uspace/lib/bithenge/src/failure.c

   1 /*
   2  * Copyright (c) 2012 Sean Bartell
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  *   notice, this list of conditions and the following disclaimer.
  11  * - Redistributions in binary form must reproduce the above copyright
  12  *   notice, this list of conditions and the following disclaimer in the
  13  *   documentation and/or other materials provided with the distribution.
  14  * - The name of the author may not be used to endorse or promote products
  15  *   derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /** @cond internal */
  30 /** @addtogroup bithenge
  31  * @{
  32  */
  33 /**
  34  * @file
  35  * Fake system call errors for testing.
  36  */
  37
  38 #include <errno.h>
  39 #include <execinfo.h>
  40 #include <fcntl.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <sys/types.h>
  44 #include <sys/wait.h>
  45 #define BITHENGE_FAILURE_DECLS_ONLY 1
  46 #include "failure.h"
  47 #include "common.h"
  48
  49 /* This file raises fake errors from system calls, to test that Bithenge
  50  * handles the errors correctly. It has two primary modes of operation,
  51  * depending on an environment variable:
  52  *
  53  * BITHENGE_FAILURE_INDEX not set: when a system call is made, a child process
  54  * returns a fake error from that call. If the child process handles the error
  55  * correctly (exit code is 1), the main process continues without errors. If
  56  * the child process has a problem, the main process raises the fake error
  57  * again and shows all stdout and stderr output. For speed, errors are only
  58  * raised when part of the backtrace has not been seen before.
  59  *
  60  * BITHENGE_FAILURE_INDEX set: the program runs normally until system call
  61  * number BITHENGE_FAILURE_INDEX is made; a fake error is returned from this
  62  * call. */
  63
  64 static int g_initialized = 0;
  65 static int g_failure_index = -1;
  66 static int g_failure_index_selected = -1;
  67
  68 typedef struct backtrace_item {
  69         struct backtrace_item *next;
  70         void *backtrace_item;
  71 } backtrace_item_t;
  72
  73 static backtrace_item_t *g_backtrace_items = NULL;
  74
  75 static void atexit_handler(void)
  76 {
  77         while (g_backtrace_items) {
  78                 backtrace_item_t *first = g_backtrace_items;
  79                 g_backtrace_items = first->next;
  80                 free(first);
  81         }
  82 }
  83
  84 static inline void initialize(void)
  85 {
  86         g_initialized = 1;
  87         int rc = atexit(atexit_handler);
  88         if (rc)
  89                 exit(127);
  90
  91         char *sel_str = getenv("BITHENGE_FAILURE_INDEX");
  92         if (sel_str)
  93                 g_failure_index_selected = strtol(sel_str, NULL, 10);
  94 }
  95
  96 /* Record a hit for a backtrace address and return whether this is the first
  97  * hit. */
  98 static inline int backtrace_item_hit(void *addr)
  99 {
 100         backtrace_item_t **bip;
 101         for (bip = &g_backtrace_items; *bip; bip = &(*bip)->next) {
 102                 backtrace_item_t *bi = *bip;
 103                 if (bi->backtrace_item == addr) {
 104                         /* Keep frequently accessed items near the front. */
 105                         *bip = bi->next;
 106                         bi->next = g_backtrace_items;
 107                         g_backtrace_items = bi;
 108                         return 0;
 109                 }
 110         }
 111
 112         /* No item found; create one. */
 113         backtrace_item_t *i = malloc(sizeof(*i));
 114         if (!i)
 115                 exit(127);
 116         i->next = g_backtrace_items;
 117         i->backtrace_item = addr;
 118         g_backtrace_items = i;
 119         return 1;
 120 }
 121
 122 int bithenge_should_fail(void)
 123 {
 124         g_failure_index++;
 125
 126         if (!g_initialized)
 127                 initialize();
 128
 129         if (g_failure_index_selected != -1) {
 130                 if (g_failure_index == g_failure_index_selected)
 131                         return 1; /* breakpoint here */
 132                 return 0;
 133         }
 134
 135         /* If all backtrace items have been seen already, there's no need to
 136          * try raising an error. */
 137         void *trace[256];
 138         int size = backtrace(trace, 256);
 139         int raise_error = 0;
 140         for (int i = 0; i < size; i++) {
 141                 if (backtrace_item_hit(trace[i]))
 142                         raise_error = 1;
 143         }
 144         if (!raise_error)
 145                 return 0;
 146
 147         if (!fork()) {
 148                 /* Child silently fails. */
 149                 int null = open("/dev/null", O_WRONLY);
 150                 if (null == -1)
 151                         exit(127);
 152                 vfs_clone(null, STDOUT_FILENO, false);
 153                 vfs_clone(null, STDERR_FILENO, false);
 154                 vfs_put(null);
 155                 return 1;
 156         }
 157
 158         /* Parent checks whether child failed correctly. */
 159         int status;
 160         wait(&status);
 161         if (WIFEXITED(status) && WEXITSTATUS(status) == 1)
 162                 return 0;
 163
 164         /* The child had an error! We couldn't easily debug it because it was
 165          * in a separate process with redirected stdout and stderr. Do it again
 166          * without redirecting or forking. */
 167         fprintf(stderr, "** Fake error raised here (BITHENGE_FAILURE_INDEX=%d)\n",
 168             g_failure_index);
 169         return 1;
 170 }
 171
 172 void *bithenge_failure_malloc(size_t size)
 173 {
 174         if (bithenge_should_fail())
 175                 return NULL;
 176         return malloc(size);
 177 }
 178
 179 void *bithenge_failure_realloc(void *ptr, size_t size)
 180 {
 181         if (bithenge_should_fail())
 182                 return NULL;
 183         return realloc(ptr, size);
 184 }
 185
 186 ssize_t bithenge_failure_read(int fd, void *buf, size_t count)
 187 {
 188         if (bithenge_should_fail()) {
 189                 errno = EIO;
 190                 return -1;
 191         }
 192         return read(fd, buf, count);
 193 }
 194
 195 off_t bithenge_failure_lseek(int fd, off_t offset, int whither)
 196 {
 197         if (bithenge_should_fail()) {
 198                 errno = EINVAL;
 199                 return (off_t) -1;
 200         }
 201         return lseek(fd, offset, whither);
 202 }
 203
 204 int bithenge_failure_ferror(FILE *stream)
 205 {
 206         if (bithenge_should_fail())
 207                 return 1;
 208         return ferror(stream);
 209 }
 210
 211 char *bithenge_failure_str_ndup(const char *s, size_t max_len)
 212 {
 213         if (bithenge_should_fail())
 214                 return NULL;
 215         return str_ndup(s, max_len);
 216 }
 217
 218 int bithenge_failure_open(const char *pathname, int flags)
 219 {
 220         if (bithenge_should_fail()) {
 221                 errno = EACCES;
 222                 return -1;
 223         }
 224         return open(pathname, flags);
 225 }
 226
 227 int bithenge_failure_fstat(int fd, struct stat *buf)
 228 {
 229         if (bithenge_should_fail()) {
 230                 errno = EIO;
 231                 return -1;
 232         }
 233         return fstat(fd, buf);
 234 }
 235
 236 /** @}
 237  */
 238 /** @endcond */