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>
26 #include <trace/syscall.h>
28 #include <asm/set_memory.h>
29 #include <asm/kprobes.h>
30 #include <asm/ftrace.h>
33 #ifdef CONFIG_DYNAMIC_FTRACE
35 int ftrace_arch_code_modify_prepare(void)
38 set_all_modules_text_rw();
42 int ftrace_arch_code_modify_post_process(void)
44 set_all_modules_text_ro();
49 union ftrace_code_union {
50 char code[MCOUNT_INSN_SIZE];
54 } __attribute__((packed));
57 static int ftrace_calc_offset(long ip, long addr)
59 return (int)(addr - ip);
62 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
64 static union ftrace_code_union calc;
67 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
70 * No locking needed, this must be called via kstop_machine
71 * which in essence is like running on a uniprocessor machine.
77 within(unsigned long addr, unsigned long start, unsigned long end)
79 return addr >= start && addr < end;
82 static unsigned long text_ip_addr(unsigned long ip)
85 * On x86_64, kernel text mappings are mapped read-only, so we use
86 * the kernel identity mapping instead of the kernel text mapping
87 * to modify the kernel text.
89 * For 32bit kernels, these mappings are same and we can use
90 * kernel identity mapping to modify code.
92 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
93 ip = (unsigned long)__va(__pa_symbol(ip));
98 static const unsigned char *ftrace_nop_replace(void)
100 return ideal_nops[NOP_ATOMIC5];
104 ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
105 unsigned const char *new_code)
107 unsigned char replaced[MCOUNT_INSN_SIZE];
109 ftrace_expected = old_code;
113 * We are paranoid about modifying text, as if a bug was to happen, it
114 * could cause us to read or write to someplace that could cause harm.
115 * Carefully read and modify the code with probe_kernel_*(), and make
116 * sure what we read is what we expected it to be before modifying it.
119 /* read the text we want to modify */
120 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
123 /* Make sure it is what we expect it to be */
124 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
127 ip = text_ip_addr(ip);
129 /* replace the text with the new text */
130 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
138 int ftrace_make_nop(struct module *mod,
139 struct dyn_ftrace *rec, unsigned long addr)
141 unsigned const char *new, *old;
142 unsigned long ip = rec->ip;
144 old = ftrace_call_replace(ip, addr);
145 new = ftrace_nop_replace();
148 * On boot up, and when modules are loaded, the MCOUNT_ADDR
149 * is converted to a nop, and will never become MCOUNT_ADDR
150 * again. This code is either running before SMP (on boot up)
151 * or before the code will ever be executed (module load).
152 * We do not want to use the breakpoint version in this case,
153 * just modify the code directly.
155 if (addr == MCOUNT_ADDR)
156 return ftrace_modify_code_direct(rec->ip, old, new);
158 ftrace_expected = NULL;
160 /* Normal cases use add_brk_on_nop */
161 WARN_ONCE(1, "invalid use of ftrace_make_nop");
165 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
167 unsigned const char *new, *old;
168 unsigned long ip = rec->ip;
170 old = ftrace_nop_replace();
171 new = ftrace_call_replace(ip, addr);
173 /* Should only be called when module is loaded */
174 return ftrace_modify_code_direct(rec->ip, old, new);
178 * The modifying_ftrace_code is used to tell the breakpoint
179 * handler to call ftrace_int3_handler(). If it fails to
180 * call this handler for a breakpoint added by ftrace, then
181 * the kernel may crash.
183 * As atomic_writes on x86 do not need a barrier, we do not
184 * need to add smp_mb()s for this to work. It is also considered
185 * that we can not read the modifying_ftrace_code before
186 * executing the breakpoint. That would be quite remarkable if
187 * it could do that. Here's the flow that is required:
193 * <trap-int3> // implicit (r)mb
194 * if (atomic_read(mfc))
195 * call ftrace_int3_handler()
197 * Then when we are finished:
201 * If we hit a breakpoint that was not set by ftrace, it does not
202 * matter if ftrace_int3_handler() is called or not. It will
203 * simply be ignored. But it is crucial that a ftrace nop/caller
204 * breakpoint is handled. No other user should ever place a
205 * breakpoint on an ftrace nop/caller location. It must only
206 * be done by this code.
208 atomic_t modifying_ftrace_code __read_mostly;
211 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
212 unsigned const char *new_code);
215 * Should never be called:
216 * As it is only called by __ftrace_replace_code() which is called by
217 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
218 * which is called to turn mcount into nops or nops into function calls
219 * but not to convert a function from not using regs to one that uses
220 * regs, which ftrace_modify_call() is for.
222 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
226 ftrace_expected = NULL;
230 static unsigned long ftrace_update_func;
232 static int update_ftrace_func(unsigned long ip, void *new)
234 unsigned char old[MCOUNT_INSN_SIZE];
237 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
239 ftrace_update_func = ip;
240 /* Make sure the breakpoints see the ftrace_update_func update */
243 /* See comment above by declaration of modifying_ftrace_code */
244 atomic_inc(&modifying_ftrace_code);
246 ret = ftrace_modify_code(ip, old, new);
248 atomic_dec(&modifying_ftrace_code);
253 int ftrace_update_ftrace_func(ftrace_func_t func)
255 unsigned long ip = (unsigned long)(&ftrace_call);
259 new = ftrace_call_replace(ip, (unsigned long)func);
260 ret = update_ftrace_func(ip, new);
262 /* Also update the regs callback function */
264 ip = (unsigned long)(&ftrace_regs_call);
265 new = ftrace_call_replace(ip, (unsigned long)func);
266 ret = update_ftrace_func(ip, new);
272 static nokprobe_inline int is_ftrace_caller(unsigned long ip)
274 if (ip == ftrace_update_func)
281 * A breakpoint was added to the code address we are about to
282 * modify, and this is the handle that will just skip over it.
283 * We are either changing a nop into a trace call, or a trace
284 * call to a nop. While the change is taking place, we treat
285 * it just like it was a nop.
287 int ftrace_int3_handler(struct pt_regs *regs)
291 if (WARN_ON_ONCE(!regs))
295 if (!ftrace_location(ip) && !is_ftrace_caller(ip))
298 regs->ip += MCOUNT_INSN_SIZE - 1;
302 NOKPROBE_SYMBOL(ftrace_int3_handler);
304 static int ftrace_write(unsigned long ip, const char *val, int size)
306 ip = text_ip_addr(ip);
308 if (probe_kernel_write((void *)ip, val, size))
314 static int add_break(unsigned long ip, const char *old)
316 unsigned char replaced[MCOUNT_INSN_SIZE];
317 unsigned char brk = BREAKPOINT_INSTRUCTION;
319 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
322 ftrace_expected = old;
324 /* Make sure it is what we expect it to be */
325 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
328 return ftrace_write(ip, &brk, 1);
331 static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
333 unsigned const char *old;
334 unsigned long ip = rec->ip;
336 old = ftrace_call_replace(ip, addr);
338 return add_break(rec->ip, old);
342 static int add_brk_on_nop(struct dyn_ftrace *rec)
344 unsigned const char *old;
346 old = ftrace_nop_replace();
348 return add_break(rec->ip, old);
351 static int add_breakpoints(struct dyn_ftrace *rec, int enable)
353 unsigned long ftrace_addr;
356 ftrace_addr = ftrace_get_addr_curr(rec);
358 ret = ftrace_test_record(rec, enable);
361 case FTRACE_UPDATE_IGNORE:
364 case FTRACE_UPDATE_MAKE_CALL:
365 /* converting nop to call */
366 return add_brk_on_nop(rec);
368 case FTRACE_UPDATE_MODIFY_CALL:
369 case FTRACE_UPDATE_MAKE_NOP:
370 /* converting a call to a nop */
371 return add_brk_on_call(rec, ftrace_addr);
377 * On error, we need to remove breakpoints. This needs to
378 * be done caefully. If the address does not currently have a
379 * breakpoint, we know we are done. Otherwise, we look at the
380 * remaining 4 bytes of the instruction. If it matches a nop
381 * we replace the breakpoint with the nop. Otherwise we replace
382 * it with the call instruction.
384 static int remove_breakpoint(struct dyn_ftrace *rec)
386 unsigned char ins[MCOUNT_INSN_SIZE];
387 unsigned char brk = BREAKPOINT_INSTRUCTION;
388 const unsigned char *nop;
389 unsigned long ftrace_addr;
390 unsigned long ip = rec->ip;
392 /* If we fail the read, just give up */
393 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
396 /* If this does not have a breakpoint, we are done */
400 nop = ftrace_nop_replace();
403 * If the last 4 bytes of the instruction do not match
404 * a nop, then we assume that this is a call to ftrace_addr.
406 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
408 * For extra paranoidism, we check if the breakpoint is on
409 * a call that would actually jump to the ftrace_addr.
