libsa/malloc.c

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 #include <string.h>
  23
  24 #include <mach/mach_types.h>
  25
  26 #include <kern/kern_types.h>
  27 #include <kern/queue.h>
  28 #include <kern/kalloc.h>
  29 #include <kern/lock.h>
  30 #include <kern/assert.h>
  31
  32 #include <vm/vm_kern.h>
  33
  34 #include "libsa/malloc.h"
  35
  36 extern void panic(const char *string, ...);
  37
  38 /*********************************************************************
  39 * Structure for a client memory block. Contains linked-list pointers,
  40 * a size field giving the TOTAL size of the block, including this
  41 * header, and the address of the client's block. The client block
  42 * field is guaranteed to lie on a 16-byte boundary.
  43 *********************************************************************/
  44 typedef struct malloc_block {
  45
  46         struct malloc_block     *malFwd;
  47         struct malloc_block     *malBwd;
  48         void                    *malActl;
  49         unsigned int            malSize;
  50 } malloc_block;
  51
  52 static malloc_block malAnchor = {&malAnchor, &malAnchor, 0, 0};
  53
  54 static int malInited = 0;
  55 static mutex_t *malloc_lock;
  56
  57 __private_extern__
  58 void * malloc(size_t size) {
  59
  60     unsigned int nsize;
  61     unsigned int nmem, rmem;
  62     malloc_block *amem;
  63
  64     assert(malInited);
  65
  66         nsize = size + sizeof(malloc_block) + 15;       /* Make sure we get enough to fit */
  67
  68         nmem = (unsigned int)kalloc(nsize);                     /* Get some */
  69         if(!nmem) {                                                                     /* Got any? */
  70                 panic("malloc: no memory for a %08X sized request\n", nsize);
  71         }
  72
  73         rmem = (nmem + 15) & -16;                                       /* Round to 16 byte boundary */
  74         amem = (malloc_block *)rmem;                            /* Point to the block */
  75         amem->malActl = nmem;                                   /* Set the actual address */
  76         amem->malSize = nsize;                                          /* Size */
  77
  78         mutex_lock(malloc_lock);
  79
  80         amem->malFwd = malAnchor.malFwd;                        /* Move anchor to our forward */
  81         amem->malBwd = &malAnchor;                                      /* We point back to anchor */
  82         malAnchor.malFwd->malBwd = amem;                        /* The old forward's back points to us */
  83         malAnchor.malFwd = amem;                                        /* Now we point the anchor to us */
  84
  85         mutex_unlock(malloc_lock);                              /* Unlock now */
  86
  87         return (void *)(rmem + 16);                                     /* Return the block */
  88
  89 } /* malloc() */
  90
  91
  92 /*********************************************************************
  93 * free()
  94 *
  95 *********************************************************************/
  96 __private_extern__
  97 void free(void * address) {
  98
  99
 100     malloc_block *amem, *fore, *aft;
 101
 102     if(!(unsigned int)address) return;                  /* Leave if they try to free nothing */
 103
 104
 105     amem = (malloc_block *)((unsigned int)address - sizeof(malloc_block));      /* Point to the header */
 106
 107         mutex_lock(malloc_lock);
 108
 109         fore = amem->malFwd;                                            /* Get the guy in front */
 110         aft  = amem->malBwd;                                            /* And the guy behind */
 111         fore->malBwd = aft;                                                     /* The next guy's previous is now my previous */
 112         aft->malFwd = fore;                                                     /* The previous guy's forward is now mine */
 113
 114         mutex_unlock(malloc_lock);                              /* Unlock now */
 115
 116         kfree(amem->malActl, amem->malSize);            /* Toss it */
 117
 118         return;
 119
 120 } /* free() */
 121
 122 /*********************************************************************
 123 * malloc_reset()
 124 *
 125 * Allocate the mutual exclusion lock that protect malloc's data.
 126 *********************************************************************/
 127 __private_extern__ void
 128 malloc_init(void)
 129 {
 130     malloc_lock = mutex_alloc(0);
 131     malInited = 1;
 132 }
 133
 134
 135 /*********************************************************************
 136 * malloc_reset()
 137 *
 138 * Walks through the list of VM-allocated regions, destroying them
 139 * all. Any subsequent access by clients to allocated data will cause
 140 * a segmentation fault.
 141 *********************************************************************/
 142 __private_extern__
 143 void malloc_reset(void) {
 144
 145     malloc_block *amem, *bmem;
 146
 147         mutex_lock(malloc_lock);
 148
 149         amem = malAnchor.malFwd;                                /* Get the first one */
 150
 151         while(amem != &malAnchor) {                             /* Go until we hit the anchor */
 152
 153                 bmem = amem->malFwd;                            /* Next one */
 154                 kfree(amem->malActl, amem->malSize);            /* Toss it */
 155                 amem = bmem;                                    /* Skip to it */
 156
 157         }
 158
 159         malAnchor.malFwd = (struct malloc_block *) 0x666;       /* Cause a fault if we try again */
 160         malAnchor.malBwd = (struct malloc_block *) 0x666;       /* Cause a fault if we try again */
 161
 162         mutex_unlock(malloc_lock);                              /* Unlock now */
 163
 164         mutex_free(malloc_lock);
 165     return;
 166
 167 } /* malloc_reset() */
 168
 169
 170 /*********************************************************************
 171 * realloc()
 172 *
 173 * This function simply allocates a new block and copies the existing
 174 * data into it. Nothing too clever here, as cleanup and efficient
 175 * memory usage are not important in this allocator package.
 176 *********************************************************************/
 177 __private_extern__
 178 void * realloc(void * address, size_t new_client_size) {
 179     void * new_address;
 180     malloc_block *amem;
 181
 182         amem = (malloc_block *)((unsigned int)address - sizeof(malloc_block));  /* Point to allocation block */
 183
 184         new_address = malloc(new_client_size);          /* get a new one */
 185         if(!new_address) {                                                      /* Did we get it? */
 186                 panic("realloc: can not reallocate one of %08X size\n", new_client_size);
 187         }
 188
 189     memcpy(new_address, address, amem->malSize - sizeof(malloc_block)); /* Copy the old in */
 190
 191     free(address);                                                              /* Toss the old one */
 192
 193     return new_address;
 194
 195 } /* realloc() */
 196
 197