summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/ftrace.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /arch/x86/kernel/ftrace.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
-rw-r--r--arch/x86/kernel/ftrace.c666
1 files changed, 666 insertions, 0 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
new file mode 100644
index 0000000000..12df54ff0e
--- /dev/null
+++ b/arch/x86/kernel/ftrace.c
@@ -0,0 +1,666 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Dynamic function tracing support.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Thanks goes to Ingo Molnar, for suggesting the idea.
+ * Mathieu Desnoyers, for suggesting postponing the modifications.
+ * Arjan van de Ven, for keeping me straight, and explaining to me
+ * the dangers of modifying code on the run.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/memory.h>
+#include <linux/vmalloc.h>
+#include <linux/set_memory.h>
+
+#include <trace/syscall.h>
+
+#include <asm/kprobes.h>
+#include <asm/ftrace.h>
+#include <asm/nops.h>
+#include <asm/text-patching.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+static int ftrace_poke_late = 0;
+
+void ftrace_arch_code_modify_prepare(void)
+ __acquires(&text_mutex)
+{
+ /*
+ * Need to grab text_mutex to prevent a race from module loading
+ * and live kernel patching from changing the text permissions while
+ * ftrace has it set to "read/write".
+ */
+ mutex_lock(&text_mutex);
+ ftrace_poke_late = 1;
+}
+
+void ftrace_arch_code_modify_post_process(void)
+ __releases(&text_mutex)
+{
+ /*
+ * ftrace_make_{call,nop}() may be called during
+ * module load, and we need to finish the text_poke_queue()
+ * that they do, here.
+ */
+ text_poke_finish();
+ ftrace_poke_late = 0;
+ mutex_unlock(&text_mutex);
+}
+
+static const char *ftrace_nop_replace(void)
+{
+ return x86_nops[5];
+}
+
+static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+ /*
+ * No need to translate into a callthunk. The trampoline does
+ * the depth accounting itself.
+ */
+ return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
+}
+
+static int ftrace_verify_code(unsigned long ip, const char *old_code)
+{
+ char cur_code[MCOUNT_INSN_SIZE];
+
+ /*
+ * Note:
+ * We are paranoid about modifying text, as if a bug was to happen, it
+ * could cause us to read or write to someplace that could cause harm.
+ * Carefully read and modify the code with probe_kernel_*(), and make
+ * sure what we read is what we expected it to be before modifying it.
+ */
+ /* read the text we want to modify */
+ if (copy_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
+ WARN_ON(1);
+ return -EFAULT;
+ }
+
+ /* Make sure it is what we expect it to be */
+ if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
+ ftrace_expected = old_code;
+ WARN_ON(1);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/*
+ * Marked __ref because it calls text_poke_early() which is .init.text. That is
+ * ok because that call will happen early, during boot, when .init sections are
+ * still present.
+ */
+static int __ref
+ftrace_modify_code_direct(unsigned long ip, const char *old_code,
+ const char *new_code)
+{
+ int ret = ftrace_verify_code(ip, old_code);
+ if (ret)
+ return ret;
+
+ /* replace the text with the new text */
+ if (ftrace_poke_late)
+ text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
+ else
+ text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
+ return 0;
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned long ip = rec->ip;
+ const char *new, *old;
+
+ old = ftrace_call_replace(ip, addr);
+ new = ftrace_nop_replace();
+
+ /*
+ * On boot up, and when modules are loaded, the MCOUNT_ADDR
+ * is converted to a nop, and will never become MCOUNT_ADDR
+ * again. This code is either running before SMP (on boot up)
+ * or before the code will ever be executed (module load).
+ * We do not want to use the breakpoint version in this case,
+ * just modify the code directly.
+ */
+ if (addr == MCOUNT_ADDR)
+ return ftrace_modify_code_direct(ip, old, new);
+
+ /*
+ * x86 overrides ftrace_replace_code -- this function will never be used
+ * in this case.
+ */
+ WARN_ONCE(1, "invalid use of ftrace_make_nop");
+ return -EINVAL;
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned long ip = rec->ip;
+ const char *new, *old;
+
+ old = ftrace_nop_replace();
+ new = ftrace_call_replace(ip, addr);
+
+ /* Should only be called when module is loaded */
+ return ftrace_modify_code_direct(rec->ip, old, new);
+}
+
+/*
+ * Should never be called:
+ * As it is only called by __ftrace_replace_code() which is called by
+ * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
+ * which is called to turn mcount into nops or nops into function calls
+ * but not to convert a function from not using regs to one that uses
+ * regs, which ftrace_modify_call() is for.
+ */
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ WARN_ON(1);
+ return -EINVAL;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ unsigned long ip;
+ const char *new;
+
+ ip = (unsigned long)(&ftrace_call);
+ new = ftrace_call_replace(ip, (unsigned long)func);
+ text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
+
+ ip = (unsigned long)(&ftrace_regs_call);
+ new = ftrace_call_replace(ip, (unsigned long)func);
+ text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
+
+ return 0;
+}
+
+void ftrace_replace_code(int enable)
+{
+ struct ftrace_rec_iter *iter;
+ struct dyn_ftrace *rec;
+ const char *new, *old;
+ int ret;
+
+ for_ftrace_rec_iter(iter) {
+ rec = ftrace_rec_iter_record(iter);
+
+ switch (ftrace_test_record(rec, enable)) {
+ case FTRACE_UPDATE_IGNORE:
+ default:
+ continue;
+
+ case FTRACE_UPDATE_MAKE_CALL:
+ old = ftrace_nop_replace();
+ break;
+
+ case FTRACE_UPDATE_MODIFY_CALL:
+ case FTRACE_UPDATE_MAKE_NOP:
+ old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
+ break;
+ }
+
+ ret = ftrace_verify_code(rec->ip, old);
+ if (ret) {
+ ftrace_expected = old;
+ ftrace_bug(ret, rec);
+ ftrace_expected = NULL;
+ return;
+ }
+ }
+
+ for_ftrace_rec_iter(iter) {
+ rec = ftrace_rec_iter_record(iter);
+
+ switch (ftrace_test_record(rec, enable)) {
+ case FTRACE_UPDATE_IGNORE:
+ default:
+ continue;
+
+ case FTRACE_UPDATE_MAKE_CALL:
+ case FTRACE_UPDATE_MODIFY_CALL:
+ new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
+ break;
+
+ case FTRACE_UPDATE_MAKE_NOP:
+ new = ftrace_nop_replace();
+ break;
+ }
+
+ text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
+ ftrace_update_record(rec, enable);
+ }
+ text_poke_finish();
+}
+
+void arch_ftrace_update_code(int command)
+{
+ ftrace_modify_all_code(command);
+}
+
+/* Currently only x86_64 supports dynamic trampolines */
+#ifdef CONFIG_X86_64
+
+#ifdef CONFIG_MODULES
+#include <linux/moduleloader.h>
+/* Module allocation simplifies allocating memory for code */
+static inline void *alloc_tramp(unsigned long size)
+{
+ return module_alloc(size);
+}
+static inline void tramp_free(void *tramp)
+{
+ module_memfree(tramp);
+}
+#else
+/* Trampolines can only be created if modules are supported */
+static inline void *alloc_tramp(unsigned long size)
+{
+ return NULL;
+}
+static inline void tramp_free(void *tramp) { }
+#endif
+
+/* Defined as markers to the end of the ftrace default trampolines */
+extern void ftrace_regs_caller_end(void);
+extern void ftrace_caller_end(void);
+extern void ftrace_caller_op_ptr(void);
+extern void ftrace_regs_caller_op_ptr(void);
+extern void ftrace_regs_caller_jmp(void);
+
+/* movq function_trace_op(%rip), %rdx */
+/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
+#define OP_REF_SIZE 7
+
+/*
+ * The ftrace_ops is passed to the function callback. Since the
+ * trampoline only services a single ftrace_ops, we can pass in
+ * that ops directly.
+ *
+ * The ftrace_op_code_union is used to create a pointer to the
+ * ftrace_ops that will be passed to the callback function.
+ */
+union ftrace_op_code_union {
+ char code[OP_REF_SIZE];
+ struct {
+ char op[3];
+ int offset;
+ } __attribute__((packed));
+};
+
+#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))
+
+static unsigned long
+create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
+{
+ unsigned long start_offset;
+ unsigned long end_offset;
+ unsigned long op_offset;
+ unsigned long call_offset;
+ unsigned long jmp_offset;
+ unsigned long offset;
+ unsigned long npages;
+ unsigned long size;
+ unsigned long *ptr;
+ void *trampoline;
+ void *ip, *dest;
+ /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
+ unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
+ unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE };
+ union ftrace_op_code_union op_ptr;
+ int ret;
+
+ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
+ start_offset = (unsigned long)ftrace_regs_caller;
+ end_offset = (unsigned long)ftrace_regs_caller_end;
+ op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
+ call_offset = (unsigned long)ftrace_regs_call;
+ jmp_offset = (unsigned long)ftrace_regs_caller_jmp;
+ } else {
+ start_offset = (unsigned long)ftrace_caller;
+ end_offset = (unsigned long)ftrace_caller_end;
+ op_offset = (unsigned long)ftrace_caller_op_ptr;
+ call_offset = (unsigned long)ftrace_call;
+ jmp_offset = 0;
+ }
+
+ size = end_offset - start_offset;
+
+ /*
+ * Allocate enough size to store the ftrace_caller code,
+ * the iret , as well as the address of the ftrace_ops this
+ * trampoline is used for.
+ */
+ trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
+ if (!trampoline)
+ return 0;
+
+ *tramp_size = size + RET_SIZE + sizeof(void *);
+ npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
+
+ /* Copy ftrace_caller onto the trampoline memory */
+ ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size);
+ if (WARN_ON(ret < 0))
+ goto fail;
+
+ ip = trampoline + size;
+ if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
+ __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, x86_return_thunk, JMP32_INSN_SIZE);
+ else
+ memcpy(ip, retq, sizeof(retq));
+
+ /* No need to test direct calls on created trampolines */
+ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
+ /* NOP the jnz 1f; but make sure it's a 2 byte jnz */
+ ip = trampoline + (jmp_offset - start_offset);
+ if (WARN_ON(*(char *)ip != 0x75))
+ goto fail;
+ ret = copy_from_kernel_nofault(ip, x86_nops[2], 2);
+ if (ret < 0)
+ goto fail;
+ }
+
+ /*
+ * The address of the ftrace_ops that is used for this trampoline
+ * is stored at the end of the trampoline. This will be used to
+ * load the third parameter for the callback. Basically, that
+ * location at the end of the trampoline takes the place of
+ * the global function_trace_op variable.
+ */
+
+ ptr = (unsigned long *)(trampoline + size + RET_SIZE);
+ *ptr = (unsigned long)ops;
+
+ op_offset -= start_offset;
+ memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
+
+ /* Are we pointing to the reference? */
+ if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
+ goto fail;
+
+ /* Load the contents of ptr into the callback parameter */
+ offset = (unsigned long)ptr;
+ offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
+
+ op_ptr.offset = offset;
+
+ /* put in the new offset to the ftrace_ops */
+ memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
+
+ /* put in the call to the function */
+ mutex_lock(&text_mutex);
+ call_offset -= start_offset;
+ /*
+ * No need to translate into a callthunk. The trampoline does
+ * the depth accounting before the call already.
+ */
+ dest = ftrace_ops_get_func(ops);
+ memcpy(trampoline + call_offset,
+ text_gen_insn(CALL_INSN_OPCODE, trampoline + call_offset, dest),
+ CALL_INSN_SIZE);
+ mutex_unlock(&text_mutex);
+
+ /* ALLOC_TRAMP flags lets us know we created it */
+ ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
+
+ set_memory_rox((unsigned long)trampoline, npages);
+ return (unsigned long)trampoline;
+fail:
+ tramp_free(trampoline);
+ return 0;
+}
+
+void set_ftrace_ops_ro(void)
+{
+ struct ftrace_ops *ops;
+ unsigned long start_offset;
+ unsigned long end_offset;
+ unsigned long npages;
+ unsigned long size;
+
+ do_for_each_ftrace_op(ops, ftrace_ops_list) {
+ if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
+ continue;
+
+ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
+ start_offset = (unsigned long)ftrace_regs_caller;
+ end_offset = (unsigned long)ftrace_regs_caller_end;
+ } else {
+ start_offset = (unsigned long)ftrace_caller;
+ end_offset = (unsigned long)ftrace_caller_end;
+ }
+ size = end_offset - start_offset;
+ size = size + RET_SIZE + sizeof(void *);
+ npages = DIV_ROUND_UP(size, PAGE_SIZE);
+ set_memory_ro((unsigned long)ops->trampoline, npages);
+ } while_for_each_ftrace_op(ops);
+}
+
+static unsigned long calc_trampoline_call_offset(bool save_regs)
+{
+ unsigned long start_offset;
+ unsigned long call_offset;
+
+ if (save_regs) {
+ start_offset = (unsigned long)ftrace_regs_caller;
+ call_offset = (unsigned long)ftrace_regs_call;
+ } else {
+ start_offset = (unsigned long)ftrace_caller;
+ call_offset = (unsigned long)ftrace_call;
+ }
+
+ return call_offset - start_offset;
+}
+
+void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
+{
+ ftrace_func_t func;
+ unsigned long offset;
+ unsigned long ip;
+ unsigned int size;
+ const char *new;
+
+ if (!ops->trampoline) {
+ ops->trampoline = create_trampoline(ops, &size);
+ if (!ops->trampoline)
+ return;
+ ops->trampoline_size = size;
+ return;
+ }
+
+ /*
+ * The ftrace_ops caller may set up its own trampoline.
