qemu

FORK: QEMU emulator
git clone https://git.neptards.moe/neptards/qemu.git
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ftrace.c (2533B)

      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 }