summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/ftrace.c
blob: 37a0aeaf89e771b63bccbeab92979469cbd96ecb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
// SPDX-License-Identifier: GPL-2.0
/*
 * Dynamic function tracing support.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 *
 * Thanks goes to Ingo Molnar, for suggesting the idea.
 * Mathieu Desnoyers, for suggesting postponing the modifications.
 * Arjan van de Ven, for keeping me straight, and explaining to me
 * the dangers of modifying code on the run.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/memory.h>
#include <linux/vmalloc.h>

#include <trace/syscall.h>

#include <asm/set_memory.h>
#include <asm/kprobes.h>
#include <asm/ftrace.h>
#include <asm/nops.h>
#include <asm/text-patching.h>

#ifdef CONFIG_DYNAMIC_FTRACE

static int ftrace_poke_late = 0;

int ftrace_arch_code_modify_prepare(void)
    __acquires(&text_mutex)
{
	/*
	 * Need to grab text_mutex to prevent a race from module loading
	 * and live kernel patching from changing the text permissions while
	 * ftrace has it set to "read/write".
	 */
	mutex_lock(&text_mutex);
	ftrace_poke_late = 1;
	return 0;
}

int ftrace_arch_code_modify_post_process(void)
    __releases(&text_mutex)
{
	/*
	 * ftrace_make_{call,nop}() may be called during
	 * module load, and we need to finish the text_poke_queue()
	 * that they do, here.
	 */
	text_poke_finish();
	ftrace_poke_late = 0;
	mutex_unlock(&text_mutex);
	return 0;
}

static const char *ftrace_nop_replace(void)
{
	return ideal_nops[NOP_ATOMIC5];
}

static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
	return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
}

static int ftrace_verify_code(unsigned long ip, const char *old_code)
{
	char cur_code[MCOUNT_INSN_SIZE];

	/*
	 * Note:
	 * We are paranoid about modifying text, as if a bug was to happen, it
	 * could cause us to read or write to someplace that could cause harm.
	 * Carefully read and modify the code with probe_kernel_*(), and make
	 * sure what we read is what we expected it to be before modifying it.
	 */
	/* read the text we want to modify */
	if (probe_kernel_read(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
		WARN_ON(1);
		return -EFAULT;
	}

	/* Make sure it is what we expect it to be */
	if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
		WARN_ON(1);
		return -EINVAL;
	}

	return 0;
}

/*
 * Marked __ref because it calls text_poke_early() which is .init.text. That is
 * ok because that call will happen early, during boot, when .init sections are
 * still present.
 */
static int __ref
ftrace_modify_code_direct(unsigned long ip, const char *old_code,
			  const char *new_code)
{
	int ret = ftrace_verify_code(ip, old_code);
	if (ret)
		return ret;

	/* replace the text with the new text */
	if (ftrace_poke_late)
		text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
	else
		text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
	return 0;
}

int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned long ip = rec->ip;
	const char *new, *old;

	old = ftrace_call_replace(ip, addr);
	new = ftrace_nop_replace();

	/*
	 * On boot up, and when modules are loaded, the MCOUNT_ADDR
	 * is converted to a nop, and will never become MCOUNT_ADDR
	 * again. This code is either running before SMP (on boot up)
	 * or before the code will ever be executed (module load).
	 * We do not want to use the breakpoint version in this case,
	 * just modify the code directly.
	 */
	if (addr == MCOUNT_ADDR)
		return ftrace_modify_code_direct(ip, old, new);

	/*
	 * x86 overrides ftrace_replace_code -- this function will never be used
	 * in this case.
	 */
	WARN_ONCE(1, "invalid use of ftrace_make_nop");
	return -EINVAL;
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned long ip = rec->ip;
	const char *new, *old;

	old = ftrace_nop_replace();
	new = ftrace_call_replace(ip, addr);

	/* Should only be called when module is loaded */
	return ftrace_modify_code_direct(rec->ip, old, new);
}

/*
 * Should never be called:
 *  As it is only called by __ftrace_replace_code() which is called by
 *  ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
 *  which is called to turn mcount into nops or nops into function calls
 *  but not to convert a function from not using regs to one that uses
 *  regs, which ftrace_modify_call() is for.
 */
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
				 unsigned long addr)
{
	WARN_ON(1);
	return -EINVAL;
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
	unsigned long ip;
	const char *new;

	ip = (unsigned long)(&ftrace_call);
	new = ftrace_call_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

	ip = (unsigned long)(&ftrace_regs_call);
	new = ftrace_call_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

	return 0;
}

void ftrace_replace_code(int enable)
{
	struct ftrace_rec_iter *iter;
	struct dyn_ftrace *rec;
	const char *new, *old;
	int ret;

	for_ftrace_rec_iter(iter) {
		rec = ftrace_rec_iter_record(iter);

		switch (ftrace_test_record(rec, enable)) {
		case FTRACE_UPDATE_IGNORE:
		default:
			continue;

		case FTRACE_UPDATE_MAKE_CALL:
			old = ftrace_nop_replace();
			break;

		case FTRACE_UPDATE_MODIFY_CALL:
		case FTRACE_UPDATE_MAKE_NOP:
			old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
			break;
		}

		ret = ftrace_verify_code(rec->ip, old);
		if (ret) {
			ftrace_bug(ret, rec);
			return;
		}
	}

	for_ftrace_rec_iter(iter) {
		rec = ftrace_rec_iter_record(iter);

		switch (ftrace_test_record(rec, enable)) {
		case FTRACE_UPDATE_IGNORE:
		default:
			continue;

		case FTRACE_UPDATE_MAKE_CALL:
		case FTRACE_UPDATE_MODIFY_CALL:
			new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
			break;

		case FTRACE_UPDATE_MAKE_NOP:
			new = ftrace_nop_replace();
			break;
		}

		text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
		ftrace_update_record(rec, enable);
	}
	text_poke_finish();
}

void arch_ftrace_update_code(int command)
{
	ftrace_modify_all_code(command);
}

int __init ftrace_dyn_arch_init(void)
{
	return 0;
}

/* Currently only x86_64 supports dynamic trampolines */
#ifdef CONFIG_X86_64

#ifdef CONFIG_MODULES
#include <linux/moduleloader.h>
/* Module allocation simplifies allocating memory for code */
static inline void *alloc_tramp(unsigned long size)
{
	return module_alloc(size);
}
static inline void tramp_free(void *tramp)
{
	module_memfree(tramp);
}
#else
/* Trampolines can only be created if modules are supported */
static inline void *alloc_tramp(unsigned long size)
{
	return NULL;
}
static inline void tramp_free(void *tramp) { }
#endif

/* Defined as markers to the end of the ftrace default trampolines */
extern void ftrace_regs_caller_end(void);
extern void ftrace_epilogue(void);
extern void ftrace_caller_op_ptr(void);
extern void ftrace_regs_caller_op_ptr(void);

/* movq function_trace_op(%rip), %rdx */
/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
#define OP_REF_SIZE	7

/*
 * The ftrace_ops is passed to the function callback. Since the
 * trampoline only services a single ftrace_ops, we can pass in
 * that ops directly.
 *
 * The ftrace_op_code_union is used to create a pointer to the
 * ftrace_ops that will be passed to the callback function.
 */
union ftrace_op_code_union {
	char code[OP_REF_SIZE];
	struct {
		char op[3];
		int offset;
	} __attribute__((packed));
};

#define RET_SIZE		1

static unsigned long
create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
{
	unsigned long start_offset;
	unsigned long end_offset;
	unsigned long op_offset;
	unsigned long call_offset;
	unsigned long offset;
	unsigned long npages;
	unsigned long size;
	unsigned long retq;
	unsigned long *ptr;
	void *trampoline;
	void *ip;
	/* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
	unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
	union ftrace_op_code_union op_ptr;
	int ret;

	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
		start_offset = (unsigned long)ftrace_regs_caller;
		end_offset = (unsigned long)ftrace_regs_caller_end;
		op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
		call_offset = (unsigned long)ftrace_regs_call;
	} else {
		start_offset = (unsigned long)ftrace_caller;
		end_offset = (unsigned long)ftrace_epilogue;
		op_offset = (unsigned long)ftrace_caller_op_ptr;
		call_offset = (unsigned long)ftrace_call;
	}

	size = end_offset - start_offset;

	/*
	 * Allocate enough size to store the ftrace_caller code,
	 * the iret , as well as the address of the ftrace_ops this
	 * trampoline is used for.
	 */
	trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
	if (!trampoline)
		return 0;

	*tramp_size = size + RET_SIZE + sizeof(void *);
	npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);

	/* Copy ftrace_caller onto the trampoline memory */
	ret = probe_kernel_read(trampoline, (void *)start_offset, size);
	if (WARN_ON(ret < 0))
		goto fail;

	ip = trampoline + size;

	/* The trampoline ends with ret(q) */
	retq = (unsigned long)ftrace_stub;
	ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
	if (WARN_ON(ret < 0))
		goto fail;

	/*
	 * The address of the ftrace_ops that is used for this trampoline
	 * is stored at the end of the trampoline. This will be used to
	 * load the third parameter for the callback. Basically, that
	 * location at the end of the trampoline takes the place of
	 * the global function_trace_op variable.
	 */

	ptr = (unsigned long *)(trampoline + size + RET_SIZE);
	*ptr = (unsigned long)ops;

	op_offset -= start_offset;
	memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);

	/* Are we pointing to the reference? */
	if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
		goto fail;

	/* Load the contents of ptr into the callback parameter */
	offset = (unsigned long)ptr;
	offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;

	op_ptr.offset = offset;

	/* put in the new offset to the ftrace_ops */
	memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);

	/* put in the call to the function */
	mutex_lock(&text_mutex);
	call_offset -= start_offset;
	memcpy(trampoline + call_offset,
	       text_gen_insn(CALL_INSN_OPCODE,
			     trampoline + call_offset,
			     ftrace_ops_get_func(ops)), CALL_INSN_SIZE);
	mutex_unlock(&text_mutex);

	/* ALLOC_TRAMP flags lets us know we created it */
	ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;

	set_vm_flush_reset_perms(trampoline);

	set_memory_ro((unsigned long)trampoline, npages);
	set_memory_x((unsigned long)trampoline, npages);
	return (unsigned long)trampoline;
fail:
	tramp_free(trampoline);
	return 0;
}

static unsigned long calc_trampoline_call_offset(bool save_regs)
{
	unsigned long start_offset;
	unsigned long call_offset;

	if (save_regs) {
		start_offset = (unsigned long)ftrace_regs_caller;
		call_offset = (unsigned long)ftrace_regs_call;
	} else {
		start_offset = (unsigned long)ftrace_caller;
		call_offset = (unsigned long)ftrace_call;
	}

	return call_offset - start_offset;
}

void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
{
	ftrace_func_t func;
	unsigned long offset;
	unsigned long ip;
	unsigned int size;
	const char *new;

	if (!ops->trampoline) {
		ops->trampoline = create_trampoline(ops, &size);
		if (!ops->trampoline)
			return;
		ops->trampoline_size = size;
		return;
	}

	/*
	 * The ftrace_ops caller may set up its own trampoline.
	 * In such a case, this code must not modify it.
	 */
	if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
		return;

	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
	ip = ops->trampoline + offset;
	func = ftrace_ops_get_func(ops);

	mutex_lock(&text_mutex);
	/* Do a safe modify in case the trampoline is executing */
	new = ftrace_call_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
	mutex_unlock(&text_mutex);
}

/* Return the address of the function the trampoline calls */
static void *addr_from_call(void *ptr)
{
	union text_poke_insn call;
	int ret;

	ret = probe_kernel_read(&call, ptr, CALL_INSN_SIZE);
	if (WARN_ON_ONCE(ret < 0))
		return NULL;

	/* Make sure this is a call */
	if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
		pr_warn("Expected E8, got %x\n", call.opcode);
		return NULL;
	}

	return ptr + CALL_INSN_SIZE + call.disp;
}

void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
			   unsigned long frame_pointer);

/*
 * If the ops->trampoline was not allocated, then it probably
 * has a static trampoline func, or is the ftrace caller itself.
 */
static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
{
	unsigned long offset;
	bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
	void *ptr;

	if (ops && ops->trampoline) {
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
		/*
		 * We only know about function graph tracer setting as static
		 * trampoline.
		 */
		if (ops->trampoline == FTRACE_GRAPH_ADDR)
			return (void *)prepare_ftrace_return;
#endif
		return NULL;
	}

	offset = calc_trampoline_call_offset(save_regs);

	if (save_regs)
		ptr = (void *)FTRACE_REGS_ADDR + offset;
	else
		ptr = (void *)FTRACE_ADDR + offset;

	return addr_from_call(ptr);
}

void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
{
	unsigned long offset;

	/* If we didn't allocate this trampoline, consider it static */
	if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
		return static_tramp_func(ops, rec);

	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
	return addr_from_call((void *)ops->trampoline + offset);
}

void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
{
	if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
		return;

	tramp_free((void *)ops->trampoline);
	ops->trampoline = 0;
}

#endif /* CONFIG_X86_64 */
#endif /* CONFIG_DYNAMIC_FTRACE */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);

static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
{
	return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
}

static int ftrace_mod_jmp(unsigned long ip, void *func)
{
	const char *new;

	new = ftrace_jmp_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
	return 0;
}

int ftrace_enable_ftrace_graph_caller(void)
{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);

	return ftrace_mod_jmp(ip, &ftrace_graph_caller);
}

int ftrace_disable_ftrace_graph_caller(void)
{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);

	return ftrace_mod_jmp(ip, &ftrace_stub);
}

#endif /* !CONFIG_DYNAMIC_FTRACE */

/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
			   unsigned long frame_pointer)
{
	unsigned long return_hooker = (unsigned long)&return_to_handler;
	unsigned long old;
	int faulted;

	/*
	 * When resuming from suspend-to-ram, this function can be indirectly
	 * called from early CPU startup code while the CPU is in real mode,
	 * which would fail miserably.  Make sure the stack pointer is a
	 * virtual address.
	 *
	 * This check isn't as accurate as virt_addr_valid(), but it should be
	 * good enough for this purpose, and it's fast.
	 */
	if (unlikely((long)__builtin_frame_address(0) >= 0))
		return;

	if (unlikely(ftrace_graph_is_dead()))
		return;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
		return;

	/*
	 * Protect against fault, even if it shouldn't
	 * happen. This tool is too much intrusive to
	 * ignore such a protection.
	 */
	asm volatile(
		"1: " _ASM_MOV " (%[parent]), %[old]\n"
		"2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
		"   movl $0, %[faulted]\n"
		"3:\n"

		".section .fixup, \"ax\"\n"
		"4: movl $1, %[faulted]\n"
		"   jmp 3b\n"
		".previous\n"

		_ASM_EXTABLE(1b, 4b)
		_ASM_EXTABLE(2b, 4b)

		: [old] "=&r" (old), [faulted] "=r" (faulted)
		: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
		: "memory"
	);

	if (unlikely(faulted)) {
		ftrace_graph_stop();
		WARN_ON(1);
		return;
	}

	if (function_graph_enter(old, self_addr, frame_pointer, parent))
		*parent = old;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */