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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 24 |
1 files changed, 22 insertions, 2 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) |