tools/lib/api/fs/tracing_path.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #ifndef _GNU_SOURCE
   3 # define _GNU_SOURCE
   4 #endif
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <linux/string.h>
  10 #include <errno.h>
  11 #include <unistd.h>
  12 #include "fs.h"
  13
  14 #include "tracing_path.h"
  15
  16 static char tracing_path[PATH_MAX]        = "/sys/kernel/tracing";
  17
  18 static void __tracing_path_set(const char *tracing, const char *mountpoint)
  19 {
  20         snprintf(tracing_path, sizeof(tracing_path), "%s/%s",
  21                  mountpoint, tracing);
  22 }
  23
  24 static const char *tracing_path_tracefs_mount(void)
  25 {
  26         const char *mnt;
  27
  28         mnt = tracefs__mount();
  29         if (!mnt)
  30                 return NULL;
  31
  32         __tracing_path_set("", mnt);
  33
  34         return tracing_path;
  35 }
  36
  37 static const char *tracing_path_debugfs_mount(void)
  38 {
  39         const char *mnt;
  40
  41         mnt = debugfs__mount();
  42         if (!mnt)
  43                 return NULL;
  44
  45         __tracing_path_set("tracing/", mnt);
  46
  47         return tracing_path;
  48 }
  49
  50 const char *tracing_path_mount(void)
  51 {
  52         const char *mnt;
  53
  54         mnt = tracing_path_tracefs_mount();
  55         if (mnt)
  56                 return mnt;
  57
  58         mnt = tracing_path_debugfs_mount();
  59
  60         return mnt;
  61 }
  62
  63 void tracing_path_set(const char *mntpt)
  64 {
  65         __tracing_path_set("tracing/", mntpt);
  66 }
  67
  68 char *get_tracing_file(const char *name)
  69 {
  70         char *file;
  71
  72         if (asprintf(&file, "%s/%s", tracing_path_mount(), name) < 0)
  73                 return NULL;
  74
  75         return file;
  76 }
  77
  78 void put_tracing_file(char *file)
  79 {
  80         free(file);
  81 }
  82
  83 char *get_events_file(const char *name)
  84 {
  85         char *file;
  86
  87         if (asprintf(&file, "%s/events/%s", tracing_path_mount(), name) < 0)
  88                 return NULL;
  89
  90         return file;
  91 }
  92
  93 void put_events_file(char *file)
  94 {
  95         free(file);
  96 }
  97
  98 DIR *tracing_events__opendir(void)
  99 {
 100         DIR *dir = NULL;
 101         char *path = get_tracing_file("events");
 102
 103         if (path) {
 104                 dir = opendir(path);
 105                 put_events_file(path);
 106         }
 107
 108         return dir;
 109 }
 110
 111 int tracing_events__scandir_alphasort(struct dirent ***namelist)
 112 {
 113         char *path = get_tracing_file("events");
 114         int ret;
 115
 116         if (!path) {
 117                 *namelist = NULL;
 118                 return 0;
 119         }
 120
 121         ret = scandir(path, namelist, NULL, alphasort);
 122         put_events_file(path);
 123
 124         return ret;
 125 }
 126
 127 int tracing_path__strerror_open_tp(int err, char *buf, size_t size,
 128                                    const char *sys, const char *name)
 129 {
 130         char sbuf[128];
 131         char filename[PATH_MAX];
 132
 133         snprintf(filename, PATH_MAX, "%s/%s", sys, name ?: "*");
 134
 135         switch (err) {
 136         case ENOENT:
 137                 /*
 138                  * We will get here if we can't find the tracepoint, but one of
 139                  * debugfs or tracefs is configured, which means you probably
 140                  * want some tracepoint which wasn't compiled in your kernel.
 141                  * - jirka
 142                  */
 143                 if (debugfs__configured() || tracefs__configured()) {
 144                         /* sdt markers */
 145                         if (!strncmp(filename, "sdt_", 4)) {
 146                                 snprintf(buf, size,
 147                                         "Error:\tFile %s/events/%s not found.\n"
 148                                         "Hint:\tSDT event cannot be directly recorded on.\n"
 149                                         "\tPlease first use 'perf probe %s:%s' before recording it.\n",
 150                                         tracing_path, filename, sys, name);
 151                         } else {
 152                                 snprintf(buf, size,
 153                                          "Error:\tFile %s/events/%s not found.\n"
 154                                          "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
 155                                          tracing_path, filename);
 156                         }
 157                         break;
 158                 }
 159                 snprintf(buf, size, "%s",
 160                          "Error:\tUnable to find debugfs/tracefs\n"
 161                          "Hint:\tWas your kernel compiled with debugfs/tracefs support?\n"
 162                          "Hint:\tIs the debugfs/tracefs filesystem mounted?\n"
 163                          "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
 164                 break;
 165         case EACCES: {
 166                 snprintf(buf, size,
 167                          "Error:\tNo permissions to read %s/events/%s\n"
 168                          "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
 169                          tracing_path, filename, tracing_path_mount());
 170         }
 171                 break;
 172         default:
 173                 snprintf(buf, size, "%s", str_error_r(err, sbuf, sizeof(sbuf)));
 174                 break;
 175         }
 176
 177         return 0;
 178 }