server/debug-flags.c

   1 /* nbdkit
   2  * Copyright (C) 2013-2019 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  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  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38
  39 #include <dlfcn.h>
  40
  41 #include "internal.h"
  42
  43 struct debug_flag {
  44   struct debug_flag *next;
  45   char *name;                   /* plugin or filter name */
  46   char *flag;                   /* flag name */
  47   char *symbol;                 /* symbol, eg. "myplugin_debug_foo" */
  48   int value;                    /* value of flag */
  49   bool used;                    /* if flag was successfully set */
  50 };
  51
  52 /* Synthesize the name of the *_debug_* variable from the plugin name
  53  * and flag.
  54  */
  55 static char *
  56 symbol_of_debug_flag (const char *name, const char *flag)
  57 {
  58   char *var;
  59   size_t i;
  60   int len;
  61
  62   len = asprintf (&var, "%s_debug_%s", name, flag);
  63   if (len == -1) {
  64     perror ("asprintf");
  65     exit (EXIT_FAILURE);
  66   }
  67
  68   /* If there are any '.'s remaining in the name, convert them to '_'. */
  69   for (i = 0; i < (size_t) len; ++i) {
  70     if (var[i] == '.')
  71       var[i] = '_';
  72   }
  73
  74   return var;                   /* caller frees */
  75 }
  76
  77 /* Parse and add a single -D flag from the command line.
  78  *
  79  * Debug Flag must be "NAME.FLAG=N".
  80  *                     ^    ^    ^
  81  *                   arg    p    q  (after +1 adjustment below)
  82  */
  83 void
  84 add_debug_flag (const char *arg)
  85 {
  86   struct debug_flag *flag;
  87   char *p, *q;
  88
  89   p = strchr (arg, '.');
  90   q = strchr (arg, '=');
  91   if (p == NULL || q == NULL) {
  92   bad_debug_flag:
  93     fprintf (stderr,
  94              "%s: -D (Debug Flag) must have the format NAME.FLAG=N\n",
  95              program_name);
  96     exit (EXIT_FAILURE);
  97   }
  98   p++;                          /* +1 adjustment */
  99   q++;
 100
 101   if (p - arg <= 1) goto bad_debug_flag; /* NAME too short */
 102   if (p > q) goto bad_debug_flag;
 103   if (q - p <= 1) goto bad_debug_flag;   /* FLAG too short */
 104   if (*q == '\0') goto bad_debug_flag;   /* N too short */
 105
 106   flag = malloc (sizeof *flag);
 107   if (flag == NULL) {
 108   debug_flag_perror:
 109     perror ("malloc");
 110     exit (EXIT_FAILURE);
 111   }
 112
 113   flag->name = strndup (arg, p-arg-1);
 114   if (!flag->name) goto debug_flag_perror;
 115   flag->flag = strndup (p, q-p-1);
 116   if (!flag->flag) goto debug_flag_perror;
 117   if (nbdkit_parse_int ("flag", q, &flag->value) == -1)
 118     goto bad_debug_flag;
 119   flag->used = false;
 120   flag->symbol = symbol_of_debug_flag (flag->name, flag->flag);
 121
 122   /* Add flag to the linked list. */
 123   flag->next = debug_flags;
 124   debug_flags = flag;
 125 }
 126
 127 /* Apply all debug flags applicable to this backend. */
 128 void
 129 apply_debug_flags (void *dl, const char *name)
 130 {
 131   struct debug_flag *flag;
 132
 133   for (flag = debug_flags; flag != NULL; flag = flag->next) {
 134     if (!flag->used && strcmp (name, flag->name) == 0) {
 135       int *sym;
 136
 137       /* Find the symbol. */
 138       sym = dlsym (dl, flag->symbol);
 139       if (sym) {
 140         /* Set the flag. */
 141         *sym = flag->value;
 142       }
 143       else {
 144         fprintf (stderr,
 145                  "%s: warning: -D %s.%s: %s does not contain a "
 146                  "global variable called %s\n",
 147                  program_name, name, flag->flag, name, flag->symbol);
 148       }
 149
 150       /* Mark this flag as used. */
 151       flag->used = true;
 152     }
 153   }
 154 }
 155
 156 void
 157 free_debug_flags (void)
 158 {
 159   while (debug_flags != NULL) {
 160     struct debug_flag *next = debug_flags->next;
 161
 162     if (!debug_flags->used)
 163       fprintf (stderr, "%s: warning: debug flag -D %s.%s was not used\n",
 164                program_name, debug_flags->name, debug_flags->flag);
 165     free (debug_flags->name);
 166     free (debug_flags->flag);
 167     free (debug_flags->symbol);
 168     free (debug_flags);
 169     debug_flags = next;
 170   }
 171 }