From 7d07ff825dc7cff7ee80b04346e0d2c49a91e190 Mon Sep 17 00:00:00 2001
From: scratko <m@scratko.xyz>
Date: Sun, 31 Mar 2024 21:05:36 +0300
Subject: Initial commit

---
 calls.asm | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 calls.asm

(limited to 'calls.asm')

diff --git a/calls.asm b/calls.asm
new file mode 100644
index 0000000..7d45fa7
--- /dev/null
+++ b/calls.asm
@@ -0,0 +1,77 @@
+global sys_write
+global sys_read
+global sys_errno
+global sys_alloc
+global sys_free
+global sys_exit
+
+section .text
+
+generic_sys_call_3:
+		push ebp
+		mov ebp, esp
+		push ebx
+		mov ebx, [ebp+8]
+		mov ecx, [ebp+12]
+		mov edx, [ebp+16]
+		int 80h
+		mov edx, eax
+		and edx, 0fffff000h
+		cmp edx, 0fffff000h
+		jnz .okay
+		mov [sys_errno], eax
+		xor eax, eax
+		not eax			; -1
+.okay:		pop ebx
+		mov esp, ebp
+		pop ebp
+		ret
+
+sys_write:	mov eax, 4
+		jmp generic_sys_call_3
+sys_read:	mov eax, 3
+		jmp generic_sys_call_3
+
+sys_alloc:	push ebp
+		mov ebp, esp	
+		mov eax, 45		; brk()
+		xor ebx, ebx
+		int 80h
+		mov [initial_break], eax
+
+		mov eax, 45
+		mov ebx, [initial_break]
+		add ebx, [ebp+8]
+		int 80h
+		cmp eax, [initial_break]
+		jz .error
+		mov eax, [initial_break]
+		jmp .quit
+.error:		mov eax, -1
+.quit:		mov esp, ebp
+		pop ebp
+		ret
+
+sys_free:	push ebp
+		mov ebp, esp
+		mov eax, 45
+		mov ebx, [ebp+8]
+		int 80h
+		mov esp, ebp
+		pop ebp
+		ret
+
+sys_exit:	push ebp
+		mov ebp, esp
+		mov eax, 1
+		mov ebx, [ebp+8]
+		int 80h
+		mov esp, ebp
+		pop ebp
+		ret 
+
+section .bss
+sys_errno 	resd	1
+
+section .data
+initial_break	dd	0
-- 
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