api/fs/tracing_path.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #ifndef _GNU_SOURCE
0003 # define _GNU_SOURCE
0004 #endif
0005
0006 #include <stdio.h>
0007 #include <stdlib.h>
0008 #include <string.h>
0009 #include <linux/string.h>
0010 #include <errno.h>
0011 #include <unistd.h>
0012 #include "fs.h"
0013
0014 #include "tracing_path.h"
0015
0016 static char tracing_mnt[PATH_MAX]  = "/sys/kernel/debug";
0017 static char tracing_path[PATH_MAX]        = "/sys/kernel/debug/tracing";
0018 static char tracing_events_path[PATH_MAX] = "/sys/kernel/debug/tracing/events";
0019
0020 static void __tracing_path_set(const char *tracing, const char *mountpoint)
0021 {
0022     snprintf(tracing_mnt, sizeof(tracing_mnt), "%s", mountpoint);
0023     snprintf(tracing_path, sizeof(tracing_path), "%s/%s",
0024          mountpoint, tracing);
0025     snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s%s",
0026          mountpoint, tracing, "events");
0027 }
0028
0029 static const char *tracing_path_tracefs_mount(void)
0030 {
0031     const char *mnt;
0032
0033     mnt = tracefs__mount();
0034     if (!mnt)
0035         return NULL;
0036
0037     __tracing_path_set("", mnt);
0038
0039     return tracing_path;
0040 }
0041
0042 static const char *tracing_path_debugfs_mount(void)
0043 {
0044     const char *mnt;
0045
0046     mnt = debugfs__mount();
0047     if (!mnt)
0048         return NULL;
0049
0050     __tracing_path_set("tracing/", mnt);
0051
0052     return tracing_path;
0053 }
0054
0055 const char *tracing_path_mount(void)
0056 {
0057     const char *mnt;
0058
0059     mnt = tracing_path_tracefs_mount();
0060     if (mnt)
0061         return mnt;
0062
0063     mnt = tracing_path_debugfs_mount();
0064
0065     return mnt;
0066 }
0067
0068 void tracing_path_set(const char *mntpt)
0069 {
0070     __tracing_path_set("tracing/", mntpt);
0071 }
0072
0073 char *get_tracing_file(const char *name)
0074 {
0075     char *file;
0076
0077     if (asprintf(&file, "%s/%s", tracing_path_mount(), name) < 0)
0078         return NULL;
0079
0080     return file;
0081 }
0082
0083 void put_tracing_file(char *file)
0084 {
0085     free(file);
0086 }
0087
0088 char *get_events_file(const char *name)
0089 {
0090     char *file;
0091
0092     if (asprintf(&file, "%s/events/%s", tracing_path_mount(), name) < 0)
0093         return NULL;
0094
0095     return file;
0096 }
0097
0098 void put_events_file(char *file)
0099 {
0100     free(file);
0101 }
0102
0103 DIR *tracing_events__opendir(void)
0104 {
0105     DIR *dir = NULL;
0106     char *path = get_tracing_file("events");
0107
0108     if (path) {
0109         dir = opendir(path);
0110         put_events_file(path);
0111     }
0112
0113     return dir;
0114 }
0115
0116 int tracing_path__strerror_open_tp(int err, char *buf, size_t size,
0117                    const char *sys, const char *name)
0118 {
0119     char sbuf[128];
0120     char filename[PATH_MAX];
0121
0122     snprintf(filename, PATH_MAX, "%s/%s", sys, name ?: "*");
0123
0124     switch (err) {
0125     case ENOENT:
0126         /*
0127          * We will get here if we can't find the tracepoint, but one of
0128          * debugfs or tracefs is configured, which means you probably
0129          * want some tracepoint which wasn't compiled in your kernel.
0130          * - jirka
0131          */
0132         if (debugfs__configured() || tracefs__configured()) {
0133             /* sdt markers */
0134             if (!strncmp(filename, "sdt_", 4)) {
0135                 snprintf(buf, size,
0136                     "Error:\tFile %s/%s not found.\n"
0137                     "Hint:\tSDT event cannot be directly recorded on.\n"
0138                     "\tPlease first use 'perf probe %s:%s' before recording it.\n",
0139                     tracing_events_path, filename, sys, name);
0140             } else {
0141                 snprintf(buf, size,
0142                      "Error:\tFile %s/%s not found.\n"
0143                      "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
0144                      tracing_events_path, filename);
0145             }
0146             break;
0147         }
0148         snprintf(buf, size, "%s",
0149              "Error:\tUnable to find debugfs/tracefs\n"
0150              "Hint:\tWas your kernel compiled with debugfs/tracefs support?\n"
0151              "Hint:\tIs the debugfs/tracefs filesystem mounted?\n"
0152              "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
0153         break;
0154     case EACCES: {
0155         snprintf(buf, size,
0156              "Error:\tNo permissions to read %s/%s\n"
0157              "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
0158              tracing_events_path, filename, tracing_path_mount());
0159     }
0160         break;
0161     default:
0162         snprintf(buf, size, "%s", str_error_r(err, sbuf, sizeof(sbuf)));
0163         break;
0164     }
0165
0166     return 0;
0167 }