2 * Dynamic function tracing support.
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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.
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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/slab.h>
21 #include <linux/init.h>
22 #include <linux/list.h>
23 #include <linux/module.h>
25 #include <trace/syscall.h>
27 #include <asm/set_memory.h>
28 #include <asm/kprobes.h>
29 #include <asm/ftrace.h>
32 #ifdef CONFIG_DYNAMIC_FTRACE
34 int ftrace_arch_code_modify_prepare(void)
37 set_all_modules_text_rw();
41 int ftrace_arch_code_modify_post_process(void)
43 set_all_modules_text_ro();
48 union ftrace_code_union {
49 char code[MCOUNT_INSN_SIZE];
53 } __attribute__((packed));
56 static int ftrace_calc_offset(long ip, long addr)
58 return (int)(addr - ip);
61 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
63 static union ftrace_code_union calc;
66 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
69 * No locking needed, this must be called via kstop_machine
70 * which in essence is like running on a uniprocessor machine.
76 within(unsigned long addr, unsigned long start, unsigned long end)
78 return addr >= start && addr < end;
81 static unsigned long text_ip_addr(unsigned long ip)
84 * On x86_64, kernel text mappings are mapped read-only, so we use
85 * the kernel identity mapping instead of the kernel text mapping
86 * to modify the kernel text.
88 * For 32bit kernels, these mappings are same and we can use
89 * kernel identity mapping to modify code.
91 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
92 ip = (unsigned long)__va(__pa_symbol(ip));
97 static const unsigned char *ftrace_nop_replace(void)
99 return ideal_nops[NOP_ATOMIC5];
103 ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
104 unsigned const char *new_code)
106 unsigned char replaced[MCOUNT_INSN_SIZE];
108 ftrace_expected = old_code;
112 * We are paranoid about modifying text, as if a bug was to happen, it
113 * could cause us to read or write to someplace that could cause harm.
114 * Carefully read and modify the code with probe_kernel_*(), and make
115 * sure what we read is what we expected it to be before modifying it.
118 /* read the text we want to modify */
119 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
122 /* Make sure it is what we expect it to be */
123 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
126 ip = text_ip_addr(ip);
128 /* replace the text with the new text */
129 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
137 int ftrace_make_nop(struct module *mod,
138 struct dyn_ftrace *rec, unsigned long addr)
140 unsigned const char *new, *old;
141 unsigned long ip = rec->ip;
143 old = ftrace_call_replace(ip, addr);
144 new = ftrace_nop_replace();
147 * On boot up, and when modules are loaded, the MCOUNT_ADDR
148 * is converted to a nop, and will never become MCOUNT_ADDR
149 * again. This code is either running before SMP (on boot up)
150 * or before the code will ever be executed (module load).
151 * We do not want to use the breakpoint version in this case,
152 * just modify the code directly.
154 if (addr == MCOUNT_ADDR)
155 return ftrace_modify_code_direct(rec->ip, old, new);
157 ftrace_expected = NULL;
159 /* Normal cases use add_brk_on_nop */
160 WARN_ONCE(1, "invalid use of ftrace_make_nop");
164 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
166 unsigned const char *new, *old;
167 unsigned long ip = rec->ip;
169 old = ftrace_nop_replace();
170 new = ftrace_call_replace(ip, addr);
172 /* Should only be called when module is loaded */
173 return ftrace_modify_code_direct(rec->ip, old, new);
177 * The modifying_ftrace_code is used to tell the breakpoint
178 * handler to call ftrace_int3_handler(). If it fails to
179 * call this handler for a breakpoint added by ftrace, then
180 * the kernel may crash.
182 * As atomic_writes on x86 do not need a barrier, we do not
183 * need to add smp_mb()s for this to work. It is also considered
184 * that we can not read the modifying_ftrace_code before
185 * executing the breakpoint. That would be quite remarkable if
186 * it could do that. Here's the flow that is required:
192 * <trap-int3> // implicit (r)mb
193 * if (atomic_read(mfc))
194 * call ftrace_int3_handler()
196 * Then when we are finished:
200 * If we hit a breakpoint that was not set by ftrace, it does not
201 * matter if ftrace_int3_handler() is called or not. It will
202 * simply be ignored. But it is crucial that a ftrace nop/caller
203 * breakpoint is handled. No other user should ever place a
204 * breakpoint on an ftrace nop/caller location. It must only
205 * be done by this code.
207 atomic_t modifying_ftrace_code __read_mostly;
210 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
211 unsigned const char *new_code);
214 * Should never be called:
215 * As it is only called by __ftrace_replace_code() which is called by
216 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
217 * which is called to turn mcount into nops or nops into function calls
218 * but not to convert a function from not using regs to one that uses
219 * regs, which ftrace_modify_call() is for.
221 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
225 ftrace_expected = NULL;
229 static unsigned long ftrace_update_func;
231 static int update_ftrace_func(unsigned long ip, void *new)
233 unsigned char old[MCOUNT_INSN_SIZE];
236 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
238 ftrace_update_func = ip;
239 /* Make sure the breakpoints see the ftrace_update_func update */
242 /* See comment above by declaration of modifying_ftrace_code */
243 atomic_inc(&modifying_ftrace_code);
245 ret = ftrace_modify_code(ip, old, new);
247 atomic_dec(&modifying_ftrace_code);
252 int ftrace_update_ftrace_func(ftrace_func_t func)
254 unsigned long ip = (unsigned long)(&ftrace_call);
258 new = ftrace_call_replace(ip, (unsigned long)func);
259 ret = update_ftrace_func(ip, new);
261 /* Also update the regs callback function */
263 ip = (unsigned long)(&ftrace_regs_call);
264 new = ftrace_call_replace(ip, (unsigned long)func);
265 ret = update_ftrace_func(ip, new);
271 static int is_ftrace_caller(unsigned long ip)
273 if (ip == ftrace_update_func)
280 * A breakpoint was added to the code address we are about to
281 * modify, and this is the handle that will just skip over it.
282 * We are either changing a nop into a trace call, or a trace
283 * call to a nop. While the change is taking place, we treat
284 * it just like it was a nop.
286 int ftrace_int3_handler(struct pt_regs *regs)
290 if (WARN_ON_ONCE(!regs))
294 if (!ftrace_location(ip) && !is_ftrace_caller(ip))
297 regs->ip += MCOUNT_INSN_SIZE - 1;
302 static int ftrace_write(unsigned long ip, const char *val, int size)
304 ip = text_ip_addr(ip);
306 if (probe_kernel_write((void *)ip, val, size))
312 static int add_break(unsigned long ip, const char *old)
314 unsigned char replaced[MCOUNT_INSN_SIZE];
315 unsigned char brk = BREAKPOINT_INSTRUCTION;
317 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
320 ftrace_expected = old;
322 /* Make sure it is what we expect it to be */
323 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
326 return ftrace_write(ip, &brk, 1);
329 static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
331 unsigned const char *old;
332 unsigned long ip = rec->ip;
334 old = ftrace_call_replace(ip, addr);
336 return add_break(rec->ip, old);
340 static int add_brk_on_nop(struct dyn_ftrace *rec)
342 unsigned const char *old;
344 old = ftrace_nop_replace();
346 return add_break(rec->ip, old);
349 static int add_breakpoints(struct dyn_ftrace *rec, int enable)
351 unsigned long ftrace_addr;
354 ftrace_addr = ftrace_get_addr_curr(rec);
356 ret = ftrace_test_record(rec, enable);
359 case FTRACE_UPDATE_IGNORE:
362 case FTRACE_UPDATE_MAKE_CALL:
363 /* converting nop to call */
364 return add_brk_on_nop(rec);
366 case FTRACE_UPDATE_MODIFY_CALL:
367 case FTRACE_UPDATE_MAKE_NOP:
368 /* converting a call to a nop */
369 return add_brk_on_call(rec, ftrace_addr);
375 * On error, we need to remove breakpoints. This needs to
376 * be done caefully. If the address does not currently have a
377 * breakpoint, we know we are done. Otherwise, we look at the
378 * remaining 4 bytes of the instruction. If it matches a nop
379 * we replace the breakpoint with the nop. Otherwise we replace
380 * it with the call instruction.
382 static int remove_breakpoint(struct dyn_ftrace *rec)
384 unsigned char ins[MCOUNT_INSN_SIZE];
385 unsigned char brk = BREAKPOINT_INSTRUCTION;
386 const unsigned char *nop;
387 unsigned long ftrace_addr;
388 unsigned long ip = rec->ip;
390 /* If we fail the read, just give up */
391 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
394 /* If this does not have a breakpoint, we are done */
398 nop = ftrace_nop_replace();
401 * If the last 4 bytes of the instruction do not match
402 * a nop, then we assume that this is a call to ftrace_addr.
404 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
406 * For extra paranoidism, we check if the breakpoint is on
407 * a call that would actually jump to the ftrace_addr.
