libsa/malloc.c

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_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. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #include <string.h>
  29
  30 #include <mach/mach_types.h>
  31
  32 #include <kern/kern_types.h>
  33 #include <kern/queue.h>
  34 #include <kern/kalloc.h>
  35 #include <kern/lock.h>
  36 #include <kern/assert.h>
  37
  38 #include <vm/vm_kern.h>
  39
  40 #include "libsa/malloc.h"
  41
  42 extern void panic(const char *string, ...);
  43
  44 /*********************************************************************
  45 * Structure for a client memory block. Contains linked-list pointers,
  46 * a size field giving the TOTAL size of the block, including this
  47 * header, and the address of the client's block. The client block
  48 * field is guaranteed to lie on a 16-byte boundary.
  49 *********************************************************************/
  50 typedef struct malloc_block {
  51
  52         struct malloc_block     *malFwd;
  53         struct malloc_block     *malBwd;
  54         void                    *malActl;
  55         unsigned int            malSize;
  56 } malloc_block;
  57
  58 static malloc_block malAnchor = {&malAnchor, &malAnchor, 0, 0};
  59
  60 static int malInited = 0;
  61 static mutex_t *malloc_lock;
  62
  63 __private_extern__
  64 void * malloc(size_t size) {
  65
  66     unsigned int nsize;
  67     unsigned int nmem, rmem;
  68     malloc_block *amem;
  69
  70     assert(malInited);
  71
  72         nsize = size + sizeof(malloc_block) + 15;       /* Make sure we get enough to fit */
  73
  74         nmem = (unsigned int)kalloc(nsize);                     /* Get some */
  75         if(!nmem) {                                                                     /* Got any? */
  76                 panic("malloc: no memory for a %08X sized request\n", nsize);
  77         }
  78
  79         rmem = (nmem + 15) & -16;                                       /* Round to 16 byte boundary */
  80         amem = (malloc_block *)rmem;                            /* Point to the block */
  81         amem->malActl = nmem;                                   /* Set the actual address */
  82         amem->malSize = nsize;                                          /* Size */
  83
  84         mutex_lock(malloc_lock);
  85
  86         amem->malFwd = malAnchor.malFwd;                        /* Move anchor to our forward */
  87         amem->malBwd = &malAnchor;                                      /* We point back to anchor */
  88         malAnchor.malFwd->malBwd = amem;                        /* The old forward's back points to us */
  89         malAnchor.malFwd = amem;                                        /* Now we point the anchor to us */
  90
  91         mutex_unlock(malloc_lock);                              /* Unlock now */
  92
  93         return (void *)(rmem + 16);                                     /* Return the block */
  94
  95 } /* malloc() */
  96
  97
  98 /*********************************************************************
  99 * free()
 100 *
 101 *********************************************************************/
 102 __private_extern__
 103 void free(void * address) {
 104
 105
 106     malloc_block *amem, *fore, *aft;
 107
 108     if(!(unsigned int)address) return;                  /* Leave if they try to free nothing */
 109
 110
 111     amem = (malloc_block *)((unsigned int)address - sizeof(malloc_block));      /* Point to the header */
 112
 113         mutex_lock(malloc_lock);
 114
 115         fore = amem->malFwd;                                            /* Get the guy in front */
 116         aft  = amem->malBwd;                                            /* And the guy behind */
 117         fore->malBwd = aft;                                                     /* The next guy's previous is now my previous */
 118         aft->malFwd = fore;                                                     /* The previous guy's forward is now mine */
 119
 120         mutex_unlock(malloc_lock);                              /* Unlock now */
 121
 122         kfree(amem->malActl, amem->malSize);            /* Toss it */
 123
 124         return;
 125
 126 } /* free() */
 127
 128 /*********************************************************************
 129 * malloc_reset()
 130 *
 131 * Allocate the mutual exclusion lock that protect malloc's data.
 132 *********************************************************************/
 133 __private_extern__ void
 134 malloc_init(void)
 135 {
 136     malloc_lock = mutex_alloc(0);
 137     malInited = 1;
 138 }
 139
 140
 141 /*********************************************************************
 142 * malloc_reset()
 143 *
 144 * Walks through the list of VM-allocated regions, destroying them
 145 * all. Any subsequent access by clients to allocated data will cause
 146 * a segmentation fault.
 147 *********************************************************************/
 148 __private_extern__
 149 void malloc_reset(void) {
 150
 151     malloc_block *amem, *bmem;
 152
 153         mutex_lock(malloc_lock);
 154
 155         amem = malAnchor.malFwd;                                /* Get the first one */
 156
 157         while(amem != &malAnchor) {                             /* Go until we hit the anchor */
 158
 159                 bmem = amem->malFwd;                            /* Next one */
 160                 kfree(amem->malActl, amem->malSize);            /* Toss it */
 161                 amem = bmem;                                    /* Skip to it */
 162
 163         }
 164
 165         malAnchor.malFwd = (struct malloc_block *) 0x666;       /* Cause a fault if we try again */
 166         malAnchor.malBwd = (struct malloc_block *) 0x666;       /* Cause a fault if we try again */
 167
 168         mutex_unlock(malloc_lock);                              /* Unlock now */
 169
 170         mutex_free(malloc_lock);
 171     return;
 172
 173 } /* malloc_reset() */
 174
 175
 176 /*********************************************************************
 177 * realloc()
 178 *
 179 * This function simply allocates a new block and copies the existing
 180 * data into it. Nothing too clever here, as cleanup and efficient
 181 * memory usage are not important in this allocator package.
 182 *********************************************************************/
 183 __private_extern__
 184 void * realloc(void * address, size_t new_client_size) {
 185     void * new_address;
 186     malloc_block *amem;
 187
 188         amem = (malloc_block *)((unsigned int)address - sizeof(malloc_block));  /* Point to allocation block */
 189
 190         new_address = malloc(new_client_size);          /* get a new one */
 191         if(!new_address) {                                                      /* Did we get it? */
 192                 panic("realloc: can not reallocate one of %08X size\n", new_client_size);
 193         }
 194
 195     memcpy(new_address, address, amem->malSize - sizeof(malloc_block)); /* Copy the old in */
 196
 197     free(address);                                                              /* Toss the old one */
 198
 199     return new_address;
 200
 201 } /* realloc() */
 202
 203