ftrace/x86: Show trampoline call function in enabled_functions
The file /sys/kernel/debug/tracing/eneabled_functions is used to debug
ftrace function hooks. Add to the output what function is being called
by the trampoline if the arch supports it.
Add support for this feature in x86_64.
Cc: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index a1d0a61..48db15b 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -48,7 +48,7 @@
union ftrace_code_union {
char code[MCOUNT_INSN_SIZE];
struct {
- char e8;
+ unsigned char e8;
int offset;
} __attribute__((packed));
};
@@ -781,11 +781,25 @@
return (unsigned long)trampoline;
}
+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)
{
unsigned char *new;
- unsigned long start_offset;
- unsigned long call_offset;
unsigned long offset;
unsigned long ip;
int ret;
@@ -803,15 +817,7 @@
return;
}
- if (ops->flags & FTRACE_OPS_FL_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;
- }
-
- offset = call_offset - start_offset;
+ offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
ip = ops->trampoline + offset;
/* Do a safe modify in case the trampoline is executing */
@@ -821,6 +827,73 @@
/* The update should never fail */
WARN_ON(ret);
}
+
+/* Return the address of the function the trampoline calls */
+static void *addr_from_call(void *ptr)
+{
+ union ftrace_code_union calc;
+ int ret;
+
+ ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
+ if (WARN_ON_ONCE(ret < 0))
+ return NULL;
+
+ /* Make sure this is a call */
+ if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
+ pr_warn("Expected e8, got %lx\n", calc.e8);
+ return NULL;
+ }
+
+ return ptr + MCOUNT_INSN_SIZE + calc.offset;
+}
+
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
+ unsigned long frame_pointer);
+
+/*
+ * 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) {
+#ifdef 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 (!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);
+}
+
+
#endif /* CONFIG_X86_64 */
#endif /* CONFIG_DYNAMIC_FTRACE */
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8f4d3c7..c59040a 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2886,6 +2886,22 @@
mutex_unlock(&ftrace_lock);
}
+void * __weak
+arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
+{
+ return NULL;
+}
+
+static void add_trampoline_func(struct seq_file *m, struct ftrace_ops *ops,
+ struct dyn_ftrace *rec)
+{
+ void *ptr;
+
+ ptr = arch_ftrace_trampoline_func(ops, rec);
+ if (ptr)
+ seq_printf(m, " ->%pS", ptr);
+}
+
static int t_show(struct seq_file *m, void *v)
{
struct ftrace_iterator *iter = m->private;
@@ -2909,19 +2925,21 @@
seq_printf(m, "%ps", (void *)rec->ip);
if (iter->flags & FTRACE_ITER_ENABLED) {
+ struct ftrace_ops *ops = NULL;
+
seq_printf(m, " (%ld)%s",
ftrace_rec_count(rec),
rec->flags & FTRACE_FL_REGS ? " R" : " ");
if (rec->flags & FTRACE_FL_TRAMP_EN) {
- struct ftrace_ops *ops;
-
ops = ftrace_find_tramp_ops_curr(rec);
if (ops && ops->trampoline)
seq_printf(m, "\ttramp: %pS",
(void *)ops->trampoline);
else
seq_printf(m, "\ttramp: ERROR!");
+
}
+ add_trampoline_func(m, ops, rec);
}
seq_printf(m, "\n");
