;; vim: syntax=fasm
-include "uefi.asm"
-
-;; "Syscalls" {{{
-
-;; [NOTE] Volatile registers Linux (syscalls) vs UEFI
+;; At compile-time we load the module given by the environment variable
+;; OS_INCLUDE. All of the following these procedures should preserve the value
+;; of RSI and RSP. They may use other registers as they like.
;;
-;; 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.
+;; The module should provide the following:
;;
-;; Input:
-;; - RCX = Pointer to buffer
-;; - RDX = Buffer length
+;; os_code_section
+;; Macro to start the text segment.
;;
-;; 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_data_section
+;; Macro to start the data segment.
;;
-;; Input:
-;; - RSI = Character buffer
+;; os_initialize
+;; Called at initialization.
;;
-;; Output:
-;; - BYTE [RSI] = Character
+;; os_print_string
+;; Takes a string buffer in RCX and the length in RDX, and prints the string
+;; to the console.
;;
-;; 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_read_char
+;; Wait for the user to type a key, and then put the corresponding ASCII byte
+;; into RAX.
+;;
+;; 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
.start:
}
-section '.text' code readable executable
+os_code_section
include "impl.asm" ; Misc. subroutines
include "bootstrap.asm" ; Forth words encoded in Assembly
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]
push rax
next
+;; When LITSTRING is encountered while executing a word, it instead reads a
+;; string from the definition of that word, and places that string on the stack
+;; as (buffer, length).
+forth_asm LITSTRING, 'LITSTRING'
+ lodsb
+ push rsi ; Buffer
+ movzx rax, al
+ push rax ; Length
+ add rsi, rax ; Skip over string before resuming execution
+ next
+
;; Given a string (a pointer following by a size), return the location of the
;; dictionary entry for that word. If no such word exists, return 0.
forth_asm FIND, 'FIND'
lea rcx, [rsp]
mov rdx, 1
- sys_print_string
+ call os_print_string
add rsp, 8
popr rax
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:
pop rdx ; Length
pop rcx ; Buffer
- sys_print_string
+ call os_print_string
popr rsi
popr rax
;; 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'
;; Print the buffer
mov rcx, .buffer
mov rdx, [.printed_length]
- sys_print_string
+ call os_print_string
;; Restore RSI and continue execution
pop rsi
mov [.length], 0
.read_char:
- mov rsi, .char_buffer
- sys_read_char
-
- mov al, [.char_buffer]
+ call os_read_char
cmp al, '"'
je .done
dq LIT, input_buffer_length
dq EXIT
-section '.data' readable writable
+os_data_section
;; The LATEST variable holds a pointer to the word that was last added to the
;; dictionary. This pointer is updated as new words are added, and its value is
;; We store some Forth code in sys.f that defined common words that the user
;; would expect to have available at startup. To execute these words, we just
;; include the file directly in the binary, and then interpret it at startup.
-sysf file 'sys.f'
+sysf:
+file 'sys.f'
+file 'example.f'
sysf.len = $ - sysf
projects / rrq / jonasforth.git / blobdiff