408 * If not, don't touch the breakpoint, we make just create
411 ftrace_addr = ftrace_get_addr_new(rec);
412 nop = ftrace_call_replace(ip, ftrace_addr);
414 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
417 /* Check both ftrace_addr and ftrace_old_addr */
418 ftrace_addr = ftrace_get_addr_curr(rec);
419 nop = ftrace_call_replace(ip, ftrace_addr);
421 ftrace_expected = nop;
423 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
428 return ftrace_write(ip, nop, 1);
431 static int add_update_code(unsigned long ip, unsigned const char *new)
433 /* skip breakpoint */
436 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
439 static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
441 unsigned long ip = rec->ip;
442 unsigned const char *new;
444 new = ftrace_call_replace(ip, addr);
445 return add_update_code(ip, new);
448 static int add_update_nop(struct dyn_ftrace *rec)
450 unsigned long ip = rec->ip;
451 unsigned const char *new;
453 new = ftrace_nop_replace();
454 return add_update_code(ip, new);
457 static int add_update(struct dyn_ftrace *rec, int enable)
459 unsigned long ftrace_addr;
462 ret = ftrace_test_record(rec, enable);
464 ftrace_addr = ftrace_get_addr_new(rec);
467 case FTRACE_UPDATE_IGNORE:
470 case FTRACE_UPDATE_MODIFY_CALL:
471 case FTRACE_UPDATE_MAKE_CALL:
472 /* converting nop to call */
473 return add_update_call(rec, ftrace_addr);
475 case FTRACE_UPDATE_MAKE_NOP:
476 /* converting a call to a nop */
477 return add_update_nop(rec);
483 static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
485 unsigned long ip = rec->ip;
486 unsigned const char *new;
488 new = ftrace_call_replace(ip, addr);
490 return ftrace_write(ip, new, 1);
493 static int finish_update_nop(struct dyn_ftrace *rec)
495 unsigned long ip = rec->ip;
496 unsigned const char *new;
498 new = ftrace_nop_replace();
500 return ftrace_write(ip, new, 1);
503 static int finish_update(struct dyn_ftrace *rec, int enable)
505 unsigned long ftrace_addr;
508 ret = ftrace_update_record(rec, enable);
510 ftrace_addr = ftrace_get_addr_new(rec);
513 case FTRACE_UPDATE_IGNORE:
516 case FTRACE_UPDATE_MODIFY_CALL:
517 case FTRACE_UPDATE_MAKE_CALL:
518 /* converting nop to call */
519 return finish_update_call(rec, ftrace_addr);
521 case FTRACE_UPDATE_MAKE_NOP:
522 /* converting a call to a nop */
523 return finish_update_nop(rec);
529 static void do_sync_core(void *data)
534 static void run_sync(void)
538 /* No need to sync if there's only one CPU */
539 if (num_online_cpus() == 1)
542 enable_irqs = irqs_disabled();
544 /* We may be called with interrupts disabled (on bootup). */
547 on_each_cpu(do_sync_core, NULL, 1);
552 void ftrace_replace_code(int enable)
554 struct ftrace_rec_iter *iter;
555 struct dyn_ftrace *rec;
556 const char *report = "adding breakpoints";
560 for_ftrace_rec_iter(iter) {
561 rec = ftrace_rec_iter_record(iter);
563 ret = add_breakpoints(rec, enable);
565 goto remove_breakpoints;
571 report = "updating code";
574 for_ftrace_rec_iter(iter) {
575 rec = ftrace_rec_iter_record(iter);
577 ret = add_update(rec, enable);
579 goto remove_breakpoints;
585 report = "removing breakpoints";
588 for_ftrace_rec_iter(iter) {
589 rec = ftrace_rec_iter_record(iter);
591 ret = finish_update(rec, enable);
593 goto remove_breakpoints;
602 pr_warn("Failed on %s (%d):\n", report, count);
603 ftrace_bug(ret, rec);
604 for_ftrace_rec_iter(iter) {
605 rec = ftrace_rec_iter_record(iter);
607 * Breakpoints are handled only when this function is in
608 * progress. The system could not work with them.
610 if (remove_breakpoint(rec))
617 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
618 unsigned const char *new_code)
622 ret = add_break(ip, old_code);
628 ret = add_update_code(ip, new_code);
634 ret = ftrace_write(ip, new_code, 1);
636 * The breakpoint is handled only when this function is in progress.
637 * The system could not work if we could not remove it.
645 /* Also here the system could not work with the breakpoint */
646 if (ftrace_write(ip, old_code, 1))
651 void arch_ftrace_update_code(int command)
653 /* See comment above by declaration of modifying_ftrace_code */
654 atomic_inc(&modifying_ftrace_code);
656 ftrace_modify_all_code(command);
658 atomic_dec(&modifying_ftrace_code);
661 int __init ftrace_dyn_arch_init(void)
666 #if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER)
667 static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
669 static union ftrace_code_union calc;
671 /* Jmp not a call (ignore the .e8) */
673 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
676 * ftrace external locks synchronize the access to the static variable.
682 /* Currently only x86_64 supports dynamic trampolines */
685 #ifdef CONFIG_MODULES
686 #include <linux/moduleloader.h>
687 /* Module allocation simplifies allocating memory for code */
688 static inline void *alloc_tramp(unsigned long size)
690 return module_alloc(size);
692 static inline void tramp_free(void *tramp)
694 module_memfree(tramp);
697 /* Trampolines can only be created if modules are supported */
698 static inline void *alloc_tramp(unsigned long size)
702 static inline void tramp_free(void *tramp) { }
705 /* Defined as markers to the end of the ftrace default trampolines */
706 extern void ftrace_regs_caller_end(void);
707 extern void ftrace_epilogue(void);
708 extern void ftrace_caller_op_ptr(void);
709 extern void ftrace_regs_caller_op_ptr(void);
711 /* movq function_trace_op(%rip), %rdx */
712 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
713 #define OP_REF_SIZE 7
716 * The ftrace_ops is passed to the function callback. Since the
717 * trampoline only services a single ftrace_ops, we can pass in
720 * The ftrace_op_code_union is used to create a pointer to the
721 * ftrace_ops that will be passed to the callback function.
723 union ftrace_op_code_union {
724 char code[OP_REF_SIZE];
728 } __attribute__((packed));
732 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
734 unsigned const char *jmp;
735 unsigned long start_offset;
736 unsigned long end_offset;
737 unsigned long op_offset;
738 unsigned long offset;
743 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
744 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
745 union ftrace_op_code_union op_ptr;
748 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
749 start_offset = (unsigned long)ftrace_regs_caller;
750 end_offset = (unsigned long)ftrace_regs_caller_end;
751 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
753 start_offset = (unsigned long)ftrace_caller;
754 end_offset = (unsigned long)ftrace_epilogue;
755 op_offset = (unsigned long)ftrace_caller_op_ptr;
758 size = end_offset - start_offset;
761 * Allocate enough size to store the ftrace_caller code,
762 * the jmp to ftrace_epilogue, as well as the address of
763 * the ftrace_ops this trampoline is used for.
765 trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *));
769 *tramp_size = size + MCOUNT_INSN_SIZE + sizeof(void *);
771 /* Copy ftrace_caller onto the trampoline memory */
772 ret = probe_kernel_read(trampoline, (void *)start_offset, size);
773 if (WARN_ON(ret < 0)) {
774 tramp_free(trampoline);
778 ip = (unsigned long)trampoline + size;
780 /* The trampoline ends with a jmp to ftrace_epilogue */
781 jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_epilogue);
782 memcpy(trampoline + size, jmp, MCOUNT_INSN_SIZE);
785 * The address of the ftrace_ops that is used for this trampoline
786 * is stored at the end of the trampoline. This will be used to
787 * load the third parameter for the callback. Basically, that
788 * location at the end of the trampoline takes the place of
789 * the global function_trace_op variable.
792 ptr = (unsigned long *)(trampoline + size + MCOUNT_INSN_SIZE);
793 *ptr = (unsigned long)ops;
795 op_offset -= start_offset;
796 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
798 /* Are we pointing to the reference? */
799 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) {
800 tramp_free(trampoline);
804 /* Load the contents of ptr into the callback parameter */
805 offset = (unsigned long)ptr;
806 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
808 op_ptr.offset = offset;
810 /* put in the new offset to the ftrace_ops */
811 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
813 /* ALLOC_TRAMP flags lets us know we created it */
814 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
816 return (unsigned long)trampoline;
819 static unsigned long calc_trampoline_call_offset(bool save_regs)
821 unsigned long start_offset;
822 unsigned long call_offset;
825 start_offset = (unsigned long)ftrace_regs_caller;
826 call_offset = (unsigned long)ftrace_regs_call;
828 start_offset = (unsigned long)ftrace_caller;
829 call_offset = (unsigned long)ftrace_call;
832 return call_offset - start_offset;
835 void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
839 unsigned long offset;
844 if (ops->trampoline) {
846 * The ftrace_ops caller may set up its own trampoline.
847 * In such a case, this code must not modify it.
849 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
852 ops->trampoline = create_trampoline(ops, &size);
853 if (!ops->trampoline)
855 ops->trampoline_size = size;
858 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
859 ip = ops->trampoline + offset;
861 func = ftrace_ops_get_func(ops);
863 /* Do a safe modify in case the trampoline is executing */
864 new = ftrace_call_replace(ip, (unsigned long)func);
865 ret = update_ftrace_func(ip, new);
867 /* The update should never fail */
871 /* Return the address of the function the trampoline calls */
872 static void *addr_from_call(void *ptr)
874 union ftrace_code_union calc;
877 ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
878 if (WARN_ON_ONCE(ret < 0))
881 /* Make sure this is a call */
882 if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
883 pr_warn("Expected e8, got %x\n", calc.e8);
887 return ptr + MCOUNT_INSN_SIZE + calc.offset;
890 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
891 unsigned long frame_pointer);
894 * If the ops->trampoline was not allocated, then it probably
895 * has a static trampoline func, or is the ftrace caller itself.
897 static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
899 unsigned long offset;
900 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
903 if (ops && ops->trampoline) {
904 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
906 * We only know about function graph tracer setting as static
909 if (ops->trampoline == FTRACE_GRAPH_ADDR)
910 return (void *)prepare_ftrace_return;
915 offset = calc_trampoline_call_offset(save_regs);
918 ptr = (void *)FTRACE_REGS_ADDR + offset;
920 ptr = (void *)FTRACE_ADDR + offset;
922 return addr_from_call(ptr);
925 void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
927 unsigned long offset;
929 /* If we didn't allocate this trampoline, consider it static */
930 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
931 return static_tramp_func(ops, rec);
933 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
934 return addr_from_call((void *)ops->trampoline + offset);
937 void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
939 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
942 tramp_free((void *)ops->trampoline);
946 #endif /* CONFIG_X86_64 */
947 #endif /* CONFIG_DYNAMIC_FTRACE */
949 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
951 #ifdef CONFIG_DYNAMIC_FTRACE
952 extern void ftrace_graph_call(void);
954 static int ftrace_mod_jmp(unsigned long ip, void *func)
958 new = ftrace_jmp_replace(ip, (unsigned long)func);
960 return update_ftrace_func(ip, new);
963 int ftrace_enable_ftrace_graph_caller(void)
965 unsigned long ip = (unsigned long)(&ftrace_graph_call);
967 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
970 int ftrace_disable_ftrace_graph_caller(void)
972 unsigned long ip = (unsigned long)(&ftrace_graph_call);
974 return ftrace_mod_jmp(ip, &ftrace_stub);
977 #endif /* !CONFIG_DYNAMIC_FTRACE */
980 * Hook the return address and push it in the stack of return addrs
981 * in current thread info.
983 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
984 unsigned long frame_pointer)
988 struct ftrace_graph_ent trace;
989 unsigned long return_hooker = (unsigned long)
993 * When resuming from suspend-to-ram, this function can be indirectly
994 * called from early CPU startup code while the CPU is in real mode,
995 * which would fail miserably. Make sure the stack pointer is a
998 * This check isn't as accurate as virt_addr_valid(), but it should be
999 * good enough for this purpose, and it's fast.
1001 if (unlikely((long)__builtin_frame_address(0) >= 0))
1004 if (unlikely(ftrace_graph_is_dead()))
1007 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
1011 * Protect against fault, even if it shouldn't
1012 * happen. This tool is too much intrusive to
1013 * ignore such a protection.
1016 "1: " _ASM_MOV " (%[parent]), %[old]\n"
1017 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1018 " movl $0, %[faulted]\n"
1021 ".section .fixup, \"ax\"\n"
1022 "4: movl $1, %[faulted]\n"
1026 _ASM_EXTABLE(1b, 4b)
1027 _ASM_EXTABLE(2b, 4b)
1029 : [old] "=&r" (old), [faulted] "=r" (faulted)
1030 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1034 if (unlikely(faulted)) {
1035 ftrace_graph_stop();
1040 trace.func = self_addr;
1041 trace.depth = current->curr_ret_stack + 1;
1043 /* Only trace if the calling function expects to */
1044 if (!ftrace_graph_entry(&trace)) {
1049 if (ftrace_push_return_trace(old, self_addr, &trace.depth,
1050 frame_pointer, parent) == -EBUSY) {
1055 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */