| 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 | void ftrace_write(const char *fmt, ...) |
| 42 | { |
| 43 | char ftrace_buf[MAX_TRACE_STRLEN]; |
| 44 | int unused __attribute__ ((unused)); |
| 45 | int trlen; |
| 46 | va_list ap; |
| 47 | |
| 48 | va_start(ap, fmt); |
| 49 | trlen = vsnprintf(ftrace_buf, MAX_TRACE_STRLEN, fmt, ap); |
| 50 | va_end(ap); |
| 51 | |
| 52 | trlen = MIN(trlen, MAX_TRACE_STRLEN - 1); |
| 53 | unused = write(trace_marker_fd, ftrace_buf, trlen); |
| 54 | } |
| 55 | |
| 56 | bool ftrace_init(void) |
| 57 | { |
| 58 | char mount_point[PATH_MAX]; |
| 59 | char path[PATH_MAX]; |
| 60 | int tracefs_found; |
| 61 | int trace_fd = -1; |
| 62 | const char *subdir = ""; |
| 63 | |
| 64 | tracefs_found = find_mount(mount_point, "tracefs"); |
| 65 | if (!tracefs_found) { |
| 66 | tracefs_found = find_mount(mount_point, "debugfs"); |
| 67 | subdir = "/tracing"; |
| 68 | } |
| 69 | |
| 70 | if (tracefs_found) { |
| 71 | if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir) |
| 72 | >= sizeof(path)) { |
| 73 | fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); |
| 74 | return false; |
| 75 | } |
| 76 | trace_fd = open(path, O_WRONLY); |
| 77 | if (trace_fd < 0) { |
| 78 | if (errno == EACCES) { |
| 79 | trace_marker_fd = open("/dev/null", O_WRONLY); |
| 80 | if (trace_marker_fd != -1) { |
| 81 | return true; |
| 82 | } |
| 83 | } |
| 84 | perror("Could not open ftrace 'tracing_on' file"); |
| 85 | return false; |
| 86 | } else { |
| 87 | if (write(trace_fd, "1", 1) < 0) { |
| 88 | perror("Could not write to 'tracing_on' file"); |
| 89 | close(trace_fd); |
| 90 | return false; |
| 91 | } |
| 92 | close(trace_fd); |
| 93 | } |
| 94 | if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir) |
| 95 | >= sizeof(path)) { |
| 96 | fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); |
| 97 | return false; |
| 98 | } |
| 99 | trace_marker_fd = open(path, O_WRONLY); |
| 100 | if (trace_marker_fd < 0) { |
| 101 | perror("Could not open ftrace 'trace_marker' file"); |
| 102 | return false; |
| 103 | } |
| 104 | } else { |
| 105 | fprintf(stderr, "tracefs is not mounted\n"); |
| 106 | return false; |
| 107 | } |
| 108 | |
| 109 | return true; |
| 110 | } |