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/cacheflush.h>
28 #include <asm/kprobes.h>
29 #include <asm/ftrace.h>
32 #if defined(CONFIG_FUNCTION_GRAPH_TRACER) && \
33 !defined(CC_USING_FENTRY) && \
34 !defined(CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE)
35 # error The following combination is not supported: ((compiler missing -mfentry) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE
38 #ifdef CONFIG_DYNAMIC_FTRACE
40 int ftrace_arch_code_modify_prepare(void)
43 set_all_modules_text_rw();
47 int ftrace_arch_code_modify_post_process(void)
49 set_all_modules_text_ro();
54 union ftrace_code_union {
55 char code[MCOUNT_INSN_SIZE];
59 } __attribute__((packed));
62 static int ftrace_calc_offset(long ip, long addr)
64 return (int)(addr - ip);
67 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
69 static union ftrace_code_union calc;
72 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
75 * No locking needed, this must be called via kstop_machine
76 * which in essence is like running on a uniprocessor machine.
82 within(unsigned long addr, unsigned long start, unsigned long end)
84 return addr >= start && addr < end;
87 static unsigned long text_ip_addr(unsigned long ip)
90 * On x86_64, kernel text mappings are mapped read-only, so we use
91 * the kernel identity mapping instead of the kernel text mapping
92 * to modify the kernel text.
94 * For 32bit kernels, these mappings are same and we can use
95 * kernel identity mapping to modify code.
97 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
98 ip = (unsigned long)__va(__pa_symbol(ip));
103 static const unsigned char *ftrace_nop_replace(void)
105 return ideal_nops[NOP_ATOMIC5];
109 ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
110 unsigned const char *new_code)
112 unsigned char replaced[MCOUNT_INSN_SIZE];
114 ftrace_expected = old_code;
118 * We are paranoid about modifying text, as if a bug was to happen, it
119 * could cause us to read or write to someplace that could cause harm.
120 * Carefully read and modify the code with probe_kernel_*(), and make
121 * sure what we read is what we expected it to be before modifying it.
124 /* read the text we want to modify */
125 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
128 /* Make sure it is what we expect it to be */
129 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
132 ip = text_ip_addr(ip);
134 /* replace the text with the new text */
135 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
143 int ftrace_make_nop(struct module *mod,
144 struct dyn_ftrace *rec, unsigned long addr)
146 unsigned const char *new, *old;
147 unsigned long ip = rec->ip;
149 old = ftrace_call_replace(ip, addr);
150 new = ftrace_nop_replace();
153 * On boot up, and when modules are loaded, the MCOUNT_ADDR
154 * is converted to a nop, and will never become MCOUNT_ADDR
155 * again. This code is either running before SMP (on boot up)
156 * or before the code will ever be executed (module load).
157 * We do not want to use the breakpoint version in this case,
158 * just modify the code directly.
160 if (addr == MCOUNT_ADDR)
161 return ftrace_modify_code_direct(rec->ip, old, new);
163 ftrace_expected = NULL;
165 /* Normal cases use add_brk_on_nop */
166 WARN_ONCE(1, "invalid use of ftrace_make_nop");
170 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
172 unsigned const char *new, *old;
173 unsigned long ip = rec->ip;
175 old = ftrace_nop_replace();
176 new = ftrace_call_replace(ip, addr);
178 /* Should only be called when module is loaded */
179 return ftrace_modify_code_direct(rec->ip, old, new);
183 * The modifying_ftrace_code is used to tell the breakpoint
184 * handler to call ftrace_int3_handler(). If it fails to
185 * call this handler for a breakpoint added by ftrace, then
186 * the kernel may crash.
188 * As atomic_writes on x86 do not need a barrier, we do not
189 * need to add smp_mb()s for this to work. It is also considered
190 * that we can not read the modifying_ftrace_code before
191 * executing the breakpoint. That would be quite remarkable if
192 * it could do that. Here's the flow that is required:
198 * <trap-int3> // implicit (r)mb
199 * if (atomic_read(mfc))
200 * call ftrace_int3_handler()
202 * Then when we are finished:
206 * If we hit a breakpoint that was not set by ftrace, it does not
207 * matter if ftrace_int3_handler() is called or not. It will
208 * simply be ignored. But it is crucial that a ftrace nop/caller
209 * breakpoint is handled. No other user should ever place a
210 * breakpoint on an ftrace nop/caller location. It must only
211 * be done by this code.
213 atomic_t modifying_ftrace_code __read_mostly;
216 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
217 unsigned const char *new_code);
220 * Should never be called:
221 * As it is only called by __ftrace_replace_code() which is called by
222 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
223 * which is called to turn mcount into nops or nops into function calls
224 * but not to convert a function from not using regs to one that uses
225 * regs, which ftrace_modify_call() is for.
227 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
231 ftrace_expected = NULL;
235 static unsigned long ftrace_update_func;
237 static int update_ftrace_func(unsigned long ip, void *new)
239 unsigned char old[MCOUNT_INSN_SIZE];
242 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
244 ftrace_update_func = ip;
245 /* Make sure the breakpoints see the ftrace_update_func update */
248 /* See comment above by declaration of modifying_ftrace_code */
249 atomic_inc(&modifying_ftrace_code);
251 ret = ftrace_modify_code(ip, old, new);
253 atomic_dec(&modifying_ftrace_code);
258 int ftrace_update_ftrace_func(ftrace_func_t func)
260 unsigned long ip = (unsigned long)(&ftrace_call);
264 new = ftrace_call_replace(ip, (unsigned long)func);
265 ret = update_ftrace_func(ip, new);
267 /* Also update the regs callback function */
269 ip = (unsigned long)(&ftrace_regs_call);
270 new = ftrace_call_replace(ip, (unsigned long)func);
271 ret = update_ftrace_func(ip, new);
277 static int is_ftrace_caller(unsigned long ip)
279 if (ip == ftrace_update_func)
286 * A breakpoint was added to the code address we are about to
287 * modify, and this is the handle that will just skip over it.
288 * We are either changing a nop into a trace call, or a trace
289 * call to a nop. While the change is taking place, we treat
290 * it just like it was a nop.
292 int ftrace_int3_handler(struct pt_regs *regs)
296 if (WARN_ON_ONCE(!regs))
300 if (!ftrace_location(ip) && !is_ftrace_caller(ip))
303 regs->ip += MCOUNT_INSN_SIZE - 1;
308 static int ftrace_write(unsigned long ip, const char *val, int size)
310 ip = text_ip_addr(ip);
312 if (probe_kernel_write((void *)ip, val, size))
318 static int add_break(unsigned long ip, const char *old)
320 unsigned char replaced[MCOUNT_INSN_SIZE];
321 unsigned char brk = BREAKPOINT_INSTRUCTION;
323 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
326 ftrace_expected = old;
328 /* Make sure it is what we expect it to be */
329 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
332 return ftrace_write(ip, &brk, 1);
335 static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
337 unsigned const char *old;
338 unsigned long ip = rec->ip;
340 old = ftrace_call_replace(ip, addr);
342 return add_break(rec->ip, old);
346 static int add_brk_on_nop(struct dyn_ftrace *rec)
348 unsigned const char *old;
350 old = ftrace_nop_replace();
352 return add_break(rec->ip, old);
355 static int add_breakpoints(struct dyn_ftrace *rec, int enable)
357 unsigned long ftrace_addr;
360 ftrace_addr = ftrace_get_addr_curr(rec);
362 ret = ftrace_test_record(rec, enable);
365 case FTRACE_UPDATE_IGNORE:
368 case FTRACE_UPDATE_MAKE_CALL:
369 /* converting nop to call */
370 return add_brk_on_nop(rec);
372 case FTRACE_UPDATE_MODIFY_CALL:
373 case FTRACE_UPDATE_MAKE_NOP:
374 /* converting a call to a nop */
375 return add_brk_on_call(rec, ftrace_addr);
381 * On error, we need to remove breakpoints. This needs to
382 * be done caefully. If the address does not currently have a
383 * breakpoint, we know we are done. Otherwise, we look at the
384 * remaining 4 bytes of the instruction. If it matches a nop
385 * we replace the breakpoint with the nop. Otherwise we replace
386 * it with the call instruction.
388 static int remove_breakpoint(struct dyn_ftrace *rec)
390 unsigned char ins[MCOUNT_INSN_SIZE];
391 unsigned char brk = BREAKPOINT_INSTRUCTION;
392 const unsigned char *nop;
393 unsigned long ftrace_addr;
394 unsigned long ip = rec->ip;
396 /* If we fail the read, just give up */
397 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
400 /* If this does not have a breakpoint, we are done */
404 nop = ftrace_nop_replace();
407 * If the last 4 bytes of the instruction do not match
408 * a nop, then we assume that this is a call to ftrace_addr.
410 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
412 * For extra paranoidism, we check if the breakpoint is on
413 * a call that would actually jump to the ftrace_addr.
414 * If not, don't touch the breakpoint, we make just create
417 ftrace_addr = ftrace_get_addr_new(rec);
418 nop = ftrace_call_replace(ip, ftrace_addr);
420 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
423 /* Check both ftrace_addr and ftrace_old_addr */
424 ftrace_addr = ftrace_get_addr_curr(rec);
425 nop = ftrace_call_replace(ip, ftrace_addr);
427 ftrace_expected = nop;
429 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
434 return ftrace_write(ip, nop, 1);
437 static int add_update_code(unsigned long ip, unsigned const char *new)
439 /* skip breakpoint */
442 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
445 static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
447 unsigned long ip = rec->ip;
448 unsigned const char *new;
450 new = ftrace_call_replace(ip, addr);
451 return add_update_code(ip, new);
454 static int add_update_nop(struct dyn_ftrace *rec)
456 unsigned long ip = rec->ip;
457 unsigned const char *new;
459 new = ftrace_nop_replace();
460 return add_update_code(ip, new);
463 static int add_update(struct dyn_ftrace *rec, int enable)
465 unsigned long ftrace_addr;
468 ret = ftrace_test_record(rec, enable);
470 ftrace_addr = ftrace_get_addr_new(rec);
473 case FTRACE_UPDATE_IGNORE:
476 case FTRACE_UPDATE_MODIFY_CALL:
477 case FTRACE_UPDATE_MAKE_CALL:
478 /* converting nop to call */
479 return add_update_call(rec, ftrace_addr);
481 case FTRACE_UPDATE_MAKE_NOP:
482 /* converting a call to a nop */
483 return add_update_nop(rec);
489 static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
491 unsigned long ip = rec->ip;
492 unsigned const char *new;
494 new = ftrace_call_replace(ip, addr);
496 return ftrace_write(ip, new, 1);
499 static int finish_update_nop(struct dyn_ftrace *rec)
501 unsigned long ip = rec->ip;
502 unsigned const char *new;
504 new = ftrace_nop_replace();
506 return ftrace_write(ip, new, 1);
509 static int finish_update(struct dyn_ftrace *rec, int enable)
511 unsigned long ftrace_addr;
514 ret = ftrace_update_record(rec, enable);
516 ftrace_addr = ftrace_get_addr_new(rec);
519 case FTRACE_UPDATE_IGNORE:
522 case FTRACE_UPDATE_MODIFY_CALL:
523 case FTRACE_UPDATE_MAKE_CALL:
524 /* converting nop to call */
525 return finish_update_call(rec, ftrace_addr);
527 case FTRACE_UPDATE_MAKE_NOP:
528 /* converting a call to a nop */
529 return finish_update_nop(rec);
535 static void do_sync_core(void *data)
540 static void run_sync(void)
542 int 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)
992 if (unlikely(ftrace_graph_is_dead()))
995 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
999 * Protect against fault, even if it shouldn't
1000 * happen. This tool is too much intrusive to
1001 * ignore such a protection.
1004 "1: " _ASM_MOV " (%[parent]), %[old]\n"
1005 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1006 " movl $0, %[faulted]\n"
1009 ".section .fixup, \"ax\"\n"
1010 "4: movl $1, %[faulted]\n"
1014 _ASM_EXTABLE(1b, 4b)
1015 _ASM_EXTABLE(2b, 4b)
1017 : [old] "=&r" (old), [faulted] "=r" (faulted)
1018 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1022 if (unlikely(faulted)) {
1023 ftrace_graph_stop();
1028 trace.func = self_addr;
1029 trace.depth = current->curr_ret_stack + 1;
1031 /* Only trace if the calling function expects to */
1032 if (!ftrace_graph_entry(&trace)) {
1037 if (ftrace_push_return_trace(old, self_addr, &trace.depth,
1038 frame_pointer, parent) == -EBUSY) {
1043 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */