Commit b3aa5577 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

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: default avatarAbhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Tested-by: default avatarAbhishek Sagar <sagar.abhishek@gmail.com>
Acked-by: default avatarAbhishek Sagar <sagar.abhishek@gmail.com>
parent c2c80529

kernel/trace/trace.c

+21 −18
Original line number Diff line number Diff line
@@ -1088,17 +1088,20 @@ static void s_stop(struct seq_file *m, void *p) 
	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 @@ seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address) 
{

#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 @@ seq_print_sym_offset(struct trace_seq *s, const char *fmt, 
{

#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;

}
@@ -1377,9 +1386,6 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu) 


		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);

		trace_seq_puts(s, ")\n");

		break;
@@ -1496,9 +1502,6 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter) 
			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);

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