutex)
39{
40 /*
41 * Need to grab text_mutex to prevent a race from module loading
42 * and live kernel patching from changing the text permissions while
43 * ftrace has it set to "read/write".
44 */
45 mutex_lock(&text_mutex);
46 set_kernel_text_rw();
47 set_all_modules_text_rw();
48 return 0;
49}
50
51int ftrace_arch_code_modify_post_process(void)
52 __releases(&text_mutex)
53{
54 set_all_modules_text_ro();
55 set_kernel_text_ro();
56 mutex_unlock(&text_mutex);
57 return 0;
58}
59
60union ftrace_code_union {
61 char code[MCOUNT_INSN_SIZE];
62 struct {
63 unsigned char op;
64 int offset;
65 } __attribute__((packed));
66};
67
68static int ftrace_calc_offset(long ip, long addr)
69{
70 return (int)(addr - ip);
71}
72
73static unsigned char *
74ftrace_text_replace(unsigned char op, unsigned long ip, unsigned long addr)
75{
76 static union ftrace_code_union calc;
77
78 calc.op = op;
79 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
80
81 return calc.code;
82}
83
84static unsigned char *
85ftrace_call_replace(unsigned long ip, unsigned long addr)
86{
87 return ftrace_text_replace(0xe8, ip, addr);
88}
89
90static inline int
91within(unsigned long addr, unsigned long start, unsigned long end)
92{
93 return addr >= start && addr < end;
94}
95
96static unsigned long text_ip_addr(unsigned long ip)
97{
98 /*
99 * On x86_64, kernel text mappings are mapped read-only, so we use
100 * the kernel identity mapping instead of the kernel text mapping
101 * to modify the kernel text.
102 *
103 * For 32bit kernels, these mappings are same and we can use
104 * kernel identity mapping to modify code.
105 */
106 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
107 ip = (unsigned long)__va(__pa_symbol(ip));
108
109 return ip;
110}
111
112static const unsigned char *ftrace_nop_replace(void)
113{
114 return ideal_nops[NOP_ATOMIC5];
115}
116
117static int
118ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
119 unsigned const char *new_code)
120{
121 unsigned char replaced[MCOUNT_INSN_SIZE];
122
123 ftrace_expected = old_code;
124
125 /*
126 * Note:
127 * We are paranoid about modifying text, as if a bug was to happen, it
128 * could cause us to read or write to someplace that could cause harm.
129 * Carefully read and modify the code with probe_kernel_*(), and make
130 * sure what we read is what we expected it to be before modifying it.
131 */
132
133 /* read the text we want to modify */
134 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
135 return -EFAULT;
136
137 /* Make sure it is what we expect it to be */
138 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
139 return -EINVAL;
140
141 ip = text_ip_addr(ip);
142
143 /* replace the text with the new text */
144 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
145 return -EPERM;
146
147 sync_core();
148
149 return 0;
150}
151
152int ftrace_make_nop(struct module *mod,
153 struct dyn_ftrace *rec, unsigned long addr)
154{
155 unsigned const char *new, *old;
156 unsigned long ip = rec->ip;
157
158 old = ftrace_call_replace(ip, addr);
159 new = ftrace_nop_replace();
160
161 /*
162 * On boot up, and when modules are loaded, the MCOUNT_ADDR
163 * is converted to a nop, and will never become MCOUNT_ADDR
164 * again. This code is either running before SMP (on boot up)
165 * or before the code will ever be executed (module load).
166 * We do not want to use the breakpoint version in this case,
167 * just modify the code directly.
168 */
169 if (addr == MCOUNT_ADDR)
170 return ftrace_modify_code_direct(rec->ip, old, new);
171
172 ftrace_expected = NULL;
173
174 /* Normal cases use add_brk_on_nop */
175 WARN_ONCE(1, "invalid use of ftrace_make_nop");
176 return -EINVAL;
177}
178
179int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
180{
181 unsigned const char *new, *old;
182 unsigned long ip = rec->ip;
183
184 old = ftrace_nop_replace();
185 new = ftrace_call_replace(ip, addr);
186
187 /* Should only be called when module is loaded */
188 return ftrace_modify_code_direct(rec->ip, old, new);
189}
190
191/*
192 * The modifying_ftrace_code is used to tell the breakpoint
193 * handler to call ftrace_int3_handler(). If it fails to
194 * call this handler for a breakpoint added by ftrace, then
195 * the kernel may crash.
196 *
197 * As atomic_writes on x86 do not need a barrier, we do not
198 * need to add smp_mb()s for this to work. It is also considered
199 * that we can not read the modifying_ftrace_code before
200 * executing the breakpoint. That would be quite remarkable if
201 * it could do that. Here's the flow that is required:
202 *
203 * CPU-0 CPU-1
204 *
205 * atomic_inc(mfc);
206 * write int3s
207 * <trap-int3> // implicit (r)mb
208 * if (atomic_read(mfc))
209 * call ftrace_int3_handler()
210 *
211 * Then when we are finished:
212 *
213 * atomic_dec(mfc);
214 *
215 * If we hit a breakpoint that was not set by ftrace, it does not
216 * matter if ftrace_int3_handler() is called or not. It will
217 * simply be ignored. But it is crucial that a ftrace nop/caller
218 * breakpoint is handled. No other user should ever place a
219 * breakpoint on an ftrace nop/caller location. It must only
220 * be done by this code.
221 */
222atomic_t modifying_ftrace_code __read_mostly;
223
224static int
225ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
226 unsigned const char *new_code);
227
228/*
229 * Should never be called:
230 * As it is only called by __ftrace_replace_code() which is called by
231 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
232 * which is called to turn mcount into nops or nops into function calls
233 * but not to convert a function from not using regs to one that uses
234 * regs, which ftrace_modify_call() is for.
235 */
236int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
237 unsigned long addr)
238{
239 WARN_ON(1);
240 ftrace_expected = NULL;
241 return -EINVAL;
242}
243
244static unsigned long ftrace_update_func;
245static unsigned long ftrace_update_func_call;
246
247static int update_ftrace_func(unsigned long ip, void *new)
248{
249 unsigned char old[MCOUNT_INSN_SIZE];
250 int ret;
251
252 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
253
254 ftrace_update_func = ip;
255 /* Make sure the breakpoints see the ftrace_update_func update */
256 smp_wmb();
257
258 /* See comment above by declaration of modifying_ftrace_code */
259 atomic_inc(&modifying_ftrace_code);
260
261 ret = ftrace_modify_code(ip, old, new);
262
263 atomic_dec(&modifying_ftrace_code);
264
265 return ret;
266}
267
268int ftrace_update_ftrace_func(ftrace_func_t func)
269{
270 unsigned long ip = (unsigned long)(&ftrace_call);
271 unsigned char *new;
272 int ret;
273
274 ftrace_update_func_call = (unsigned long)func;
275
276 new = ftrace_call_replace(ip, (unsigned long)func);
277 ret = update_ftrace_func(ip, new);
278
279 /* Also update the regs callback function */
280 if (!ret) {
281 ip = (unsigned long)(&ftrace_regs_call);
282 new = ftrace_call_replace(ip, (unsigned long)func);
283 ret = update_ftrace_func(ip, new);
284 }
285
286 return ret;
287}
288
289static nokprobe_inline int is_ftrace_caller(unsigned long ip)
290{
291 if (ip == ftrace_update_func)
292 return 1;
293
294 return 0;
295}
296
297/*
298 * A breakpoint was added to the code address we are about to
299 * modify, and this is the handle that will just skip over it.
300 * We are either changing a nop into a trace call, or a trace
301 * call to a nop. While the change is taking place, we treat
302 * it just like it was a nop.
303 */
304int ftrace_int3_handler(struct pt_regs *regs)
305{
306 unsigned long ip;
307
308 if (WARN_ON_ONCE(!regs))
309 return 0;
310
311 ip = regs->ip - INT3_INSN_SIZE;
312
313 if (ftrace_location(ip)) {
314 int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);
315 return 1;
316 } else if (is_ftrace_caller(ip)) {
317 if (!ftrace_update_func_call) {
318 int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
319 return 1;
320 }
321 int3_emulate_call(regs, ftrace_update_func_call);
322 return 1;
323 }
324
325 return 0;
326}
327NOKPROBE_SYMBOL(ftrace_int3_handler);
328
329static int ftrace_write(unsigned long ip, const char *val, int size)
330{
331 ip = text_ip_addr(ip);
332
333 if (probe_kernel_write((void *)ip, val, size))
334 return -EPERM;
335
336 return 0;
337}
338
339static int add_break(unsigned long ip, const char *old)
340{
341 unsigned char replaced[MCOUNT_INSN_SIZE];
342 unsigned char brk = BREAKPOINT_INSTRUCTION;
343
344 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
345 return -EFAULT;
346
347 ftrace_expected = old;
348
349 /* Make sure it is what we expect it to be */
350 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
351 return -EINVAL;
352
353 return ftrace_write(ip, &brk, 1);
354}
355
356static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
357{
358 unsigned const char *old;
359 unsigned long ip = rec->ip;
360
361 old = ftrace_call_replace(ip, addr);
362
363 return add_break(rec->ip, old);
364}
365
366
367static int add_brk_on_nop(struct dyn_ftrace *rec)
368{
369 unsigned const char *old;
370
371 old = ftrace_nop_replace();
372
373 return add_break(rec->ip, old);
374}
375
376static int add_breakpoints(struct dyn_ftrace *rec, bool enable)
377{
378 unsigned long ftrace_addr;
379 int ret;
380
381 ftrace_addr = ftrace_get_addr_curr(rec);
382
383 ret = ftrace_test_record(rec, enable);
384
385 switch (ret) {
386 case FTRACE_UPDATE_IGNORE:
387 return 0;
388
389 case FTRACE_UPDATE_MAKE_CALL:
390 /* converting nop to call */
391 return add_brk_on_nop(rec);
392
393 case FTRACE_UPDATE_MODIFY_CALL:
394 case FTRACE_UPDATE_MAKE_NOP:
395 /* converting a call to a nop */
396 return add_brk_on_call(rec, ftrace_addr);
397 }
398 return 0;
399}
400
401/*
402 * On error, we need to remove breakpoints. This needs to
403 * be done caefully. If the address does not currently have a
404 * breakpoint, we know we are done. Otherwise, we look at the
405 * remaining 4 bytes of the instruction. If it matches a nop
406 * we replace the breakpoint with the nop. Otherwise we replace
407 * it with the call instruction.
408 */
409static int remove_breakpoint(struct dyn_ftrace *rec)
410{
411 unsigned char ins[MCOUNT_INSN_SIZE];
412 unsigned char brk = BREAKPOINT_INSTRUCTION;
413 const unsigned char *nop;
414 unsigned long ftrace_addr;
415 unsigned long ip = rec->ip;
416
417 /* If we fail the read, just give up */
418 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
419 return -EFAULT;
420
421 /* If this does not have a breakpoint, we are done */
422 if (ins[0] != brk)
423 return 0;
424
425 nop = ftrace_nop_replace();
426
427 /*
428 * If the last 4 bytes of the instruction do not match
429 * a nop, then we assume that this is a call to ftrace_addr.
430 */
431 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
432 /*
433 * For extra paranoidism, we check if the breakpoint is on
434 * a call that would actually jump to the ftrace_addr.
435 * If not, don't touch the breakpoint, we make just create
436 * a disaster.
437 */
438 ftrace_addr = ftrace_get_addr_new(rec);
439 nop = ftrace_call_replace(ip, ftrace_addr);
440
441 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
442 goto update;
443
444 /* Check both ftrace_addr and ftrace_old_addr */
445 ftrace_addr = ftrace_get_addr_curr(rec);
446 nop = ftrace_call_replace(ip, ftrace_addr);
447
448 ftrace_expected = nop;
449
450 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
451 return -EINVAL;
452 }
453
454 update:
455 return ftrace_write(ip, nop, 1);
456}
457
458static int add_update_code(unsigned long ip, unsigned const char *new)
459{
460 /* skip breakpoint */
461 ip++;
462 new++;
463 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
464}
465
466static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
467{
468 unsigned long ip = rec->ip;
469 unsigned const char *new;
470
471 new = ftrace_call_replace(ip, addr);
472 return add_update_code(ip, new);
473}
474
475static int add_update_nop(struct dyn_ftrace *rec)
476{
477 unsigned long ip = rec->ip;
478 unsigned const char *new;
479
480 new = ftrace_nop_replace();
481 return add_update_code(ip, new);
482}
483
484static int add_update(struct dyn_ftrace *rec, bool enable)
485{
486 unsigned long ftrace_addr;
487 int ret;
488
489 ret = ftrace_test_record(rec, enable);
490
491 ftrace_addr = ftrace_get_addr_new(rec);
492
493 switch (ret) {
494 case FTRACE_UPDATE_IGNORE:
495 return 0;
496
497 case FTRACE_UPDATE_MODIFY_CALL:
498 case FTRACE_UPDATE_MAKE_CALL:
499 /* converting nop to call */
500 return add_update_call(rec, ftrace_addr);
501
502 case FTRACE_UPDATE_MAKE_NOP:
503 /* converting a call to a nop */
504 return add_update_nop(rec);
505 }
506
507 return 0;
508}
509
510static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
511{
512 unsigned long ip = rec->ip;
513 unsigned const char *new;
514
515 new = ftrace_call_replace(ip, addr);
516
517 return ftrace_write(ip, new, 1);
518}
519
520static int finish_update_nop(struct dyn_ftrace *rec)
521{
522 unsigned long ip = rec->ip;
523 unsigned const char *new;
524
525 new = ftrace_nop_replace();
526
527 return ftrace_write(ip, new, 1);
528}
529
530static int finish_update(struct dyn_ftrace *rec, bool enable)
531{
532 unsigned long ftrace_addr;
533 int ret;
534
535 ret = ftrace_update_record(rec, enable);
536
537 ftrace_addr = ftrace_get_addr_new(rec);
538
539 switch (ret) {
540 case FTRACE_UPDATE_IGNORE:
541 return 0;
542
543 case FTRACE_UPDATE_MODIFY_CALL:
544 case FTRACE_UPDATE_MAKE_CALL:
545 /* converting nop to call */
546 return finish_update_call(rec, ftrace_addr);
547
548 case FTRACE_UPDATE_MAKE_NOP:
549 /* converting a call to a nop */
550 return finish_update_nop(rec);
551 }
552
553 return 0;
554}
555
556static void do_sync_core(void *data)
557{
558 sync_core();
559}
560
561static void run_sync(void)
562{
563 int enable_irqs;
564
565 /* No need to sync if there's only one CPU */
566 if (num_online_cpus() == 1)
567 return;
568
569 enable_irqs = irqs_disabled();
570
571 /* We may be called with interrupts disabled (on bootup). */
572 if (enable_irqs)
573 local_irq_enable();
574 on_each_cpu(do_sync_core, NULL, 1);
575 if (enable_irqs)
576 local_irq_disable();
577}
578
579void ftrace_replace_code(int enable)
580{
581 struct ftrace_rec_iter *iter;
582 struct dyn_ftrace *rec;
583 const char *report = "adding breakpoints";
584 int count = 0;
585 int ret;
586
587 for_ftrace_rec_iter(iter) {
588 rec = ftrace_rec_iter_record(iter);
589
590 ret = add_breakpoints(rec, enable);
591 if (ret)
592 goto remove_breakpoints;
593 count++;
594 }
595
596 run_sync();
597
598 report = "updating code";
599 count = 0;
600
601 for_ftrace_rec_iter(iter) {
602 rec = ftrace_rec_iter_record(iter);
603
604 ret = add_update(rec, enable);
605 if (ret)
606 goto remove_breakpoints;
607 count++;
608 }
609
610 run_sync();
611
612 report = "removing breakpoints";
613 count = 0;
614
615 for_ftrace_rec_iter(iter) {
616 rec = ftrace_rec_iter_record(iter);
617
618 ret = finish_update(rec, enable);
619 if (ret)
620 goto remove_breakpoints;
621 count++;
622 }
623
624 run_sync();
625
626 return;
627
628 remove_breakpoints:
629 pr_warn("Failed on %s (%d):\n", report, count);
630 ftrace_bug(ret, rec);
631 for_ftrace_rec_iter(iter) {
632 rec = ftrace_rec_iter_record(iter);
633 /*
634 * Breakpoints are handled only when this function is in
635 * progress. The system could not work with them.
636 */
637 if (remove_breakpoint(rec))
638 BUG();
639 }
640 run_sync();
641}
642
643static int
644ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
645 unsigned const char *new_code)
646{
647 int ret;
648
649 ret = add_break(ip, old_code);
650 if (ret)
651 goto out;
652
653 run_sync();
654
655 ret = add_update_code(ip, new_code);
656 if (ret)
657 goto fail_update;
658
659 run_sync();
660
661 ret = ftrace_write(ip, new_code, 1);
662 /*
663 * The breakpoint is handled only when this function is in progress.
664 * The system could not work if we could not remove it.
665 */
666 BUG_ON(ret);
667 out:
668 run_sync();
669 return ret;
670
671 fail_update:
672 /* Also here the system could not work with the breakpoint */
673 if (ftrace_write(ip, old_code, 1))
674 BUG();
675 goto out;
676}
677
678void arch_ftrace_update_code(int command)
679{
680 /* See comment above by declaration of modifying_ftrace_code */
681 atomic_inc(&modifying_ftrace_code);
682
683 ftrace_modify_all_code(command);
684
685 atomic_dec(&modifying_ftrace_code);
686}
687
688int __init ftrace_dyn_arch_init(void)
689{
690 return 0;
691}
692
693/* Currently only x86_64 supports dynamic trampolines */
694#ifdef CONFIG_X86_64
695
696#ifdef CONFIG_MODULES
697#include <linux/moduleloader.h>
698/* Module allocation simplifies allocating memory for code */
699static inline void *alloc_tramp(unsigned long size)
700{
701 return module_alloc(size);
702}
703static inline void tramp_free(void *tramp)
704{
705 module_memfree(tramp);
706}
707#else
708/* Trampolines can only be created if modules are supported */
709static inline void *alloc_tramp(unsigned long size)
710{
711 return NULL;
712}
713static inline void tramp_free(void *tramp) { }
714#endif
715
716/* Defined as markers to the end of the ftrace default trampolines */
717extern void ftrace_regs_caller_end(void);
718extern void ftrace_epilogue(void);
719extern void ftrace_caller_op_ptr(void);
720extern void ftrace_regs_caller_op_ptr(void);
721
722/* movq function_trace_op(%rip), %rdx */
723/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
724#define OP_REF_SIZE 7
725
726/*
727 * The ftrace_ops is passed to the function callback. Since the
728 * trampoline only services a single ftrace_ops, we can pass in
729 * that ops directly.
730 *
731 * The ftrace_op_code_union is used to create a pointer to the
732 * ftrace_ops that will be passed to the callback function.
733 */
734union ftrace_op_code_union {
735 char code[OP_REF_SIZE];
736 struct {
737 char op[3];
738 int offset;
739 } __attribute__((packed));
740};
741
742#define RET_SIZE 1
743
744static unsigned long
745create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
746{
747 unsigned long start_offset;
748 unsigned long end_offset;
749 unsigned long op_offset;
750 unsigned long offset;
751 unsigned long npages;
752 unsigned long size;
753 unsigned long retq;
754 unsigned long *ptr;
755 void *trampoline;
756 void *ip;
757 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
758 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
759 union ftrace_op_code_union op_ptr;
760 int ret;
761
762 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
763 start_offset = (unsigned long)ftrace_regs_caller;
764 end_offset = (unsigned long)ftrace_regs_caller_end;
765 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
766 } else {
767 start_offset = (unsigned long)ftrace_caller;
768 end_offset = (unsigned long)ftrace_epilogue;
769 op_offset = (unsigned long)ftrace_caller_op_ptr;
770 }
771
772 size = end_offset - start_offset;
773
774 /*
775 * Allocate enough size to store the ftrace_caller code,
776 * the iret , as well as the address of the ftrace_ops this
777 * trampoline is used for.
778 */
779 trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
780 if (!trampoline)
781 return 0;
782
783 *tramp_size = size + RET_SIZE + sizeof(void *);
784 npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
785
786 /* Copy ftrace_caller onto the trampoline memory */
787 ret = probe_kernel_read(trampoline, (void *)start_offset, size);
788 if (WARN_ON(ret < 0))
789 goto fail;
790
791 ip = trampoline + size;
792
793 /* The trampoline ends with ret(q) */
794 retq = (unsigned long)ftrace_stub;
795 ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
796 if (WARN_ON(ret < 0))
797 goto fail;
798
799 /*
800 * The address of the ftrace_ops that is used for this trampoline
801 * is stored at the end of the trampoline. This will be used to
802 * load the third parameter for the callback. Basically, that
803 * location at the end of the trampoline takes the place of
804 * the global function_trace_op variable.
805 */
806
807 ptr = (unsigned long *)(trampoline + size + RET_SIZE);
808 *ptr = (unsigned long)ops;
809
810 op_offset -= start_offset;
811 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
812
813 /* Are we pointing to the reference? */
814 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
815 goto fail;
816
817 /* Load the contents of ptr into the callback parameter */
818 offset = (unsigned long)ptr;
819 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
820
821 op_ptr.offset = offset;
822
823 /* put in the new offset to the ftrace_ops */
824 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
825
826 /* ALLOC_TRAMP flags lets us know we created it */
827 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
828
829 set_vm_flush_reset_perms(trampoline);
830
831 /*
832 * Module allocation needs to be completed by making the page
833 * executable. The page is still writable, which is a security hazard,
834 * but anyhow ftrace breaks W^X completely.
835 */
836 set_memory_x((unsigned long)trampoline, npages);
837 return (unsigned long)trampoline;
838fail:
839 tramp_free(trampoline);
840 return 0;
841}
842
843static unsigned long calc_trampoline_call_offset(bool save_regs)
844{
845 unsigned long start_offset;
846 unsigned long call_offset;
847
848 if (save_regs) {
849 start_offset = (unsigned long)ftrace_regs_caller;
850 call_offset = (unsigned long)ftrace_regs_call;
851 } else {
852 start_offset = (unsigned long)ftrace_caller;
853 call_offset = (unsigned long)ftrace_call;
854 }
855
856 return call_offset - start_offset;
857}
858
859void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
860{
861 ftrace_func_t func;
862 unsigned char *new;
863 unsigned long offset;
864 unsigned long ip;
865 unsigned int size;
866 int ret, npages;
867
868 if (ops->trampoline) {
869 /*
870 * The ftrace_ops caller may set up its own trampoline.
871 * In such a case, this code must not modify it.
872 */
873 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
874 return;
875 npages = PAGE_ALIGN(ops->trampoline_size) >> PAGE_SHIFT;
876 set_memory_rw(ops->trampoline, npages);
877 } else {
878 ops->trampoline = create_trampoline(ops, &size);
879 if (!ops->trampoline)
880 return;
881 ops->trampoline_size = size;
882 npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
883 }
884
885 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
886 ip = ops->trampoline + offset;
887
888 func = ftrace_ops_get_func(ops);
889
890 ftrace_update_func_call = (unsigned long)func;
891
892 /* Do a safe modify in case the trampoline is executing */
893 new = ftrace_call_replace(ip, (unsigned long)func);
894 ret = update_ftrace_func(ip, new);
895 set_memory_ro(ops->trampoline, npages);
896
897 /* The update should never fail */
898 WARN_ON(ret);
899}
900
901/* Return the address of the function the trampoline calls */
902static void *addr_from_call(void *ptr)
903{
904 union ftrace_code_union calc;
905 int ret;
906
907 ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
908 if (WARN_ON_ONCE(ret < 0))
909 return NULL;
910
911 /* Make sure this is a call */
912 if (WARN_ON_ONCE(calc.op != 0xe8)) {
913 pr_warn("Expected e8, got %x\n", calc.op);
914 return NULL;
915 }
916
917 return ptr + MCOUNT_INSN_SIZE + calc.offset;
918}
919
920void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
921 unsigned long frame_pointer);
922
923/*
924 * If the ops->trampoline was not allocated, then it probably
925 * has a static trampoline func, or is the ftrace caller itself.
926 */
927static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
928{
929 unsigned long offset;
930 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
931 void *ptr;
932
933 if (ops && ops->trampoline) {
934#ifdef CONFIG_FUNCTION_GRAPH_TRACER
935 /*
936 * We only know about function graph tracer setting as static
937 * trampoline.
938 */
939 if (ops->trampoline == FTRACE_GRAPH_ADDR)
940 return (void *)prepare_ftrace_return;
941#endif
942 return NULL;
943 }
944
945 offset = calc_trampoline_call_offset(save_regs);
946
947 if (save_regs)
948 ptr = (void *)FTRACE_REGS_ADDR + offset;
949 else
950 ptr = (void *)FTRACE_ADDR + offset;
951
952 return addr_from_call(ptr);
953}
954
955void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
956{
957 unsigned long offset;
958
959 /* If we didn't allocate this trampoline, consider it static */
960 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
961 return static_tramp_func(ops, rec);
962
963 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
964 return addr_from_call((void *)ops->trampoline + offset);
965}
966
967void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
968{
969 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
970 return;
971
972 tramp_free((void *)ops->trampoline);
973 ops->trampoline = 0;
974}
975
976#endif /* CONFIG_X86_64 */
977#endif /* CONFIG_DYNAMIC_FTRACE */
978
979#ifdef CONFIG_FUNCTION_GRAPH_TRACER
980
981#ifdef CONFIG_DYNAMIC_FTRACE
982extern void ftrace_graph_call(void);
983
984static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
985{
986 return ftrace_text_replace(0xe9, ip, addr);
987}
988
989static int ftrace_mod_jmp(unsigned long ip, void *func)
990{
991 unsigned char *new;
992
993 ftrace_update_func_call = 0UL;
994 new = ftrace_jmp_replace(ip, (unsigned long)func);
995
996 return update_ftrace_func(ip, new);
997}
998
999int ftrace_enable_ftrace_graph_caller(void)
1000{
1001 unsigned long ip = (unsigned long)(&ftrace_graph_call);
1002
1003 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
1004}
1005
1006int ftrace_disable_ftrace_graph_caller(void)
1007{
1008 unsigned long ip = (unsigned long)(&ftrace_graph_call);
1009
1010 return ftrace_mod_jmp(ip, &ftrace_stub);
1011}
1012
1013#endif /* !CONFIG_DYNAMIC_FTRACE */
1014
1015/*
1016 * Hook the return address and push it in the stack of return addrs
1017 * in current thread info.
1018 */
1019void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
1020 unsigned long frame_pointer)
1021{
1022 unsigned long old;
1023 int faulted;
1024 unsigned long return_hooker = (unsigned long)
1025 &return_to_handler;
1026
1027 /*
1028 * When resuming from suspend-to-ram, this function can be indirectly
1029 * called from early CPU startup code while the CPU is in real mode,
1030 * which would fail miserably. Make sure the stack pointer is a
1031 * virtual address.
1032 *
1033 * This check isn't as accurate as virt_addr_valid(), but it should be
1034 * good enough for this purpose, and it's fast.
1035 */
1036 if (unlikely((long)__builtin_frame_address(0) >= 0))
1037 return;
1038
1039 if (unlikely(ftrace_graph_is_dead()))
1040 return;
1041
1042 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
1043 return;
1044
1045 /*
1046 * Protect against fault, even if it shouldn't
1047 * happen. This tool is too much intrusive to
1048 * ignore such a protection.
1049 */
1050 asm volatile(
1051 "1: " _ASM_MOV " (%[parent]), %[old]\n"
1052 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1053 " movl $0, %[faulted]\n"
1054 "3:\n"
1055
1056 ".section .fixup, \"ax\"\n"
1057 "4: movl $1, %[faulted]\n"
1058 " jmp 3b\n"
1059 ".previous\n"
1060
1061 _ASM_EXTABLE(1b, 4b)
1062 _ASM_EXTABLE(2b, 4b)
1063
1064 : [old] "=&r" (old), [faulted] "=r" (faulted)
1065 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1066 : "memory"
1067 );
1068
1069 if (unlikely(faulted)) {
1070 ftrace_graph_stop();
1071 WARN_ON(1);
1072 return;
1073 }
1074
1075 if (function_graph_enter(old, self_addr, frame_pointer, parent))
1076 *parent = old;
1077}
1078#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
1/*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 *
6 * Thanks goes to Ingo Molnar, for suggesting the idea.
7 * Mathieu Desnoyers, for suggesting postponing the modifications.
8 * Arjan van de Ven, for keeping me straight, and explaining to me
9 * the dangers of modifying code on the run.
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#include <linux/spinlock.h>
15#include <linux/hardirq.h>
16#include <linux/uaccess.h>
17#include <linux/ftrace.h>
18#include <linux/percpu.h>
19#include <linux/sched.h>
20#include <linux/slab.h>
21#include <linux/init.h>
22#include <linux/list.h>
23#include <linux/module.h>
24
25#include <trace/syscall.h>
26
27#include <asm/cacheflush.h>
28#include <asm/kprobes.h>
29#include <asm/ftrace.h>
30#include <asm/nops.h>
31
32#ifdef CONFIG_DYNAMIC_FTRACE
33
34int ftrace_arch_code_modify_prepare(void)
35{
36 set_kernel_text_rw();
37 set_all_modules_text_rw();
38 return 0;
39}
40
41int ftrace_arch_code_modify_post_process(void)
42{
43 set_all_modules_text_ro();
44 set_kernel_text_ro();
45 return 0;
46}
47
48union ftrace_code_union {
49 char code[MCOUNT_INSN_SIZE];
50 struct {
51 unsigned char e8;
52 int offset;
53 } __attribute__((packed));
54};
55
56static int ftrace_calc_offset(long ip, long addr)
57{
58 return (int)(addr - ip);
59}
60
61static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
62{
63 static union ftrace_code_union calc;
64
65 calc.e8 = 0xe8;
66 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
67
68 /*
69 * No locking needed, this must be called via kstop_machine
70 * which in essence is like running on a uniprocessor machine.
71 */
72 return calc.code;
73}
74
75static inline int
76within(unsigned long addr, unsigned long start, unsigned long end)
77{
78 return addr >= start && addr < end;
79}
80
81static unsigned long text_ip_addr(unsigned long ip)
82{
83 /*
84 * On x86_64, kernel text mappings are mapped read-only, so we use
85 * the kernel identity mapping instead of the kernel text mapping
86 * to modify the kernel text.
87 *
88 * For 32bit kernels, these mappings are same and we can use
89 * kernel identity mapping to modify code.
90 */
91 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
92 ip = (unsigned long)__va(__pa_symbol(ip));
93
94 return ip;
95}
96
97static const unsigned char *ftrace_nop_replace(void)
98{
99 return ideal_nops[NOP_ATOMIC5];
100}
101
102static int
103ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
104 unsigned const char *new_code)
105{
106 unsigned char replaced[MCOUNT_INSN_SIZE];
107
108 ftrace_expected = old_code;
109
110 /*
111 * Note:
112 * We are paranoid about modifying text, as if a bug was to happen, it
113 * could cause us to read or write to someplace that could cause harm.
114 * Carefully read and modify the code with probe_kernel_*(), and make
115 * sure what we read is what we expected it to be before modifying it.
116 */
117
118 /* read the text we want to modify */
119 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
120 return -EFAULT;
121
122 /* Make sure it is what we expect it to be */
123 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
124 return -EINVAL;
125
126 ip = text_ip_addr(ip);
127
128 /* replace the text with the new text */
129 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
130 return -EPERM;
131
132 sync_core();
133
134 return 0;
135}
136
137int ftrace_make_nop(struct module *mod,
138 struct dyn_ftrace *rec, unsigned long addr)
139{
140 unsigned const char *new, *old;
141 unsigned long ip = rec->ip;
142
143 old = ftrace_call_replace(ip, addr);
144 new = ftrace_nop_replace();
145
146 /*
147 * On boot up, and when modules are loaded, the MCOUNT_ADDR
148 * is converted to a nop, and will never become MCOUNT_ADDR
149 * again. This code is either running before SMP (on boot up)
150 * or before the code will ever be executed (module load).
151 * We do not want to use the breakpoint version in this case,
152 * just modify the code directly.
153 */
154 if (addr == MCOUNT_ADDR)
155 return ftrace_modify_code_direct(rec->ip, old, new);
156
157 ftrace_expected = NULL;
158
159 /* Normal cases use add_brk_on_nop */
160 WARN_ONCE(1, "invalid use of ftrace_make_nop");
161 return -EINVAL;
162}
163
164int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
165{
166 unsigned const char *new, *old;
167 unsigned long ip = rec->ip;
168
169 old = ftrace_nop_replace();
170 new = ftrace_call_replace(ip, addr);
171
172 /* Should only be called when module is loaded */
173 return ftrace_modify_code_direct(rec->ip, old, new);
174}
175
176/*
177 * The modifying_ftrace_code is used to tell the breakpoint
178 * handler to call ftrace_int3_handler(). If it fails to
179 * call this handler for a breakpoint added by ftrace, then
180 * the kernel may crash.
181 *
182 * As atomic_writes on x86 do not need a barrier, we do not
183 * need to add smp_mb()s for this to work. It is also considered
184 * that we can not read the modifying_ftrace_code before
185 * executing the breakpoint. That would be quite remarkable if
186 * it could do that. Here's the flow that is required:
187 *
188 * CPU-0 CPU-1
189 *
190 * atomic_inc(mfc);
191 * write int3s
192 * <trap-int3> // implicit (r)mb
193 * if (atomic_read(mfc))
194 * call ftrace_int3_handler()
195 *
196 * Then when we are finished:
197 *
198 * atomic_dec(mfc);
199 *
200 * If we hit a breakpoint that was not set by ftrace, it does not
201 * matter if ftrace_int3_handler() is called or not. It will
202 * simply be ignored. But it is crucial that a ftrace nop/caller
203 * breakpoint is handled. No other user should ever place a
204 * breakpoint on an ftrace nop/caller location. It must only
205 * be done by this code.
206 */
207atomic_t modifying_ftrace_code __read_mostly;
208
209static int
210ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
211 unsigned const char *new_code);
212
213/*
214 * Should never be called:
215 * As it is only called by __ftrace_replace_code() which is called by
216 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
217 * which is called to turn mcount into nops or nops into function calls
218 * but not to convert a function from not using regs to one that uses
219 * regs, which ftrace_modify_call() is for.
220 */
221int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
222 unsigned long addr)
223{
224 WARN_ON(1);
225 ftrace_expected = NULL;
226 return -EINVAL;
227}
228
229static unsigned long ftrace_update_func;
230
231static int update_ftrace_func(unsigned long ip, void *new)
232{
233 unsigned char old[MCOUNT_INSN_SIZE];
234 int ret;
235
236 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
237
238 ftrace_update_func = ip;
239 /* Make sure the breakpoints see the ftrace_update_func update */
240 smp_wmb();
241
242 /* See comment above by declaration of modifying_ftrace_code */
243 atomic_inc(&modifying_ftrace_code);
244
245 ret = ftrace_modify_code(ip, old, new);
246
247 atomic_dec(&modifying_ftrace_code);
248
249 return ret;
250}
251
252int ftrace_update_ftrace_func(ftrace_func_t func)
253{
254 unsigned long ip = (unsigned long)(&ftrace_call);
255 unsigned char *new;
256 int ret;
257
258 new = ftrace_call_replace(ip, (unsigned long)func);
259 ret = update_ftrace_func(ip, new);
260
261 /* Also update the regs callback function */
262 if (!ret) {
263 ip = (unsigned long)(&ftrace_regs_call);
264 new = ftrace_call_replace(ip, (unsigned long)func);
265 ret = update_ftrace_func(ip, new);
266 }
267
268 return ret;
269}
270
271static int is_ftrace_caller(unsigned long ip)
272{
273 if (ip == ftrace_update_func)
274 return 1;
275
276 return 0;
277}
278
279/*
280 * A breakpoint was added to the code address we are about to
281 * modify, and this is the handle that will just skip over it.
282 * We are either changing a nop into a trace call, or a trace
283 * call to a nop. While the change is taking place, we treat
284 * it just like it was a nop.
285 */
286int ftrace_int3_handler(struct pt_regs *regs)
287{
288 unsigned long ip;
289
290 if (WARN_ON_ONCE(!regs))
291 return 0;
292
293 ip = regs->ip - 1;
294 if (!ftrace_location(ip) && !is_ftrace_caller(ip))
295 return 0;
296
297 regs->ip += MCOUNT_INSN_SIZE - 1;
298
299 return 1;
300}
301
302static int ftrace_write(unsigned long ip, const char *val, int size)
303{
304 ip = text_ip_addr(ip);
305
306 if (probe_kernel_write((void *)ip, val, size))
307 return -EPERM;
308
309 return 0;
310}
311
312static int add_break(unsigned long ip, const char *old)
313{
314 unsigned char replaced[MCOUNT_INSN_SIZE];
315 unsigned char brk = BREAKPOINT_INSTRUCTION;
316
317 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
318 return -EFAULT;
319
320 ftrace_expected = old;
321
322 /* Make sure it is what we expect it to be */
323 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
324 return -EINVAL;
325
326 return ftrace_write(ip, &brk, 1);
327}
328
329static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
330{
331 unsigned const char *old;
332 unsigned long ip = rec->ip;
333
334 old = ftrace_call_replace(ip, addr);
335
336 return add_break(rec->ip, old);
337}
338
339
340static int add_brk_on_nop(struct dyn_ftrace *rec)
341{
342 unsigned const char *old;
343
344 old = ftrace_nop_replace();
345
346 return add_break(rec->ip, old);
347}
348
349static int add_breakpoints(struct dyn_ftrace *rec, int enable)
350{
351 unsigned long ftrace_addr;
352 int ret;
353
354 ftrace_addr = ftrace_get_addr_curr(rec);
355
356 ret = ftrace_test_record(rec, enable);
357
358 switch (ret) {
359 case FTRACE_UPDATE_IGNORE:
360 return 0;
361
362 case FTRACE_UPDATE_MAKE_CALL:
363 /* converting nop to call */
364 return add_brk_on_nop(rec);
365
366 case FTRACE_UPDATE_MODIFY_CALL:
367 case FTRACE_UPDATE_MAKE_NOP:
368 /* converting a call to a nop */
369 return add_brk_on_call(rec, ftrace_addr);
370 }
371 return 0;
372}
373
374/*
375 * On error, we need to remove breakpoints. This needs to
376 * be done caefully. If the address does not currently have a
377 * breakpoint, we know we are done. Otherwise, we look at the
378 * remaining 4 bytes of the instruction. If it matches a nop
379 * we replace the breakpoint with the nop. Otherwise we replace
380 * it with the call instruction.
381 */
382static int remove_breakpoint(struct dyn_ftrace *rec)
383{
384 unsigned char ins[MCOUNT_INSN_SIZE];
385 unsigned char brk = BREAKPOINT_INSTRUCTION;
386 const unsigned char *nop;
387 unsigned long ftrace_addr;
388 unsigned long ip = rec->ip;
389
390 /* If we fail the read, just give up */
391 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
392 return -EFAULT;
393
394 /* If this does not have a breakpoint, we are done */
395 if (ins[0] != brk)
396 return 0;
397
398 nop = ftrace_nop_replace();
399
400 /*
401 * If the last 4 bytes of the instruction do not match
402 * a nop, then we assume that this is a call to ftrace_addr.
403 */
404 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
405 /*
406 * For extra paranoidism, we check if the breakpoint is on
407 * a call that would actually jump to the ftrace_addr.
408 * If not, don't touch the breakpoint, we make just create
409 * a disaster.
410 */
411 ftrace_addr = ftrace_get_addr_new(rec);
412 nop = ftrace_call_replace(ip, ftrace_addr);
413
414 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
415 goto update;
416
417 /* Check both ftrace_addr and ftrace_old_addr */
418 ftrace_addr = ftrace_get_addr_curr(rec);
419 nop = ftrace_call_replace(ip, ftrace_addr);
420
421 ftrace_expected = nop;
422
423 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
424 return -EINVAL;
425 }
426
427 update:
428 return ftrace_write(ip, nop, 1);
429}
430
431static int add_update_code(unsigned long ip, unsigned const char *new)
432{
433 /* skip breakpoint */
434 ip++;
435 new++;
436 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
437}
438
439static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
440{
441 unsigned long ip = rec->ip;
442 unsigned const char *new;
443
444 new = ftrace_call_replace(ip, addr);
445 return add_update_code(ip, new);
446}
447
448static int add_update_nop(struct dyn_ftrace *rec)
449{
450 unsigned long ip = rec->ip;
451 unsigned const char *new;
452
453 new = ftrace_nop_replace();
454 return add_update_code(ip, new);
455}
456
457static int add_update(struct dyn_ftrace *rec, int enable)
458{
459 unsigned long ftrace_addr;
460 int ret;
461
462 ret = ftrace_test_record(rec, enable);
463
464 ftrace_addr = ftrace_get_addr_new(rec);
465
466 switch (ret) {
467 case FTRACE_UPDATE_IGNORE:
468 return 0;
469
470 case FTRACE_UPDATE_MODIFY_CALL:
471 case FTRACE_UPDATE_MAKE_CALL:
472 /* converting nop to call */
473 return add_update_call(rec, ftrace_addr);
474
475 case FTRACE_UPDATE_MAKE_NOP:
476 /* converting a call to a nop */
477 return add_update_nop(rec);
478 }
479
480 return 0;
481}
482
483static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
484{
485 unsigned long ip = rec->ip;
486 unsigned const char *new;
487
488 new = ftrace_call_replace(ip, addr);
489
490 return ftrace_write(ip, new, 1);
491}
492
493static int finish_update_nop(struct dyn_ftrace *rec)
494{
495 unsigned long ip = rec->ip;
496 unsigned const char *new;
497
498 new = ftrace_nop_replace();
499
500 return ftrace_write(ip, new, 1);
501}
502
503static int finish_update(struct dyn_ftrace *rec, int enable)
504{
505 unsigned long ftrace_addr;
506 int ret;
507
508 ret = ftrace_update_record(rec, enable);
509
510 ftrace_addr = ftrace_get_addr_new(rec);
511
512 switch (ret) {
513 case FTRACE_UPDATE_IGNORE:
514 return 0;
515
516 case FTRACE_UPDATE_MODIFY_CALL:
517 case FTRACE_UPDATE_MAKE_CALL:
518 /* converting nop to call */
519 return finish_update_call(rec, ftrace_addr);
520
521 case FTRACE_UPDATE_MAKE_NOP:
522 /* converting a call to a nop */
523 return finish_update_nop(rec);
524 }
525
526 return 0;
527}
528
529static void do_sync_core(void *data)
530{
531 sync_core();
532}
533
534static void run_sync(void)
535{
536 int enable_irqs = irqs_disabled();
537
538 /* We may be called with interrupts disbled (on bootup). */
539 if (enable_irqs)
540 local_irq_enable();
541 on_each_cpu(do_sync_core, NULL, 1);
542 if (enable_irqs)
543 local_irq_disable();
544}
545
546void ftrace_replace_code(int enable)
547{
548 struct ftrace_rec_iter *iter;
549 struct dyn_ftrace *rec;
550 const char *report = "adding breakpoints";
551 int count = 0;
552 int ret;
553
554 for_ftrace_rec_iter(iter) {
555 rec = ftrace_rec_iter_record(iter);
556
557 ret = add_breakpoints(rec, enable);
558 if (ret)
559 goto remove_breakpoints;
560 count++;
561 }
562
563 run_sync();
564
565 report = "updating code";
566 count = 0;
567
568 for_ftrace_rec_iter(iter) {
569 rec = ftrace_rec_iter_record(iter);
570
571 ret = add_update(rec, enable);
572 if (ret)
573 goto remove_breakpoints;
574 count++;
575 }
576
577 run_sync();
578
579 report = "removing breakpoints";
580 count = 0;
581
582 for_ftrace_rec_iter(iter) {
583 rec = ftrace_rec_iter_record(iter);
584
585 ret = finish_update(rec, enable);
586 if (ret)
587 goto remove_breakpoints;
588 count++;
589 }
590
591 run_sync();
592
593 return;
594
595 remove_breakpoints:
596 pr_warn("Failed on %s (%d):\n", report, count);
597 ftrace_bug(ret, rec);
598 for_ftrace_rec_iter(iter) {
599 rec = ftrace_rec_iter_record(iter);
600 /*
601 * Breakpoints are handled only when this function is in
602 * progress. The system could not work with them.
603 */
604 if (remove_breakpoint(rec))
605 BUG();
606 }
607 run_sync();
608}
609
610static int
611ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
612 unsigned const char *new_code)
613{
614 int ret;
615
616 ret = add_break(ip, old_code);
617 if (ret)
618 goto out;
619
620 run_sync();
621
622 ret = add_update_code(ip, new_code);
623 if (ret)
624 goto fail_update;
625
626 run_sync();
627
628 ret = ftrace_write(ip, new_code, 1);
629 /*
630 * The breakpoint is handled only when this function is in progress.
631 * The system could not work if we could not remove it.
632 */
633 BUG_ON(ret);
634 out:
635 run_sync();
636 return ret;
637
638 fail_update:
639 /* Also here the system could not work with the breakpoint */
640 if (ftrace_write(ip, old_code, 1))
641 BUG();
642 goto out;
643}
644
645void arch_ftrace_update_code(int command)
646{
647 /* See comment above by declaration of modifying_ftrace_code */
648 atomic_inc(&modifying_ftrace_code);
649
650 ftrace_modify_all_code(command);
651
652 atomic_dec(&modifying_ftrace_code);
653}
654
655int __init ftrace_dyn_arch_init(void)
656{
657 return 0;
658}
659
660#if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER)
661static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
662{
663 static union ftrace_code_union calc;
664
665 /* Jmp not a call (ignore the .e8) */
666 calc.e8 = 0xe9;
667 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
668
669 /*
670 * ftrace external locks synchronize the access to the static variable.
671 */
672 return calc.code;
673}
674#endif
675
676/* Currently only x86_64 supports dynamic trampolines */
677#ifdef CONFIG_X86_64
678
679#ifdef CONFIG_MODULES
680#include <linux/moduleloader.h>
681/* Module allocation simplifies allocating memory for code */
682static inline void *alloc_tramp(unsigned long size)
683{
684 return module_alloc(size);
685}
686static inline void tramp_free(void *tramp)
687{
688 module_memfree(tramp);
689}
690#else
691/* Trampolines can only be created if modules are supported */
692static inline void *alloc_tramp(unsigned long size)
693{
694 return NULL;
695}
696static inline void tramp_free(void *tramp) { }
697#endif
698
699/* Defined as markers to the end of the ftrace default trampolines */
700extern void ftrace_regs_caller_end(void);
701extern void ftrace_epilogue(void);
702extern void ftrace_caller_op_ptr(void);
703extern void ftrace_regs_caller_op_ptr(void);
704
705/* movq function_trace_op(%rip), %rdx */
706/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
707#define OP_REF_SIZE 7
708
709/*
710 * The ftrace_ops is passed to the function callback. Since the
711 * trampoline only services a single ftrace_ops, we can pass in
712 * that ops directly.
713 *
714 * The ftrace_op_code_union is used to create a pointer to the
715 * ftrace_ops that will be passed to the callback function.
716 */
717union ftrace_op_code_union {
718 char code[OP_REF_SIZE];
719 struct {
720 char op[3];
721 int offset;
722 } __attribute__((packed));
723};
724
725static unsigned long
726create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
727{
728 unsigned const char *jmp;
729 unsigned long start_offset;
730 unsigned long end_offset;
731 unsigned long op_offset;
732 unsigned long offset;
733 unsigned long size;
734 unsigned long ip;
735 unsigned long *ptr;
736 void *trampoline;
737 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
738 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
739 union ftrace_op_code_union op_ptr;
740 int ret;
741
742 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
743 start_offset = (unsigned long)ftrace_regs_caller;
744 end_offset = (unsigned long)ftrace_regs_caller_end;
745 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
746 } else {
747 start_offset = (unsigned long)ftrace_caller;
748 end_offset = (unsigned long)ftrace_epilogue;
749 op_offset = (unsigned long)ftrace_caller_op_ptr;
750 }
751
752 size = end_offset - start_offset;
753
754 /*
755 * Allocate enough size to store the ftrace_caller code,
756 * the jmp to ftrace_epilogue, as well as the address of
757 * the ftrace_ops this trampoline is used for.
758 */
759 trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *));
760 if (!trampoline)
761 return 0;
762
763 *tramp_size = size + MCOUNT_INSN_SIZE + sizeof(void *);
764
765 /* Copy ftrace_caller onto the trampoline memory */
766 ret = probe_kernel_read(trampoline, (void *)start_offset, size);
767 if (WARN_ON(ret < 0)) {
768 tramp_free(trampoline);
769 return 0;
770 }
771
772 ip = (unsigned long)trampoline + size;
773
774 /* The trampoline ends with a jmp to ftrace_epilogue */
775 jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_epilogue);
776 memcpy(trampoline + size, jmp, MCOUNT_INSN_SIZE);
777
778 /*
779 * The address of the ftrace_ops that is used for this trampoline
780 * is stored at the end of the trampoline. This will be used to
781 * load the third parameter for the callback. Basically, that
782 * location at the end of the trampoline takes the place of
783 * the global function_trace_op variable.
