1 // SPDX-License-Identifier: GPL-2.0
3 * Dynamic function tracing support.
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
7 * Thanks goes to Ingo Molnar, for suggesting the idea.
8 * Mathieu Desnoyers, for suggesting postponing the modifications.
9 * Arjan van de Ven, for keeping me straight, and explaining to me
10 * the dangers of modifying code on the run.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 #include <linux/spinlock.h>
16 #include <linux/hardirq.h>
17 #include <linux/uaccess.h>
18 #include <linux/ftrace.h>
19 #include <linux/percpu.h>
20 #include <linux/sched.h>
21 #include <linux/slab.h>
22 #include <linux/init.h>
23 #include <linux/list.h>
24 #include <linux/module.h>
25 #include <linux/memory.h>
27 #include <trace/syscall.h>
29 #include <asm/set_memory.h>
30 #include <asm/kprobes.h>
31 #include <asm/ftrace.h>
33 #include <asm/text-patching.h>
35 #ifdef CONFIG_DYNAMIC_FTRACE
37 int ftrace_arch_code_modify_prepare(void)
38 __acquires(&text_mutex)
41 * Need to grab text_mutex to prevent a race from module loading
42 * and live kernel patching from changing the text permissions while
43 * ftrace has it set to "read/write".
45 mutex_lock(&text_mutex);
47 set_all_modules_text_rw();
51 int ftrace_arch_code_modify_post_process(void)
52 __releases(&text_mutex)
54 set_all_modules_text_ro();
56 mutex_unlock(&text_mutex);
60 union ftrace_code_union {
61 char code[MCOUNT_INSN_SIZE];
65 } __attribute__((packed));
68 static int ftrace_calc_offset(long ip, long addr)
70 return (int)(addr - ip);
73 static unsigned char *
74 ftrace_text_replace(unsigned char op, unsigned long ip, unsigned long addr)
76 static union ftrace_code_union calc;
79 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
84 static unsigned char *
85 ftrace_call_replace(unsigned long ip, unsigned long addr)
87 return ftrace_text_replace(0xe8, ip, addr);
91 within(unsigned long addr, unsigned long start, unsigned long end)
93 return addr >= start && addr < end;
96 static unsigned long text_ip_addr(unsigned long ip)
99 * On x86_64, kernel text mappings are mapped read-only, so we use
100 * the kernel identity mapping instead of the kernel text mapping
101 * to modify the kernel text.
103 * For 32bit kernels, these mappings are same and we can use
104 * kernel identity mapping to modify code.
106 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
107 ip = (unsigned long)__va(__pa_symbol(ip));
112 static const unsigned char *ftrace_nop_replace(void)
114 return ideal_nops[NOP_ATOMIC5];
118 ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
119 unsigned const char *new_code)
121 unsigned char replaced[MCOUNT_INSN_SIZE];
123 ftrace_expected = old_code;
127 * We are paranoid about modifying text, as if a bug was to happen, it
128 * could cause us to read or write to someplace that could cause harm.
129 * Carefully read and modify the code with probe_kernel_*(), and make
130 * sure what we read is what we expected it to be before modifying it.
133 /* read the text we want to modify */
134 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
137 /* Make sure it is what we expect it to be */
138 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
141 ip = text_ip_addr(ip);
143 /* replace the text with the new text */
144 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
152 int ftrace_make_nop(struct module *mod,
153 struct dyn_ftrace *rec, unsigned long addr)
155 unsigned const char *new, *old;
156 unsigned long ip = rec->ip;
158 old = ftrace_call_replace(ip, addr);
159 new = ftrace_nop_replace();
162 * On boot up, and when modules are loaded, the MCOUNT_ADDR
163 * is converted to a nop, and will never become MCOUNT_ADDR
164 * again. This code is either running before SMP (on boot up)
165 * or before the code will ever be executed (module load).
166 * We do not want to use the breakpoint version in this case,
167 * just modify the code directly.
