X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=e510410a5069b239621a1c14edb58893bce05dac;hb=fe5967a09f12cc09640d8284ac6f554ee3bf4357;hp=e6b0ac280cfc359bbad93881900df086e3e0379e;hpb=4d233157714c21c1c15e7b271460a1692da55f52;p=rrq%2Fjonasforth.git

diff --git a/main.asm b/main.asm
index e6b0ac2..e510410 100644
--- a/main.asm
+++ b/main.asm
@@ -1,4 +1,31 @@
-format ELF64 executable
+;; vim: syntax=fasm
+
+;; 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.
+;;
+;; The module should provide the following:
+;;
+;; os_code_section
+;;   Macro to start the text segment.
+;;
+;; os_data_section
+;;   Macro to start the data segment.
+;;
+;; os_initialize
+;;   Called at initialization.
+;;
+;; os_print_string
+;;   Takes a string buffer in RCX and the length in RDX, and prints the string
+;;   to the console.
+;;
+;; 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
@@ -57,23 +84,17 @@ macro forth_asm label, name, immediate {
 .start:
 }
 
-;; Define a Forth word that is implemented in Forth. (The body will be a list of
-;; 'dq' statements.)
-macro forth label, name, immediate {
-  header label, name, immediate
-  dq DOCOL
-}
-
-segment readable executable
+include "impl.asm"      ; Misc. subroutines
+include "bootstrap.asm" ; Forth words encoded in Assembly
 
-entry main
-
-include "impl.asm"
+os_code_section
 
 main:
   cld                        ; Clear direction flag so LODSQ does the right thing.
   mov rbp, return_stack_top  ; Initialize return stack
 
+  call os_initialize
+
   mov rax, MAIN
   jmp qword [rax]
 
@@ -100,6 +121,17 @@ forth_asm LIT, 'LIT'
   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'
@@ -161,38 +193,82 @@ forth_asm EXEC, 'EXEC'
 forth_asm EMIT, 'EMIT'
   pushr rsi
   pushr rax
-  mov rax, 1
-  mov rdi, 1
-  lea rsi, [rsp]
+
+  lea rcx, [rsp]
   mov rdx, 1
-  syscall
+  call os_print_string
+
   add rsp, 8
   popr rax
   popr rsi
   next
 
-;; Prints a newline to standard output.
-forth NEWLINE, 'NEWLINE'
-  dq LIT, $A
-  dq EMIT
-  dq EXIT
+;; Read a single character from the current input stream. Usually, this will wait
+;; for the user to press a key, and then return the corresponding character. When
+;; reading from a special buffer, it will instead return the next characater from
+;; that buffer.
+;;
+;; The ASCII character code is placed on the stack.
+forth_asm KEY, 'KEY'
+  call .impl
+  push rax
+  next
 
-;; Prints a space to standard output.
-forth SPACE, 'SPACE'
-  dq LIT, ' '
-  dq EMIT
-  dq EXIT
+;; Result in RAX
+.impl:
+  ;; Are we reading from user input or from the input buffer?
+  cmp [input_buffer], 0
+  jne .from_buffer
+
+  ;; Reading user input
+  call os_read_char
+  ret
+
+.from_buffer:
+  ;; Reading from buffer
+  mov rax, [input_buffer]
+  movzx rax, byte [rax]
+
+  inc [input_buffer]
+  dec [input_buffer_length]
+  ret
 
-;; Read a word from standard input and push it onto the stack as a pointer and a
-;; size. The pointer is valid until the next call to READ_WORD.
+;; Read a word and push it onto the stack as a pointer and a size. The pointer
+;; is valid until the next call to READ_WORD.
 forth_asm READ_WORD, 'READ-WORD'
-  mov [.rsi], rsi
+  push rsi
+.skip_whitespace:
+  ;; Read characters until one of them is not whitespace.
+  call KEY.impl
+  ;; We consider newlines and spaces to be whitespace.
+  cmp al, ' '
+  je .skip_whitespace
+  cmp al, $A
+  je .skip_whitespace
+
+  ;; We got a character that wasn't whitespace. Now read the actual word.
+  mov [.length], 0
 
-  call read_word
-  push rdi                      ; Buffer
-  push rdx                      ; Length
+.read_alpha:
+  movzx rbx, [.length]
+  mov rsi, .buffer
+  add rsi, rbx
+  mov [rsi], al
+  inc [.length]
+
+  call KEY.impl
+
+  cmp al, ' '
+  je .end
+  cmp al, $A
+  jne .read_alpha
+
+.end:
+  pop rsi
+  push .buffer
+  movzx rax, [.length]
+  push rax
 
-  mov rsi, [.rsi]
   next
 
 ;; Takes a string on the stack and replaces it with the decimal number that the
@@ -208,42 +284,24 @@ forth_asm PARSE_NUMBER, 'PARSE-NUMBER'
   push rax                      ; Result
   next
 
-forth READ_NUMBER, 'READ-NUMBER'
-  dq READ_WORD
-  dq PARSE_NUMBER
-  dq EXIT
-
 ;; Takes a string (in the form of a pointer and a length on the stack) and
 ;; prints it to standard output.
 forth_asm TELL, 'TELL'
-  mov rbx, rsi
-  mov rcx, rax
+  pushr rax
+  pushr rsi
 
-  mov rax, 1
-  mov rdi, 1
-  pop rdx     ; Length
-  pop rsi     ; Buffer
-  syscall
+  pop rdx ; Length
+  pop rcx ; Buffer
+  call os_print_string
 
-  mov rax, rcx
-  mov rsi, rbx
+  popr rsi
+  popr rax
   next
 
 ;; Exit the program cleanly.
 forth_asm TERMINATE, 'TERMINATE'
-  mov rax, $3C
-  mov rdi, 0
-  syscall
-
-forth HELLO, 'HELLO'
-  dq LIT, 'H', EMIT
-  dq LIT, 'e', EMIT
-  dq LIT, 'l', EMIT
-  dq LIT, 'l', EMIT
-  dq LIT, 'o', EMIT
-  dq LIT, '!', EMIT
-  dq NEWLINE
-  dq EXIT
+  mov rax, 0
+  call os_terminate
 
 ;; Duplicate a pair of elements.
 forth_asm PAIRDUP, '2DUP'
@@ -279,54 +337,6 @@ forth_asm NOT_, 'NOT'
   push 1
   next
 
-;; The INTERPRET word reads and interprets user input. It's behavior depends on
-;; the current STATE. It provides special handling for integers.
-forth INTERPRET, 'INTERPRET'
-  ;; Read word
-  dq READ_WORD
-  dq PAIRDUP
-  ;; Stack is (word length word length).
-  dq FIND                       ; Try to find word
-  dq DUP_
-  dq ZBRANCH, 8 * 20            ; Check if word is found
-
-  ;; - Word is found -
-
-  dq STATE, GET, ZBRANCH, 8 * 9 ; Check whether we are in compilation or immediate mode
-
-  ;; (Word found, compilation mode)
-  dq DUP_, IS_IMMEDIATE, NOT_, ZBRANCH, 8 * 4 ; If the word is immediate, continue as we would in immediate mode
-
-  ;; Otherwise, we want to compile this word
-  dq TCFA
-  dq COMMA
-  dq EXIT
-
-  ;; (Word found, immediate mode)
-  ;; Execute word
-  dq TCFA
-  ;; Stack is (word length addr)
-  dq SWAP, DROP
-  dq SWAP, DROP
-  ;; Stack is (addr)
-  dq EXEC
-  dq EXIT
-
-  ;; - No word is found, assume it is an integer literal -
-  ;; Stack is (word length addr)
-  dq DROP
-  dq PARSE_NUMBER
-
-  dq STATE, GET, ZBRANCH, 8 * 5 ; Check whether we are in compilation or immediate mode
-
-  ;; (Number, compilation mode)
-  dq LIT, LIT, COMMA
-  dq COMMA
-  dq EXIT
-
-  ;; (Number, immediate mode)
-  dq EXIT
-
 ;; .U prints the value on the stack as an unsigned integer in hexadecimal.
 forth_asm DOTU, '.U'
   mov [.length], 0
@@ -378,11 +388,9 @@ forth_asm DOTU, '.U'
   loop .flip
 
   ;; Print the buffer
-  mov rax, 1
-  mov rdi, 1
-  mov rsi, .buffer
+  mov rcx, .buffer
   mov rdx, [.printed_length]
-  syscall
+  call os_print_string
 
   ;; Restore RSI and continue execution
   pop rsi
@@ -442,47 +450,20 @@ forth_asm TIMESMOD, '/MOD'
   push rdx                      ; a % b
   next
 
-;; Get the location of the STATE variable. It can be set with '!' and read with
-;; '@'.
-forth STATE, 'STATE'
-  dq LIT, var_STATE
-  dq EXIT
-
-;; Get the location of the LATEST variable. It can be set with '!' and read with
-;; '@'.
-forth LATEST, 'LATEST'
-  dq LIT, latest_entry
-  dq EXIT
-
-;; Get the location at which compiled words are expected to be added. This
-;; pointer is usually modified automatically when calling ',', but we can also
-;; read it manually with 'HERE'.
-forth HERE, 'HERE'
-  dq LIT, here
-  dq EXIT
-
-forth COMMA, ','
-  dq HERE, GET, PUT             ; Set the memory at the address pointed to by HERE
-  dq HERE, GET, LIT, 8, PLUS    ; Calculate new address for HERE to point to
-  dq HERE, PUT                  ; Update HERE to point to the new address
-  dq EXIT
-
-;; Read user input until next " character is found. Push a string containing the
+;; Read input until next " character is found. Push a string containing the
 ;; input on the stack as (buffer length). Note that the buffer is only valid
-;; until the next call to S" and that no more than 255 character can be read.
+;; until the next call to S" and that no more than 255 characters can be read.
 forth_asm READ_STRING, 'S"'
+  ;; If the input buffer is set, we should read from there instead.
+  cmp [input_buffer], 0
+  jne read_string_buffer
+
   push rsi
 
   mov [.length], 0
 
 .read_char:
-  mov rax, 0
-  mov rdi, 0
-  mov rsi, .char_buffer
-  mov rdx, 1
-  syscall
-
-  mov al, [.char_buffer]
+  call os_read_char
   cmp al, '"'
   je .done
 
@@ -500,6 +481,40 @@ forth_asm READ_STRING, 'S"'
 
   next
 
+read_string_buffer:
+  push rsi
+
+  ;; We borrow READ_STRING's buffer. They won't mind.
+  mov [READ_STRING.length], 0
+
+.read_char:
+  mov rbx, [input_buffer]
+  mov al, [rbx]
+  cmp al, '"'
+  je .done
+
+  mov rdx, READ_STRING.buffer
+  add rdx, [READ_STRING.length]
+  mov [rdx], al
+  inc [READ_STRING.length]
+
+  inc [input_buffer]
+  dec [input_buffer_length]
+
+  jmp .read_char
+
+.done:
+  pop rsi
+
+  ;; Skip closing "
+  inc [input_buffer]
+  dec [input_buffer_length]
+
+  push READ_STRING.buffer
+  push [READ_STRING.length]
+
+  next
+
 ;; CREATE inserts a new header in the dictionary, and updates LATEST so that it
 ;; points to the header. To compile a word, the user can then call ',' to
 ;; continue to append data after the header.
@@ -533,37 +548,137 @@ forth_asm CREATE, 'CREATE'
 
   next
 
-;; Mark the last added word as immediate.
-forth IMMEDIATE, 'IMMEDIATE', 1
-  dq LIT, 1
-  dq LATEST, GET
-  dq LIT, 8, PLUS
-  dq PUT_BYTE
-  dq EXIT
+forth_asm TICK, "'"
+  lodsq
+  push rax
+  next
 
-;; Given the address of a word, return 0 if the given word is not immediate.
-forth IS_IMMEDIATE, 'IMMEDIATE?'
-  dq LIT, 8, PLUS
-  dq GET_BYTE
-  dq EXIT
+forth_asm ROT, 'ROT'
+  pop rax
+  pop rbx
+  pop rdx
+  push rax
+  push rdx
+  push rbx
+  next
 
-;; Enter immediate mode, immediately
-forth INTO_IMMEDIATE, '[', 1
-  dq LIT, 0, STATE, PUT_BYTE
-  dq EXIT
+forth_asm PICK, 'PICK'
+  pop rax
+  lea rax, [rsp + 8 * rax]
+  mov rax, [rax]
+  push rax
+  next
 
-;; Enter compilation mode
-forth OUTOF_IMMEDIATE, ']'
-  dq LIT, 1, STATE, PUT_BYTE
-  dq EXIT
+forth_asm EQL, '='
+  pop rax
+  pop rbx
+  cmp rax, rbx
+  je .eq
+.noteq:
+  push 0
+  next
+.eq:
+  push 1
+  next
 
 forth MAIN, 'MAIN'
-  dq HELLO
+  dq SYSCODE
+  dq INTERPRET_STRING
   dq INTERPRET
   dq BRANCH, -8 * 2
   dq TERMINATE
 
-segment readable writable
+;; EFI:
+
+forth EFI_SYSTEM_TABLE_CONSTANT, 'SystemTable'
+  dq LIT, system_table, GET
+  dq EXIT
+
+forth_asm EFICALL2, 'EFICALL2'
+  pop rax ; function pointer
+  pop rdx ; 2nd argument
+  pop rcx ; 1st argument
+
+  sub rsp, 32
+  call rax
+  add rsp, 32
+
+  next
+
+forth_asm EFICALL3, 'EFICALL3'
+  pop rax ; function pointer
+  pop r8  ; 3rd argument
+  pop rdx ; 2nd argument
+  pop rcx ; 1st argument
+
+  sub rsp, 32
+  call rax
+  add rsp, 32
+
+  push rax
+
+  next
+
+forth_asm EFICALL10, 'EFICALL10'
+  pop rax ; function pointer
+
+  mov rcx, [rsp + 8 * 9]
+  mov rdx, [rsp + 8 * 8]
+  mov r8, [rsp + 8 * 7]
+  mov r9, [rsp + 8 * 6]
+
+  ;; Reverse order of stack arguments
+  mov r10, [rsp + 8 * 5]
+  mov r11, [rsp + 8 * 0]
+  mov [rsp + 8 * 5], r11
+  mov [rsp + 8 * 0], r10
+
+  mov r10, [rsp + 8 * 4]
+  mov r11, [rsp + 8 * 1]
+  mov [rsp + 8 * 4], r11
+  mov [rsp + 8 * 1], r10
+
+  mov r10, [rsp + 8 * 3]
+  mov r11, [rsp + 8 * 2]
+  mov [rsp + 8 * 3], r11
+  mov [rsp + 8 * 2], r10
+
+  sub rsp, 32
+  call rax
+  add rsp, 32 + 8 * 10
+
+  push rax
+
+  next
+
+;; Built-in variables:
+
+forth STATE, 'STATE'
+  dq LIT, var_STATE
+  dq EXIT
+
+forth LATEST, 'LATEST'
+  dq LIT, latest_entry
+  dq EXIT
+
+forth HERE, 'HERE'
+  dq LIT, here
+  dq EXIT
+
+forth SYSCODE, 'SYSCODE'
+  dq LIT, sysf
+  dq LIT, sysf.len
+  dq EXIT
+
+forth INPUT_BUFFER, 'INPUT-BUFFER'
+  dq LIT, input_buffer
+  dq EXIT
+
+forth INPUT_LENGTH, 'INPUT-LENGTH'
+  dq LIT, input_buffer_length
+  dq EXIT
+
+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
@@ -574,6 +689,12 @@ latest_entry dq initial_latest_entry
 ;; it is compiling.
 var_STATE dq 0
 
+;; The interpreter can read either from standard input or from a buffer. When
+;; input-buffer is set (non-null), words like READ-WORD and S" will use this
+;; buffer instead of reading user input.
+input_buffer dq 0
+input_buffer_length dq 0
+
 FIND.rsi dq ?
 
 READ_WORD.rsi dq ?
@@ -589,10 +710,24 @@ DOTU.rbuffer rq 16
 DOTU.length dq ?
 DOTU.printed_length dq ?
 
+KEY.buffer dq ?
+
+READ_WORD.buffer rb $FF
+READ_WORD.length db ?
+
 ;; Reserve space for compiled words, accessed through HERE.
 here dq here_top
-here_top rq $2000
+here_top rq $4000
 
 ;; Return stack
 rq $2000
 return_stack_top:
+
+;; 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'
+file 'uefi.f'
+sysf.len = $ - sysf
+