784 */
785
786 ptr = (unsigned long *)(trampoline + size + MCOUNT_INSN_SIZE);
787 *ptr = (unsigned long)ops;
788
789 op_offset -= start_offset;
790 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
791
792 /* Are we pointing to the reference? */
793 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) {
794 tramp_free(trampoline);
795 return 0;
796 }
797
798 /* Load the contents of ptr into the callback parameter */
799 offset = (unsigned long)ptr;
800 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
801
802 op_ptr.offset = offset;
803
804 /* put in the new offset to the ftrace_ops */
805 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
806
807 /* ALLOC_TRAMP flags lets us know we created it */
808 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
809
810 return (unsigned long)trampoline;
811}
812
813static unsigned long calc_trampoline_call_offset(bool save_regs)
814{
815 unsigned long start_offset;
816 unsigned long call_offset;
817
818 if (save_regs) {
819 start_offset = (unsigned long)ftrace_regs_caller;
820 call_offset = (unsigned long)ftrace_regs_call;
821 } else {
822 start_offset = (unsigned long)ftrace_caller;
823 call_offset = (unsigned long)ftrace_call;
824 }
825
826 return call_offset - start_offset;
827}
828
829void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
830{
831 ftrace_func_t func;
832 unsigned char *new;
833 unsigned long offset;
834 unsigned long ip;
835 unsigned int size;
836 int ret;
837
838 if (ops->trampoline) {
839 /*
840 * The ftrace_ops caller may set up its own trampoline.
841 * In such a case, this code must not modify it.
842 */
843 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
844 return;
845 } else {
846 ops->trampoline = create_trampoline(ops, &size);
847 if (!ops->trampoline)
848 return;
849 ops->trampoline_size = size;
850 }
851
852 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
853 ip = ops->trampoline + offset;
854
855 func = ftrace_ops_get_func(ops);
856
857 /* Do a safe modify in case the trampoline is executing */
858 new = ftrace_call_replace(ip, (unsigned long)func);
859 ret = update_ftrace_func(ip, new);
860
861 /* The update should never fail */
862 WARN_ON(ret);
863}
864
865/* Return the address of the function the trampoline calls */
866static void *addr_from_call(void *ptr)
867{
868 union ftrace_code_union calc;
869 int ret;
870
871 ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
872 if (WARN_ON_ONCE(ret < 0))
873 return NULL;
874
875 /* Make sure this is a call */
876 if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
877 pr_warn("Expected e8, got %x\n", calc.e8);
878 return NULL;
879 }
880
881 return ptr + MCOUNT_INSN_SIZE + calc.offset;
882}
883
884void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
885 unsigned long frame_pointer);
886
887/*
888 * If the ops->trampoline was not allocated, then it probably
889 * has a static trampoline func, or is the ftrace caller itself.
890 */
891static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
892{
893 unsigned long offset;
894 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
895 void *ptr;
896
897 if (ops && ops->trampoline) {
898#ifdef CONFIG_FUNCTION_GRAPH_TRACER
899 /*
900 * We only know about function graph tracer setting as static
901 * trampoline.
902 */
903 if (ops->trampoline == FTRACE_GRAPH_ADDR)
904 return (void *)prepare_ftrace_return;
905#endif
906 return NULL;
907 }
908
909 offset = calc_trampoline_call_offset(save_regs);
910
911 if (save_regs)
912 ptr = (void *)FTRACE_REGS_ADDR + offset;
913 else
914 ptr = (void *)FTRACE_ADDR + offset;
915
916 return addr_from_call(ptr);
917}
918
919void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
920{
921 unsigned long offset;
922
923 /* If we didn't allocate this trampoline, consider it static */
924 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
925 return static_tramp_func(ops, rec);
926
927 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
928 return addr_from_call((void *)ops->trampoline + offset);
929}
930
931void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
932{
933 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
934 return;
935
936 tramp_free((void *)ops->trampoline);
937 ops->trampoline = 0;
938}
939
940#endif /* CONFIG_X86_64 */
941#endif /* CONFIG_DYNAMIC_FTRACE */
942
943#ifdef CONFIG_FUNCTION_GRAPH_TRACER
944
945#ifdef CONFIG_DYNAMIC_FTRACE
946extern void ftrace_graph_call(void);
947
948static int ftrace_mod_jmp(unsigned long ip, void *func)
949{
950 unsigned char *new;
951
952 new = ftrace_jmp_replace(ip, (unsigned long)func);
953
954 return update_ftrace_func(ip, new);
955}
956
957int ftrace_enable_ftrace_graph_caller(void)
958{
959 unsigned long ip = (unsigned long)(&ftrace_graph_call);
960
961 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
962}
963
964int ftrace_disable_ftrace_graph_caller(void)
965{
966 unsigned long ip = (unsigned long)(&ftrace_graph_call);
967
968 return ftrace_mod_jmp(ip, &ftrace_stub);
969}
970
971#endif /* !CONFIG_DYNAMIC_FTRACE */
972
973/*
974 * Hook the return address and push it in the stack of return addrs
975 * in current thread info.
976 */
977void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
978 unsigned long frame_pointer)
979{
980 unsigned long old;
981 int faulted;
982 struct ftrace_graph_ent trace;
983 unsigned long return_hooker = (unsigned long)
984 &return_to_handler;
985
986 if (unlikely(ftrace_graph_is_dead()))
987 return;
988
989 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
990 return;
991
992 /*
993 * Protect against fault, even if it shouldn't
994 * happen. This tool is too much intrusive to
995 * ignore such a protection.
996 */
997 asm volatile(
998 "1: " _ASM_MOV " (%[parent]), %[old]\n"
999 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1000 " movl $0, %[faulted]\n"
1001 "3:\n"
1002
1003 ".section .fixup, \"ax\"\n"
1004 "4: movl $1, %[faulted]\n"
1005 " jmp 3b\n"
1006 ".previous\n"
1007
1008 _ASM_EXTABLE(1b, 4b)
1009 _ASM_EXTABLE(2b, 4b)
1010
1011 : [old] "=&r" (old), [faulted] "=r" (faulted)
1012 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1013 : "memory"
1014 );
1015
1016 if (unlikely(faulted)) {
1017 ftrace_graph_stop();
1018 WARN_ON(1);
1019 return;
1020 }
1021
1022 trace.func = self_addr;
1023 trace.depth = current->curr_ret_stack + 1;
1024
1025 /* Only trace if the calling function expects to */
1026 if (!ftrace_graph_entry(&trace)) {
1027 *parent = old;
1028 return;
1029 }
1030
1031 if (ftrace_push_return_trace(old, self_addr, &trace.depth,
1032 frame_pointer) == -EBUSY) {
1033 *parent = old;
1034 return;
1035 }
1036}
1037#endif /* CONFIG_FUNCTION_GRAPH_TRACER */