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 #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)
536 int enable_irqs
= irqs_disabled();
538 /* We may be called with interrupts disbled (on bootup). */
541 on_each_cpu(do_sync_core
, NULL
, 1);
546 void ftrace_replace_code(int enable
)
548 struct ftrace_rec_iter
*iter
;
549 struct dyn_ftrace
*rec
;
550 const char *report
= "adding breakpoints";
554 for_ftrace_rec_iter(iter
) {
555 rec
= ftrace_rec_iter_record(iter
);
557 ret
= add_breakpoints(rec
, enable
);
559 goto remove_breakpoints
;
565 report
= "updating code";
568 for_ftrace_rec_iter(iter
) {
569 rec
= ftrace_rec_iter_record(iter
);
571 ret
= add_update(rec
, enable
);
573 goto remove_breakpoints
;
579 report
= "removing breakpoints";
582 for_ftrace_rec_iter(iter
) {
583 rec
= ftrace_rec_iter_record(iter
);
585 ret
= finish_update(rec
, enable
);
587 goto remove_breakpoints
;
596 pr_warn("Failed on %s (%d):\n", report
, count
);
597 ftrace_bug(ret
, rec
);
598 for_ftrace_rec_iter(iter
) {
599 rec
= ftrace_rec_iter_record(iter
);
601 * Breakpoints are handled only when this function is in
602 * progress. The system could not work with them.
604 if (remove_breakpoint(rec
))
611 ftrace_modify_code(unsigned long ip
, unsigned const char *old_code
,
612 unsigned const char *new_code
)
616 ret
= add_break(ip
, old_code
);
622 ret
= add_update_code(ip
, new_code
);
628 ret
= ftrace_write(ip
, new_code
, 1);
630 * The breakpoint is handled only when this function is in progress.
631 * The system could not work if we could not remove it.
639 /* Also here the system could not work with the breakpoint */
640 if (ftrace_write(ip
, old_code
, 1))
645 void arch_ftrace_update_code(int command
)
647 /* See comment above by declaration of modifying_ftrace_code */
648 atomic_inc(&modifying_ftrace_code
);
650 ftrace_modify_all_code(command
);
652 atomic_dec(&modifying_ftrace_code
);
655 int __init
ftrace_dyn_arch_init(void)
660 #if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER)
661 static unsigned char *ftrace_jmp_replace(unsigned long ip
, unsigned long addr
)
663 static union ftrace_code_union calc
;
665 /* Jmp not a call (ignore the .e8) */
667 calc
.offset
= ftrace_calc_offset(ip
+ MCOUNT_INSN_SIZE
, addr
);
670 * ftrace external locks synchronize the access to the static variable.
676 /* Currently only x86_64 supports dynamic trampolines */
679 #ifdef CONFIG_MODULES
680 #include <linux/moduleloader.h>
681 /* Module allocation simplifies allocating memory for code */
682 static inline void *alloc_tramp(unsigned long size
)
684 return module_alloc(size
);
686 static inline void tramp_free(void *tramp
)
688 module_memfree(tramp
);
691 /* Trampolines can only be created if modules are supported */
692 static inline void *alloc_tramp(unsigned long size
)
696 static inline void tramp_free(void *tramp
) { }
699 /* Defined as markers to the end of the ftrace default trampolines */
700 extern void ftrace_regs_caller_end(void);
701 extern void ftrace_epilogue(void);
702 extern void ftrace_caller_op_ptr(void);
703 extern void ftrace_regs_caller_op_ptr(void);
705 /* movq function_trace_op(%rip), %rdx */
706 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
707 #define OP_REF_SIZE 7
710 * The ftrace_ops is passed to the function callback. Since the
711 * trampoline only services a single ftrace_ops, we can pass in
714 * The ftrace_op_code_union is used to create a pointer to the
715 * ftrace_ops that will be passed to the callback function.
717 union ftrace_op_code_union
{
718 char code
[OP_REF_SIZE
];
722 } __attribute__((packed
));
726 create_trampoline(struct ftrace_ops
*ops
, unsigned int *tramp_size
)
728 unsigned const char *jmp
;
729 unsigned long start_offset
;
730 unsigned long end_offset
;
731 unsigned long op_offset
;
732 unsigned long offset
;
737 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
738 unsigned const char op_ref
[] = { 0x48, 0x8b, 0x15 };
739 union ftrace_op_code_union op_ptr
;
742 if (ops
->flags
& FTRACE_OPS_FL_SAVE_REGS
) {
743 start_offset
= (unsigned long)ftrace_regs_caller
;
744 end_offset
= (unsigned long)ftrace_regs_caller_end
;
745 op_offset
= (unsigned long)ftrace_regs_caller_op_ptr
;
747 start_offset
= (unsigned long)ftrace_caller
;
748 end_offset
= (unsigned long)ftrace_epilogue
;
749 op_offset
= (unsigned long)ftrace_caller_op_ptr
;
752 size
= end_offset
- start_offset
;
755 * Allocate enough size to store the ftrace_caller code,
756 * the jmp to ftrace_epilogue, as well as the address of
757 * the ftrace_ops this trampoline is used for.
759 trampoline
= alloc_tramp(size
+ MCOUNT_INSN_SIZE
+ sizeof(void *));
763 *tramp_size
= size
+ MCOUNT_INSN_SIZE
+ sizeof(void *);
765 /* Copy ftrace_caller onto the trampoline memory */
766 ret
= probe_kernel_read(trampoline
, (void *)start_offset
, size
);
767 if (WARN_ON(ret
< 0)) {
768 tramp_free(trampoline
);
772 ip
= (unsigned long)trampoline
+ size
;
774 /* The trampoline ends with a jmp to ftrace_epilogue */
775 jmp
= ftrace_jmp_replace(ip
, (unsigned long)ftrace_epilogue
);
776 memcpy(trampoline
+ size
, jmp
, MCOUNT_INSN_SIZE
);
779 * The address of the ftrace_ops that is used for this trampoline
780 * is stored at the end of the trampoline. This will be used to
781 * load the third parameter for the callback. Basically, that
782 * location at the end of the trampoline takes the place of
783 * the global function_trace_op variable.
786 ptr
= (unsigned long *)(trampoline
+ size
+ MCOUNT_INSN_SIZE
);
787 *ptr
= (unsigned long)ops
;
789 op_offset
-= start_offset
;
790 memcpy(&op_ptr
, trampoline
+ op_offset
, OP_REF_SIZE
);
792 /* Are we pointing to the reference? */
793 if (WARN_ON(memcmp(op_ptr
.op
, op_ref
, 3) != 0)) {
794 tramp_free(trampoline
);
798 /* Load the contents of ptr into the callback parameter */
799 offset
= (unsigned long)ptr
;
800 offset
-= (unsigned long)trampoline
+ op_offset
+ OP_REF_SIZE
;
802 op_ptr
.offset
= offset
;
804 /* put in the new offset to the ftrace_ops */
805 memcpy(trampoline
+ op_offset
, &op_ptr
, OP_REF_SIZE
);
807 /* ALLOC_TRAMP flags lets us know we created it */
808 ops
->flags
|= FTRACE_OPS_FL_ALLOC_TRAMP
;
810 return (unsigned long)trampoline
;
813 static unsigned long calc_trampoline_call_offset(bool save_regs
)
815 unsigned long start_offset
;
816 unsigned long call_offset
;
819 start_offset
= (unsigned long)ftrace_regs_caller
;
820 call_offset
= (unsigned long)ftrace_regs_call
;
822 start_offset
= (unsigned long)ftrace_caller
;
823 call_offset
= (unsigned long)ftrace_call
;
826 return call_offset
- start_offset
;
829 void arch_ftrace_update_trampoline(struct ftrace_ops
*ops
)
833 unsigned long offset
;
838 if (ops
->trampoline
) {
840 * The ftrace_ops caller may set up its own trampoline.
841 * In such a case, this code must not modify it.
843 if (!(ops
->flags
& FTRACE_OPS_FL_ALLOC_TRAMP
))
846 ops
->trampoline
= create_trampoline(ops
, &size
);
847 if (!ops
->trampoline
)
849 ops
->trampoline_size
= size
;
852 offset
= calc_trampoline_call_offset(ops
->flags
& FTRACE_OPS_FL_SAVE_REGS
);
853 ip
= ops
->trampoline
+ offset
;
855 func
= ftrace_ops_get_func(ops
);
857 /* Do a safe modify in case the trampoline is executing */
858 new = ftrace_call_replace(ip
, (unsigned long)func
);
859 ret
= update_ftrace_func(ip
, new);
861 /* The update should never fail */
865 /* Return the address of the function the trampoline calls */
866 static void *addr_from_call(void *ptr
)
868 union ftrace_code_union calc
;
871 ret
= probe_kernel_read(&calc
, ptr
, MCOUNT_INSN_SIZE
);
872 if (WARN_ON_ONCE(ret
< 0))
875 /* Make sure this is a call */
876 if (WARN_ON_ONCE(calc
.e8
!= 0xe8)) {
877 pr_warn("Expected e8, got %x\n", calc
.e8
);
881 return ptr
+ MCOUNT_INSN_SIZE
+ calc
.offset
;
884 void prepare_ftrace_return(unsigned long self_addr
, unsigned long *parent
,
885 unsigned long frame_pointer
);
888 * If the ops->trampoline was not allocated, then it probably
889 * has a static trampoline func, or is the ftrace caller itself.
