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|
; =============================================================================
; programs.asm - userland program images (text-in-ROM model) + the shell.
;
; Programs are linked to run from the ROMX window ($4000-$7FFF) and live in
; their own ROM banks. exec() maps the bank and jumps in. Programs talk to the
; kernel only via `rst $30`.
; =============================================================================
INCLUDE "include/gbos.inc"
; the shell keeps its line buffer + scratch at the bottom of its RAM bank
DEF SH_LINEBUF EQU $A000 ; up to 32 bytes
DEF SH_PROGID EQU $A040 ; chosen program id (survives fork via bank copy)
DEF SH_MAXLINE EQU 32
; -----------------------------------------------------------------------------
; PROG_WORKER (bank 2) - print a line, exit(0).
; -----------------------------------------------------------------------------
SECTION "prog_worker", ROMX[$4000], BANK[2]
ProgWorker:
ld de, .msg
ld b, .msgend - .msg
ld c, SYS_WRITE
rst $30
ld b, 0
ld c, SYS_EXIT
rst $30
.msg
db "worker!", $0D, $0A
.msgend
; -----------------------------------------------------------------------------
; PROG_HELLO (bank 4) - print a line, exit(0).
; -----------------------------------------------------------------------------
SECTION "prog_hello", ROMX[$4000], BANK[4]
ProgHello:
ld de, .msg
ld b, .msgend - .msg
ld c, SYS_WRITE
rst $30
ld b, 0
ld c, SYS_EXIT
rst $30
.msg
db "hello world!", $0D, $0A
.msgend
; -----------------------------------------------------------------------------
; PROG_CHELLO (bank 5) - a program written in C, compiled with SDCC to a
; self-contained ROM-bank image (crt0 + libc + code) and included verbatim.
; Rebuild with: sh c/build.sh c/chello.c c/chello.bin
; -----------------------------------------------------------------------------
SECTION "prog_chello", ROMX[$4000], BANK[5]
ProgChello:
INCBIN "c/chello.bin"
SECTION "prog_echo", ROMX[$4000], BANK[6]
ProgEcho:
INCBIN "c/echo.bin"
SECTION "prog_true", ROMX[$4000], BANK[7]
ProgTrue:
INCBIN "c/true.bin"
SECTION "prog_false", ROMX[$4000], BANK[8]
ProgFalse:
INCBIN "c/false.bin"
SECTION "prog_uname", ROMX[$4000], BANK[9]
ProgUname:
INCBIN "c/uname.bin"
SECTION "prog_pid", ROMX[$4000], BANK[10]
ProgPid:
INCBIN "c/pid.bin"
SECTION "prog_cat", ROMX[$4000], BANK[11]
ProgCat:
INCBIN "c/cat.bin"
; -----------------------------------------------------------------------------
; PROG_SH (bank 3) - a tiny shell.
; prompt -> read a line (with echo) -> match a command -> fork+exec+wait.
; -----------------------------------------------------------------------------
SECTION "prog_sh", ROMX[$4000], BANK[3]
ProgSh:
.prompt
ld de, .ps1
ld b, 2
ld c, SYS_WRITE
rst $30
; read a line into SH_LINEBUF, echoing as we go
ld hl, SH_LINEBUF
.rd
push hl ; syscalls clobber HL (trap uses it to dispatch)
ld c, SYS_READ
rst $30 ; A = input byte
pop hl
cp $04
jr z, .eof ; Ctrl-D / EOF: exit the shell
cp $0D
jr z, .eol
cp $0A
jr z, .eol
ld [hl], a ; store in the line buffer (A preserved)
inc hl
ld [$FF01], a ; echo the char straight to serial
ld a, $81
ld [$FF02], a
ld a, l
cp LOW(SH_LINEBUF) + SH_MAXLINE - 1
jr c, .rd ; keep reading unless the buffer is full
.eof
ld b, 0
ld c, SYS_EXIT ; exit init/shell -> system idle
rst $30
.eol
ld [hl], 0 ; NUL-terminate
ld de, .crlf
ld b, 2
ld c, SYS_WRITE
rst $30
ld a, [SH_LINEBUF]
or a
jp z, .prompt ; empty line
; split off the first word: replace the first space with a NUL so command
; matching sees just the command, and the args survive at SH_LINEBUF+n
; (inherited by the child through fork, read back via main(char *args)).
ld hl, SH_LINEBUF
.split
ld a, [hl]
or a
jr z, .lookup ; no space -> no args
cp $20
jr z, .cut
inc hl
jr .split
.cut
ld [hl], 0 ; isolate the command word
.lookup
; look the command up in the table
ld de, .cmdtab
.scan
ld a, [de]
or a
jr z, .unknown ; empty name = end of table
push de
ld hl, SH_LINEBUF
call StrEqual ; Z set if equal
pop de
jr z, .match
call SkipName ; DE -> NUL after this name
inc de ; -> program id
inc de ; -> next entry
jr .scan
.match
call SkipName
inc de ; DE -> program id
ld a, [de]
ld [SH_PROGID], a
ld c, SYS_FORK
rst $30
or a
jr z, .exec
ld c, SYS_WAIT ; parent: reap the command
rst $30
jp .prompt
.exec
ld a, [SH_PROGID]
ld b, a
ld c, SYS_EXEC
rst $30 ; child becomes the command
.unknown
ld de, .huh
ld b, 3
ld c, SYS_WRITE
rst $30
jp .prompt
.ps1
db "$ "
.crlf
db $0D, $0A
.huh
db "?", $0D, $0A
.cmdtab
db "worker", 0
db PROG_WORKER
db "hello", 0
db PROG_HELLO
db "chello", 0
db PROG_CHELLO
db "echo", 0
db PROG_ECHO
db "true", 0
db PROG_TRUE
db "false", 0
db PROG_FALSE
db "uname", 0
db PROG_UNAME
db "pid", 0
db PROG_PID
db "cat", 0
db PROG_CAT
db 0 ; terminator
; -----------------------------------------------------------------------------
; Shell string helpers (ROM0, always mapped).
; -----------------------------------------------------------------------------
SECTION "shell_lib", ROM0
; StrEqual(HL, DE) - compare NUL-terminated strings. Z set if equal.
; Clobbers A, B; advances HL and DE.
StrEqual::
.l
ld a, [de]
ld b, a
ld a, [hl]
cp b
ret nz
or a
ret z ; both NUL -> equal
inc hl
inc de
jr .l
; SkipName(DE) - advance DE to its NUL terminator.
SkipName::
.l
ld a, [de]
or a
ret z
inc de
jr .l
; -----------------------------------------------------------------------------
; Program table (ROM0). Index = program id. Entry: bank (2) + entry addr (2).
; -----------------------------------------------------------------------------
SECTION "progtab", ROM0
ProgramTable::
db LOW(BANK(ProgWorker)), HIGH(BANK(ProgWorker))
dw ProgWorker
db LOW(BANK(ProgSh)), HIGH(BANK(ProgSh))
dw ProgSh
db LOW(BANK(ProgHello)), HIGH(BANK(ProgHello))
dw ProgHello
db LOW(BANK(ProgChello)), HIGH(BANK(ProgChello))
dw ProgChello
db LOW(BANK(ProgEcho)), HIGH(BANK(ProgEcho))
dw ProgEcho
db LOW(BANK(ProgTrue)), HIGH(BANK(ProgTrue))
dw ProgTrue
db LOW(BANK(ProgFalse)), HIGH(BANK(ProgFalse))
dw ProgFalse
db LOW(BANK(ProgUname)), HIGH(BANK(ProgUname))
dw ProgUname
db LOW(BANK(ProgPid)), HIGH(BANK(ProgPid))
dw ProgPid
db LOW(BANK(ProgCat)), HIGH(BANK(ProgCat))
dw ProgCat
|
