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1 | /* | |
2 | * Ftrace trace backend | |
3 | * | |
4 | * Copyright (C) 2013 Hitachi, Ltd. | |
5 | * Created by Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com> | |
6 | * | |
7 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
8 | * the COPYING file in the top-level directory. | |
9 | * | |
10 | */ | |
11 | ||
12 | #include "qemu/osdep.h" | |
13 | #include "trace/control.h" | |
14 | #include "trace/ftrace.h" | |
15 | ||
16 | int trace_marker_fd; | |
17 | ||
18 | static int find_mount(char *mount_point, const char *fstype) | |
19 | { | |
20 | char type[100]; | |
21 | FILE *fp; | |
22 | int ret = 0; | |
23 | ||
24 | fp = fopen("/proc/mounts", "r"); | |
25 | if (fp == NULL) { | |
26 | return 0; | |
27 | } | |
28 | ||
29 | while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n", | |
30 | mount_point, type) == 2) { | |
31 | if (strcmp(type, fstype) == 0) { | |
32 | ret = 1; | |
33 | break; | |
34 | } | |
35 | } | |
36 | fclose(fp); | |
37 | ||
38 | return ret; | |
39 | } | |
40 | ||
41 | bool ftrace_init(void) | |
42 | { | |
43 | char mount_point[PATH_MAX]; | |
44 | char path[PATH_MAX]; | |
45 | int tracefs_found; | |
46 | int trace_fd = -1; | |
47 | const char *subdir = ""; | |
48 | ||
49 | tracefs_found = find_mount(mount_point, "tracefs"); | |
50 | if (!tracefs_found) { | |
51 | tracefs_found = find_mount(mount_point, "debugfs"); | |
52 | subdir = "/tracing"; | |
53 | } | |
54 | ||
55 | if (tracefs_found) { | |
56 | if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir) | |
57 | >= sizeof(path)) { | |
58 | fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); | |
59 | return false; | |
60 | } | |
61 | trace_fd = open(path, O_WRONLY); | |
62 | if (trace_fd < 0) { | |
63 | if (errno == EACCES) { | |
64 | trace_marker_fd = open("/dev/null", O_WRONLY); | |
65 | if (trace_marker_fd != -1) { | |
66 | return true; | |
67 | } | |
68 | } | |
69 | perror("Could not open ftrace 'tracing_on' file"); | |
70 | return false; | |
71 | } else { | |
72 | if (write(trace_fd, "1", 1) < 0) { | |
73 | perror("Could not write to 'tracing_on' file"); | |
74 | close(trace_fd); | |
75 | return false; | |
76 | } | |
77 | close(trace_fd); | |
78 | } | |
79 | if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir) | |
80 | >= sizeof(path)) { | |
81 | fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); | |
82 | return false; | |
83 | } | |
84 | trace_marker_fd = open(path, O_WRONLY); | |
85 | if (trace_marker_fd < 0) { | |
86 | perror("Could not open ftrace 'trace_marker' file"); | |
87 | return false; | |
88 | } | |
89 | } else { | |
90 | fprintf(stderr, "tracefs is not mounted\n"); | |
91 | return false; | |
92 | } | |
93 | ||
94 | return true; | |
95 | } |