libbacktrace/alloc.c

   1 /* alloc.c -- Memory allocation without mmap.
   2    Copyright (C) 2012-2021 Free Software Foundation, Inc.
   3    Written by Ian Lance Taylor, Google.
   4
   5 Redistribution and use in source and binary forms, with or without
   6 modification, are permitted provided that the following conditions are
   7 met:
   8
   9     (1) Redistributions of source code must retain the above copyright
  10     notice, this list of conditions and the following disclaimer.
  11
  12     (2) Redistributions in binary form must reproduce the above copyright
  13     notice, this list of conditions and the following disclaimer in
  14     the documentation and/or other materials provided with the
  15     distribution.
  16
  17     (3) The name of the author may not be used to
  18     endorse or promote products derived from this software without
  19     specific prior written permission.
  20
  21 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  23 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  24 DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  25 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  26 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  27 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  29 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  30 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31 POSSIBILITY OF SUCH DAMAGE.  */
  32
  33 #include "config.h"
  34
  35 #include <errno.h>
  36 #include <stdlib.h>
  37 #include <sys/types.h>
  38
  39 #include "backtrace.h"
  40 #include "internal.h"
  41
  42 /* Allocation routines to use on systems that do not support anonymous
  43    mmap.  This implementation just uses malloc, which means that the
  44    backtrace functions may not be safely invoked from a signal
  45    handler.  */
  46
  47 /* Allocate memory like malloc.  If ERROR_CALLBACK is NULL, don't
  48    report an error.  */
  49
  50 void *
  51 backtrace_alloc (struct backtrace_state *state ATTRIBUTE_UNUSED,
  52                  size_t size, backtrace_error_callback error_callback,
  53                  void *data)
  54 {
  55   void *ret;
  56
  57   ret = malloc (size);
  58   if (ret == NULL)
  59     {
  60       if (error_callback)
  61         error_callback (data, "malloc", errno);
  62     }
  63   return ret;
  64 }
  65
  66 /* Free memory.  */
  67
  68 void
  69 backtrace_free (struct backtrace_state *state ATTRIBUTE_UNUSED,
  70                 void *p, size_t size ATTRIBUTE_UNUSED,
  71                 backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
  72                 void *data ATTRIBUTE_UNUSED)
  73 {
  74   free (p);
  75 }
  76
  77 /* Grow VEC by SIZE bytes.  */
  78
  79 void *
  80 backtrace_vector_grow (struct backtrace_state *state ATTRIBUTE_UNUSED,
  81                        size_t size, backtrace_error_callback error_callback,
  82                        void *data, struct backtrace_vector *vec)
  83 {
  84   void *ret;
  85
  86   if (size > vec->alc)
  87     {
  88       size_t alc;
  89       void *base;
  90
  91       if (vec->size == 0)
  92         alc = 32 * size;
  93       else if (vec->size >= 4096)
  94         alc = vec->size + 4096;
  95       else
  96         alc = 2 * vec->size;
  97
  98       if (alc < vec->size + size)
  99         alc = vec->size + size;
 100
 101       base = realloc (vec->base, alc);
 102       if (base == NULL)
 103         {
 104           error_callback (data, "realloc", errno);
 105           return NULL;
 106         }
 107
 108       vec->base = base;
 109       vec->alc = alc - vec->size;
 110     }
 111
 112   ret = (char *) vec->base + vec->size;
 113   vec->size += size;
 114   vec->alc -= size;
 115   return ret;
 116 }
 117
 118 /* Finish the current allocation on VEC.  */
 119
 120 void *
 121 backtrace_vector_finish (struct backtrace_state *state,
 122                          struct backtrace_vector *vec,
 123                          backtrace_error_callback error_callback,
 124                          void *data)
 125 {
 126   void *ret;
 127
 128   /* With this allocator we call realloc in backtrace_vector_grow,
 129      which means we can't easily reuse the memory here.  So just
 130      release it.  */
 131   if (!backtrace_vector_release (state, vec, error_callback, data))
 132     return NULL;
 133   ret = vec->base;
 134   vec->base = NULL;
 135   vec->size = 0;
 136   vec->alc = 0;
 137   return ret;
 138 }
 139
 140 /* Release any extra space allocated for VEC.  */
 141
 142 int
 143 backtrace_vector_release (struct backtrace_state *state ATTRIBUTE_UNUSED,
 144                           struct backtrace_vector *vec,
 145                           backtrace_error_callback error_callback,
 146                           void *data)
 147 {
 148   vec->alc = 0;
 149
 150   if (vec->size == 0)
 151     {
 152       /* As of C17, realloc with size 0 is marked as an obsolescent feature, use
 153          free instead.  */
 154       free (vec->base);
 155       vec->base = NULL;
 156       return 1;
 157     }
 158
 159   vec->base = realloc (vec->base, vec->size);
 160   if (vec->base == NULL)
 161     {
 162       error_callback (data, "realloc", errno);
 163       return 0;
 164     }
 165
 166   return 1;
 167 }