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
  17 char tracing_mnt[PATH_MAX]         = "/sys/kernel/debug";
  18 char tracing_path[PATH_MAX]        = "/sys/kernel/debug/tracing";
  19 char tracing_events_path[PATH_MAX] = "/sys/kernel/debug/tracing/events";
  20
  21
  22 static void __tracing_path_set(const char *tracing, const char *mountpoint)
  23 {
  24         snprintf(tracing_mnt, sizeof(tracing_mnt), "%s", mountpoint);
  25         snprintf(tracing_path, sizeof(tracing_path), "%s/%s",
  26                  mountpoint, tracing);
  27         snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s%s",
  28                  mountpoint, tracing, "events");
  29 }
  30
  31 static const char *tracing_path_tracefs_mount(void)
  32 {
  33         const char *mnt;
  34
  35         mnt = tracefs__mount();
  36         if (!mnt)
  37                 return NULL;
  38
  39         __tracing_path_set("", mnt);
  40
  41         return mnt;
  42 }
  43
  44 static const char *tracing_path_debugfs_mount(void)
  45 {
  46         const char *mnt;
  47
  48         mnt = debugfs__mount();
  49         if (!mnt)
  50                 return NULL;
  51
  52         __tracing_path_set("tracing/", mnt);
  53
  54         return mnt;
  55 }
  56
  57 const char *tracing_path_mount(void)
  58 {
  59         const char *mnt;
  60
  61         mnt = tracing_path_tracefs_mount();
  62         if (mnt)
  63                 return mnt;
  64
  65         mnt = tracing_path_debugfs_mount();
  66
  67         return mnt;
  68 }
  69
  70 void tracing_path_set(const char *mntpt)
  71 {
  72         __tracing_path_set("tracing/", mntpt);
  73 }
  74
  75 char *get_tracing_file(const char *name)
  76 {
  77         char *file;
  78
  79         if (asprintf(&file, "%s/%s", tracing_path, name) < 0)
  80                 return NULL;
  81
  82         return file;
  83 }
  84
  85 void put_tracing_file(char *file)
  86 {
  87         free(file);
  88 }
  89
  90 int tracing_path__strerror_open_tp(int err, char *buf, size_t size,
  91                                    const char *sys, const char *name)
  92 {
  93         char sbuf[128];
  94         char filename[PATH_MAX];
  95
  96         snprintf(filename, PATH_MAX, "%s/%s", sys, name ?: "*");
  97
  98         switch (err) {
  99         case ENOENT:
 100                 /*
 101                  * We will get here if we can't find the tracepoint, but one of
 102                  * debugfs or tracefs is configured, which means you probably
 103                  * want some tracepoint which wasn't compiled in your kernel.
 104                  * - jirka
 105                  */
 106                 if (debugfs__configured() || tracefs__configured()) {
 107                         /* sdt markers */
 108                         if (!strncmp(filename, "sdt_", 4)) {
 109                                 snprintf(buf, size,
 110                                         "Error:\tFile %s/%s not found.\n"
 111                                         "Hint:\tSDT event cannot be directly recorded on.\n"
 112                                         "\tPlease first use 'perf probe %s:%s' before recording it.\n",
 113                                         tracing_events_path, filename, sys, name);
 114                         } else {
 115                                 snprintf(buf, size,
 116                                          "Error:\tFile %s/%s not found.\n"
 117                                          "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
 118                                          tracing_events_path, filename);
 119                         }
 120                         break;
 121                 }
 122                 snprintf(buf, size, "%s",
 123                          "Error:\tUnable to find debugfs/tracefs\n"
 124                          "Hint:\tWas your kernel compiled with debugfs/tracefs support?\n"
 125                          "Hint:\tIs the debugfs/tracefs filesystem mounted?\n"
 126                          "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
 127                 break;
 128         case EACCES: {
 129                 snprintf(buf, size,
 130                          "Error:\tNo permissions to read %s/%s\n"
 131                          "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
 132                          tracing_events_path, filename, tracing_mnt);
 133         }
 134                 break;
 135         default:
 136                 snprintf(buf, size, "%s", str_error_r(err, sbuf, sizeof(sbuf)));
 137                 break;
 138         }
 139
 140         return 0;
 141 }