[PATCH v2 04/10] trace-cmd library: New API for setting a custom kallsyms to an output handler

[PATCH v2 04/10] trace-cmd library: New API for setting a custom kallsyms to an output handler

[Tzvetomir Stoyanov (VMware)]

The new API associates an output file handler with a custom kernel symbols
file. It is used when creating the trace file instead of the system default
kernel symbols file.
 tracecmd_output_set_kallsyms()

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 .../include/private/trace-cmd-private.h       |  1 +
 lib/trace-cmd/trace-output.c                  | 32 +++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/lib/trace-cmd/include/private/trace-cmd-private.h b/lib/trace-cmd/include/private/trace-cmd-private.h
index eb173a39..23e86107 100644
--- a/lib/trace-cmd/include/private/trace-cmd-private.h
+++ b/lib/trace-cmd/include/private/trace-cmd-private.h
@@ -273,6 +273,7 @@ struct tracecmd_output *tracecmd_output_allocate(int fd);
 int tracecmd_output_set_msg(struct tracecmd_output *handler,
 			    struct tracecmd_msg_handle *msg_handle);
 int tracecmd_output_set_trace_dir(struct tracecmd_output *handler, const char *tracing_dir);
+int tracecmd_output_set_kallsyms(struct tracecmd_output *handler, const char *kallsyms);
 struct tracecmd_output *tracecmd_create_file_latency(const char *output_file, int cpus);
 struct tracecmd_output *
 tracecmd_create_init_file_glob(const char *output_file,
diff --git a/lib/trace-cmd/trace-output.c b/lib/trace-cmd/trace-output.c
index a5d7ed5f..c654561a 100644
--- a/lib/trace-cmd/trace-output.c
+++ b/lib/trace-cmd/trace-output.c
@@ -54,6 +54,7 @@ struct tracecmd_output {
 	int			cpus;
 	struct tep_handle	*pevent;
 	char			*tracing_dir;
+	char			*kallsyms;
 	int			nr_options;
 	bool			quiet;
 	unsigned long		file_state;
@@ -767,8 +768,8 @@ static int read_proc_kallsyms(struct tracecmd_output *handle,
 		return -1;
 	}
 
-	if (kallsyms)
-		path = kallsyms;
+	if (handle->kallsyms)
+		path = handle->kallsyms;
 
 	ret = stat(path, &st);
 	if (ret < 0) {
@@ -968,6 +969,33 @@ int tracecmd_output_set_trace_dir(struct tracecmd_output *handler, const char *t
 	return 0;
 }
 
+/**
+ * tracecmd_output_set_kallsyms - Set a custom kernel symbols file, instead of system default
+ * @handle: output handler to a trace file.
+ * @tracing_dir: full path to a file with kernel symbols
+ *
+ * This API associates an output file handler with a custom kernel symbols file, to be used when
+ * creating the trace file instead of the system default kernel symbols file.
+ * This API must be called before tracecmd_output_write_init().
+ *
+ * Returns 0 on success, or -1 if the output file handler is not allocated or not in expected state.
+ */
+int tracecmd_output_set_kallsyms(struct tracecmd_output *handler, const char *kallsyms)
+{
+	if (!handler || handler->file_state != TRACECMD_FILE_ALLOCATED)
+		return -1;
+
+	free(handler->kallsyms);
+	if (kallsyms) {
+		handler->kallsyms = strdup(kallsyms);
+		if (!handler->kallsyms)
+			return -1;
+	} else
+		handler->kallsyms = NULL;
+
+	return 0;
+}
+
 static int select_file_version(struct tracecmd_output *handle,
 				struct tracecmd_input *ihandle)
 {
-- 
2.33.1

Re: [PATCH v2 04/10] trace-cmd library: New API for setting a custom kallsyms to an output handler

[Steven Rostedt]

On Thu, 11 Nov 2021 17:06:58 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> +int tracecmd_output_set_kallsyms(struct tracecmd_output *handler, const char *kallsyms)
> +{
> +	if (!handler || handler->file_state != TRACECMD_FILE_ALLOCATED)
> +		return -1;
> +
> +	free(handler->kallsyms);

Nit, this isn't a fast path, so the code could be a little cleaner with:

	handler->kallsyms = NULL;

here

> +	if (kallsyms) {
> +		handler->kallsyms = strdup(kallsyms);
> +		if (!handler->kallsyms)
> +			return -1;
> +	} else
> +		handler->kallsyms = NULL;

Then removing the else case.

-- Steve

> +
> +	return 0;
> +}
> +