891 static void *static_tramp_func(struct ftrace_ops
*ops
, struct dyn_ftrace
*rec
)
893 unsigned long offset
;
894 bool save_regs
= rec
->flags
& FTRACE_FL_REGS_EN
;
897 if (ops
&& ops
->trampoline
) {
898 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
900 * We only know about function graph tracer setting as static
903 if (ops
->trampoline
== FTRACE_GRAPH_ADDR
)
904 return (void *)prepare_ftrace_return
;
909 offset
= calc_trampoline_call_offset(save_regs
);
912 ptr
= (void *)FTRACE_REGS_ADDR
+ offset
;
914 ptr
= (void *)FTRACE_ADDR
+ offset
;
916 return addr_from_call(ptr
);
919 void *arch_ftrace_trampoline_func(struct ftrace_ops
*ops
, struct dyn_ftrace
*rec
)
921 unsigned long offset
;
923 /* If we didn't allocate this trampoline, consider it static */
924 if (!ops
|| !(ops
->flags
& FTRACE_OPS_FL_ALLOC_TRAMP
))
925 return static_tramp_func(ops
, rec
);
927 offset
= calc_trampoline_call_offset(ops
->flags
& FTRACE_OPS_FL_SAVE_REGS
);
928 return addr_from_call((void *)ops
->trampoline
+ offset
);
931 void arch_ftrace_trampoline_free(struct ftrace_ops
*ops
)
933 if (!ops
|| !(ops
->flags
& FTRACE_OPS_FL_ALLOC_TRAMP
))
936 tramp_free((void *)ops
->trampoline
);
940 #endif /* CONFIG_X86_64 */
941 #endif /* CONFIG_DYNAMIC_FTRACE */
943 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
945 #ifdef CONFIG_DYNAMIC_FTRACE
946 extern void ftrace_graph_call(void);
948 static int ftrace_mod_jmp(unsigned long ip
, void *func
)
952 new = ftrace_jmp_replace(ip
, (unsigned long)func
);
954 return update_ftrace_func(ip
, new);
957 int ftrace_enable_ftrace_graph_caller(void)
959 unsigned long ip
= (unsigned long)(&ftrace_graph_call
);
961 return ftrace_mod_jmp(ip
, &ftrace_graph_caller
);
964 int ftrace_disable_ftrace_graph_caller(void)
966 unsigned long ip
= (unsigned long)(&ftrace_graph_call
);
968 return ftrace_mod_jmp(ip
, &ftrace_stub
);
971 #endif /* !CONFIG_DYNAMIC_FTRACE */
974 * Hook the return address and push it in the stack of return addrs
975 * in current thread info.
977 void prepare_ftrace_return(unsigned long self_addr
, unsigned long *parent
,
978 unsigned long frame_pointer
)
982 struct ftrace_graph_ent trace
;
983 unsigned long return_hooker
= (unsigned long)
986 if (unlikely(ftrace_graph_is_dead()))
989 if (unlikely(atomic_read(¤t
->tracing_graph_pause
)))
993 * Protect against fault, even if it shouldn't
994 * happen. This tool is too much intrusive to
995 * ignore such a protection.
998 "1: " _ASM_MOV
" (%[parent]), %[old]\n"
999 "2: " _ASM_MOV
" %[return_hooker], (%[parent])\n"
1000 " movl $0, %[faulted]\n"
1003 ".section .fixup, \"ax\"\n"
1004 "4: movl $1, %[faulted]\n"
1008 _ASM_EXTABLE(1b
, 4b
)
1009 _ASM_EXTABLE(2b
, 4b
)
1011 : [old
] "=&r" (old
), [faulted
] "=r" (faulted
)
1012 : [parent
] "r" (parent
), [return_hooker
] "r" (return_hooker
)
1016 if (unlikely(faulted
)) {
1017 ftrace_graph_stop();
1022 trace
.func
= self_addr
;
1023 trace
.depth
= current
->curr_ret_stack
+ 1;
1025 /* Only trace if the calling function expects to */
1026 if (!ftrace_graph_entry(&trace
)) {
1031 if (ftrace_push_return_trace(old
, self_addr
, &trace
.depth
,
1032 frame_pointer
) == -EBUSY
) {
1037 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */