184 lines
5.5 KiB
C
184 lines
5.5 KiB
C
/***************************************************************************
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* Copyright (C) 02/2008 by Olaf Rempel *
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* razzor@kopf-tisch.de *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; version 2 of the License *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, write to the *
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* Free Software Foundation, Inc., *
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
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***************************************************************************/
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#include <stdint.h>
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#include <stdio.h>
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#include "AT91SAM7S256.h"
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#include "board.h"
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#include "memalloc.h"
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// TODO: make generic version and find better place
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#define ALIGN(x) (((x) +3) & ~3)
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/* extern symbols, defined in ldscript */
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extern void * __bss_end__;
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extern void * __stack_top__;
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static uint32_t static_alloc_pos;
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void * static_alloc(uint32_t size)
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{
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if (static_alloc_pos == 0)
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static_alloc_pos = ALIGN((uint32_t)&__bss_end__);
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uint32_t retval = static_alloc_pos;
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size = ALIGN(size);
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static_alloc_pos += size;
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return (void *)retval;
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}
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uint32_t static_alloc_used(void)
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{
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return static_alloc_pos - (uint32_t)&__bss_end__;
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}
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// TODO: find a better place
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uint32_t next_powerof2(uint32_t value)
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{
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uint32_t i;
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value--;
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for (i = 1; i < 32; i = i * 2)
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value |= value >> i;
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return value +1;
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}
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/*
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* (pos->next) - (pos) = size_of_the_chunk
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* we use the lower 2 bits of the pointers to store some information.
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* (since they point to 4byte aligned structs == are always zero)
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*/
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#define FLAG_CHUNKINUSE 0x01
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#define FLAG_ENDOFBLOCK 0x02
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#define FLAG_MASK 0x03
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#define SET_FLAGS(p, f) ((typeof (p))((uint32_t)(p) | (f)))
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#define GET_FLAGS(p) ((uint32_t)((p)->next) & FLAG_MASK)
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#define GET_NEXT(p) ((typeof (p))((uint32_t)((p)->next) & ~(FLAG_MASK)))
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struct memchunk {
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struct memchunk *next;
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uint8_t data[0];
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};
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static struct memchunk first_memchunk;
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static struct memchunk *last_endblock;
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/* add a new block to the dynamic memory allocator */
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static struct memchunk * alloc_add(uint32_t size)
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{
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size = ALIGN(size);
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printf("alloc_add(%ld)\n\r", size);
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/* struct at begin of memory block */
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struct memchunk *newblock = static_alloc(size);
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/* struct at end of memory block */
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struct memchunk *endblock = (void *)((uint32_t)newblock + size - sizeof(struct memchunk));
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/* link between them */
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newblock->next = endblock;
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/* next pointer of last block goes to NULL */
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endblock->next = SET_FLAGS(NULL, FLAG_ENDOFBLOCK);
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/* first block add? */
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if (first_memchunk.next == NULL) {
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first_memchunk.next = newblock;
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last_endblock = endblock;
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} else {
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/* the old endblock points to the new block, but keeps its flag */
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last_endblock->next = SET_FLAGS(newblock, FLAG_ENDOFBLOCK);
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last_endblock = endblock;
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}
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return newblock;
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}
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void * alloc(uint32_t size)
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{
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size = ALIGN(size) + sizeof(struct memchunk);
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/* found & search are always real pointers (without flags) */
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struct memchunk *found = NULL;
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struct memchunk *search = GET_NEXT(&first_memchunk);
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while (search && GET_NEXT(search)) {
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/* already used chunk OR a endofblock structure */
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if (GET_FLAGS(search) & (FLAG_CHUNKINUSE | FLAG_ENDOFBLOCK))
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goto try_next;
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uint32_t nextflags = GET_FLAGS(GET_NEXT(search)) & (FLAG_CHUNKINUSE | FLAG_ENDOFBLOCK);
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/* next chunk is unused AND an endofblock structure AND is not the last */
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if (nextflags == FLAG_ENDOFBLOCK && GET_NEXT(search) != last_endblock) {
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search->next = SET_FLAGS(GET_NEXT(GET_NEXT(search)), 0);
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continue;
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/* next chunk is unused -> chain them and then retry */
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} else if (nextflags == 0) {
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search->next = SET_FLAGS(GET_NEXT(GET_NEXT(search)), 0);
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continue;
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}
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uint32_t length = (uint32_t)GET_NEXT(search) - (uint32_t)search;
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/* perfect match */
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if (length == size) {
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found = search;
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break;
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/* chunk is bigger than needed, remember smallest */
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} else if (length >= size) {
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if (!found || (((uint32_t)GET_NEXT(found) - (uint32_t)found) > length))
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found = search;
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}
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try_next:
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search = GET_NEXT(search);
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}
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/* nothing useful found, add a new block of memory */
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if (!found)
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found = alloc_add(MAX(1024, size));
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/* if we split the chunk, the remaining piece must be large enough */
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if (((uint32_t)GET_NEXT(found) - (uint32_t)found) > (size + 2 * sizeof(struct memchunk))) {
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struct memchunk *end = (void *)((uint32_t)found + size);
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end->next = SET_FLAGS(GET_NEXT(found), 0);
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found->next = SET_FLAGS(end, FLAG_CHUNKINUSE);
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} else {
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found->next = SET_FLAGS(GET_NEXT(found), FLAG_CHUNKINUSE);
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}
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return (void *)(found +1);
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}
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void free(void *p)
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{
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/* mark the chunk as unused and keep the pointer */
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struct memchunk *chunk = (struct memchunk *)p -1;
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chunk->next = SET_FLAGS(GET_NEXT(chunk), 0);
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}
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