169 if (addr == MCOUNT_ADDR)
170 return ftrace_modify_code_direct(rec->ip, old, new);
172 ftrace_expected = NULL;
174 /* Normal cases use add_brk_on_nop */
175 WARN_ONCE(1, "invalid use of ftrace_make_nop");
179 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
181 unsigned const char *new, *old;
182 unsigned long ip = rec->ip;
184 old = ftrace_nop_replace();
185 new = ftrace_call_replace(ip, addr);
187 /* Should only be called when module is loaded */
188 return ftrace_modify_code_direct(rec->ip, old, new);
192 * The modifying_ftrace_code is used to tell the breakpoint
193 * handler to call ftrace_int3_handler(). If it fails to
194 * call this handler for a breakpoint added by ftrace, then
195 * the kernel may crash.
197 * As atomic_writes on x86 do not need a barrier, we do not
198 * need to add smp_mb()s for this to work. It is also considered
199 * that we can not read the modifying_ftrace_code before
200 * executing the breakpoint. That would be quite remarkable if
201 * it could do that. Here's the flow that is required:
207 * <trap-int3> // implicit (r)mb
208 * if (atomic_read(mfc))
209 * call ftrace_int3_handler()
211 * Then when we are finished:
215 * If we hit a breakpoint that was not set by ftrace, it does not
216 * matter if ftrace_int3_handler() is called or not. It will
217 * simply be ignored. But it is crucial that a ftrace nop/caller
218 * breakpoint is handled. No other user should ever place a
219 * breakpoint on an ftrace nop/caller location. It must only
220 * be done by this code.
222 atomic_t modifying_ftrace_code __read_mostly;
225 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
226 unsigned const char *new_code);
229 * Should never be called:
230 * As it is only called by __ftrace_replace_code() which is called by
231 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
232 * which is called to turn mcount into nops or nops into function calls
233 * but not to convert a function from not using regs to one that uses
234 * regs, which ftrace_modify_call() is for.
236 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
240 ftrace_expected = NULL;
244 static unsigned long ftrace_update_func;
245 static unsigned long ftrace_update_func_call;
247 static int update_ftrace_func(unsigned long ip, void *new)
249 unsigned char old[MCOUNT_INSN_SIZE];
252 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
254 ftrace_update_func = ip;
255 /* Make sure the breakpoints see the ftrace_update_func update */
258 /* See comment above by declaration of modifying_ftrace_code */
259 atomic_inc(&modifying_ftrace_code);
261 ret = ftrace_modify_code(ip, old, new);
263 atomic_dec(&modifying_ftrace_code);
268 int ftrace_update_ftrace_func(ftrace_func_t func)
270 unsigned long ip = (unsigned long)(&ftrace_call);
274 ftrace_update_func_call = (unsigned long)func;
276 new = ftrace_call_replace(ip, (unsigned long)func);
277 ret = update_ftrace_func(ip, new);
279 /* Also update the regs callback function */
281 ip = (unsigned long)(&ftrace_regs_call);
282 new = ftrace_call_replace(ip, (unsigned long)func);
283 ret = update_ftrace_func(ip, new);
289 static nokprobe_inline int is_ftrace_caller(unsigned long ip)
291 if (ip == ftrace_update_func)
298 * A breakpoint was added to the code address we are about to
299 * modify, and this is the handle that will just skip over it.
300 * We are either changing a nop into a trace call, or a trace
301 * call to a nop. While the change is taking place, we treat
302 * it just like it was a nop.
304 int ftrace_int3_handler(struct pt_regs *regs)
308 if (WARN_ON_ONCE(!regs))
311 ip = regs->ip - INT3_INSN_SIZE;
314 if (ftrace_location(ip)) {
315 int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);
317 } else if (is_ftrace_caller(ip)) {
318 if (!ftrace_update_func_call) {
319 int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
322 int3_emulate_call(regs, ftrace_update_func_call);
326 if (ftrace_location(ip) || is_ftrace_caller(ip)) {
327 int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
334 NOKPROBE_SYMBOL(ftrace_int3_handler);
336 static int ftrace_write(unsigned long ip, const char *val, int size)
338 ip = text_ip_addr(ip);
340 if (probe_kernel_write((void *)ip, val, size))
346 static int add_break(unsigned long ip, const char *old)
348 unsigned char replaced[MCOUNT_INSN_SIZE];
349 unsigned char brk = BREAKPOINT_INSTRUCTION;
351 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
354 ftrace_expected = old;
356 /* Make sure it is what we expect it to be */
357 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
360 return ftrace_write(ip, &brk, 1);
363 static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
365 unsigned const char *old;
366 unsigned long ip = rec->ip;
368 old = ftrace_call_replace(ip, addr);
370 return add_break(rec->ip, old);
374 static int add_brk_on_nop(struct dyn_ftrace *rec)
376 unsigned const char *old;
378 old = ftrace_nop_replace();
380 return add_break(rec->ip, old);
383 static int add_breakpoints(struct dyn_ftrace *rec, int enable)
385 unsigned long ftrace_addr;
388 ftrace_addr = ftrace_get_addr_curr(rec);
390 ret = ftrace_test_record(rec, enable);
393 case FTRACE_UPDATE_IGNORE:
396 case FTRACE_UPDATE_MAKE_CALL:
397 /* converting nop to call */
398 return add_brk_on_nop(rec);
400 case FTRACE_UPDATE_MODIFY_CALL:
401 case FTRACE_UPDATE_MAKE_NOP:
402 /* converting a call to a nop */
403 return add_brk_on_call(rec, ftrace_addr);
409 * On error, we need to remove breakpoints. This needs to
410 * be done caefully. If the address does not currently have a
411 * breakpoint, we know we are done. Otherwise, we look at the
412 * remaining 4 bytes of the instruction. If it matches a nop
413 * we replace the breakpoint with the nop. Otherwise we replace
414 * it with the call instruction.
416 static int remove_breakpoint(struct dyn_ftrace *rec)
418 unsigned char ins[MCOUNT_INSN_SIZE];
419 unsigned char brk = BREAKPOINT_INSTRUCTION;
420 const unsigned char *nop;
421 unsigned long ftrace_addr;
422 unsigned long ip = rec->ip;
424 /* If we fail the read, just give up */
425 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
428 /* If this does not have a breakpoint, we are done */
432 nop = ftrace_nop_replace();
435 * If the last 4 bytes of the instruction do not match
436 * a nop, then we assume that this is a call to ftrace_addr.
438 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
440 * For extra paranoidism, we check if the breakpoint is on
441 * a call that would actually jump to the ftrace_addr.
442 * If not, don't touch the breakpoint, we make just create
445 ftrace_addr = ftrace_get_addr_new(rec);
446 nop = ftrace_call_replace(ip, ftrace_addr);
448 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
451 /* Check both ftrace_addr and ftrace_old_addr */
452 ftrace_addr = ftrace_get_addr_curr(rec);
453 nop = ftrace_call_replace(ip, ftrace_addr);
455 ftrace_expected = nop;
457 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
462 return ftrace_write(ip, nop, 1);
465 static int add_update_code(unsigned long ip, unsigned const char *new)
467 /* skip breakpoint */
470 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
473 static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
475 unsigned long ip = rec->ip;
476 unsigned const char *new;
478 new = ftrace_call_replace(ip, addr);
479 return add_update_code(ip, new);
482 static int add_update_nop(struct dyn_ftrace *rec)
484 unsigned long ip = rec->ip;
485 unsigned const char *new;
487 new = ftrace_nop_replace();
488 return add_update_code(ip, new);
491 static int add_update(struct dyn_ftrace *rec, int enable)
493 unsigned long ftrace_addr;
496 ret = ftrace_test_record(rec, enable);
498 ftrace_addr = ftrace_get_addr_new(rec);
501 case FTRACE_UPDATE_IGNORE:
504 case FTRACE_UPDATE_MODIFY_CALL:
505 case FTRACE_UPDATE_MAKE_CALL:
506 /* converting nop to call */
507 return add_update_call(rec, ftrace_addr);
509 case FTRACE_UPDATE_MAKE_NOP:
510 /* converting a call to a nop */
511 return add_update_nop(rec);
517 static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
519 unsigned long ip = rec->ip;
520 unsigned const char *new;
522 new = ftrace_call_replace(ip, addr);
524 return ftrace_write(ip, new, 1);
527 static int finish_update_nop(struct dyn_ftrace *rec)
529 unsigned long ip = rec->ip;
530 unsigned const char *new;
532 new = ftrace_nop_replace();
534 return ftrace_write(ip, new, 1);
537 static int finish_update(struct dyn_ftrace *rec, int enable)
539 unsigned long ftrace_addr;
542 ret = ftrace_update_record(rec, enable);
544 ftrace_addr = ftrace_get_addr_new(rec);
547 case FTRACE_UPDATE_IGNORE:
550 case FTRACE_UPDATE_MODIFY_CALL:
551 case FTRACE_UPDATE_MAKE_CALL:
552 /* converting nop to call */
553 return finish_update_call(rec, ftrace_addr);
555 case FTRACE_UPDATE_MAKE_NOP:
556 /* converting a call to a nop */
557 return finish_update_nop(rec);
563 static void do_sync_core(void *data)
568 static void run_sync(void)
572 /* No need to sync if there's only one CPU */
573 if (num_online_cpus() == 1)
576 enable_irqs = irqs_disabled();
578 /* We may be called with interrupts disabled (on bootup). */
581 on_each_cpu(do_sync_core, NULL, 1);
586 void ftrace_replace_code(int enable)
588 struct ftrace_rec_iter *iter;
589 struct dyn_ftrace *rec;
590 const char *report = "adding breakpoints";
594 for_ftrace_rec_iter(iter) {
595 rec = ftrace_rec_iter_record(iter);
597 ret = add_breakpoints(rec, enable);
599 goto remove_breakpoints;
605 report = "updating code";
608 for_ftrace_rec_iter(iter) {
609 rec = ftrace_rec_iter_record(iter);
611 ret = add_update(rec, enable);
613 goto remove_breakpoints;
619 report = "removing breakpoints";
622 for_ftrace_rec_iter(iter) {
623 rec = ftrace_rec_iter_record(iter);
625 ret = finish_update(rec, enable);
627 goto remove_breakpoints;
636 pr_warn("Failed on %s (%d):\n", report, count);
637 ftrace_bug(ret, rec);
638 for_ftrace_rec_iter(iter) {
639 rec = ftrace_rec_iter_record(iter);
641 * Breakpoints are handled only when this function is in
642 * progress. The system could not work with them.
644 if (remove_breakpoint(rec))
651 ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
652 unsigned const char *new_code)
656 ret = add_break(ip, old_code);
662 ret = add_update_code(ip, new_code);
668 ret = ftrace_write(ip, new_code, 1);
670 * The breakpoint is handled only when this function is in progress.
671 * The system could not work if we could not remove it.
679 /* Also here the system could not work with the breakpoint */
680 if (ftrace_write(ip, old_code, 1))
685 void arch_ftrace_update_code(int command)
687 /* See comment above by declaration of modifying_ftrace_code */
688 atomic_inc(&modifying_ftrace_code);
690 ftrace_modify_all_code(command);
692 atomic_dec(&modifying_ftrace_code);
695 int __init ftrace_dyn_arch_init(void)
700 /* Currently only x86_64 supports dynamic trampolines */
703 #ifdef CONFIG_MODULES
704 #include <linux/moduleloader.h>
705 /* Module allocation simplifies allocating memory for code */
706 static inline void *alloc_tramp(unsigned long size)
708 return module_alloc(size);
710 static inline void tramp_free(void *tramp)
712 module_memfree(tramp);
715 /* Trampolines can only be created if modules are supported */
716 static inline void *alloc_tramp(unsigned long size)
720 static inline void tramp_free(void *tramp) { }
723 /* Defined as markers to the end of the ftrace default trampolines */
724 extern void ftrace_regs_caller_end(void);
725 extern void ftrace_epilogue(void);
726 extern void ftrace_caller_op_ptr(void);
727 extern void ftrace_regs_caller_op_ptr(void);
729 /* movq function_trace_op(%rip), %rdx */
730 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
731 #define OP_REF_SIZE 7
734 * The ftrace_ops is passed to the function callback. Since the
735 * trampoline only services a single ftrace_ops, we can pass in
738 * The ftrace_op_code_union is used to create a pointer to the
739 * ftrace_ops that will be passed to the callback function.
