diff options
| -rw-r--r-- | README.md | 24 | ||||
| -rw-r--r-- | src/programs.asm | 6 |
2 files changed, 27 insertions, 3 deletions
@@ -41,7 +41,10 @@ $FFEF-$FFF2 HRAM bank shadows + switch target ## Syscall ABI -User loads `C` = syscall number, args in `DE`/`B`, then `rst $30`. Return in `A`. +User loads `C` = syscall number, args in `DE`/`B`/`HL`, then `rst $30`. +Return in `A` (and `B` for `wait`). **The trap clobbers `BC`/`DE`/`HL`** (it uses +`HL` to index the dispatch table), so userland must save any pointer it needs +across a syscall (`push hl` / `pop hl`). Libc syscall stubs handle this for C. | # | name | status | |---|---------|--------| @@ -52,7 +55,24 @@ User loads `C` = syscall number, args in `DE`/`B`, then `rst $30`. Return in `A` | 7 | wait | ✅ blocks; reaps a zombie child → `A`=pid `B`=code | | 8 | getpid | ✅ | | 11| yield | ✅ cooperative switch | -| 2,4,5,9,10 | read/open/close/kill/brk | ⛔ `ENOSYS` | +| 2 | read | ✅ blocking console input (1 byte) via external-clock serial | +| 4,5,9,10 | open/close/kill/brk | ⛔ `ENOSYS` | + +### The shell (PROG_SH) + +init `exec`s a tiny shell: **prompt → read a line (with echo) → match a command +→ `fork`+`exec`+`wait`**. Commands live in a table (`worker`, `hello`). Runs +entirely over the headless serial console: + +``` +$ hello +hello world! +$ worker +worker! +$ foo +? +$ +``` ### Process lifecycle (exit / wait / reaping) diff --git a/src/programs.asm b/src/programs.asm index df2b98d..d4ae89f 100644 --- a/src/programs.asm +++ b/src/programs.asm @@ -59,8 +59,10 @@ ProgSh: ; 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 $0D jr z, .eol cp $0A @@ -70,7 +72,9 @@ ProgSh: ld [$FF01], a ; echo the char straight to serial ld a, $81 ld [$FF02], a - jr .rd + ld a, l + cp LOW(SH_LINEBUF) + SH_MAXLINE - 1 + jr c, .rd ; keep reading unless the buffer is full .eol ld [hl], 0 ; NUL-terminate |