'\" t
.\"     Title: libtraceevent
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 03/09/2026
.\"    Manual: libtraceevent Manual
.\"    Source: libtraceevent
.\"  Language: English
.\"
.TH "LIBTRACEEVENT" "3" "03/09/2026" "libtraceevent" "libtraceevent Manual"
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.SH "NAME"
tep_parse_saved_cmdlines, tep_parse_printk_formats, tep_parse_kallsyms, tep_parse_last_boot_info, tep_load_modules \- Parsing functions to load mappings
.SH "SYNOPSIS"
.sp
.nf
\fB#include <event\-parse\&.h>\fR

int \fBtep_parse_saved_cmdlines\fR(struct tep_handle *\fItep\fR, const char *\fIbuf\fR);
int \fBtep_parse_printk_formats\fR(struct tep_handle *\fItep\fR, const char *\fIbuf\fR);
int \fBtep_parse_kallsyms\fR(struct tep_handle *\fItep\fR, const char *\fIbuf\fR);
int \fBtep_parse_last_boot_info\fR(struct tep_handle *\fItep\fR, const char *\fIlbi\fR);
int \fBtep_load_modules\fR(struct tep_handle *\fItep\fR, char *\fImodules\fR, size_t \fIsize\fR);
.fi
.SH "DESCRIPTION"
.sp
\fBtep_parse_saved_cmdlines()\fR 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 \fIbuf\fR) and loads the mapping of the process IDs (pid) to the comm names in the \fItep\fR 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 \fIbuf\fR that holds the content of saved_cmdlines and ends with a nul character (\fI\e0\fR)\&.
.sp
\fBtep_parse_printk_formats()\fR 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 \fIbuf\fR) 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 \fIbuf\fR that holds the content of printk_formats and ends with a nul character (\fI\e0\fR)\&.
.sp
\fBtep_parse_kallsyms()\fR is a helper function to parse the Linux kernel /proc/kallsyms format (stored in a string buffer passed in by \fIbuf\fR) and load the functions into the \fItep\fR 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 \fIbuf\fR that holds the content of /proc/kallsyms and ends with a nul character (\fI\e0\fR)\&.
.sp
\fBtep_parse_last_boot_info()\fR 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 \fBtep_parse_kallsyms()\fR) into the \fItep\fR handler\&. The \fIlbi\fR is a nul terminated string that contains the content of the last_boot_info file from the persistent ring buffer instance\&.
.sp
\fBtep_load_modules()\fR loads the contents of the file /proc/modules into the \fItep\fR handler\&. This will be used to match the modules found in the last_boot_info (loaded by \fBtep_parse_last_boot_info()\fR) 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 \fImodules\fR\&. The \fImodules\fR parameter does not need to be nul terminated, but \fIsize\fR is used to denote the size of the \fImodules\fR string\&. This function is useless if \fBtep_parse_last_boot_info()\fR isnt used\&.
.SH "RETURN VALUE"
.sp
The \fBtep_parse_saved_cmdlines\fR() function returns 0 in case of success, or \-1 in case of an error\&.
.sp
The \fBtep_parse_printk_formats\fR() function returns 0 in case of success, or \-1 in case of an error\&.
.sp
The \fBtep_parse_kallsyms\fR() function returns 0 in case of success, or \-1 in case of an error\&.
.sp
The \fBtep_parse_last_boot_info\fR() function retuns 0 in case of success, or \-1 in case of error\&.
.sp
The \fBtep_load_modules\fR() function returns 0 in case of success, or \-1 in case of error\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
\&.\&.\&.
#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;
}
\&.\&.\&.
.fi
.if n \{\
.RE
.\}
.SH "FILES"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBevent\-parse\&.h\fR
        Header file to include in order to have access to the library APIs\&.
\fB\-ltraceevent\fR
        Linker switch to add when building a program that uses the library\&.
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBlibtraceevent\fR(3), \fBtrace\-cmd\fR(1), \fBtep_register_comm\fR(3), \fBtep_register_function\fR(3), \fBtep_register_print_string\fR(3)
.SH "AUTHOR"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBSteven Rostedt\fR <\m[blue]\fBrostedt@goodmis\&.org\fR\m[]\&\s-2\u[1]\d\s+2>, author of \fBlibtraceevent\fR\&.
\fBTzvetomir Stoyanov\fR <\m[blue]\fBtz\&.stoyanov@gmail\&.com\fR\m[]\&\s-2\u[2]\d\s+2>, coauthor of \fBlibtraceevent\fR\&.
.fi
.if n \{\
.RE
.\}
.SH "REPORTING BUGS"
.sp
Report bugs to <\m[blue]\fBlinux\-trace\-devel@vger\&.kernel\&.org\fR\m[]\&\s-2\u[3]\d\s+2>
.SH "LICENSE"
.sp
libtraceevent is Free Software licensed under the GNU LGPL 2\&.1
.SH "RESOURCES"
.sp
\m[blue]\fBhttps://git\&.kernel\&.org/pub/scm/libs/libtrace/libtraceevent\&.git/\fR\m[]
.SH "NOTES"
.IP " 1." 4
rostedt@goodmis.org
.RS 4
\%mailto:rostedt@goodmis.org
.RE
.IP " 2." 4
tz.stoyanov@gmail.com
.RS 4
\%mailto:tz.stoyanov@gmail.com
.RE
.IP " 3." 4
linux-trace-devel@vger.kernel.org
.RS 4
\%mailto:linux-trace-devel@vger.kernel.org
.RE