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/*
* Ftrace trace backend
*
* Copyright (C) 2013 Hitachi, Ltd.
* Created by Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "trace/control.h"
#include "trace/ftrace.h"
int trace_marker_fd;
static int find_mount(char *mount_point, const char *fstype)
{
char type[100];
FILE *fp;
int ret = 0;
fp = fopen("/proc/mounts", "r");
if (fp == NULL) {
return 0;
}
while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
mount_point, type) == 2) {
if (strcmp(type, fstype) == 0) {
ret = 1;
break;
}
}
fclose(fp);
return ret;
}
bool ftrace_init(void)
{
char mount_point[PATH_MAX];
char path[PATH_MAX];
int tracefs_found;
int trace_fd = -1;
const char *subdir = "";
tracefs_found = find_mount(mount_point, "tracefs");
if (!tracefs_found) {
tracefs_found = find_mount(mount_point, "debugfs");
subdir = "/tracing";
}
if (tracefs_found) {
if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir)
>= sizeof(path)) {
fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n");
return false;
}
trace_fd = open(path, O_WRONLY);
if (trace_fd < 0) {
if (errno == EACCES) {
trace_marker_fd = open("/dev/null", O_WRONLY);
if (trace_marker_fd != -1) {
return true;
}
}
perror("Could not open ftrace 'tracing_on' file");
return false;
} else {
if (write(trace_fd, "1", 1) < 0) {
perror("Could not write to 'tracing_on' file");
close(trace_fd);
return false;
}
close(trace_fd);
}
if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir)
>= sizeof(path)) {
fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n");
return false;
}
trace_marker_fd = open(path, O_WRONLY);
if (trace_marker_fd < 0) {
perror("Could not open ftrace 'trace_marker' file");
return false;
}
} else {
fprintf(stderr, "tracefs is not mounted\n");
return false;
}
return true;
}
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