push from SNAPKITTYWEST/snapkitty-twin-mars-asm

42fb483 verified 2 months ago

860 Bytes

; memory.asm — bump allocator via brk/mmap
%include "include/syscall.inc"
%include "include/memory.inc"

section .bss
align 16
heap_base: resq 1
heap_ptr:  resq 1
heap_end:  resq 1

section .text
global mem_init
global mem_alloc

; void mem_init()
mem_init:
    push rbp
    mov rbp, rsp
    ; brk(0) to get current break
    xor rdi, rdi
    mov rax, SYS_BRK
    syscall
    mov [rel heap_base], rax
    mov [rel heap_ptr], rax
    ; brk(base + HEAP_SIZE)
    add rax, HEAP_SIZE
    mov rdi, rax
    mov rax, SYS_BRK
    syscall
    mov [rel heap_end], rax
    pop rbp
    ret

; void* mem_alloc(size_t bytes) — bump allocator
mem_alloc:
    ; align to 8
    add rdi, 7
    and rdi, ~7
    mov rax, [rel heap_ptr]
    mov rcx, rax
    add rcx, rdi
    cmp rcx, [rel heap_end]
    jg .oom
    mov [rel heap_ptr], rcx
    ret
.oom:
    xor rax, rax
    ret

	; memory.asm — bump allocator via brk/mmap
	%include "include/syscall.inc"
	%include "include/memory.inc"

	section .bss
	align 16
	heap_base: resq 1
	heap_ptr: resq 1
	heap_end: resq 1

	section .text
	global mem_init
	global mem_alloc

	; void mem_init()
	mem_init:
	push rbp
	mov rbp, rsp
	; brk(0) to get current break
	xor rdi, rdi
	mov rax, SYS_BRK
	syscall
	mov [rel heap_base], rax
	mov [rel heap_ptr], rax
	; brk(base + HEAP_SIZE)
	add rax, HEAP_SIZE
	mov rdi, rax
	mov rax, SYS_BRK
	syscall
	mov [rel heap_end], rax
	pop rbp
	ret

	; void* mem_alloc(size_t bytes) — bump allocator
	mem_alloc:
	; align to 8
	add rdi, 7
	and rdi, ~7
	mov rax, [rel heap_ptr]
	mov rcx, rax
	add rcx, rdi
	cmp rcx, [rel heap_end]
	jg .oom
	mov [rel heap_ptr], rcx
	ret
	.oom:
	xor rax, rax
	ret