diff options
| author | user <user@clank> | 2026-07-16 00:31:27 +0200 |
|---|---|---|
| committer | user <user@clank> | 2026-07-16 00:31:27 +0200 |
| commit | d5c06116d3d1257b46c476cf73b634cf089bcb82 (patch) | |
| tree | 8912008c1ca483d9a8192961d703161dcf274411 /src/syscall.asm | |
| parent | kernel: complete the process lifecycle (exit/wait/reap + bank free list) (diff) | |
| download | gbos-d5c06116d3d1257b46c476cf73b634cf089bcb82.tar.gz gbos-d5c06116d3d1257b46c476cf73b634cf089bcb82.tar.xz gbos-d5c06116d3d1257b46c476cf73b634cf089bcb82.zip | |
wip: sys_read + serial console shell (read-store bug under investigation)
- sys_read (SYS_READ): blocking console input via external-clock serial poll;
yields while waiting. Verified working (direct-echo cat: 'hi' -> 'hi').
- shell (PROG_SH): prompt/read/parse/fork+exec+wait; worker+hello programs;
StrEqual/SkipName helpers; command table.
- init now execs the shell.
- KNOWN BUG: storing the typed char to the line buffer at $A000 (cart RAM of an
exec'd program) corrupts the following sys_read; sys_write reading $A000 also
returns $3E. Kernel syscalls themselves are correct; isolating the cart-RAM /
exec RAM-bank interaction next.
Diffstat (limited to 'src/syscall.asm')
| -rw-r--r-- | src/syscall.asm | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/src/syscall.asm b/src/syscall.asm index 4b8771c..bf75865 100644 --- a/src/syscall.asm +++ b/src/syscall.asm @@ -36,7 +36,7 @@ SyscallTrap:: SyscallTable: dw sys_exit ; 0 dw sys_fork ; 1 FORK - dw sys_nosys ; 2 READ (TODO) + dw sys_read ; 2 READ dw sys_write ; 3 WRITE dw sys_nosys ; 4 OPEN (TODO) dw sys_nosys ; 5 CLOSE (TODO) @@ -71,6 +71,25 @@ sys_write: ret ; ----------------------------------------------------------------------------- +; sys_read() -> A = one input byte from the console (blocking). +; Uses an external-clock serial transfer as a clean RX: it completes only when +; the host has a byte (no stdout echo). While waiting we yield so other procs +; run. Preserves BC/DE/HL (the context switch saves/restores them). +; ----------------------------------------------------------------------------- +sys_read: +.poll + ld a, $80 + ld [rSC], a ; request a byte (external clock) + ld a, [rSC] + bit 7, a + jr z, .got ; bit7 clear => transfer completed + call SchedYield ; nothing yet: let others run, then retry + jr .poll +.got + ld a, [rSB] + ret + +; ----------------------------------------------------------------------------- ; sys_getpid() -> A = current pid ; ----------------------------------------------------------------------------- sys_getpid: |