libsa/malloc.c

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 #include <string.h>
  24
  25 #include <mach/mach_types.h>
  26
  27 #include <kern/kern_types.h>
  28 #include <kern/queue.h>
  29 #include <kern/kalloc.h>
  30 #include <kern/lock.h>
  31 #include <kern/assert.h>
  32
  33 #include <vm/vm_kern.h>
  34
  35 #include "libsa/malloc.h"
  36
  37 extern void panic(const char *string, ...);
  38
  39 /*********************************************************************
  40 * Structure for a client memory block. Contains linked-list pointers,
  41 * a size field giving the TOTAL size of the block, including this
  42 * header, and the address of the client's block. The client block
  43 * field is guaranteed to lie on a 16-byte boundary.
  44 *********************************************************************/
  45 typedef struct malloc_block {
  46
  47         struct malloc_block     *malFwd;
  48         struct malloc_block     *malBwd;
  49         void                    *malActl;
  50         unsigned int            malSize;
  51 } malloc_block;
  52
  53 static malloc_block malAnchor = {&malAnchor, &malAnchor, 0, 0};
  54
  55 static int malInited = 0;
  56 static mutex_t *malloc_lock;
  57
  58 __private_extern__
  59 void * malloc(size_t size) {
  60
  61     unsigned int nsize;
  62     unsigned int nmem, rmem;
  63     malloc_block *amem;
  64
  65     assert(malInited);
  66
  67         nsize = size + sizeof(malloc_block) + 15;       /* Make sure we get enough to fit */
  68
  69         nmem = (unsigned int)kalloc(nsize);                     /* Get some */
  70         if(!nmem) {                                                                     /* Got any? */
  71                 panic("malloc: no memory for a %08X sized request\n", nsize);
  72         }
  73
  74         rmem = (nmem + 15) & -16;                                       /* Round to 16 byte boundary */
  75         amem = (malloc_block *)rmem;                            /* Point to the block */
  76         amem->malActl = nmem;                                   /* Set the actual address */
  77         amem->malSize = nsize;                                          /* Size */
  78
  79         mutex_lock(malloc_lock);
  80
  81         amem->malFwd = malAnchor.malFwd;                        /* Move anchor to our forward */
  82         amem->malBwd = &malAnchor;                                      /* We point back to anchor */
  83         malAnchor.malFwd->malBwd = amem;                        /* The old forward's back points to us */
  84         malAnchor.malFwd = amem;                                        /* Now we point the anchor to us */
  85
  86         mutex_unlock(malloc_lock);                              /* Unlock now */
  87
  88         return (void *)(rmem + 16);                                     /* Return the block */
  89
  90 } /* malloc() */
  91
  92
  93 /*********************************************************************
  94 * free()
  95 *
  96 *********************************************************************/
  97 __private_extern__
  98 void free(void * address) {
  99
 100
 101     malloc_block *amem, *fore, *aft;
 102
 103     if(!(unsigned int)address) return;                  /* Leave if they try to free nothing */
 104
 105
 106     amem = (malloc_block *)((unsigned int)address - sizeof(malloc_block));      /* Point to the header */
 107
 108         mutex_lock(malloc_lock);
 109
 110         fore = amem->malFwd;                                            /* Get the guy in front */
 111         aft  = amem->malBwd;                                            /* And the guy behind */
 112         fore->malBwd = aft;                                                     /* The next guy's previous is now my previous */
 113         aft->malFwd = fore;                                                     /* The previous guy's forward is now mine */
 114
 115         mutex_unlock(malloc_lock);                              /* Unlock now */
 116
 117         kfree(amem->malActl, amem->malSize);            /* Toss it */
 118
 119         return;
 120
 121 } /* free() */
 122
 123 /*********************************************************************
 124 * malloc_reset()
 125 *
 126 * Allocate the mutual exclusion lock that protect malloc's data.
 127 *********************************************************************/
 128 __private_extern__ void
 129 malloc_init(void)
 130 {
 131     malloc_lock = mutex_alloc(0);
 132     malInited = 1;
 133 }
 134
 135
 136 /*********************************************************************
 137 * malloc_reset()
 138 *
 139 * Walks through the list of VM-allocated regions, destroying them
 140 * all. Any subsequent access by clients to allocated data will cause
 141 * a segmentation fault.
 142 *********************************************************************/
 143 __private_extern__
 144 void malloc_reset(void) {
 145
 146     malloc_block *amem, *bmem;
 147
 148         mutex_lock(malloc_lock);
 149
 150         amem = malAnchor.malFwd;                                /* Get the first one */
 151
 152         while(amem != &malAnchor) {                             /* Go until we hit the anchor */
 153
 154                 bmem = amem->malFwd;                            /* Next one */
 155                 kfree(amem->malActl, amem->malSize);            /* Toss it */
 156                 amem = bmem;                                    /* Skip to it */
 157
 158         }
 159
 160         malAnchor.malFwd = (struct malloc_block *) 0x666;       /* Cause a fault if we try again */
 161         malAnchor.malBwd = (struct malloc_block *) 0x666;       /* Cause a fault if we try again */
 162
 163         mutex_unlock(malloc_lock);                              /* Unlock now */
 164
 165         mutex_free(malloc_lock);
 166     return;
 167
 168 } /* malloc_reset() */
 169
 170
 171 /*********************************************************************
 172 * realloc()
 173 *
 174 * This function simply allocates a new block and copies the existing
 175 * data into it. Nothing too clever here, as cleanup and efficient
 176 * memory usage are not important in this allocator package.
 177 *********************************************************************/
 178 __private_extern__
 179 void * realloc(void * address, size_t new_client_size) {
 180     void * new_address;
 181     malloc_block *amem;
 182
 183         amem = (malloc_block *)((unsigned int)address - sizeof(malloc_block));  /* Point to allocation block */
 184
 185         new_address = malloc(new_client_size);          /* get a new one */
 186         if(!new_address) {                                                      /* Did we get it? */
 187                 panic("realloc: can not reallocate one of %08X size\n", new_client_size);
 188         }
 189
 190     memcpy(new_address, address, amem->malSize - sizeof(malloc_block)); /* Copy the old in */
 191
 192     free(address);                                                              /* Toss the old one */
 193
 194     return new_address;
 195
 196 } /* realloc() */
 197
 198