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1/*
2 * Code for replacing ftrace calls with jumps.
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/init.h>
21#include <linux/list.h>
22#include <linux/module.h>
23
24#include <trace/syscall.h>
25
26#include <asm/cacheflush.h>
27#include <asm/kprobes.h>
28#include <asm/ftrace.h>
29#include <asm/nops.h>
30
31#ifdef CONFIG_DYNAMIC_FTRACE
32
33int ftrace_arch_code_modify_prepare(void)
34{
35 set_kernel_text_rw();
36 set_all_modules_text_rw();
37 return 0;
38}
39
40int ftrace_arch_code_modify_post_process(void)
41{
42 set_all_modules_text_ro();
43 set_kernel_text_ro();
44 return 0;
45}
46
47union ftrace_code_union {
48 char code[MCOUNT_INSN_SIZE];
49 struct {
50 char e8;
51 int offset;
52 } __attribute__((packed));
53};
54
55static int ftrace_calc_offset(long ip, long addr)
56{
57 return (int)(addr - ip);
58}
59
60static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
61{
62 static union ftrace_code_union calc;
63
64 calc.e8 = 0xe8;
65 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
66
67 /*
68 * No locking needed, this must be called via kstop_machine
69 * which in essence is like running on a uniprocessor machine.
70 */
71 return calc.code;
72}
73
74static inline int
75within(unsigned long addr, unsigned long start, unsigned long end)
76{
77 return addr >= start && addr < end;
78}
79
80static int
81do_ftrace_mod_code(unsigned long ip, const void *new_code)
82{
83 /*
84 * On x86_64, kernel text mappings are mapped read-only with
85 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
86 * of the kernel text mapping 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(ip));
93
94 return probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE);
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 /*
109 * Note: Due to modules and __init, code can
110 * disappear and change, we need to protect against faulting
111 * as well as code changing. We do this by using the
112 * probe_kernel_* functions.
113 *
114 * No real locking needed, this code is run through
115 * kstop_machine, or before SMP starts.
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 /* replace the text with the new text */
127 if (do_ftrace_mod_code(ip, new_code))
128 return -EPERM;
129
130 sync_core();
131
132 return 0;
133}
134
135int ftrace_make_nop(struct module *mod,
136 struct dyn_ftrace *rec, unsigned long addr)
137{
138 unsigned const char *new, *old;
139 unsigned long ip = rec->ip;
140
141 old = ftrace_call_replace(ip, addr);
142 new = ftrace_nop_replace();
143
144 /*
145 * On boot up, and when modules are loaded, the MCOUNT_ADDR
146 * is converted to a nop, and will never become MCOUNT_ADDR
147 * again. This code is either running before SMP (on boot up)
148 * or before the code will ever be executed (module load).
149 * We do not want to use the breakpoint version in this case,
150 * just modify the code directly.
151 */
152 if (addr == MCOUNT_ADDR)
153 return ftrace_modify_code_direct(rec->ip, old, new);
154
155 /* Normal cases use add_brk_on_nop */
156 WARN_ONCE(1, "invalid use of ftrace_make_nop");
157 return -EINVAL;
158}
159
160int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
161{
162 unsigned const char *new, *old;
163 unsigned long ip = rec->ip;
164
165 old = ftrace_nop_replace();
166 new = ftrace_call_replace(ip, addr);
167
168 /* Should only be called when module is loaded */
169 return ftrace_modify_code_direct(rec->ip, old, new);
170}
171
172/*
173 * The modifying_ftrace_code is used to tell the breakpoint
174 * handler to call ftrace_int3_handler(). If it fails to
175 * call this handler for a breakpoint added by ftrace, then
176 * the kernel may crash.
177 *
178 * As atomic_writes on x86 do not need a barrier, we do not
179 * need to add smp_mb()s for this to work. It is also considered
180 * that we can not read the modifying_ftrace_code before
181 * executing the breakpoint. That would be quite remarkable if
182 * it could do that. Here's the flow that is required:
183 *
184 * CPU-0 CPU-1
185 *
186 * atomic_inc(mfc);
187 * write int3s
188 * <trap-int3> // implicit (r)mb
189 * if (atomic_read(mfc))
190 * call ftrace_int3_handler()
191 *
192 * Then when we are finished:
193 *
194 * atomic_dec(mfc);
195 *
196 * If we hit a breakpoint that was not set by ftrace, it does not
197 * matter if ftrace_int3_handler() is called or not. It will
198 * simply be ignored. But it is crucial that a ftrace nop/caller
199 * breakpoint is handled. No other user should ever place a
200 * breakpoint on an ftrace nop/caller location. It must only
201 * be done by this code.
