tep_parse_saved_cmdlines - Man Page

#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);
int tep_parse_last_boot_info(struct tep_handle *tep, const char *lbi);
int tep_load_modules(struct tep_handle *tep, char *modules, size_t size);

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)​.

tep_parse_last_boot_info() loads information from the last_boot_info file of a persistent ring buffer instance​. If a tracefs instance is declared as a persistent ring buffer and contains data from a previous boot, the last_boot_info file will have the addresses of the kernel as well as modules​. It will use this information to base the function offsets in the binary buffer to match the function offsets in the kallsyms (loaded by tep_parse_kallsyms()) into the tep handler​. The lbi is a nul terminated string that contains the content of the last_boot_info file from the persistent ring buffer instance​.

tep_load_modules() loads the contents of the file /proc/modules into the tep handler​. This will be used to match the modules found in the last_boot_info (loaded by tep_parse_last_boot_info()) to match the offsets of the binary data in in a persistent ring buffer that matches the address of a module from the previous boot to a module address found in modules​. The modules parameter does not need to be nul terminated, but size is used to denote the size of the modules string​. This function is useless if tep_parse_last_boot_info() isnt used​.

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​.

The tep_parse_last_boot_info() function retuns 0 in case of success, or -1 in case of error​.

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

​.​.​.
#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;
}

static char *read_file(const char *file, size_t *size)
{
        FILE *fp;
        char *line = NULL;
        char *buf = NULL;
        size_t sz = 0;
        size_t len = 0;
        int r;

        fp = fopen(file, "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 NULL;
        buf[len] = 0;
        *size = len;
        return buf;
}

int load_kallsyms(struct tep_handle *tep)
{
        char *buf;
        size_t sz;
        int r;

        buf = read_file("/proc/kallsyms", &sz);
        if (!buf)
                return -1;
        r = tep_parse_kallsyms(tep, buf);
        free(buf);
        return r;
}

int load_last_boot(struct tep_handle *tep, struct tracefs_instance *instance)
{
        char *buf;
        size_t sz;
        int r;

        buf = tracefs_instance_file_read(instance, "last_boot_info", NULL);
        if (!buf)
                return 0;

        r = tep_parse_last_boot_info(tep, buf);
        free(buf);
        if (r < 0)
                return r;

        buf = read_file("/proc/modules", &sz);
        if (!buf)
                return -1;
        r = tep_parse_kallsyms(tep, buf);
        free(buf);
        return r;
}
​.​.​.

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​.

libtraceevent(3), trace-cmd(1), tep_register_comm(3), tep_register_function(3), tep_register_print_string(3)

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

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

libtraceevent is Free Software licensed under the GNU LGPL 2​.1

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

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