mirror of
https://github.com/xemu-project/xemu.git
synced 2024-11-25 04:30:02 +00:00
8ed5372874
If the ftrace backend is compiled into QEMU, any attempt to start QEMU while non-root will fail due to the inability to open /sys/kernel/debug/tracing/tracing_on. Add a fallback into the code so that it connects up the trace_marker_fd variable to /dev/null when getting EACCES on the 'trace_on' file. This allows QEMU to run, with ftrace turned into a no-op. [Fixed s/setting/getting/ and s/EACCESS/EACCES/ errors pointed out by Eric Blake <eblake@redhat.com>. --Stefan] Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 1475588159-30598-13-git-send-email-berrange@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
83 lines
2.0 KiB
C
83 lines
2.0 KiB
C
/*
|
|
* 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.h"
|
|
#include "trace/control.h"
|
|
|
|
int trace_marker_fd;
|
|
|
|
static int find_debugfs(char *debugfs)
|
|
{
|
|
char type[100];
|
|
FILE *fp;
|
|
|
|
fp = fopen("/proc/mounts", "r");
|
|
if (fp == NULL) {
|
|
return 0;
|
|
}
|
|
|
|
while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
|
|
debugfs, type) == 2) {
|
|
if (strcmp(type, "debugfs") == 0) {
|
|
break;
|
|
}
|
|
}
|
|
fclose(fp);
|
|
|
|
if (strcmp(type, "debugfs") != 0) {
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
bool ftrace_init(void)
|
|
{
|
|
char debugfs[PATH_MAX];
|
|
char path[PATH_MAX];
|
|
int debugfs_found;
|
|
int trace_fd = -1;
|
|
|
|
debugfs_found = find_debugfs(debugfs);
|
|
if (debugfs_found) {
|
|
snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs);
|
|
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);
|
|
}
|
|
snprintf(path, PATH_MAX, "%s/tracing/trace_marker", debugfs);
|
|
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, "debugfs is not mounted\n");
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|