202 */
203atomic_t modifying_ftrace_code __read_mostly;
204
205static int
206ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
207 unsigned const char *new_code);
208
209int ftrace_update_ftrace_func(ftrace_func_t func)
210{
211 unsigned long ip = (unsigned long)(&ftrace_call);
212 unsigned char old[MCOUNT_INSN_SIZE], *new;
213 int ret;
214
215 memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
216 new = ftrace_call_replace(ip, (unsigned long)func);
217
218 /* See comment above by declaration of modifying_ftrace_code */
219 atomic_inc(&modifying_ftrace_code);
220
221 ret = ftrace_modify_code(ip, old, new);
222
223 atomic_dec(&modifying_ftrace_code);
224
225 return ret;
226}
227
228/*
229 * A breakpoint was added to the code address we are about to
230 * modify, and this is the handle that will just skip over it.
231 * We are either changing a nop into a trace call, or a trace
232 * call to a nop. While the change is taking place, we treat
233 * it just like it was a nop.
234 */
235int ftrace_int3_handler(struct pt_regs *regs)
236{
237 if (WARN_ON_ONCE(!regs))
238 return 0;
239
240 if (!ftrace_location(regs->ip - 1))
241 return 0;
242
243 regs->ip += MCOUNT_INSN_SIZE - 1;
244
245 return 1;
246}
247
248static int ftrace_write(unsigned long ip, const char *val, int size)
249{
250 /*
251 * On x86_64, kernel text mappings are mapped read-only with
252 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
253 * of the kernel text mapping to modify the kernel text.
254 *
255 * For 32bit kernels, these mappings are same and we can use
256 * kernel identity mapping to modify code.
257 */
258 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
259 ip = (unsigned long)__va(__pa(ip));
260
261 return probe_kernel_write((void *)ip, val, size);
262}
263
264static int add_break(unsigned long ip, const char *old)
265{
266 unsigned char replaced[MCOUNT_INSN_SIZE];
267 unsigned char brk = BREAKPOINT_INSTRUCTION;
268
269 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
270 return -EFAULT;
271
272 /* Make sure it is what we expect it to be */
273 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
274 return -EINVAL;
275
276 if (ftrace_write(ip, &brk, 1))
277 return -EPERM;
278
279 return 0;
280}
281
282static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
283{
284 unsigned const char *old;
285 unsigned long ip = rec->ip;
286
287 old = ftrace_call_replace(ip, addr);
288
289 return add_break(rec->ip, old);
290}
291
292
293static int add_brk_on_nop(struct dyn_ftrace *rec)
294{
295 unsigned const char *old;
296
297 old = ftrace_nop_replace();
298
299 return add_break(rec->ip, old);
300}
301
302static int add_breakpoints(struct dyn_ftrace *rec, int enable)
303{
304 unsigned long ftrace_addr;
305 int ret;
306
307 ret = ftrace_test_record(rec, enable);
308
309 ftrace_addr = (unsigned long)FTRACE_ADDR;
310
311 switch (ret) {
312 case FTRACE_UPDATE_IGNORE:
313 return 0;
314
315 case FTRACE_UPDATE_MAKE_CALL:
316 /* converting nop to call */
317 return add_brk_on_nop(rec);
318
319 case FTRACE_UPDATE_MAKE_NOP:
320 /* converting a call to a nop */
321 return add_brk_on_call(rec, ftrace_addr);
322 }
323 return 0;
324}
325
326/*
327 * On error, we need to remove breakpoints. This needs to
328 * be done caefully. If the address does not currently have a
329 * breakpoint, we know we are done. Otherwise, we look at the
330 * remaining 4 bytes of the instruction. If it matches a nop
331 * we replace the breakpoint with the nop. Otherwise we replace
332 * it with the call instruction.
333 */
334static int remove_breakpoint(struct dyn_ftrace *rec)
335{
336 unsigned char ins[MCOUNT_INSN_SIZE];
337 unsigned char brk = BREAKPOINT_INSTRUCTION;
338 const unsigned char *nop;
339 unsigned long ftrace_addr;
340 unsigned long ip = rec->ip;
341
342 /* If we fail the read, just give up */
343 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
344 return -EFAULT;
345
346 /* If this does not have a breakpoint, we are done */
347 if (ins[0] != brk)
348 return -1;
349
350 nop = ftrace_nop_replace();
351
352 /*
353 * If the last 4 bytes of the instruction do not match
354 * a nop, then we assume that this is a call to ftrace_addr.
355 */
356 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
357 /*
358 * For extra paranoidism, we check if the breakpoint is on
359 * a call that would actually jump to the ftrace_addr.
360 * If not, don't touch the breakpoint, we make just create
361 * a disaster.
362 */
363 ftrace_addr = (unsigned long)FTRACE_ADDR;
364 nop = ftrace_call_replace(ip, ftrace_addr);
365
366 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
367 return -EINVAL;
368 }
369
370 return probe_kernel_write((void *)ip, &nop[0], 1);
371}
372
373static int add_update_code(unsigned long ip, unsigned const char *new)
374{
375 /* skip breakpoint */
376 ip++;
377 new++;
378 if (ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1))
379 return -EPERM;
380 return 0;
381}
382
383static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
384{
385 unsigned long ip = rec->ip;
386 unsigned const char *new;
387
388 new = ftrace_call_replace(ip, addr);
389 return add_update_code(ip, new);
390}
391
392static int add_update_nop(struct dyn_ftrace *rec)
393{
394 unsigned long ip = rec->ip;
395 unsigned const char *new;
396
397 new = ftrace_nop_replace();
398 return add_update_code(ip, new);
399}
400
401static int add_update(struct dyn_ftrace *rec, int enable)
402{
403 unsigned long ftrace_addr;
404 int ret;
405
406 ret = ftrace_test_record(rec, enable);
407
408 ftrace_addr = (unsigned long)FTRACE_ADDR;
409
410 switch (ret) {
411 case FTRACE_UPDATE_IGNORE:
412 return 0;
413
414 case FTRACE_UPDATE_MAKE_CALL:
415 /* converting nop to call */
416 return add_update_call(rec, ftrace_addr);
417
418 case FTRACE_UPDATE_MAKE_NOP:
419 /* converting a call to a nop */
420 return add_update_nop(rec);
421 }
422
423 return 0;
424}
425
426static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
427{
428 unsigned long ip = rec->ip;
429 unsigned const char *new;
430
431 new = ftrace_call_replace(ip, addr);
432
433 if (ftrace_write(ip, new, 1))
434 return -EPERM;
435
436 return 0;
437}
438
439static int finish_update_nop(struct dyn_ftrace *rec)
440{
441 unsigned long ip = rec->ip;
442 unsigned const char *new;
443
444 new = ftrace_nop_replace();
445
446 if (ftrace_write(ip, new, 1))
447 return -EPERM;
448 return 0;
449}
450
451static int finish_update(struct dyn_ftrace *rec, int enable)
452{
453 unsigned long ftrace_addr;
454 int ret;
455
456 ret = ftrace_update_record(rec, enable);
457
458 ftrace_addr = (unsigned long)FTRACE_ADDR;
459
460 switch (ret) {
461 case FTRACE_UPDATE_IGNORE:
462 return 0;
463
464 case FTRACE_UPDATE_MAKE_CALL:
465 /* converting nop to call */
466 return finish_update_call(rec, ftrace_addr);
467
468 case FTRACE_UPDATE_MAKE_NOP:
469 /* converting a call to a nop */
470 return finish_update_nop(rec);
471 }
472
473 return 0;
474}
475
476static void do_sync_core(void *data)
477{
478 sync_core();
479}
480
481static void run_sync(void)
482{
483 int enable_irqs = irqs_disabled();
484
485 /* We may be called with interrupts disbled (on bootup). */
486 if (enable_irqs)
487 local_irq_enable();
488 on_each_cpu(do_sync_core, NULL, 1);
489 if (enable_irqs)
490 local_irq_disable();
491}
492
493void ftrace_replace_code(int enable)
494{
495 struct ftrace_rec_iter *iter;
496 struct dyn_ftrace *rec;
497 const char *report = "adding breakpoints";
498 int count = 0;
499 int ret;
500
501 for_ftrace_rec_iter(iter) {
502 rec = ftrace_rec_iter_record(iter);
503
504 ret = add_breakpoints(rec, enable);
505 if (ret)
506 goto remove_breakpoints;
507 count++;
508 }
509
510 run_sync();
511
512 report = "updating code";
513
514 for_ftrace_rec_iter(iter) {
515 rec = ftrace_rec_iter_record(iter);
516
517 ret = add_update(rec, enable);
518 if (ret)
519 goto remove_breakpoints;
520 }
521
522 run_sync();
523
524 report = "removing breakpoints";
525
526 for_ftrace_rec_iter(iter) {
527 rec = ftrace_rec_iter_record(iter);
528
529 ret = finish_update(rec, enable);
530 if (ret)
531 goto remove_breakpoints;
532 }
533
534 run_sync();
535
536 return;
537
538 remove_breakpoints:
539 ftrace_bug(ret, rec ? rec->ip : 0);
540 printk(KERN_WARNING "Failed on %s (%d):\n", report, count);
541 for_ftrace_rec_iter(iter) {
542 rec = ftrace_rec_iter_record(iter);
543 remove_breakpoint(rec);
544 }
545}
546
547static int
548ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
549 unsigned const char *new_code)
550{
551 int ret;
552
553 ret = add_break(ip, old_code);
554 if (ret)
555 goto out;
556
557 run_sync();
558
559 ret = add_update_code(ip, new_code);
560 if (ret)
561 goto fail_update;
562
563 run_sync();
564
565 ret = ftrace_write(ip, new_code, 1);
566 if (ret) {
567 ret = -EPERM;
568 goto out;
569 }
570 run_sync();
571 out:
572 return ret;
573
574 fail_update:
575 probe_kernel_write((void *)ip, &old_code[0], 1);
576 goto out;
577}
578
579void arch_ftrace_update_code(int command)
580{
581 /* See comment above by declaration of modifying_ftrace_code */
582 atomic_inc(&modifying_ftrace_code);
583
584 ftrace_modify_all_code(command);
585
586 atomic_dec(&modifying_ftrace_code);
587}
588
589int __init ftrace_dyn_arch_init(void *data)
590{
591 /* The return code is retured via data */
592 *(unsigned long *)data = 0;
593
594 return 0;
595}
596#endif
597
598#ifdef CONFIG_FUNCTION_GRAPH_TRACER
599
600#ifdef CONFIG_DYNAMIC_FTRACE
601extern void ftrace_graph_call(void);
602
603static int ftrace_mod_jmp(unsigned long ip,
604 int old_offset, int new_offset)
605{
606 unsigned char code[MCOUNT_INSN_SIZE];
607
608 if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
609 return -EFAULT;
610
611 if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
612 return -EINVAL;
613
614 *(int *)(&code[1]) = new_offset;
615
616 if (do_ftrace_mod_code(ip, &code))
617 return -EPERM;
618
619 return 0;
620}
621
622int ftrace_enable_ftrace_graph_caller(void)
623{
624 unsigned long ip = (unsigned long)(&ftrace_graph_call);
625 int old_offset, new_offset;
626
627 old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
628 new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
629
630 return ftrace_mod_jmp(ip, old_offset, new_offset);
631}
632
633int ftrace_disable_ftrace_graph_caller(void)
634{
635 unsigned long ip = (unsigned long)(&ftrace_graph_call);
636 int old_offset, new_offset;
637
638 old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
639 new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
640
641 return ftrace_mod_jmp(ip, old_offset, new_offset);
642}
643
644#endif /* !CONFIG_DYNAMIC_FTRACE */
645
646/*
647 * Hook the return address and push it in the stack of return addrs
648 * in current thread info.
649 */
650void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
651 unsigned long frame_pointer)
652{
653 unsigned long old;
654 int faulted;
655 struct ftrace_graph_ent trace;
656 unsigned long return_hooker = (unsigned long)
657 &return_to_handler;
658
659 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
660 return;
661
662 /*
663 * Protect against fault, even if it shouldn't
664 * happen. This tool is too much intrusive to
665 * ignore such a protection.
666 */
667 asm volatile(
668 "1: " _ASM_MOV " (%[parent]), %[old]\n"
669 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
670 " movl $0, %[faulted]\n"
671 "3:\n"
672
673 ".section .fixup, \"ax\"\n"
674 "4: movl $1, %[faulted]\n"
675 " jmp 3b\n"
676 ".previous\n"
677
678 _ASM_EXTABLE(1b, 4b)
679 _ASM_EXTABLE(2b, 4b)
680
681 : [old] "=&r" (old), [faulted] "=r" (faulted)
682 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
683 : "memory"
684 );
685
686 if (unlikely(faulted)) {
687 ftrace_graph_stop();
688 WARN_ON(1);
689 return;
690 }
691
692 trace.func = self_addr;
693 trace.depth = current->curr_ret_stack + 1;
694
695 /* Only trace if the calling function expects to */
696 if (!ftrace_graph_entry(&trace)) {
697 *parent = old;
698 return;
699 }
700
701 if (ftrace_push_return_trace(old, self_addr, &trace.depth,
702 frame_pointer) == -EBUSY) {
703 *parent = old;
704 return;
705 }
706}
707#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 */