LIBTRACEEVENT

NAME

tep_parse_saved_cmdlines, tep_parse_printk_formats, tep_parse_kallsyms - Parsing functions to load mappings

SYNOPSIS

#include <event-parse.h>

int tep_parse_saved_cmdlines(struct tep_handle *tep, const char *buf);
int tep_parse_printk_formats(struct tep_handle *tep, const char *buf);
int tep_parse_kallsyms(struct tep_handle *tep, const char *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).

tep_parse_printk_formats() is a helper function to parse content in the tracefs file system of the "printk_formats" file (stored in a string buffer passed in by buf) and loads the mapping of addresses of strings that may be referenced by events. Events only store the address of constant strings in the kernel, and the mapping of their address to the string is exported to user space in the printk_formats file. It parses the string buf that holds the content of printk_formats and ends with a nul character (\0).

tep_parse_kallsyms() is a helper function to parse the Linux kernel /proc/kallsyms format (stored in a string buffer passed in by buf) and load the functions into the tep handler such that function IP addresses can be mapped to their name when parsing events with %pS in the print format field. It parses the string buf that holds the content of /proc/kallsyms 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.

The tep_parse_printk_formats() function returns 0 in case of success, or -1 in case of an error.

The tep_parse_kallsyms() function returns 0 in case of success, or -1 in case of an error.

EXAMPLE

...
#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;
}

int load_print_strings(struct tep_handle *tep)
{
char *buf = NULL;
int r;

buf = tracefs_instance_file_read(NULL, "printk_formats", NULL);
if (!buf)
return -1;
r = tep_parse_printk_formats(tep, buf);
free(buf);
return r;
}

int load_kallsyms(struct tep_handle *tep)
{
char *line = NULL;
char *buf = NULL;
size_t sz = 0;
FILE *fp;
int len = 0;
int r;

fp = fopen("/proc/kallsyms", "r");
while ((r = getline(&line, &sz, fp)) >= 0) {
buf = realloc(buf, len + r + 1);
memcpy(buf + len, line, r);
len += r;
}
free(line);
fclose(fp);
if (!buf)
return -1;
buf[len] = 0;

r = tep_parse_kallsyms(tep, buf);
free(buf);
return r;
}
...

FILES

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), tep_register_function(3), tep_register_print_string(3)

AUTHOR

Steven Rostedt <rostedt@goodmis.org [1] >, author of libtraceevent.
Tzvetomir Stoyanov <tz.stoyanov@gmail.com [2] >, coauthor of libtraceevent.

REPORTING BUGS

Report bugs to <linux-trace-devel@vger.kernel.org [3] >

LICENSE

libtraceevent is Free Software licensed under the GNU LGPL 2.1

RESOURCES

https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/

NOTES

1.

rostedt@goodmis.org

mailto:rostedt@goodmis.org

2.

tz.stoyanov@gmail.com

mailto:tz.stoyanov@gmail.com

3.

linux-trace-devel@vger.kernel.org

mailto:linux-trace-devel@vger.kernel.org