1 // SPDX-License-Identifier: GPL-2.0
3 * Dynamic function tracing support.
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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 #include <linux/set_memory.h>
29 #include <trace/syscall.h>
31 #include <asm/kprobes.h>
32 #include <asm/ftrace.h>
34 #include <asm/text-patching.h>
36 #ifdef CONFIG_DYNAMIC_FTRACE
38 static int ftrace_poke_late = 0;
40 void ftrace_arch_code_modify_prepare(void)
41 __acquires(&text_mutex)
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".
48 mutex_lock(&text_mutex);
52 void ftrace_arch_code_modify_post_process(void)
53 __releases(&text_mutex)
56 * ftrace_make_{call,nop}() may be called during
57 * module load, and we need to finish the text_poke_queue()
62 mutex_unlock(&text_mutex);
65 static const char *ftrace_nop_replace(void)
70 static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
73 * No need to translate into a callthunk. The trampoline does
74 * the depth accounting itself.
76 return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
79 static int ftrace_verify_code(unsigned long ip, const char *old_code)
81 char cur_code[MCOUNT_INSN_SIZE];
85 * We are paranoid about modifying text, as if a bug was to happen, it
86 * could cause us to read or write to someplace that could cause harm.
87 * Carefully read and modify the code with probe_kernel_*(), and make
88 * sure what we read is what we expected it to be before modifying it.
90 /* read the text we want to modify */
91 if (copy_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
96 /* Make sure it is what we expect it to be */
97 if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
98 ftrace_expected = old_code;
107 * Marked __ref because it calls text_poke_early() which is .init.text. That is
108 * ok because that call will happen early, during boot, when .init sections are
112 ftrace_modify_code_direct(unsigned long ip, const char *old_code,
113 const char *new_code)
115 int ret = ftrace_verify_code(ip, old_code);
119 /* replace the text with the new text */
120 if (ftrace_poke_late)
121 text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
123 text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
127 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
129 unsigned long ip = rec->ip;
130 const char *new, *old;
132 old = ftrace_call_replace(ip, addr);
133 new = ftrace_nop_replace();
136 * On boot up, and when modules are loaded, the MCOUNT_ADDR
137 * is converted to a nop, and will never become MCOUNT_ADDR
138 * again. This code is either running before SMP (on boot up)
139 * or before the code will ever be executed (module load).
140 * We do not want to use the breakpoint version in this case,
141 * just modify the code directly.
143 if (addr == MCOUNT_ADDR)
144 return ftrace_modify_code_direct(ip, old, new);
147 * x86 overrides ftrace_replace_code -- this function will never be used
150 WARN_ONCE(1, "invalid use of ftrace_make_nop");
154 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
156 unsigned long ip = rec->ip;
157 const char *new, *old;
159 old = ftrace_nop_replace();
160 new = ftrace_call_replace(ip, addr);
162 /* Should only be called when module is loaded */
163 return ftrace_modify_code_direct(rec->ip, old, new);
167 * Should never be called:
168 * As it is only called by __ftrace_replace_code() which is called by
169 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
170 * which is called to turn mcount into nops or nops into function calls
171 * but not to convert a function from not using regs to one that uses
172 * regs, which ftrace_modify_call() is for.
174 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
181 int ftrace_update_ftrace_func(ftrace_func_t func)
186 ip = (unsigned long)(&ftrace_call);
187 new = ftrace_call_replace(ip, (unsigned long)func);
188 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
190 ip = (unsigned long)(&ftrace_regs_call);
191 new = ftrace_call_replace(ip, (unsigned long)func);
192 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
197 void ftrace_replace_code(int enable)
199 struct ftrace_rec_iter *iter;
200 struct dyn_ftrace *rec;
201 const char *new, *old;
204 for_ftrace_rec_iter(iter) {
205 rec = ftrace_rec_iter_record(iter);
207 switch (ftrace_test_record(rec, enable)) {
208 case FTRACE_UPDATE_IGNORE:
212 case FTRACE_UPDATE_MAKE_CALL:
213 old = ftrace_nop_replace();
216 case FTRACE_UPDATE_MODIFY_CALL:
217 case FTRACE_UPDATE_MAKE_NOP:
218 old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
222 ret = ftrace_verify_code(rec->ip, old);
224 ftrace_expected = old;
225 ftrace_bug(ret, rec);
226 ftrace_expected = NULL;
231 for_ftrace_rec_iter(iter) {
232 rec = ftrace_rec_iter_record(iter);
234 switch (ftrace_test_record(rec, enable)) {
235 case FTRACE_UPDATE_IGNORE:
239 case FTRACE_UPDATE_MAKE_CALL:
240 case FTRACE_UPDATE_MODIFY_CALL:
241 new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
244 case FTRACE_UPDATE_MAKE_NOP:
245 new = ftrace_nop_replace();
249 text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
250 ftrace_update_record(rec, enable);
255 void arch_ftrace_update_code(int command)
257 ftrace_modify_all_code(command);
260 /* Currently only x86_64 supports dynamic trampolines */
263 #ifdef CONFIG_MODULES
264 #include <linux/moduleloader.h>
265 /* Module allocation simplifies allocating memory for code */
266 static inline void *alloc_tramp(unsigned long size)
268 return module_alloc(size);
270 static inline void tramp_free(void *tramp)
272 module_memfree(tramp);
275 /* Trampolines can only be created if modules are supported */
276 static inline void *alloc_tramp(unsigned long size)
280 static inline void tramp_free(void *tramp) { }
283 /* Defined as markers to the end of the ftrace default trampolines */
284 extern void ftrace_regs_caller_end(void);
285 extern void ftrace_caller_end(void);
286 extern void ftrace_caller_op_ptr(void);
287 extern void ftrace_regs_caller_op_ptr(void);
288 extern void ftrace_regs_caller_jmp(void);
290 /* movq function_trace_op(%rip), %rdx */
291 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
292 #define OP_REF_SIZE 7
295 * The ftrace_ops is passed to the function callback. Since the
296 * trampoline only services a single ftrace_ops, we can pass in
299 * The ftrace_op_code_union is used to create a pointer to the
300 * ftrace_ops that will be passed to the callback function.
302 union ftrace_op_code_union {
303 char code[OP_REF_SIZE];
307 } __attribute__((packed));
310 #define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))
313 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
315 unsigned long start_offset;
316 unsigned long end_offset;
317 unsigned long op_offset;
318 unsigned long call_offset;
319 unsigned long jmp_offset;
320 unsigned long offset;
321 unsigned long npages;
326 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
327 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
328 unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE };
329 union ftrace_op_code_union op_ptr;
332 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
333 start_offset = (unsigned long)ftrace_regs_caller;
334 end_offset = (unsigned long)ftrace_regs_caller_end;
335 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
336 call_offset = (unsigned long)ftrace_regs_call;
337 jmp_offset = (unsigned long)ftrace_regs_caller_jmp;
339 start_offset = (unsigned long)ftrace_caller;
340 end_offset = (unsigned long)ftrace_caller_end;
341 op_offset = (unsigned long)ftrace_caller_op_ptr;
342 call_offset = (unsigned long)ftrace_call;
346 size = end_offset - start_offset;
349 * Allocate enough size to store the ftrace_caller code,
350 * the iret , as well as the address of the ftrace_ops this
351 * trampoline is used for.
353 trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
357 *tramp_size = size + RET_SIZE + sizeof(void *);
358 npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
360 /* Copy ftrace_caller onto the trampoline memory */
361 ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size);
362 if (WARN_ON(ret < 0))
365 ip = trampoline + size;
366 if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
367 __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, x86_return_thunk, JMP32_INSN_SIZE);
369 memcpy(ip, retq, sizeof(retq));
371 /* No need to test direct calls on created trampolines */
372 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
373 /* NOP the jnz 1f; but make sure it's a 2 byte jnz */
374 ip = trampoline + (jmp_offset - start_offset);
375 if (WARN_ON(*(char *)ip != 0x75))
377 ret = copy_from_kernel_nofault(ip, x86_nops[2], 2);
383 * The address of the ftrace_ops that is used for this trampoline
384 * is stored at the end of the trampoline. This will be used to
385 * load the third parameter for the callback. Basically, that
386 * location at the end of the trampoline takes the place of
387 * the global function_trace_op variable.
390 ptr = (unsigned long *)(trampoline + size + RET_SIZE);
391 *ptr = (unsigned long)ops;
393 op_offset -= start_offset;
394 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
396 /* Are we pointing to the reference? */
397 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
400 /* Load the contents of ptr into the callback parameter */
401 offset = (unsigned long)ptr;
402 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
404 op_ptr.offset = offset;
406 /* put in the new offset to the ftrace_ops */
407 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
409 /* put in the call to the function */
410 mutex_lock(&text_mutex);
411 call_offset -= start_offset;
413 * No need to translate into a callthunk. The trampoline does
414 * the depth accounting before the call already.
416 dest = ftrace_ops_get_func(ops);
417 memcpy(trampoline + call_offset,
418 text_gen_insn(CALL_INSN_OPCODE, trampoline + call_offset, dest),
420 mutex_unlock(&text_mutex);
422 /* ALLOC_TRAMP flags lets us know we created it */
423 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
425 set_memory_rox((unsigned long)trampoline, npages);
426 return (unsigned long)trampoline;
428 tramp_free(trampoline);
432 void set_ftrace_ops_ro(void)
434 struct ftrace_ops *ops;
435 unsigned long start_offset;
436 unsigned long end_offset;
437 unsigned long npages;
440 do_for_each_ftrace_op(ops, ftrace_ops_list) {
441 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
444 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
445 start_offset = (unsigned long)ftrace_regs_caller;
446 end_offset = (unsigned long)ftrace_regs_caller_end;
448 start_offset = (unsigned long)ftrace_caller;
449 end_offset = (unsigned long)ftrace_caller_end;
451 size = end_offset - start_offset;
452 size = size + RET_SIZE + sizeof(void *);
453 npages = DIV_ROUND_UP(size, PAGE_SIZE);
454 set_memory_ro((unsigned long)ops->trampoline, npages);
455 } while_for_each_ftrace_op(ops);
458 static unsigned long calc_trampoline_call_offset(bool save_regs)
460 unsigned long start_offset;
461 unsigned long call_offset;
464 start_offset = (unsigned long)ftrace_regs_caller;
465 call_offset = (unsigned long)ftrace_regs_call;
467 start_offset = (unsigned long)ftrace_caller;
468 call_offset = (unsigned long)ftrace_call;
471 return call_offset - start_offset;
474 void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
477 unsigned long offset;
482 if (!ops->trampoline) {
483 ops->trampoline = create_trampoline(ops, &size);
484 if (!ops->trampoline)
486 ops->trampoline_size = size;
491 * The ftrace_ops caller may set up its own trampoline.
492 * In such a case, this code must not modify it.
494 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
497 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
498 ip = ops->trampoline + offset;
499 func = ftrace_ops_get_func(ops);
501 mutex_lock(&text_mutex);
502 /* Do a safe modify in case the trampoline is executing */
503 new = ftrace_call_replace(ip, (unsigned long)func);
504 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
505 mutex_unlock(&text_mutex);
508 /* Return the address of the function the trampoline calls */
509 static void *addr_from_call(void *ptr)
511 union text_poke_insn call;
514 ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE);
515 if (WARN_ON_ONCE(ret < 0))
518 /* Make sure this is a call */
519 if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
520 pr_warn("Expected E8, got %x\n", call.opcode);
524 return ptr + CALL_INSN_SIZE + call.disp;
528 * If the ops->trampoline was not allocated, then it probably
529 * has a static trampoline func, or is the ftrace caller itself.
531 static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
533 unsigned long offset;
534 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
537 if (ops && ops->trampoline) {
538 #if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) && \
539 defined(CONFIG_FUNCTION_GRAPH_TRACER)
541 * We only know about function graph tracer setting as static
544 if (ops->trampoline == FTRACE_GRAPH_ADDR)
545 return (void *)prepare_ftrace_return;
550 offset = calc_trampoline_call_offset(save_regs);
553 ptr = (void *)FTRACE_REGS_ADDR + offset;
555 ptr = (void *)FTRACE_ADDR + offset;
557 return addr_from_call(ptr);
560 void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
562 unsigned long offset;
564 /* If we didn't allocate this trampoline, consider it static */
565 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
566 return static_tramp_func(ops, rec);
568 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
569 return addr_from_call((void *)ops->trampoline + offset);
572 void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
574 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
577 tramp_free((void *)ops->trampoline);
581 #endif /* CONFIG_X86_64 */
582 #endif /* CONFIG_DYNAMIC_FTRACE */
584 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
586 #if defined(CONFIG_DYNAMIC_FTRACE) && !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS)
587 extern void ftrace_graph_call(void);
588 static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
590 return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
593 static int ftrace_mod_jmp(unsigned long ip, void *func)
597 new = ftrace_jmp_replace(ip, (unsigned long)func);
598 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
602 int ftrace_enable_ftrace_graph_caller(void)
604 unsigned long ip = (unsigned long)(&ftrace_graph_call);
606 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
609 int ftrace_disable_ftrace_graph_caller(void)
611 unsigned long ip = (unsigned long)(&ftrace_graph_call);
613 return ftrace_mod_jmp(ip, &ftrace_stub);
615 #endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
618 * Hook the return address and push it in the stack of return addrs
619 * in current thread info.
621 void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
622 unsigned long frame_pointer)
624 unsigned long return_hooker = (unsigned long)&return_to_handler;
628 * When resuming from suspend-to-ram, this function can be indirectly
629 * called from early CPU startup code while the CPU is in real mode,
630 * which would fail miserably. Make sure the stack pointer is a
633 * This check isn't as accurate as virt_addr_valid(), but it should be
634 * good enough for this purpose, and it's fast.
636 if (unlikely((long)__builtin_frame_address(0) >= 0))
639 if (unlikely(ftrace_graph_is_dead()))
642 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
645 bit = ftrace_test_recursion_trylock(ip, *parent);
649 if (!function_graph_enter(*parent, ip, frame_pointer, parent))
650 *parent = return_hooker;
652 ftrace_test_recursion_unlock(bit);
655 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
656 void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
657 struct ftrace_ops *op, struct ftrace_regs *fregs)
659 struct pt_regs *regs = &fregs->regs;
660 unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs);
662 prepare_ftrace_return(ip, (unsigned long *)stack, 0);
666 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */