From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Currently, trace-cmd has a tracecmd_parse_cmdlines() function that
reads a string that holds the content of saved_cmdlines from the tracefs
file system, and then passes the pid to comm mapping to the tep handler.
There's no reason for this to be specific to trace-cmd as other
applications can easily read the saved_cmdlines with the tracefs API and
then pass it to the tep handler.
Add the same functionality to libtraceevent as tep_parse_saved_cmdlines().
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
.../libtraceevent-parse_saved_cmdlines.txt | 86 +++++++++++++++++++
src/event-parse.c | 42 +++++++++
src/event-parse.h | 1 +
3 files changed, 129 insertions(+)
create mode 100644 Documentation/libtraceevent-parse_saved_cmdlines.txt
diff --git a/Documentation/libtraceevent-parse_saved_cmdlines.txt b/Documentation/libtraceevent-parse_saved_cmdlines.txt
new file mode 100644
index 0000000..6c8313a
--- /dev/null
+++ b/Documentation/libtraceevent-parse_saved_cmdlines.txt
@@ -0,0 +1,86 @@
+libtraceevent(3)
+================
+
+NAME
+----
+tep_parse_saved_cmdlines - Parses mappings of process IDs (pids) to the process names
+
+SYNOPSIS
+--------
+[verse]
+--
+*#include <event-parse.h>*
+
+int *tep_parse_saved_cmdlines*(struct tep_handle pass:[*]_tep_, const char pass:[*]_buf_);
+--
+
+DESCRIPTION
+-----------
+*tep_parse_saved_cmdlines* is a helper function to parse content in the tracefs
+file system of the "saved_cmdlines" file (stored in a string buffer passed in by _buf_)
+and loads the mapping of the process IDs (pid) to the comm names in the
+_tep_ handler. The events store the pid and this is used to be able to show the
+process names associated to those process ids. It parses the string _buf_ that
+holds the content of saved_cmdlines and ends with a nul character ('\0').
+
+RETURN VALUE
+------------
+The *tep_parse_saved_cmdlines*() function returns 0 in case of success, or -1
+in case of an error.
+
+EXAMPLE
+-------
+[source,c]
+--
+...
+#include <event-parse.h>
+#include <tracefs.h>
+#include <stdlib.h>
+
+int load_cmdlines(struct tep_handle *tep)
+{
+ char *buf = NULL;
+ int r;
+
+ buf = tracefs_instance_file_read(NULL, "saved_cmdlines", NULL);
+ if (!buf)
+ return -1;
+ r = tep_parse_saved_cmdlines(tep, buf);
+ free(buf);
+ return r;
+}
+...
+--
+
+FILES
+-----
+[verse]
+--
+*event-parse.h*
+ Header file to include in order to have access to the library APIs.
+*-ltraceevent*
+ Linker switch to add when building a program that uses the library.
+--
+
+SEE ALSO
+--------
+_libtraceevent(3)_, _trace-cmd(1)_, _tep_register_comm(3)_
+
+AUTHOR
+------
+[verse]
+--
+*Steven Rostedt* <rostedt@xxxxxxxxxxx>, author of *libtraceevent*.
+*Tzvetomir Stoyanov* <tz.stoyanov@xxxxxxxxx>, coauthor of *libtraceevent*.
+--
+REPORTING BUGS
+--------------
+Report bugs to <linux-trace-devel@xxxxxxxxxxxxxxx>
+
+LICENSE
+-------
+libtraceevent is Free Software licensed under the GNU LGPL 2.1
+
+RESOURCES
+---------
+https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
diff --git a/src/event-parse.c b/src/event-parse.c
index 6bf293d..0d12ec4 100644
--- a/src/event-parse.c
+++ b/src/event-parse.c
@@ -387,6 +387,48 @@ int tep_override_comm(struct tep_handle *tep, const char *comm, int pid)
return _tep_register_comm(tep, comm, pid, true);
}
+/**
+ * tep_parse_saved_cmdlines - parse the comms from the saved_cmdlines file
+ * @tep: a handle to the trace event parser
+ * @buf: A string buffer that holds the content of saved_cmdlines and ends with '\0'
+ *
+ * This is a helper function to parse the comms in the tracefs saved_cmdlines
+ * file (stored in a string buffer) and load the comms into the @tep handler
+ * such that comm name matches an process ID (pid). This is used to show
+ * the names of the processes as the events only hold the pid.
+ *
+ * Returns 0 on success, and -1 on error.
+ */
+int tep_parse_saved_cmdlines(struct tep_handle *tep, const char *buf)
+{
+ char *copy;
+ char *comm;
+ char *line;
+ char *next = NULL;
+ int pid;
+ int ret = -1;
+ int n;
+
+ copy = strdup(buf);
+ if (!copy)
+ return -1;
+
+ line = strtok_r(copy, "\n", &next);
+ while (line) {
+ errno = 0;
+ n = sscanf(line, "%d %m[^\n]s", &pid, &comm);
+ if (errno || n != 2 || !comm)
+ goto out;
+ tep_register_comm(tep, comm, pid);
+ free(comm);
+ line = strtok_r(NULL, "\n", &next);
+ }
+ ret = 0;
+ out:
+ free(copy);
+ return ret;
+}
+
struct func_map {
unsigned long long addr;
char *func;
diff --git a/src/event-parse.h b/src/event-parse.h
index 3fbd3c4..078b202 100644
--- a/src/event-parse.h
+++ b/src/event-parse.h
@@ -439,6 +439,7 @@ int tep_set_function_resolver(struct tep_handle *tep,
void tep_reset_function_resolver(struct tep_handle *tep);
int tep_register_comm(struct tep_handle *tep, const char *comm, int pid);
int tep_override_comm(struct tep_handle *tep, const char *comm, int pid);
+int tep_parse_saved_cmdlines(struct tep_handle *tep, const char *buf);
int tep_parse_kallsyms(struct tep_handle *tep, const char *kallsyms);
int tep_register_function(struct tep_handle *tep, char *name,
unsigned long long addr, char *mod);
--
2.29.2
|