src/bin/lttng-sessiond/utils.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <limits.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27
  28 #include <common/error.h>
  29
  30 #include "utils.h"
  31
  32 /*
  33  * Write to writable pipe used to notify a thread.
  34  */
  35 int notify_thread_pipe(int wpipe)
  36 {
  37         int ret;
  38
  39         ret = write(wpipe, "!", 1);
  40         if (ret < 0) {
  41                 PERROR("write poll pipe");
  42         }
  43
  44         return ret;
  45 }
  46
  47 /*
  48  * Return pointer to home directory path using the env variable HOME.
  49  *
  50  * No home, NULL is returned.
  51  */
  52 const char *get_home_dir(void)
  53 {
  54         return ((const char *) getenv("HOME"));
  55 }
  56
  57 /*
  58  * Create a pipe in dst.
  59  */
  60 int utils_create_pipe(int *dst)
  61 {
  62         int ret;
  63
  64         if (dst == NULL) {
  65                 return -1;
  66         }
  67
  68         ret = pipe(dst);
  69         if (ret < 0) {
  70                 PERROR("create pipe");
  71         }
  72
  73         return ret;
  74 }
  75
  76 /*
  77  * Create pipe and set CLOEXEC flag to both fd.
  78  *
  79  * Make sure the pipe opened by this function are closed at some point. Use
  80  * utils_close_pipe().
  81  */
  82 int utils_create_pipe_cloexec(int *dst)
  83 {
  84         int ret, i;
  85
  86         if (dst == NULL) {
  87                 return -1;
  88         }
  89
  90         ret = utils_create_pipe(dst);
  91         if (ret < 0) {
  92                 goto error;
  93         }
  94
  95         for (i = 0; i < 2; i++) {
  96                 ret = fcntl(dst[i], F_SETFD, FD_CLOEXEC);
  97                 if (ret < 0) {
  98                         PERROR("fcntl pipe cloexec");
  99                         goto error;
 100                 }
 101         }
 102
 103 error:
 104         return ret;
 105 }
 106
 107 /*
 108  * Close both read and write side of the pipe.
 109  */
 110 void utils_close_pipe(int *src)
 111 {
 112         int i, ret;
 113
 114         if (src == NULL) {
 115                 return;
 116         }
 117
 118         for (i = 0; i < 2; i++) {
 119                 /* Safety check */
 120                 if (src[i] < 0) {
 121                         continue;
 122                 }
 123
 124                 ret = close(src[i]);
 125                 if (ret) {
 126                         PERROR("close pipe");
 127                 }
 128         }
 129 }