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