gpxe/src/core/malloc.c

   1 /*
   2  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 FILE_LICENCE ( GPL2_OR_LATER );
  20
  21 #include <stddef.h>
  22 #include <stdint.h>
  23 #include <string.h>
  24 #include <strings.h>
  25 #include <gpxe/io.h>
  26 #include <gpxe/list.h>
  27 #include <gpxe/init.h>
  28 #include <gpxe/malloc.h>
  29
  30 /** @file
  31  *
  32  * Dynamic memory allocation
  33  *
  34  */
  35
  36 /** A free block of memory */
  37 struct memory_block {
  38         /** List of free blocks */
  39         struct list_head list;
  40         /** Size of this block */
  41         size_t size;
  42 };
  43
  44 #define MIN_MEMBLOCK_SIZE \
  45         ( ( size_t ) ( 1 << ( fls ( sizeof ( struct memory_block ) - 1 ) ) ) )
  46
  47 /** A block of allocated memory complete with size information */
  48 struct autosized_block {
  49         /** Size of this block */
  50         size_t size;
  51         /** Remaining data */
  52         char data[0];
  53 };
  54
  55 /**
  56  * Address for zero-length memory blocks
  57  *
  58  * @c malloc(0) or @c realloc(ptr,0) will return the special value @c
  59  * NOWHERE.  Calling @c free(NOWHERE) will have no effect.
  60  *
  61  * This is consistent with the ANSI C standards, which state that
  62  * "either NULL or a pointer suitable to be passed to free()" must be
  63  * returned in these cases.  Using a special non-NULL value means that
  64  * the caller can take a NULL return value to indicate failure,
  65  * without first having to check for a requested size of zero.
  66  *
  67  * Code outside of malloc.c do not ever need to refer to the actual
  68  * value of @c NOWHERE; this is an internal definition.
  69  */
  70 #define NOWHERE ( ( void * ) ~( ( intptr_t ) 0 ) )
  71
  72 /** List of free memory blocks */
  73 static LIST_HEAD ( free_blocks );
  74
  75 /** Total amount of free memory */
  76 size_t freemem;
  77
  78 /**
  79  * Heap size
  80  *
  81  * Currently fixed at 512kB.
  82  */
  83 #define HEAP_SIZE ( 512 * 1024 )
  84
  85 /** The heap itself */
  86 static char heap[HEAP_SIZE] __attribute__ (( aligned ( __alignof__(void *) )));
  87
  88 /**
  89  * Allocate a memory block
  90  *
  91  * @v size              Requested size
  92  * @v align             Physical alignment
  93  * @ret ptr             Memory block, or NULL
  94  *
  95  * Allocates a memory block @b physically aligned as requested.  No
  96  * guarantees are provided for the alignment of the virtual address.
  97  *
  98  * @c align must be a power of two.  @c size may not be zero.
  99  */
 100 void * alloc_memblock ( size_t size, size_t align ) {
 101         struct memory_block *block;
 102         size_t align_mask;
 103         size_t pre_size;
 104         ssize_t post_size;
 105         struct memory_block *pre;
 106         struct memory_block *post;
 107
 108         /* Round up size to multiple of MIN_MEMBLOCK_SIZE and
 109          * calculate alignment mask.
 110          */
 111         size = ( size + MIN_MEMBLOCK_SIZE - 1 ) & ~( MIN_MEMBLOCK_SIZE - 1 );
 112         align_mask = ( align - 1 ) | ( MIN_MEMBLOCK_SIZE - 1 );
 113
 114         DBG ( "Allocating %#zx (aligned %#zx)\n", size, align );
 115
 116         /* Search through blocks for the first one with enough space */
 117         list_for_each_entry ( block, &free_blocks, list ) {
 118                 pre_size = ( - virt_to_phys ( block ) ) & align_mask;
 119                 post_size = block->size - pre_size - size;
 120                 if ( post_size >= 0 ) {
 121                         /* Split block into pre-block, block, and
 122                          * post-block.  After this split, the "pre"
 123                          * block is the one currently linked into the
 124                          * free list.
 125                          */
 126                         pre   = block;
 127                         block = ( ( ( void * ) pre   ) + pre_size );
 128                         post  = ( ( ( void * ) block ) + size     );
 129                         DBG ( "[%p,%p) -> [%p,%p) + [%p,%p)\n", pre,
 130                               ( ( ( void * ) pre ) + pre->size ), pre, block,
 131                               post, ( ( ( void * ) pre ) + pre->size ) );
 132                         /* If there is a "post" block, add it in to
 133                          * the free list.  Leak it if it is too small
 134                          * (which can happen only at the very end of
 135                          * the heap).
 136                          */
 137                         if ( ( size_t ) post_size >= MIN_MEMBLOCK_SIZE ) {
 138                                 post->size = post_size;
 139                                 list_add ( &post->list, &pre->list );
 140                         }
 141                         /* Shrink "pre" block, leaving the main block
 142                          * isolated and no longer part of the free
 143                          * list.
 144                          */
 145                         pre->size = pre_size;
 146                         /* If there is no "pre" block, remove it from
 147                          * the list.  Also remove it (i.e. leak it) if
 148                          * it is too small, which can happen only at
 149                          * the very start of the heap.
 150                          */
 151                         if ( pre_size < MIN_MEMBLOCK_SIZE )
 152                                 list_del ( &pre->list );
 153                         /* Update total free memory */
 154                         freemem -= size;
 155                         /* Return allocated block */
 156                         DBG ( "Allocated [%p,%p)\n", block,
 157                               ( ( ( void * ) block ) + size ) );
 158                         return block;
 159                 }
 160         }
 161
 162         DBG ( "Failed to allocate %#zx (aligned %#zx)\n", size, align );
 163         return NULL;
 164 }
 165
 166 /**
 167  * Free a memory block
 168  *
 169  * @v ptr               Memory allocated by alloc_memblock(), or NULL
 170  * @v size              Size of the memory
 171  *
 172  * If @c ptr is NULL, no action is taken.
 173  */
 174 void free_memblock ( void *ptr, size_t size ) {
 175         struct memory_block *freeing;
 176         struct memory_block *block;
 177         ssize_t gap_before;
 178         ssize_t gap_after = -1;
 179
 180         /* Allow for ptr==NULL */
 181         if ( ! ptr )
 182                 return;
 183
 184         /* Round up size to match actual size that alloc_memblock()
 185          * would have used.
 186          */
 187         size = ( size + MIN_MEMBLOCK_SIZE - 1 ) & ~( MIN_MEMBLOCK_SIZE - 1 );
 188         freeing = ptr;
 189         freeing->size = size;
 190         DBG ( "Freeing [%p,%p)\n", freeing, ( ( ( void * ) freeing ) + size ));
 191
 192         /* Insert/merge into free list */
 193         list_for_each_entry ( block, &free_blocks, list ) {
 194                 /* Calculate gaps before and after the "freeing" block */
 195                 gap_before = ( ( ( void * ) freeing ) -
 196                                ( ( ( void * ) block ) + block->size ) );
 197                 gap_after = ( ( ( void * ) block ) -
 198                               ( ( ( void * ) freeing ) + freeing->size ) );
 199                 /* Merge with immediately preceding block, if possible */
 200                 if ( gap_before == 0 ) {
 201                         DBG ( "[%p,%p) + [%p,%p) -> [%p,%p)\n", block,
 202                               ( ( ( void * ) block ) + block->size ), freeing,
 203                               ( ( ( void * ) freeing ) + freeing->size ),block,
 204                               ( ( ( void * ) freeing ) + freeing->size ) );
 205                         block->size += size;
 206                         list_del ( &block->list );
 207                         freeing = block;
 208                 }
 209                 /* Stop processing as soon as we reach a following block */
 210                 if ( gap_after >= 0 )
 211                         break;
 212         }
 213
 214         /* Insert before the immediately following block.  If
 215          * possible, merge the following block into the "freeing"
 216          * block.
 217          */
 218         DBG ( "[%p,%p)\n", freeing, ( ( ( void * ) freeing ) + freeing->size));
 219         list_add_tail ( &freeing->list, &block->list );
 220         if ( gap_after == 0 ) {
 221                 DBG ( "[%p,%p) + [%p,%p) -> [%p,%p)\n", freeing,
 222                       ( ( ( void * ) freeing ) + freeing->size ), block,
 223                       ( ( ( void * ) block ) + block->size ), freeing,
 224                       ( ( ( void * ) block ) + block->size ) );
 225                 freeing->size += block->size;
 226                 list_del ( &block->list );
 227         }
 228
 229         /* Update free memory counter */
 230         freemem += size;
 231 }
 232
 233 /**
 234  * Reallocate memory
 235  *
 236  * @v old_ptr           Memory previously allocated by malloc(), or NULL
 237  * @v new_size          Requested size
 238  * @ret new_ptr         Allocated memory, or NULL
 239  *
 240  * Allocates memory with no particular alignment requirement.  @c
 241  * new_ptr will be aligned to at least a multiple of sizeof(void*).
 242  * If @c old_ptr is non-NULL, then the contents of the newly allocated
 243  * memory will be the same as the contents of the previously allocated
 244  * memory, up to the minimum of the old and new sizes.  The old memory
 245  * will be freed.
 246  *
 247  * If allocation fails the previously allocated block is left
 248  * untouched and NULL is returned.
 249  *
 250  * Calling realloc() with a new size of zero is a valid way to free a
 251  * memory block.
 252  */
 253 void * realloc ( void *old_ptr, size_t new_size ) {
 254         struct autosized_block *old_block;
 255         struct autosized_block *new_block;
 256         size_t old_total_size;
 257         size_t new_total_size;
 258         size_t old_size;
 259         void *new_ptr = NOWHERE;
 260
 261         /* Allocate new memory if necessary.  If allocation fails,
 262          * return without touching the old block.
 263          */
 264         if ( new_size ) {
 265                 new_total_size = ( new_size +
 266                                    offsetof ( struct autosized_block, data ) );
 267                 new_block = alloc_memblock ( new_total_size, 1 );
 268                 if ( ! new_block )
 269                         return NULL;
 270                 new_block->size = new_total_size;
 271                 new_ptr = &new_block->data;
 272         }
 273
 274         /* Copy across relevant part of the old data region (if any),
 275          * then free it.  Note that at this point either (a) new_ptr
 276          * is valid, or (b) new_size is 0; either way, the memcpy() is
 277          * valid.
 278          */
 279         if ( old_ptr && ( old_ptr != NOWHERE ) ) {
 280                 old_block = container_of ( old_ptr, struct autosized_block,
 281                                            data );
 282                 old_total_size = old_block->size;
 283                 old_size = ( old_total_size -
 284                              offsetof ( struct autosized_block, data ) );
 285                 memcpy ( new_ptr, old_ptr,
 286                          ( ( old_size < new_size ) ? old_size : new_size ) );
 287                 free_memblock ( old_block, old_total_size );
 288         }
 289
 290         return new_ptr;
 291 }
 292
 293 /**
 294  * Allocate memory
 295  *
 296  * @v size              Requested size
 297  * @ret ptr             Memory, or NULL
 298  *
 299  * Allocates memory with no particular alignment requirement.  @c ptr
 300  * will be aligned to at least a multiple of sizeof(void*).
 301  */
 302 void * malloc ( size_t size ) {
 303         return realloc ( NULL, size );
 304 }
 305
 306 /**
 307  * Free memory
 308  *
 309  * @v ptr               Memory allocated by malloc(), or NULL
 310  *
 311  * Memory allocated with malloc_dma() cannot be freed with free(); it
 312  * must be freed with free_dma() instead.
 313  *
 314  * If @c ptr is NULL, no action is taken.
 315  */
 316 void free ( void *ptr ) {
 317         realloc ( ptr, 0 );
 318 }
 319
 320 /**
 321  * Allocate cleared memory
 322  *
 323  * @v size              Requested size
 324  * @ret ptr             Allocated memory
 325  *
 326  * Allocate memory as per malloc(), and zero it.
 327  *
 328  * This function name is non-standard, but pretty intuitive.
 329  * zalloc(size) is always equivalent to calloc(1,size)
 330  */
 331 void * zalloc ( size_t size ) {
 332         void *data;
 333
 334         data = malloc ( size );
 335         if ( data )
 336                 memset ( data, 0, size );
 337         return data;
 338 }
 339
 340 /**
 341  * Add memory to allocation pool
 342  *
 343  * @v start             Start address
 344  * @v end               End address
 345  *
 346  * Adds a block of memory [start,end) to the allocation pool.  This is
 347  * a one-way operation; there is no way to reclaim this memory.
 348  *
 349  * @c start must be aligned to at least a multiple of sizeof(void*).
 350  */
 351 void mpopulate ( void *start, size_t len ) {
 352         /* Prevent free_memblock() from rounding up len beyond the end
 353          * of what we were actually given...
 354          */
 355         free_memblock ( start, ( len & ~( MIN_MEMBLOCK_SIZE - 1 ) ) );
 356 }
 357
 358 /**
 359  * Initialise the heap
 360  *
 361  */
 362 static void init_heap ( void ) {
 363         mpopulate ( heap, sizeof ( heap ) );
 364 }
 365
 366 /** Memory allocator initialisation function */
 367 struct init_fn heap_init_fn __init_fn ( INIT_EARLY ) = {
 368         .initialise = init_heap,
 369 };
 370
 371 #if 0
 372 #include <stdio.h>
 373 /**
 374  * Dump free block list
 375  *
 376  */
 377 void mdumpfree ( void ) {
 378         struct memory_block *block;
 379
 380         printf ( "Free block list:\n" );
 381         list_for_each_entry ( block, &free_blocks, list ) {
 382                 printf ( "[%p,%p] (size %#zx)\n", block,
 383                          ( ( ( void * ) block ) + block->size ), block->size );
 384         }
 385 }
 386 #endif