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#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include "utils/tracefs.h"
#include "utils/utils.h"
#define PROC_MOUNTINFO "/proc/self/mountinfo"
static char *TRACING_DIR = NULL;
static bool find_tracing_dir(void)
{
FILE *fp;
char *line = NULL, fs_type[NAME_MAX], mount_point[PATH_MAX];
static char debugfs_suffix[] = "tracing";
bool debugfs_found = false;
size_t len;
if (TRACING_DIR)
return false;
fp = fopen(PROC_MOUNTINFO, "r");
if (fp == NULL)
return false;
while (getline(&line, &len, fp) > 0) {
/*
* /proc/<pid>/mountinfo format:
* 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 .... ....
* (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
* mount_point fs_type
*
* (9) is the file system type, (5) is the mount point relative
* to self's root directory.
*/
sscanf(line, "%*i %*i %*u:%*u %*s %s %*s %*s - %s %*s %*s\n", mount_point, fs_type);
if (!strcmp(fs_type, "tracefs")) {
/* discard previously kept debugfs tracing dir */
if (TRACING_DIR)
free(TRACING_DIR);
xasprintf(&TRACING_DIR, "%s", mount_point);
pr_dbg2("Found tracefs at %s\n", mount_point);
pr_dbg2("Use %s as TRACING_DIR\n", TRACING_DIR);
return true;
}
if (!strcmp(fs_type, "debugfs")) {
xasprintf(&TRACING_DIR, "%s/%s", mount_point, debugfs_suffix);
pr_dbg2("Found debugfs at %s\n", mount_point);
pr_dbg2("Keep searching for tracefs...\n");
debugfs_found = true;
}
}
/* we couldn't find a tracefs, but found a debugfs... */
if (debugfs_found) {
pr_dbg2("Use %s as TRACING_DIR\n", TRACING_DIR);
return true;
}
pr_dbg2("No tracefs or debugfs found..!\n");
return false;
}
char *get_tracing_file(const char *name)
{
char *file = NULL;
if (!TRACING_DIR && !find_tracing_dir())
return NULL;
xasprintf(&file, "%s/%s", TRACING_DIR, name);
return file;
}
void put_tracing_file(char *file)
{
free(file);
}
int open_tracing_file(const char *name, int flags)
{
char *file;
int fd;
file = get_tracing_file(name);
if (!file) {
pr_dbg("cannot get tracing file: %s: %m\n", name);
return -1;
}
fd = open(file, flags);
if (fd < 0)
pr_dbg("cannot open tracing file: %s: %m\n", name);
put_tracing_file(file);
return fd;
}
ssize_t read_tracing_file(const char *name, char *buf, size_t len)
{
ssize_t ret;
int fd = open_tracing_file(name, O_RDONLY);
if (fd < 0)
return -1;
ret = read(fd, buf, len);
close(fd);
return ret;
}
int __write_tracing_file(int fd, const char *name, const char *val, bool append,
bool correct_sys_prefix)
{
int ret = -1;
ssize_t size = strlen(val);
if (correct_sys_prefix) {
char *newval = (char *)val;
if (!strncmp(val, "sys_", 4))
newval[0] = newval[2] = 'S';
else if (!strncmp(val, "compat_sys_", 11))
newval[7] = newval[9] = 'S';
else
correct_sys_prefix = false;
}
pr_dbg2("%s '%s' to tracing/%s\n", append ? "appending" : "writing", val, name);
if (write(fd, val, size) == size)
ret = 0;
if (correct_sys_prefix) {
char *newval = (char *)val;
if (!strncmp(val, "SyS_", 4))
newval[0] = newval[2] = 's';
else if (!strncmp(val, "compat_SyS_", 11))
newval[7] = newval[9] = 's';
/* write a whitespace to distinguish the previous pattern */
if (write(fd, " ", 1) < 0)
ret = -1;
pr_dbg2("%s '%s' to tracing/%s\n", append ? "appending" : "writing", val, name);
if (write(fd, val, size) == size)
ret = 0;
}
if (ret < 0)
pr_dbg("write '%s' to tracing/%s failed: %m\n", val, name);
return ret;
}
int write_tracing_file(const char *name, const char *val)
{
int ret;
int fd = open_tracing_file(name, O_WRONLY | O_TRUNC);
if (fd < 0)
return -1;
ret = __write_tracing_file(fd, name, val, false, false);
close(fd);
return ret;
}
int append_tracing_file(const char *name, const char *val)
{
int ret;
int fd = open_tracing_file(name, O_WRONLY | O_APPEND);
if (fd < 0)
return -1;
ret = __write_tracing_file(fd, name, val, true, false);
close(fd);
return ret;
}
int set_tracing_pid(int pid)
{
char buf[16];
snprintf(buf, sizeof(buf), "%d", pid);
if (append_tracing_file("set_ftrace_pid", buf) < 0)
return -1;
/* ignore error on old kernel */
append_tracing_file("set_event_pid", buf);
return 0;
}
int set_tracing_clock(char *clock_str)
{
/* set to default clock source if not given */
if (clock_str == NULL)
clock_str = "mono";
return write_tracing_file("trace_clock", clock_str);
}
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