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/*
* Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/cdefs.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdatomic.h>
#include <stdio.h>
#include <stdbool.h>
#define HEAP_SIZE 0x1001A8
#define HEAP_MAGIC 0x05306A /* "OSMORA" :~) */
#define HEAP_ALIGN 4
#define HEAP_PROT PROT_READ | PROT_WRITE
#define BYTE_PTR(PTR) ((char *)(PTR))
#define HEAP_NEXT(BLOCKP, SIZE) \
PTR_OFFSET((BLOCKP), sizeof(struct mem_block) + (SIZE))
struct __aligned(HEAP_ALIGN) mem_block {
uint32_t magic;
uint32_t size;
uint8_t allocated : 1;
struct mem_block *next;
};
static struct mem_block *mem_head;
static struct mem_block *mem_tail;
/*
* The size of the heap including data on the heap
* as well as the sizes of their respective block
* headers.
*/
static ssize_t heap_len = 0;
static off_t heap_pos = 0;
/*
* During the initial state of malloc() when the C library
* first starts up. We can assume that there is zero fragmentation
* in our heap pool. This allows us to initially allocate memory
* by bumping a pointer which is O(1). During this state, even after
* any calls to free(), we can assume that there is more memory ahead
* of us that is free (due to the initial zero-fragmentation). However,
* once we've reached the end of the pool, if any memory has been previously
* freed (indicated by heap_len > 0), we can wrap the tail and start allocating
* in a best-fit fashion as we can assume that the heap is now fragmented.
*/
static bool wrap = false;
void __malloc_mem_init(void);
/*
* Terminate program abnormally due to any heap
* errors.
*
* TODO: Raise SIGABRT instead of using _Exit()
*/
__dead static void
__heap_abort(const char *str)
{
printf(str);
_Exit(1);
__builtin_unreachable();
}
/*
* Find a free block
*
* TODO: This is currently a first-fit style
* routine. This should be best-fit instead
* as it doesn't waste memory.
*/
static struct mem_block *
malloc_find_free(size_t size)
{
struct mem_block *cur = mem_head;
while (cur != NULL) {
if (cur->size >= size) {
return cur;
}
cur = cur->next;
}
return NULL;
}
void *
malloc(size_t size)
{
struct mem_block *next_block;
struct mem_block *tail;
size_t inc_len = 0;
size = ALIGN_UP(size, HEAP_ALIGN);
inc_len = sizeof(*next_block) + size;
if (heap_len < 0) {
heap_len = 0;
}
if (heap_len < 0) {
heap_len = 0;
return NULL;
}
/* Any memory left to allocate? */
if ((heap_len + inc_len) >= HEAP_SIZE) {
return NULL;
}
if (heap_pos >= HEAP_SIZE - inc_len) {
wrap = true;
mem_tail = mem_head;
}
tail = wrap ? malloc_find_free(size) : mem_tail;
if (tail == NULL) {
return NULL;
}
next_block = mem_tail;
mem_tail = HEAP_NEXT(mem_tail, size);
mem_tail->next = NULL;
next_block->next = mem_tail;
next_block->size = size;
next_block->allocated = 1;
next_block->magic = HEAP_MAGIC;
heap_len += inc_len;
heap_pos += inc_len;
return PTR_OFFSET(next_block, sizeof(*next_block));
}
void
free(void *ptr)
{
struct mem_block *blk;
blk = PTR_NOFFSET(ptr, sizeof(*blk));
if (blk->magic != HEAP_MAGIC) {
__heap_abort("free: bad free block detected\n");
}
if (!blk->allocated) {
__heap_abort("free: double free detected\n");
}
blk->allocated = 0;
heap_len -= (blk->size + sizeof(*blk));
if (heap_len < 0) {
heap_len = 0;
}
}
void
__malloc_mem_init(void)
{
mem_head = mmap(NULL, HEAP_SIZE, HEAP_PROT, MAP_ANON, 0, 0);
if (mem_head == NULL) {
__heap_abort("__malloc_mem_init: mem_head is NULL, out of memory\n");
}
mem_head->size = 0;
mem_head->next = NULL;
mem_head->allocated = 0;
mem_tail = mem_head;
}
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