741 union ftrace_op_code_union {
742 char code[OP_REF_SIZE];
746 } __attribute__((packed));
752 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
754 unsigned long start_offset;
755 unsigned long end_offset;
756 unsigned long op_offset;
757 unsigned long offset;
758 unsigned long npages;
764 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
765 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
766 union ftrace_op_code_union op_ptr;
769 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
770 start_offset = (unsigned long)ftrace_regs_caller;
771 end_offset = (unsigned long)ftrace_regs_caller_end;
772 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
774 start_offset = (unsigned long)ftrace_caller;
775 end_offset = (unsigned long)ftrace_epilogue;
776 op_offset = (unsigned long)ftrace_caller_op_ptr;
779 size = end_offset - start_offset;
782 * Allocate enough size to store the ftrace_caller code,
783 * the iret , as well as the address of the ftrace_ops this
784 * trampoline is used for.
786 trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
790 *tramp_size = size + RET_SIZE + sizeof(void *);
791 npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
793 /* Copy ftrace_caller onto the trampoline memory */
794 ret = probe_kernel_read(trampoline, (void *)start_offset, size);
795 if (WARN_ON(ret < 0))
798 ip = trampoline + size;
800 /* The trampoline ends with ret(q) */
801 retq = (unsigned long)ftrace_stub;
802 ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
803 if (WARN_ON(ret < 0))
807 * The address of the ftrace_ops that is used for this trampoline
808 * is stored at the end of the trampoline. This will be used to
809 * load the third parameter for the callback. Basically, that
810 * location at the end of the trampoline takes the place of
811 * the global function_trace_op variable.
814 ptr = (unsigned long *)(trampoline + size + RET_SIZE);
815 *ptr = (unsigned long)ops;
817 op_offset -= start_offset;
818 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
820 /* Are we pointing to the reference? */
821 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
824 /* Load the contents of ptr into the callback parameter */
825 offset = (unsigned long)ptr;
826 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
828 op_ptr.offset = offset;
830 /* put in the new offset to the ftrace_ops */
831 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
833 /* ALLOC_TRAMP flags lets us know we created it */
834 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
836 set_vm_flush_reset_perms(trampoline);
839 * Module allocation needs to be completed by making the page
840 * executable. The page is still writable, which is a security hazard,
841 * but anyhow ftrace breaks W^X completely.
843 set_memory_x((unsigned long)trampoline, npages);
844 return (unsigned long)trampoline;
846 tramp_free(trampoline);
850 static unsigned long calc_trampoline_call_offset(bool save_regs)
852 unsigned long start_offset;
853 unsigned long call_offset;
856 start_offset = (unsigned long)ftrace_regs_caller;
857 call_offset = (unsigned long)ftrace_regs_call;
859 start_offset = (unsigned long)ftrace_caller;
860 call_offset = (unsigned long)ftrace_call;
863 return call_offset - start_offset;
866 void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
870 unsigned long offset;
875 if (ops->trampoline) {
877 * The ftrace_ops caller may set up its own trampoline.
878 * In such a case, this code must not modify it.
880 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
882 npages = PAGE_ALIGN(ops->trampoline_size) >> PAGE_SHIFT;
883 set_memory_rw(ops->trampoline, npages);
885 ops->trampoline = create_trampoline(ops, &size);
886 if (!ops->trampoline)
888 ops->trampoline_size = size;
889 npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
892 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
893 ip = ops->trampoline + offset;
895 func = ftrace_ops_get_func(ops);
897 ftrace_update_func_call = (unsigned long)func;
899 /* Do a safe modify in case the trampoline is executing */
900 new = ftrace_call_replace(ip, (unsigned long)func);
901 ret = update_ftrace_func(ip, new);
902 set_memory_ro(ops->trampoline, npages);
904 /* The update should never fail */
908 /* Return the address of the function the trampoline calls */
909 static void *addr_from_call(void *ptr)
911 union ftrace_code_union calc;
914 ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
915 if (WARN_ON_ONCE(ret < 0))
918 /* Make sure this is a call */
919 if (WARN_ON_ONCE(calc.op != 0xe8)) {
920 pr_warn("Expected e8, got %x\n", calc.op);
924 return ptr + MCOUNT_INSN_SIZE + calc.offset;
927 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
928 unsigned long frame_pointer);
931 * If the ops->trampoline was not allocated, then it probably
932 * has a static trampoline func, or is the ftrace caller itself.
934 static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
936 unsigned long offset;
937 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
940 if (ops && ops->trampoline) {
941 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
943 * We only know about function graph tracer setting as static
946 if (ops->trampoline == FTRACE_GRAPH_ADDR)
947 return (void *)prepare_ftrace_return;
952 offset = calc_trampoline_call_offset(save_regs);
955 ptr = (void *)FTRACE_REGS_ADDR + offset;
957 ptr = (void *)FTRACE_ADDR + offset;
959 return addr_from_call(ptr);
962 void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
964 unsigned long offset;
966 /* If we didn't allocate this trampoline, consider it static */
967 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
968 return static_tramp_func(ops, rec);
970 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
971 return addr_from_call((void *)ops->trampoline + offset);
974 void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
976 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
979 tramp_free((void *)ops->trampoline);
983 #endif /* CONFIG_X86_64 */
984 #endif /* CONFIG_DYNAMIC_FTRACE */
986 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
988 #ifdef CONFIG_DYNAMIC_FTRACE
989 extern void ftrace_graph_call(void);
991 static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
993 return ftrace_text_replace(0xe9, ip, addr);
996 static int ftrace_mod_jmp(unsigned long ip, void *func)
1000 ftrace_update_func_call = 0UL;
1001 new = ftrace_jmp_replace(ip, (unsigned long)func);
1003 return update_ftrace_func(ip, new);
1006 int ftrace_enable_ftrace_graph_caller(void)
1008 unsigned long ip = (unsigned long)(&ftrace_graph_call);
1010 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
1013 int ftrace_disable_ftrace_graph_caller(void)
1015 unsigned long ip = (unsigned long)(&ftrace_graph_call);
1017 return ftrace_mod_jmp(ip, &ftrace_stub);
1020 #endif /* !CONFIG_DYNAMIC_FTRACE */
1023 * Hook the return address and push it in the stack of return addrs
1024 * in current thread info.
1026 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
1027 unsigned long frame_pointer)
1031 unsigned long return_hooker = (unsigned long)
1035 * When resuming from suspend-to-ram, this function can be indirectly
1036 * called from early CPU startup code while the CPU is in real mode,
1037 * which would fail miserably. Make sure the stack pointer is a
1040 * This check isn't as accurate as virt_addr_valid(), but it should be
1041 * good enough for this purpose, and it's fast.
1043 if (unlikely((long)__builtin_frame_address(0) >= 0))
1046 if (unlikely(ftrace_graph_is_dead()))
1049 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
1053 * Protect against fault, even if it shouldn't
1054 * happen. This tool is too much intrusive to
1055 * ignore such a protection.
1058 "1: " _ASM_MOV " (%[parent]), %[old]\n"
1059 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1060 " movl $0, %[faulted]\n"
1063 ".section .fixup, \"ax\"\n"
1064 "4: movl $1, %[faulted]\n"
1068 _ASM_EXTABLE(1b, 4b)
1069 _ASM_EXTABLE(2b, 4b)
1071 : [old] "=&r" (old), [faulted] "=r" (faulted)
1072 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1076 if (unlikely(faulted)) {
1077 ftrace_graph_stop();
1082 if (function_graph_enter(old, self_addr, frame_pointer, parent))
1085 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */