xref: /openbmc/linux/arch/x86/kernel/ftrace.c (revision 2a9eb57e)
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 #include <linux/vmalloc.h>
27 
28 #include <trace/syscall.h>
29 
30 #include <asm/set_memory.h>
31 #include <asm/kprobes.h>
32 #include <asm/ftrace.h>
33 #include <asm/nops.h>
34 #include <asm/text-patching.h>
35 
36 #ifdef CONFIG_DYNAMIC_FTRACE
37 
38 static int ftrace_poke_late = 0;
39 
40 void ftrace_arch_code_modify_prepare(void)
41     __acquires(&text_mutex)
42 {
43 	/*
44 	 * Need to grab text_mutex to prevent a race from module loading
45 	 * and live kernel patching from changing the text permissions while
46 	 * ftrace has it set to "read/write".
47 	 */
48 	mutex_lock(&text_mutex);
49 	ftrace_poke_late = 1;
50 }
51 
52 void ftrace_arch_code_modify_post_process(void)
53     __releases(&text_mutex)
54 {
55 	/*
56 	 * ftrace_make_{call,nop}() may be called during
57 	 * module load, and we need to finish the text_poke_queue()
58 	 * that they do, here.
59 	 */
60 	text_poke_finish();
61 	ftrace_poke_late = 0;
62 	mutex_unlock(&text_mutex);
63 }
64 
65 static const char *ftrace_nop_replace(void)
66 {
67 	return x86_nops[5];
68 }
69 
70 static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
71 {
72 	return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
73 }
74 
75 static int ftrace_verify_code(unsigned long ip, const char *old_code)
76 {
77 	char cur_code[MCOUNT_INSN_SIZE];
78 
79 	/*
80 	 * Note:
81 	 * We are paranoid about modifying text, as if a bug was to happen, it
82 	 * could cause us to read or write to someplace that could cause harm.
83 	 * Carefully read and modify the code with probe_kernel_*(), and make
84 	 * sure what we read is what we expected it to be before modifying it.
85 	 */
86 	/* read the text we want to modify */
87 	if (copy_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
88 		WARN_ON(1);
89 		return -EFAULT;
90 	}
91 
92 	/* Make sure it is what we expect it to be */
93 	if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
94 		ftrace_expected = old_code;
95 		WARN_ON(1);
96 		return -EINVAL;
97 	}
98 
99 	return 0;
100 }
101 
102 /*
103  * Marked __ref because it calls text_poke_early() which is .init.text. That is
104  * ok because that call will happen early, during boot, when .init sections are
105  * still present.
106  */
107 static int __ref
108 ftrace_modify_code_direct(unsigned long ip, const char *old_code,
109 			  const char *new_code)
110 {
111 	int ret = ftrace_verify_code(ip, old_code);
112 	if (ret)
113 		return ret;
114 
115 	/* replace the text with the new text */
116 	if (ftrace_poke_late)
117 		text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
118 	else
119 		text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
120 	return 0;
121 }
122 
123 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
124 {
125 	unsigned long ip = rec->ip;
126 	const char *new, *old;
127 
128 	old = ftrace_call_replace(ip, addr);
129 	new = ftrace_nop_replace();
130 
131 	/*
132 	 * On boot up, and when modules are loaded, the MCOUNT_ADDR
133 	 * is converted to a nop, and will never become MCOUNT_ADDR
134 	 * again. This code is either running before SMP (on boot up)
135 	 * or before the code will ever be executed (module load).
136 	 * We do not want to use the breakpoint version in this case,
137 	 * just modify the code directly.
138 	 */
139 	if (addr == MCOUNT_ADDR)
140 		return ftrace_modify_code_direct(ip, old, new);
141 
142 	/*
143 	 * x86 overrides ftrace_replace_code -- this function will never be used
144 	 * in this case.
145 	 */
146 	WARN_ONCE(1, "invalid use of ftrace_make_nop");
147 	return -EINVAL;
148 }
149 
150 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
151 {
152 	unsigned long ip = rec->ip;
153 	const char *new, *old;
154 
155 	old = ftrace_nop_replace();
156 	new = ftrace_call_replace(ip, addr);
157 
158 	/* Should only be called when module is loaded */
159 	return ftrace_modify_code_direct(rec->ip, old, new);
160 }
161 
162 /*
163  * Should never be called:
164  *  As it is only called by __ftrace_replace_code() which is called by
165  *  ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
166  *  which is called to turn mcount into nops or nops into function calls
167  *  but not to convert a function from not using regs to one that uses
168  *  regs, which ftrace_modify_call() is for.
169  */
170 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
171 				 unsigned long addr)
172 {
173 	WARN_ON(1);
174 	return -EINVAL;
175 }
176 
177 int ftrace_update_ftrace_func(ftrace_func_t func)
178 {
179 	unsigned long ip;
180 	const char *new;
181 
182 	ip = (unsigned long)(&ftrace_call);
183 	new = ftrace_call_replace(ip, (unsigned long)func);
184 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
185 
186 	ip = (unsigned long)(&ftrace_regs_call);
187 	new = ftrace_call_replace(ip, (unsigned long)func);
188 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
189 
190 	return 0;
191 }
192 
193 void ftrace_replace_code(int enable)
194 {
195 	struct ftrace_rec_iter *iter;
196 	struct dyn_ftrace *rec;
197 	const char *new, *old;
198 	int ret;
199 
200 	for_ftrace_rec_iter(iter) {
201 		rec = ftrace_rec_iter_record(iter);
202 
203 		switch (ftrace_test_record(rec, enable)) {
204 		case FTRACE_UPDATE_IGNORE:
205 		default:
206 			continue;
207 
208 		case FTRACE_UPDATE_MAKE_CALL:
209 			old = ftrace_nop_replace();
210 			break;
211 
212 		case FTRACE_UPDATE_MODIFY_CALL:
213 		case FTRACE_UPDATE_MAKE_NOP:
214 			old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
215 			break;
216 		}
217 
218 		ret = ftrace_verify_code(rec->ip, old);
219 		if (ret) {
220 			ftrace_bug(ret, rec);
221 			return;
222 		}
223 	}
224 
225 	for_ftrace_rec_iter(iter) {
226 		rec = ftrace_rec_iter_record(iter);
227 
228 		switch (ftrace_test_record(rec, enable)) {
229 		case FTRACE_UPDATE_IGNORE:
230 		default:
231 			continue;
232 
233 		case FTRACE_UPDATE_MAKE_CALL:
234 		case FTRACE_UPDATE_MODIFY_CALL:
235 			new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
236 			break;
237 
238 		case FTRACE_UPDATE_MAKE_NOP:
239 			new = ftrace_nop_replace();
240 			break;
241 		}
242 
243 		text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
244 		ftrace_update_record(rec, enable);
245 	}
246 	text_poke_finish();
247 }
248 
249 void arch_ftrace_update_code(int command)
250 {
251 	ftrace_modify_all_code(command);
252 }
253 
254 /* Currently only x86_64 supports dynamic trampolines */
255 #ifdef CONFIG_X86_64
256 
257 #ifdef CONFIG_MODULES
258 #include <linux/moduleloader.h>
259 /* Module allocation simplifies allocating memory for code */
260 static inline void *alloc_tramp(unsigned long size)
261 {
262 	return module_alloc(size);
263 }
264 static inline void tramp_free(void *tramp)
265 {
266 	module_memfree(tramp);
267 }
268 #else
269 /* Trampolines can only be created if modules are supported */
270 static inline void *alloc_tramp(unsigned long size)
271 {
272 	return NULL;
273 }
274 static inline void tramp_free(void *tramp) { }
275 #endif
276 
277 /* Defined as markers to the end of the ftrace default trampolines */
278 extern void ftrace_regs_caller_end(void);
279 extern void ftrace_regs_caller_ret(void);
280 extern void ftrace_caller_end(void);
281 extern void ftrace_caller_op_ptr(void);
282 extern void ftrace_regs_caller_op_ptr(void);
283 extern void ftrace_regs_caller_jmp(void);
284 
285 /* movq function_trace_op(%rip), %rdx */
286 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
287 #define OP_REF_SIZE	7
288 
289 /*
290  * The ftrace_ops is passed to the function callback. Since the
291  * trampoline only services a single ftrace_ops, we can pass in
292  * that ops directly.
293  *
294  * The ftrace_op_code_union is used to create a pointer to the
295  * ftrace_ops that will be passed to the callback function.
296  */
297 union ftrace_op_code_union {
298 	char code[OP_REF_SIZE];
299 	struct {
300 		char op[3];
301 		int offset;
302 	} __attribute__((packed));
303 };
304 
305 #define RET_SIZE		(IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))
306 
307 static unsigned long
308 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
309 {
310 	unsigned long start_offset;
311 	unsigned long end_offset;
312 	unsigned long op_offset;
313 	unsigned long call_offset;
314 	unsigned long jmp_offset;
315 	unsigned long offset;
316 	unsigned long npages;
317 	unsigned long size;
318 	unsigned long *ptr;
319 	void *trampoline;
320 	void *ip;
321 	/* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
322 	unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
323 	unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE };
324 	union ftrace_op_code_union op_ptr;
325 	int ret;
326 
327 	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
328 		start_offset = (unsigned long)ftrace_regs_caller;
329 		end_offset = (unsigned long)ftrace_regs_caller_end;
330 		op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
331 		call_offset = (unsigned long)ftrace_regs_call;
332 		jmp_offset = (unsigned long)ftrace_regs_caller_jmp;
333 	} else {
334 		start_offset = (unsigned long)ftrace_caller;
335 		end_offset = (unsigned long)ftrace_caller_end;
336 		op_offset = (unsigned long)ftrace_caller_op_ptr;
337 		call_offset = (unsigned long)ftrace_call;
338 		jmp_offset = 0;
339 	}
340 
341 	size = end_offset - start_offset;
342 
343 	/*
344 	 * Allocate enough size to store the ftrace_caller code,
345 	 * the iret , as well as the address of the ftrace_ops this
346 	 * trampoline is used for.
347 	 */
348 	trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
349 	if (!trampoline)
350 		return 0;
351 
352 	*tramp_size = size + RET_SIZE + sizeof(void *);
353 	npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
354 
355 	/* Copy ftrace_caller onto the trampoline memory */
356 	ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size);
357 	if (WARN_ON(ret < 0))
358 		goto fail;
359 
360 	ip = trampoline + size;
361 	if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
362 		__text_gen_insn(ip, JMP32_INSN_OPCODE, ip, &__x86_return_thunk, JMP32_INSN_SIZE);
363 	else
364 		memcpy(ip, retq, sizeof(retq));
365 
366 	/* No need to test direct calls on created trampolines */
367 	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
368 		/* NOP the jnz 1f; but make sure it's a 2 byte jnz */
369 		ip = trampoline + (jmp_offset - start_offset);
370 		if (WARN_ON(*(char *)ip != 0x75))
371 			goto fail;
372 		ret = copy_from_kernel_nofault(ip, x86_nops[2], 2);
373 		if (ret < 0)
374 			goto fail;
375 	}
376 
377 	/*
378 	 * The address of the ftrace_ops that is used for this trampoline
379 	 * is stored at the end of the trampoline. This will be used to
380 	 * load the third parameter for the callback. Basically, that
381 	 * location at the end of the trampoline takes the place of
382 	 * the global function_trace_op variable.
383 	 */
384 
385 	ptr = (unsigned long *)(trampoline + size + RET_SIZE);
386 	*ptr = (unsigned long)ops;
387 
388 	op_offset -= start_offset;
389 	memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
390 
391 	/* Are we pointing to the reference? */
392 	if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
393 		goto fail;
394 
395 	/* Load the contents of ptr into the callback parameter */
396 	offset = (unsigned long)ptr;
397 	offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
398 
399 	op_ptr.offset = offset;
400 
401 	/* put in the new offset to the ftrace_ops */
402 	memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
403 
404 	/* put in the call to the function */
405 	mutex_lock(&text_mutex);
406 	call_offset -= start_offset;
407 	memcpy(trampoline + call_offset,
408 	       text_gen_insn(CALL_INSN_OPCODE,
409 			     trampoline + call_offset,
410 			     ftrace_ops_get_func(ops)), CALL_INSN_SIZE);
411 	mutex_unlock(&text_mutex);
412 
413 	/* ALLOC_TRAMP flags lets us know we created it */
414 	ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
415 
416 	set_vm_flush_reset_perms(trampoline);
417 
418 	if (likely(system_state != SYSTEM_BOOTING))
419 		set_memory_ro((unsigned long)trampoline, npages);
420 	set_memory_x((unsigned long)trampoline, npages);
421 	return (unsigned long)trampoline;
422 fail:
423 	tramp_free(trampoline);
424 	return 0;
425 }
426 
427 void set_ftrace_ops_ro(void)
428 {
429 	struct ftrace_ops *ops;
430 	unsigned long start_offset;
431 	unsigned long end_offset;
432 	unsigned long npages;
433 	unsigned long size;
434 
435 	do_for_each_ftrace_op(ops, ftrace_ops_list) {
436 		if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
437 			continue;
438 
439 		if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
440 			start_offset = (unsigned long)ftrace_regs_caller;
441 			end_offset = (unsigned long)ftrace_regs_caller_end;
442 		} else {
443 			start_offset = (unsigned long)ftrace_caller;
444 			end_offset = (unsigned long)ftrace_caller_end;
445 		}
446 		size = end_offset - start_offset;
447 		size = size + RET_SIZE + sizeof(void *);
448 		npages = DIV_ROUND_UP(size, PAGE_SIZE);
449 		set_memory_ro((unsigned long)ops->trampoline, npages);
450 	} while_for_each_ftrace_op(ops);
451 }
452 
453 static unsigned long calc_trampoline_call_offset(bool save_regs)
454 {
455 	unsigned long start_offset;
456 	unsigned long call_offset;
457 
458 	if (save_regs) {
459 		start_offset = (unsigned long)ftrace_regs_caller;
460 		call_offset = (unsigned long)ftrace_regs_call;
461 	} else {
462 		start_offset = (unsigned long)ftrace_caller;
463 		call_offset = (unsigned long)ftrace_call;
464 	}
465 
466 	return call_offset - start_offset;
467 }
468 
469 void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
470 {
471 	ftrace_func_t func;
472 	unsigned long offset;
473 	unsigned long ip;
474 	unsigned int size;
475 	const char *new;
476 
477 	if (!ops->trampoline) {
478 		ops->trampoline = create_trampoline(ops, &size);
479 		if (!ops->trampoline)
480 			return;
481 		ops->trampoline_size = size;
482 		return;
483 	}
484 
485 	/*
486 	 * The ftrace_ops caller may set up its own trampoline.
487 	 * In such a case, this code must not modify it.
488 	 */
489 	if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
490 		return;
491 
492 	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
493 	ip = ops->trampoline + offset;
494 	func = ftrace_ops_get_func(ops);
495 
496 	mutex_lock(&text_mutex);
497 	/* Do a safe modify in case the trampoline is executing */
498 	new = ftrace_call_replace(ip, (unsigned long)func);
499 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
500 	mutex_unlock(&text_mutex);
501 }
502 
503 /* Return the address of the function the trampoline calls */
504 static void *addr_from_call(void *ptr)
505 {
506 	union text_poke_insn call;
507 	int ret;
508 
509 	ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE);
510 	if (WARN_ON_ONCE(ret < 0))
511 		return NULL;
512 
513 	/* Make sure this is a call */
514 	if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
515 		pr_warn("Expected E8, got %x\n", call.opcode);
516 		return NULL;
517 	}
518 
519 	return ptr + CALL_INSN_SIZE + call.disp;
520 }
521 
522 void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
523 			   unsigned long frame_pointer);
524 
525 /*
526  * If the ops->trampoline was not allocated, then it probably
527  * has a static trampoline func, or is the ftrace caller itself.
528  */
529 static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
530 {
531 	unsigned long offset;
532 	bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
533 	void *ptr;
534 
535 	if (ops && ops->trampoline) {
536 #if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) && \
537 	defined(CONFIG_FUNCTION_GRAPH_TRACER)
538 		/*
539 		 * We only know about function graph tracer setting as static
540 		 * trampoline.
541 		 */
542 		if (ops->trampoline == FTRACE_GRAPH_ADDR)
543 			return (void *)prepare_ftrace_return;
544 #endif
545 		return NULL;
546 	}
547 
548 	offset = calc_trampoline_call_offset(save_regs);
549 
550 	if (save_regs)
551 		ptr = (void *)FTRACE_REGS_ADDR + offset;
552 	else
553 		ptr = (void *)FTRACE_ADDR + offset;
554 
555 	return addr_from_call(ptr);
556 }
557 
558 void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
559 {
560 	unsigned long offset;
561 
562 	/* If we didn't allocate this trampoline, consider it static */
563 	if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
564 		return static_tramp_func(ops, rec);
565 
566 	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
567 	return addr_from_call((void *)ops->trampoline + offset);
568 }
569 
570 void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
571 {
572 	if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
573 		return;
574 
575 	tramp_free((void *)ops->trampoline);
576 	ops->trampoline = 0;
577 }
578 
579 #endif /* CONFIG_X86_64 */
580 #endif /* CONFIG_DYNAMIC_FTRACE */
581 
582 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
583 
584 #if defined(CONFIG_DYNAMIC_FTRACE) && !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS)
585 extern void ftrace_graph_call(void);
586 static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
587 {
588 	return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
589 }
590 
591 static int ftrace_mod_jmp(unsigned long ip, void *func)
592 {
593 	const char *new;
594 
595 	new = ftrace_jmp_replace(ip, (unsigned long)func);
596 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
597 	return 0;
598 }
599 
600 int ftrace_enable_ftrace_graph_caller(void)
601 {
602 	unsigned long ip = (unsigned long)(&ftrace_graph_call);
603 
604 	return ftrace_mod_jmp(ip, &ftrace_graph_caller);
605 }
606 
607 int ftrace_disable_ftrace_graph_caller(void)
608 {
609 	unsigned long ip = (unsigned long)(&ftrace_graph_call);
610 
611 	return ftrace_mod_jmp(ip, &ftrace_stub);
612 }
613 #endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
614 
615 /*
616  * Hook the return address and push it in the stack of return addrs
617  * in current thread info.
618  */
619 void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
620 			   unsigned long frame_pointer)
621 {
622 	unsigned long return_hooker = (unsigned long)&return_to_handler;
623 	int bit;
624 
625 	/*
626 	 * When resuming from suspend-to-ram, this function can be indirectly
627 	 * called from early CPU startup code while the CPU is in real mode,
628 	 * which would fail miserably.  Make sure the stack pointer is a
629 	 * virtual address.
630 	 *
631 	 * This check isn't as accurate as virt_addr_valid(), but it should be
632 	 * good enough for this purpose, and it's fast.
633 	 */
634 	if (unlikely((long)__builtin_frame_address(0) >= 0))
635 		return;
636 
637 	if (unlikely(ftrace_graph_is_dead()))
638 		return;
639 
640 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
641 		return;
642 
643 	bit = ftrace_test_recursion_trylock(ip, *parent);
644 	if (bit < 0)
645 		return;
646 
647 	if (!function_graph_enter(*parent, ip, frame_pointer, parent))
648 		*parent = return_hooker;
649 
650 	ftrace_test_recursion_unlock(bit);
651 }
652 
653 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
654 void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
655 		       struct ftrace_ops *op, struct ftrace_regs *fregs)
656 {
657 	struct pt_regs *regs = &fregs->regs;
658 	unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs);
659 
660 	prepare_ftrace_return(ip, (unsigned long *)stack, 0);
661 }
662 #endif
663 
664 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
665