+ * In such a case, this code must not modify it.
+ */
+ if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
+ return;
+
+ offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
+ ip = ops->trampoline + offset;
+ func = ftrace_ops_get_func(ops);
+
+ mutex_lock(&text_mutex);
+ /* Do a safe modify in case the trampoline is executing */
+ new = ftrace_call_replace(ip, (unsigned long)func);
+ text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
+ mutex_unlock(&text_mutex);
+}
+
+/* Return the address of the function the trampoline calls */
+static void *addr_from_call(void *ptr)
+{
+ union text_poke_insn call;
+ int ret;
+
+ ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE);
+ if (WARN_ON_ONCE(ret < 0))
+ return NULL;
+
+ /* Make sure this is a call */
+ if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
+ pr_warn("Expected E8, got %x\n", call.opcode);
+ return NULL;
+ }
+
+ return ptr + CALL_INSN_SIZE + call.disp;
+}
+
+/*
+ * If the ops->trampoline was not allocated, then it probably
+ * has a static trampoline func, or is the ftrace caller itself.
+ */
+static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
+{
+ unsigned long offset;
+ bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
+ void *ptr;
+
+ if (ops && ops->trampoline) {
+#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) && \
+ defined(CONFIG_FUNCTION_GRAPH_TRACER)
+ /*
+ * We only know about function graph tracer setting as static
+ * trampoline.
+ */
+ if (ops->trampoline == FTRACE_GRAPH_ADDR)
+ return (void *)prepare_ftrace_return;
+#endif
+ return NULL;
+ }
+
+ offset = calc_trampoline_call_offset(save_regs);
+
+ if (save_regs)
+ ptr = (void *)FTRACE_REGS_ADDR + offset;
+ else
+ ptr = (void *)FTRACE_ADDR + offset;
+
+ return addr_from_call(ptr);
+}
+
+void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
+{
+ unsigned long offset;
+
+ /* If we didn't allocate this trampoline, consider it static */
+ if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
+ return static_tramp_func(ops, rec);
+
+ offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
+ return addr_from_call((void *)ops->trampoline + offset);
+}
+
+void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
+{
+ if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
+ return;
+
+ tramp_free((void *)ops->trampoline);
+ ops->trampoline = 0;
+}
+
+#endif /* CONFIG_X86_64 */
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+#if defined(CONFIG_DYNAMIC_FTRACE) && !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS)
+extern void ftrace_graph_call(void);
+static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
+{
+ return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
+}
+
+static int ftrace_mod_jmp(unsigned long ip, void *func)
+{
+ const char *new;
+
+ new = ftrace_jmp_replace(ip, (unsigned long)func);
+ text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
+ return 0;
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ unsigned long ip = (unsigned long)(&ftrace_graph_call);
+
+ return ftrace_mod_jmp(ip, &ftrace_graph_caller);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ unsigned long ip = (unsigned long)(&ftrace_graph_call);
+
+ return ftrace_mod_jmp(ip, &ftrace_stub);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
+ unsigned long frame_pointer)
+{
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ int bit;
+
+ /*
+ * When resuming from suspend-to-ram, this function can be indirectly
+ * called from early CPU startup code while the CPU is in real mode,
+ * which would fail miserably. Make sure the stack pointer is a
+ * virtual address.
+ *
+ * This check isn't as accurate as virt_addr_valid(), but it should be
+ * good enough for this purpose, and it's fast.
+ */
+ if (unlikely((long)__builtin_frame_address(0) >= 0))
+ return;
+
+ if (unlikely(ftrace_graph_is_dead()))
+ return;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ bit = ftrace_test_recursion_trylock(ip, *parent);
+ if (bit < 0)
+ return;
+
+ if (!function_graph_enter(*parent, ip, frame_pointer, parent))
+ *parent = return_hooker;
+
+ ftrace_test_recursion_unlock(bit);
+}
+
+#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+ struct pt_regs *regs = &fregs->regs;
+ unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs);
+
+ prepare_ftrace_return(ip, (unsigned long *)stack, 0);
+}
+#endif
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */