diff options
Diffstat (limited to 'contrib/syslinux-4.02/com32/lib/malloc.c')
| -rw-r--r-- | contrib/syslinux-4.02/com32/lib/malloc.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/com32/lib/malloc.c b/contrib/syslinux-4.02/com32/lib/malloc.c new file mode 100644 index 0000000..ec103ab --- /dev/null +++ b/contrib/syslinux-4.02/com32/lib/malloc.c @@ -0,0 +1,156 @@ +/* + * malloc.c + * + * Very simple linked-list based malloc()/free(). + */ + +#include <stdlib.h> +#include <string.h> +#include <com32.h> +#include <syslinux/memscan.h> +#include "init.h" +#include "malloc.h" + +struct free_arena_header __malloc_head = { + { + ARENA_TYPE_HEAD, + 0, + &__malloc_head, + &__malloc_head, + }, + &__malloc_head, + &__malloc_head +}; + +/* This is extern so it can be overridden by the user application */ +extern size_t __stack_size; +extern void *__mem_end; /* Produced after argv parsing */ + +static inline size_t sp(void) +{ + size_t sp; + asm volatile ("movl %%esp,%0":"=rm" (sp)); + return sp; +} + +#define E820_MEM_MAX 0xfff00000 /* 4 GB - 1 MB */ + +static int consider_memory_area(void *dummy, addr_t start, + addr_t len, bool valid) +{ + struct free_arena_header *fp; + addr_t end; + + (void)dummy; + + if (valid && start < E820_MEM_MAX) { + if (len > E820_MEM_MAX - start) + len = E820_MEM_MAX - start; + + end = start + len; + + if (end > __com32.cs_memsize) { + if (start <= __com32.cs_memsize) { + start = __com32.cs_memsize; + len = end - start; + } + + if (len >= 2 * sizeof(struct arena_header)) { + fp = (struct free_arena_header *)start; + fp->a.size = len; + __inject_free_block(fp); + } + } + } + + return 0; +} + +static void __constructor init_memory_arena(void) +{ + struct free_arena_header *fp; + size_t start, total_space; + + start = (size_t) ARENA_ALIGN_UP(__mem_end); + total_space = sp() - start; + + if (__stack_size == 0 || __stack_size > total_space >> 1) + __stack_size = total_space >> 1; /* Half for the stack, half for the heap... */ + + if (total_space < __stack_size + 4 * sizeof(struct arena_header)) + __stack_size = total_space - 4 * sizeof(struct arena_header); + + fp = (struct free_arena_header *)start; + fp->a.size = total_space - __stack_size; + + __inject_free_block(fp); + + /* Scan the memory map to look for other suitable regions */ + if (!__com32.cs_memsize) + return; /* Old Syslinux core, can't do this... */ + + syslinux_scan_memory(consider_memory_area, NULL); +} + +static void *__malloc_from_block(struct free_arena_header *fp, size_t size) +{ + size_t fsize; + struct free_arena_header *nfp, *na; + + fsize = fp->a.size; + + /* We need the 2* to account for the larger requirements of a free block */ + if (fsize >= size + 2 * sizeof(struct arena_header)) { + /* Bigger block than required -- split block */ + nfp = (struct free_arena_header *)((char *)fp + size); + na = fp->a.next; + + nfp->a.type = ARENA_TYPE_FREE; + nfp->a.size = fsize - size; + fp->a.type = ARENA_TYPE_USED; + fp->a.size = size; + + /* Insert into all-block chain */ + nfp->a.prev = fp; + nfp->a.next = na; + na->a.prev = nfp; + fp->a.next = nfp; + + /* Replace current block on free chain */ + nfp->next_free = fp->next_free; + nfp->prev_free = fp->prev_free; + fp->next_free->prev_free = nfp; + fp->prev_free->next_free = nfp; + } else { + /* Allocate the whole block */ + fp->a.type = ARENA_TYPE_USED; + + /* Remove from free chain */ + fp->next_free->prev_free = fp->prev_free; + fp->prev_free->next_free = fp->next_free; + } + + return (void *)(&fp->a + 1); +} + +void *malloc(size_t size) +{ + struct free_arena_header *fp; + + if (size == 0) + return NULL; + + /* Add the obligatory arena header, and round up */ + size = (size + 2 * sizeof(struct arena_header) - 1) & ARENA_SIZE_MASK; + + for (fp = __malloc_head.next_free; fp->a.type != ARENA_TYPE_HEAD; + fp = fp->next_free) { + if (fp->a.size >= size) { + /* Found fit -- allocate out of this block */ + return __malloc_from_block(fp, size); + } + } + + /* Nothing found... need to request a block from the kernel */ + return NULL; /* No kernel to get stuff from */ +} |