410 * If not, don't touch the breakpoint, we make just create
413 ftrace_addr = ftrace_get_addr_new(rec);
414 nop = ftrace_call_replace(ip, ftrace_addr);
416 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
419 /* Check both ftrace_addr and ftrace_old_addr */
420 ftrace_addr = ftrace_get_addr_curr(rec);
421 nop = ftrace_call_replace(ip, ftrace_addr);
423 ftrace_expected = nop;
425 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
430 return ftrace_write(ip, nop, 1);
433 static int add_update_code(unsigned long ip, unsigned const char *new)
435 /* skip breakpoint */
438 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
441 static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
443 unsigned long ip = rec->ip;
444 unsigned const char *new;
446 new = ftrace_call_replace(ip, addr);
447 return add_update_code(ip, new);
450 static int add_update_nop(struct dyn_ftrace *rec)
452 unsigned long ip = rec->ip;
453 unsigned const char *new;
455 new = ftrace_nop_replace();
456 return add_update_code(ip, new);
459 static int add_update(struct dyn_ftrace *rec, int enable)
461 unsigned long ftrace_addr;
464 ret = ftrace_test_record(rec, enable);
466 ftrace_addr = ftrace_get_addr_new(rec);
469 case FTRACE_UPDATE_IGNORE:
472 case FTRACE_UPDATE_MODIFY_CALL:
473 case FTRACE_UPDATE_MAKE_CALL:
474 /* converting nop to call */
475 return add_update_call(rec, ftrace_addr);
477 case FTRACE_UPDATE_MAKE_NOP:
478 /* converting a call to a nop */
479 return add_update_nop(rec);
485 static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
487 unsigned long ip = rec->ip;
488 unsigned const char *new;
490 new = ftrace_call_replace(ip, addr);
492 return ftrace_write(ip, new, 1);
495 static int finish_update_nop(struct dyn_ftrace *rec)
497 unsigned long ip = rec->ip;
498 unsigned const char *new;
500 new = ftrace_nop_replace();
502 return ftrace_write(ip, new, 1);
505 static int finish_update(struct dyn_ftrace *rec, int enable)
507 unsigned long ftrace_addr;
510 ret = ftrace_update_record(rec, enable);
512 ftrace_addr = ftrace_get_addr_new(rec);
515 case FTRACE_UPDATE_IGNORE:
518 case FTRACE_UPDATE_MODIFY_CALL:
519 case FTRACE_UPDATE_MAKE_CALL:
520 /* converting nop to call */
521 return finish_update_call(rec, ftrace_addr);
523 case FTRACE_UPDATE_MAKE_NOP:
524 /* converting a call to a nop */
525 return finish_update_nop(rec);
531 static void do_sync_core(void *data)
536 static void run_sync(void)
540 /* No need to sync if there's only one CPU */
541 if (num_online_cpus() == 1)
544 enable_irqs = irqs_disabled();
546 /* We may be called with interrupts disabled (on bootup). */
549 on_each_cpu(do_sync_core, NULL, 1);
554 void ftrace_replace_code(int enable)
556 struct ftrace_rec_iter *iter;
557 struct dyn_ftrace *rec;
558 const char *report = "adding breakpoints";
562 for_ftrace_rec_iter(iter) {
563 rec = ftrace_rec_iter_record(iter);
565 ret = add_breakpoints(rec, enable);
567 goto remove_breakpoints;
573 report = "updating code";
576 for_ftrace_rec_iter(iter) {
577 rec = ftrace_rec_iter_record(iter);
579 ret = add_update(rec, enable);
581 goto remove_breakpoints;
587 report = "removing breakpoints";
590 for_ftrace_rec_iter(iter) {
591 rec = ftrace_rec_iter_record(iter);
593 ret = finish_update(rec, enable);
595 goto remove_breakpoints;
604 pr_warn("Failed on %s (%d):\n", report, count);
605 ftrace_bug(ret, rec);
606 for_ftrace_rec_iter(iter) {
607 rec = ftrace_rec_iter_record(iter);
609 * Breakpoints are handled only when this function is in
610 * progress. The system could not work with them.
612 if (remove_breakpoint(rec))
619 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
620 unsigned const char *new_code)
624 ret = add_break(ip, old_code);
630 ret = add_update_code(ip, new_code);
636 ret = ftrace_write(ip, new_code, 1);
638 * The breakpoint is handled only when this function is in progress.
639 * The system could not work if we could not remove it.
647 /* Also here the system could not work with the breakpoint */
648 if (ftrace_write(ip, old_code, 1))
653 void arch_ftrace_update_code(int command)
655 /* See comment above by declaration of modifying_ftrace_code */
656 atomic_inc(&modifying_ftrace_code);
658 ftrace_modify_all_code(command);
660 atomic_dec(&modifying_ftrace_code);
663 int __init ftrace_dyn_arch_init(void)
668 #if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER)
669 static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
671 static union ftrace_code_union calc;
673 /* Jmp not a call (ignore the .e8) */
675 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
678 * ftrace external locks synchronize the access to the static variable.
684 /* Currently only x86_64 supports dynamic trampolines */
687 #ifdef CONFIG_MODULES
688 #include <linux/moduleloader.h>
689 /* Module allocation simplifies allocating memory for code */
690 static inline void *alloc_tramp(unsigned long size)
692 return module_alloc(size);
694 static inline void tramp_free(void *tramp, int size)
696 int npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
698 set_memory_nx((unsigned long)tramp, npages);
699 set_memory_rw((unsigned long)tramp, npages);
700 module_memfree(tramp);
703 /* Trampolines can only be created if modules are supported */
704 static inline void *alloc_tramp(unsigned long size)
708 static inline void tramp_free(void *tramp, int size) { }
711 /* Defined as markers to the end of the ftrace default trampolines */
712 extern void ftrace_regs_caller_end(void);
713 extern void ftrace_epilogue(void);
714 extern void ftrace_caller_op_ptr(void);
715 extern void ftrace_regs_caller_op_ptr(void);
717 /* movq function_trace_op(%rip), %rdx */
718 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
719 #define OP_REF_SIZE 7
722 * The ftrace_ops is passed to the function callback. Since the
723 * trampoline only services a single ftrace_ops, we can pass in
726 * The ftrace_op_code_union is used to create a pointer to the
727 * ftrace_ops that will be passed to the callback function.
729 union ftrace_op_code_union {
730 char code[OP_REF_SIZE];
734 } __attribute__((packed));
740 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
742 unsigned long start_offset;
743 unsigned long end_offset;
744 unsigned long op_offset;
745 unsigned long offset;
751 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
752 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
753 union ftrace_op_code_union op_ptr;
756 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
757 start_offset = (unsigned long)ftrace_regs_caller;
758 end_offset = (unsigned long)ftrace_regs_caller_end;
759 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
761 start_offset = (unsigned long)ftrace_caller;
762 end_offset = (unsigned long)ftrace_epilogue;
763 op_offset = (unsigned long)ftrace_caller_op_ptr;
766 size = end_offset - start_offset;
769 * Allocate enough size to store the ftrace_caller code,
770 * the iret , as well as the address of the ftrace_ops this
771 * trampoline is used for.
773 trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
777 *tramp_size = size + RET_SIZE + sizeof(void *);
779 /* Copy ftrace_caller onto the trampoline memory */
780 ret = probe_kernel_read(trampoline, (void *)start_offset, size);
781 if (WARN_ON(ret < 0))
784 ip = trampoline + size;
786 /* The trampoline ends with ret(q) */
787 retq = (unsigned long)ftrace_stub;
788 ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
789 if (WARN_ON(ret < 0))
793 * The address of the ftrace_ops that is used for this trampoline
794 * is stored at the end of the trampoline. This will be used to
795 * load the third parameter for the callback. Basically, that
796 * location at the end of the trampoline takes the place of
797 * the global function_trace_op variable.
800 ptr = (unsigned long *)(trampoline + size + RET_SIZE);
801 *ptr = (unsigned long)ops;
803 op_offset -= start_offset;
804 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
806 /* Are we pointing to the reference? */
807 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
810 /* Load the contents of ptr into the callback parameter */
811 offset = (unsigned long)ptr;
812 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
814 op_ptr.offset = offset;
816 /* put in the new offset to the ftrace_ops */
817 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
819 /* ALLOC_TRAMP flags lets us know we created it */
820 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
822 return (unsigned long)trampoline;
824 tramp_free(trampoline, *tramp_size);
828 static unsigned long calc_trampoline_call_offset(bool save_regs)
830 unsigned long start_offset;
831 unsigned long call_offset;
834 start_offset = (unsigned long)ftrace_regs_caller;
835 call_offset = (unsigned long)ftrace_regs_call;
837 start_offset = (unsigned long)ftrace_caller;
838 call_offset = (unsigned long)ftrace_call;
841 return call_offset - start_offset;
844 void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
848 unsigned long offset;
853 if (ops->trampoline) {
855 * The ftrace_ops caller may set up its own trampoline.
856 * In such a case, this code must not modify it.
858 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
860 npages = PAGE_ALIGN(ops->trampoline_size) >> PAGE_SHIFT;
861 set_memory_rw(ops->trampoline, npages);
863 ops->trampoline = create_trampoline(ops, &size);
864 if (!ops->trampoline)
866 ops->trampoline_size = size;
867 npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
870 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
871 ip = ops->trampoline + offset;
873 func = ftrace_ops_get_func(ops);
875 /* Do a safe modify in case the trampoline is executing */
876 new = ftrace_call_replace(ip, (unsigned long)func);
877 ret = update_ftrace_func(ip, new);
878 set_memory_ro(ops->trampoline, npages);
880 /* The update should never fail */
884 /* Return the address of the function the trampoline calls */
885 static void *addr_from_call(void *ptr)
887 union ftrace_code_union calc;
890 ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
891 if (WARN_ON_ONCE(ret < 0))
894 /* Make sure this is a call */
895 if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
896 pr_warn("Expected e8, got %x\n", calc.e8);
900 return ptr + MCOUNT_INSN_SIZE + calc.offset;
903 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
904 unsigned long frame_pointer);
907 * If the ops->trampoline was not allocated, then it probably
908 * has a static trampoline func, or is the ftrace caller itself.
910 static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
912 unsigned long offset;
913 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
916 if (ops && ops->trampoline) {
917 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
919 * We only know about function graph tracer setting as static
922 if (ops->trampoline == FTRACE_GRAPH_ADDR)
923 return (void *)prepare_ftrace_return;
928 offset = calc_trampoline_call_offset(save_regs);
931 ptr = (void *)FTRACE_REGS_ADDR + offset;
933 ptr = (void *)FTRACE_ADDR + offset;
935 return addr_from_call(ptr);
938 void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
940 unsigned long offset;
942 /* If we didn't allocate this trampoline, consider it static */
943 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
944 return static_tramp_func(ops, rec);
946 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
947 return addr_from_call((void *)ops->trampoline + offset);
950 void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
952 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
955 tramp_free((void *)ops->trampoline, ops->trampoline_size);
959 #endif /* CONFIG_X86_64 */
960 #endif /* CONFIG_DYNAMIC_FTRACE */
962 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
964 #ifdef CONFIG_DYNAMIC_FTRACE
965 extern void ftrace_graph_call(void);
967 static int ftrace_mod_jmp(unsigned long ip, void *func)
971 new = ftrace_jmp_replace(ip, (unsigned long)func);
973 return update_ftrace_func(ip, new);
976 int ftrace_enable_ftrace_graph_caller(void)
978 unsigned long ip = (unsigned long)(&ftrace_graph_call);
980 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
983 int ftrace_disable_ftrace_graph_caller(void)
985 unsigned long ip = (unsigned long)(&ftrace_graph_call);
987 return ftrace_mod_jmp(ip, &ftrace_stub);
990 #endif /* !CONFIG_DYNAMIC_FTRACE */
993 * Hook the return address and push it in the stack of return addrs
994 * in current thread info.
996 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
997 unsigned long frame_pointer)
1001 unsigned long return_hooker = (unsigned long)
1005 * When resuming from suspend-to-ram, this function can be indirectly
1006 * called from early CPU startup code while the CPU is in real mode,
1007 * which would fail miserably. Make sure the stack pointer is a
1010 * This check isn't as accurate as virt_addr_valid(), but it should be
1011 * good enough for this purpose, and it's fast.
1013 if (unlikely((long)__builtin_frame_address(0) >= 0))
1016 if (unlikely(ftrace_graph_is_dead()))
1019 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
1023 * Protect against fault, even if it shouldn't
1024 * happen. This tool is too much intrusive to
1025 * ignore such a protection.
1028 "1: " _ASM_MOV " (%[parent]), %[old]\n"
1029 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1030 " movl $0, %[faulted]\n"
1033 ".section .fixup, \"ax\"\n"
1034 "4: movl $1, %[faulted]\n"
1038 _ASM_EXTABLE(1b, 4b)
1039 _ASM_EXTABLE(2b, 4b)
1041 : [old] "=&r" (old), [faulted] "=r" (faulted)
1042 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1046 if (unlikely(faulted)) {
1047 ftrace_graph_stop();
1052 if (function_graph_enter(old, self_addr, frame_pointer, parent))
1055 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */