; ============================================================================= ; gbos.inc - core constants, memory map, PCB layout, syscall numbers ; Target: Game Boy Color, MBC5 + RAM + BATTERY ; ============================================================================= IF !DEF(GBOS_INC) DEF GBOS_INC EQU 1 ; ----------------------------------------------------------------------------- ; Hardware registers we touch (subset; full defs would come from hardware.inc) ; ----------------------------------------------------------------------------- DEF rIF EQU $FF0F ; interrupt flags DEF rIE EQU $FFFF ; interrupt enable DEF rSVBK EQU $FF70 ; CGB WRAM bank select ($D000-$DFFF): 1..7 DEF rKEY1 EQU $FF4D ; CGB speed switch DEF rSB EQU $FF01 ; serial data DEF rSC EQU $FF02 ; serial control DEF rLCDC EQU $FF40 DEF rSTAT EQU $FF41 DEF rLY EQU $FF44 ; ----------------------------------------------------------------------------- ; MBC5 mapper register addresses (writes to ROM space hit the mapper) ; ----------------------------------------------------------------------------- DEF MBC5_RAM_ENABLE EQU $0000 ; write $0A to enable cart RAM DEF MBC5_ROMB_LO EQU $2000 ; ROM bank bits 0..7 DEF MBC5_ROMB_HI EQU $3000 ; ROM bank bit 8 DEF MBC5_RAMB EQU $4000 ; RAM bank bits 0..3 ($A000-$BFFF) ; ----------------------------------------------------------------------------- ; Memory map (the gbos plan) ; $0000-$3FFF ROM0 kernel core (fixed, always mapped) ; $4000-$7FFF ROMX current task TEXT (read-only program code) ; $8000-$9FFF VRAM graphics ; $A000-$BFFF SRAM current task DATA/BSS/HEAP/STACK (MBC5 RAM bank) ; $C000-$CFFF WRAM0 kernel globals + kernel stack (never swapped) ; $D000-$DFFF WRAMX per-process u-area (SVBK bank) ; $FF80-$FFFE HRAM bank-switch trampoline + context switch ; ----------------------------------------------------------------------------- DEF TASK_RAM_BASE EQU $A000 DEF TASK_RAM_TOP EQU $C000 ; one past end of the 8 KiB window DEF TASK_STACK_TOP EQU $BFFF ; task stacks grow down from here DEF KSTACK_TOP EQU $D000 ; kernel stack top (grows down into WRAM0) ; ----------------------------------------------------------------------------- ; Process table ; ----------------------------------------------------------------------------- DEF MAX_PROCS EQU 8 DEF NUM_RAM_BANKS EQU 4 ; MBC5 cart RAM banks available (-r 3 = 32 KiB) DEF KSTACK_TOP2 EQU $D000 ; kernel stack top reused for syscalls (fork) DEF INIT_PID EQU 1 ; pid of the init task (orphan reaper) ; process states DEF PS_FREE EQU 0 DEF PS_READY EQU 1 DEF PS_RUN EQU 2 DEF PS_BLOCKED EQU 3 DEF PS_ZOMBIE EQU 4 ; PCB (process control block) field offsets RSRESET DEF PROC_STATE RB 1 ; PS_* DEF PROC_PID RB 1 DEF PROC_SP RW 1 ; saved stack pointer (into task's RAM bank) DEF PROC_ROMB RW 1 ; text ROM bank (16-bit; MBC5 up to 511) DEF PROC_RAMB RB 1 ; data/stack cart-RAM bank DEF PROC_WRAMB RB 1 ; u-area SVBK bank (1..7) DEF PROC_PARENT RB 1 DEF PROC_EXIT RB 1 ; exit code (valid when PS_ZOMBIE) DEF PROC_STDIN RB 1 ; $FF = console, else an open-file fd DEF PROC_STDOUT RB 1 ; $FF = console, else an open-file fd DEF PROC_PROG RB 1 ; program id currently running ($FF = none), for ps DEF PROC_SIZE RB 0 DEF KILL_CODE EQU 137 ; exit status of a killed process (128 + SIGKILL) DEF STD_CONSOLE EQU $FF ; ----------------------------------------------------------------------------- ; Syscall numbers (passed in C; args in DE/HL/B per call, ret in A) ; ----------------------------------------------------------------------------- DEF SYS_EXIT EQU 0 DEF SYS_FORK EQU 1 DEF SYS_READ EQU 2 DEF SYS_WRITE EQU 3 DEF SYS_OPEN EQU 4 DEF SYS_CLOSE EQU 5 DEF SYS_EXEC EQU 6 DEF SYS_WAIT EQU 7 DEF SYS_GETPID EQU 8 DEF SYS_KILL EQU 9 DEF SYS_BRK EQU 10 DEF SYS_YIELD EQU 11 DEF SYS_GETB EQU 12 ; read a byte from an open file (B=fd -> A, CF=EOF) DEF SYS_PUTB EQU 13 ; append a byte to an open file (B=fd, E=byte) DEF SYS_LIST EQU 14 ; list a directory slot (B=slot, DE=namebuf) DEF SYS_REMOVE EQU 15 ; delete a file (DE=name) DEF SYS_PUTC EQU 16 ; write a byte to stdout (E=byte) DEF SYS_SETIN EQU 17 ; set current stdin fd (B=fd, $FF=console) DEF SYS_SETOUT EQU 18 ; set current stdout fd (B=fd, $FF=console) DEF SYS_LOOKUP EQU 19 ; program id for a command name (DE=name -> A=id/$FF) DEF SYS_PS EQU 20 ; process table entry (B=slot, DE=buf3 -> A=1/0) DEF SYS_PROGNAME EQU 21 ; program id -> name (B=id, DE=namebuf) DEF SYS_REAP EQU 22 ; reap a zombie child, nohang (-> A=pid or 0) DEF SYS_MAX EQU 23 ; SYS_KILL (9) is now implemented (B=pid -> A=0/$FF; pid 1 is immortal) ; (SYS_OPEN=4 / SYS_CLOSE=5 are now implemented by the filesystem) ; ----------------------------------------------------------------------------- ; RAM filesystem (lives in WRAMX $D000-$DFFF, 4 KiB; fixed in DMG mode). ; 8 files x 512 bytes: name[8] (first byte 0 = free) + len[2] + data[502]. ; ----------------------------------------------------------------------------- DEF FS_BASE EQU $D000 DEF FS_MAX_FILES EQU 8 DEF FS_FILE_SIZE EQU 512 DEF FS_NAME EQU 0 DEF FS_LEN EQU 8 DEF FS_DATA EQU 10 DEF FS_MAX_DATA EQU 502 ; open-file table (kernel WRAM0): inuse, slot, mode, pos(2) DEF OF_MAX EQU 4 DEF OF_INUSE EQU 0 DEF OF_SLOT EQU 1 DEF OF_MODE EQU 2 DEF OF_POS EQU 3 DEF OF_SIZE EQU 5 ; ----------------------------------------------------------------------------- ; Program table indices (see programs.asm). exec() takes one of these in B. ; ----------------------------------------------------------------------------- DEF PROG_WORKER EQU 0 DEF PROG_SH EQU 1 DEF PROG_HELLO EQU 2 DEF PROG_CHELLO EQU 3 ; C programs (compiled with SDCC), see c/ DEF PROG_ECHO EQU 4 DEF PROG_TRUE EQU 5 DEF PROG_FALSE EQU 6 DEF PROG_UNAME EQU 7 DEF PROG_PID EQU 8 DEF PROG_CAT EQU 9 DEF PROG_WC EQU 10 DEF PROG_HEAD EQU 11 DEF PROG_ARGS EQU 12 DEF PROG_LS EQU 13 DEF PROG_SAVE EQU 14 DEF PROG_RM EQU 15 DEF PROG_PS EQU 16 DEF PROG_KILL EQU 17 DEF PROG_SPIN EQU 18 ENDC