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fd9858317a
If the tracefs mountpoint has a very long path we may exceed PATH_MAX. This is a system misconfiguration and the user must resolve it so that applications can perform path-based system calls successfully. This issue does not occur on real-world systems since tracefs is mounted on /sys/kernel/debug/tracing/, but the compiler is smart enough to foresee the possibility and warn about the unchecked snprintf(3) return value. This patch fixes the compiler warning. Reported-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Message-id: 20190321170831.6539-2-stefanha@redhat.com Message-Id: <20190321170831.6539-2-stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
96 lines
2.5 KiB
C
96 lines
2.5 KiB
C
/*
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* Ftrace trace backend
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*
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* Copyright (C) 2013 Hitachi, Ltd.
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* Created by Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "trace/control.h"
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#include "trace/ftrace.h"
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int trace_marker_fd;
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static int find_mount(char *mount_point, const char *fstype)
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{
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char type[100];
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FILE *fp;
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int ret = 0;
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fp = fopen("/proc/mounts", "r");
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if (fp == NULL) {
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return 0;
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}
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while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
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mount_point, type) == 2) {
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if (strcmp(type, fstype) == 0) {
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ret = 1;
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break;
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}
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}
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fclose(fp);
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return ret;
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}
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bool ftrace_init(void)
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{
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char mount_point[PATH_MAX];
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char path[PATH_MAX];
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int tracefs_found;
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int trace_fd = -1;
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const char *subdir = "";
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tracefs_found = find_mount(mount_point, "tracefs");
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if (!tracefs_found) {
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tracefs_found = find_mount(mount_point, "debugfs");
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subdir = "/tracing";
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}
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if (tracefs_found) {
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if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir)
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>= sizeof(path)) {
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fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n");
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return false;
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}
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trace_fd = open(path, O_WRONLY);
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if (trace_fd < 0) {
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if (errno == EACCES) {
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trace_marker_fd = open("/dev/null", O_WRONLY);
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if (trace_marker_fd != -1) {
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return true;
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}
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}
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perror("Could not open ftrace 'tracing_on' file");
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return false;
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} else {
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if (write(trace_fd, "1", 1) < 0) {
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perror("Could not write to 'tracing_on' file");
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close(trace_fd);
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return false;
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}
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close(trace_fd);
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}
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if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir)
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>= sizeof(path)) {
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fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n");
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return false;
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}
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trace_marker_fd = open(path, O_WRONLY);
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if (trace_marker_fd < 0) {
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perror("Could not open ftrace 'trace_marker' file");
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return false;
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}
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} else {
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fprintf(stderr, "tracefs is not mounted\n");
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return false;
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}
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return true;
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}
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