ftrace: use kretprobe trampoline name to test in output
Impact: ia64+tracing build fix
When a function is kprobed, the return address is set to the
kprobe_trampoline, or something similar. This caused the output
of the trace to look confusing when the parent seemed to be this
"kprobe_trampoline" function.
To fix this, Abhishek Sagar added a test of the instruction pointer
of the parent to see if it matched the kprobe_trampoline. If it
did, the output would print a "[unknown/kretprobe'd]" instead.
Unfortunately, not all archs do this the same way, and the trampoline
function may not be exported, which causes failures in builds.
This patch will compare the name instead of the pointer to see
if it matches. This prevents us from depending on a function from
being exported, and should work on all archs. The worst that can
happen is that an arch might use a different name and then we
go back to the confusing output. At least the arch will still build.
Reported-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Acked-by: Abhishek Sagar <sagar.abhishek@gmail.com>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 85bee77..9f3b478 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1088,17 +1088,20 @@
mutex_unlock(&trace_types_lock);
}
-#define KRETPROBE_MSG "[unknown/kretprobe'd]"
-
#ifdef CONFIG_KRETPROBES
-static inline int kretprobed(unsigned long addr)
+static inline const char *kretprobed(const char *name)
{
- return addr == (unsigned long)kretprobe_trampoline;
+ static const char tramp_name[] = "kretprobe_trampoline";
+ int size = sizeof(tramp_name);
+
+ if (strncmp(tramp_name, name, size) == 0)
+ return "[unknown/kretprobe'd]";
+ return name;
}
#else
-static inline int kretprobed(unsigned long addr)
+static inline const char *kretprobed(const char *name)
{
- return 0;
+ return name;
}
#endif /* CONFIG_KRETPROBES */
@@ -1107,10 +1110,13 @@
{
#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
+ const char *name;
kallsyms_lookup(address, NULL, NULL, NULL, str);
- return trace_seq_printf(s, fmt, str);
+ name = kretprobed(str);
+
+ return trace_seq_printf(s, fmt, name);
#endif
return 1;
}
@@ -1121,9 +1127,12 @@
{
#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
+ const char *name;
sprint_symbol(str, address);
- return trace_seq_printf(s, fmt, str);
+ name = kretprobed(str);
+
+ return trace_seq_printf(s, fmt, name);
#endif
return 1;
}
@@ -1377,10 +1386,7 @@
seq_print_ip_sym(s, field->ip, sym_flags);
trace_seq_puts(s, " (");
- if (kretprobed(field->parent_ip))
- trace_seq_puts(s, KRETPROBE_MSG);
- else
- seq_print_ip_sym(s, field->parent_ip, sym_flags);
+ seq_print_ip_sym(s, field->parent_ip, sym_flags);
trace_seq_puts(s, ")\n");
break;
}
@@ -1496,12 +1502,9 @@
ret = trace_seq_printf(s, " <-");
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
- if (kretprobed(field->parent_ip))
- ret = trace_seq_puts(s, KRETPROBE_MSG);
- else
- ret = seq_print_ip_sym(s,
- field->parent_ip,
- sym_flags);
+ ret = seq_print_ip_sym(s,
+ field->parent_ip,
+ sym_flags);
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;
}