Clean up OS interface

[rrq/jonasforth.git] / main.asm

diff --git a/main.asm b/main.asm
index 43eef7a7e52ab27a253ad343ec775ae83e0a8b22..407d3a30a9baad7bbd6b05b9818d50d29cf889b6 100644 (file)
--- a/main.asm
+++ b/main.asm
@@ -1,70 +1,25 @@
 ;; vim: syntax=fasm
 
-include "uefi.asm"
-
-;; "Syscalls" {{{
-
-;; [NOTE] Volatile registers Linux (syscalls) vs UEFI
-;;
-;;   Linux syscalls: RAX, RCX, R11
-;;   UEFI:           RAX, RCX, R11, RDX, R8, R9, R10
-
-;; We are in the process of replacing our dependency on Linux with a dependency
-;; on UEFI. The following macros attempt to isolate what would be syscalls in
-;; Linux; thus, we will be able to replace these with UEFI-based implementations,
-;; and in theory we should expect the program to work.
-
-;; Print a string of a given length.
+;; At compile-time we load the module given by the environment variable
+;; OS_INCLUDE. This module should define the following macros:
 ;;
-;; Input:
-;; - RCX = Pointer to buffer
-;; - RDX = Buffer length
+;; Each of these functions should preserve the value of RSI and RSP. They may
+;; use other registers as they like.
 ;;
-;; Clobbers: RAX, RCX, R11, RDI, RSI
-macro sys_print_string {
-  push r8
-  push r9
-  push r10
-
-  call uefi_print_string
-
-  pop r10
-  pop r9
-  pop r8
-}
-
-;; Read a character from the user into the given buffer.
+;; os_initialize
+;;   Called at initialization.
 ;;
-;; Input:
-;; - RSI = Character buffer
+;; os_print_string
+;;   Takes a string buffer in RCX and the length in RDX, and prints the string
+;;   to the console.
 ;;
-;; Output:
-;; - BYTE [RSI] = Character
+;; os_read_char
+;;   Wait for the user to type a key, and then put the corresponding ASCII byte
+;;   into RAX.
 ;;
-;; Clobbers: RAX, RCX, R11, RDI, RSI, RDX
-macro sys_read_char {
-  push rbx
-  push r8
-  push r9
-  push r10
-  push r15
-
-  mov rcx, rsi
-  call uefi_read_char
-
-  pop r15
-  pop r10
-  pop r9
-  pop r8
-  pop rbx
-}
-
-macro sys_terminate code {
-  mov rax, code
-  call uefi_terminate
-}
-
-;; }}}
+;; os_terminate
+;;   Shut down the system, returning the error code given in RAX.
+include '%OS_INCLUDE%'
 
 ;; The code in this macro is placed at the end of each Forth word. When we are
 ;; executing a definition, this code is what causes execution to resume at the
@@ -132,7 +87,7 @@ main:
   cld                        ; Clear direction flag so LODSQ does the right thing.
   mov rbp, return_stack_top  ; Initialize return stack
 
-  call uefi_initialize
+  call os_initialize
 
   mov rax, MAIN
   jmp qword [rax]
@@ -235,7 +190,7 @@ forth_asm EMIT, 'EMIT'
 
   lea rcx, [rsp]
   mov rdx, 1
-  sys_print_string
+  call os_print_string
 
   add rsp, 8
   popr rax
@@ -260,12 +215,7 @@ forth_asm KEY, 'KEY'
   jne .from_buffer
 
   ;; Reading user input
-  push rsi
-  mov rsi, .buffer
-  sys_read_char
-  pop rsi
-
-  movzx rax, byte [.buffer]
+  call os_read_char
   ret
 
 .from_buffer:
@@ -336,7 +286,7 @@ forth_asm TELL, 'TELL'
 
   pop rdx ; Length
   pop rcx ; Buffer
-  sys_print_string
+  call os_print_string
 
   popr rsi
   popr rax
@@ -344,7 +294,8 @@ forth_asm TELL, 'TELL'
 
 ;; Exit the program cleanly.
 forth_asm TERMINATE, 'TERMINATE'
-  sys_terminate 0
+  mov rax, 0
+  call os_terminate
 
 ;; Duplicate a pair of elements.
 forth_asm PAIRDUP, '2DUP'
@@ -433,7 +384,7 @@ forth_asm DOTU, '.U'
   ;; Print the buffer
   mov rcx, .buffer
   mov rdx, [.printed_length]
-  sys_print_string
+  call os_print_string
 
   ;; Restore RSI and continue execution
   pop rsi
@@ -506,10 +457,7 @@ forth_asm READ_STRING, 'S"'
   mov [.length], 0
 
 .read_char:
-  mov rsi, .char_buffer
-  sys_read_char
-
-  mov al, [.char_buffer]
+  call os_read_char
   cmp al, '"'
   je .done