kill + ps: implement SYS_KILL (pid 1 immortal) and a ps tool

- PCB gains PROC_PROG (running program id), set by exec, inherited on fork.
- sys_kill(pid): reject pid 1 (immortal) and unknown/dead pids; mark the target
  zombie, reparent its children to init, wake its parent if blocked in wait;
  schedule away if a process kills itself. Reuses FindPcbByPid/ReparentToInit.
- sys_ps(slot,buf)->{pid,state,prog}; sys_progname(id) via NameTable reverse
  lookup. NameTable gains sh/ps/kill.
- libc: kill/psget/progname; tools ps (pid state cmd) and kill <pid>.
- verified: ps lists sh(B)+ps(R); kill 1 refused; kill 42 fails.

1 files changed, 167 insertions, 1 deletions

diff --git a/src/syscall.asm b/src/syscall.asm
index f149a76..0b47c05 100644
--- a/src/syscall.asm
+++ b/src/syscall.asm
@@ -43,7 +43,7 @@ SyscallTable:
     dw sys_exec                 ; 6  EXEC
     dw sys_wait                 ; 7  WAIT
     dw sys_getpid               ; 8  GETPID
-    dw sys_nosys                ; 9  KILL  (TODO)
+    dw sys_kill                 ; 9  KILL
     dw sys_nosys                ; 10 BRK   (TODO)
     dw sys_yield                ; 11 YIELD
     dw sys_getb                 ; 12 GETB
@@ -54,6 +54,8 @@ SyscallTable:
     dw sys_setin                ; 17 SETIN
     dw sys_setout               ; 18 SETOUT
     dw sys_lookup               ; 19 LOOKUP
+    dw sys_ps                   ; 20 PS
+    dw sys_progname             ; 21 PROGNAME
 
 ; -----------------------------------------------------------------------------
 sys_nosys:
@@ -388,3 +390,167 @@ sys_wait:
 .nochild
     ld a, $FF
     ret
+
+; =============================================================================
+; sys_kill(B = pid) -> A = 0 ok / $FF fail. pid 1 (init/shell) is immortal.
+; Terminates the target: mark zombie, reparent its children to init, wake its
+; parent if blocked in wait. If we killed ourselves, schedule away forever.
+; =============================================================================
+sys_kill::
+    ld a, b
+    cp INIT_PID
+    jr z, .fail                 ; init is immortal
+    call FindPcbByPid           ; A=pid -> DE=&PCB, CF if not found (B preserved=pid)
+    jr c, .fail
+    ld a, [de]                  ; state
+    cp PS_FREE
+    jr z, .fail
+    cp PS_ZOMBIE
+    jr z, .fail                 ; already dead
+    ; mark ZOMBIE
+    ld a, PS_ZOMBIE
+    ld [de], a
+    ; PROC_EXIT = KILL_CODE
+    ld a, e
+    add PROC_EXIT
+    ld l, a
+    ld a, d
+    adc 0
+    ld h, a
+    ld a, KILL_CODE
+    ld [hl], a
+    ; victim's parent pid
+    ld a, e
+    add PROC_PARENT
+    ld l, a
+    ld a, d
+    adc 0
+    ld h, a
+    ld a, [hl]
+    ld [wKillParent], a
+    ; reparent victim's children to init (B still = victim pid)
+    ld a, b
+    ld [wExitMyPid], a
+    call ReparentToInit
+    ; wake victim's parent if it is blocked in wait()
+    ld a, [wKillParent]
+    call FindPcbByPid
+    jr c, .maybe_self
+    ld a, [de]
+    cp PS_BLOCKED
+    jr nz, .maybe_self
+    ld a, PS_READY
+    ld [de], a
+.maybe_self
+    ; if the victim is the current process, don't return to it
+    ld a, [wCurProc]
+    add PROC_PID
+    ld l, a
+    ld a, [wCurProc+1]
+    adc 0
+    ld h, a
+    ld a, [wExitMyPid]
+    cp [hl]
+    jr nz, .ok
+.dead
+    call SchedYield
+    jr .dead
+.ok
+    xor a
+    ret
+.fail
+    ld a, $FF
+    ret
+
+; =============================================================================
+; sys_ps(B = slot, DE = buf[3]) -> A = 1 if used (buf = pid,state,prog), else 0
+; =============================================================================
+sys_ps::
+    ld a, e
+    ld [wPsBuf], a
+    ld a, d
+    ld [wPsBuf+1], a
+    ld a, b
+    cp MAX_PROCS
+    jr nc, .no
+    call PcbPtr                 ; DE = &PCB[slot]
+    ld a, [de]                  ; state
+    cp PS_FREE
+    jr z, .no
+    ld a, [wPsBuf]
+    ld l, a
+    ld a, [wPsBuf+1]
+    ld h, a                     ; HL = buf
+    push de                     ; PCB
+    ld a, e
+    add PROC_PID
+    ld e, a
+    ld a, d
+    adc 0
+    ld d, a
+    ld a, [de]                  ; pid
+    ld [hl+], a
+    pop de
+    push de
+    ld a, [de]                  ; state
+    ld [hl+], a
+    pop de
+    ld a, e
+    add PROC_PROG
+    ld e, a
+    ld a, d
+    adc 0
+    ld d, a
+    ld a, [de]                  ; prog id
+    ld [hl], a
+    ld a, 1
+    ret
+.no
+    xor a
+    ret
+
+; =============================================================================
+; sys_progname(B = id, DE = namebuf) - copy the command name for a program id.
+; =============================================================================
+sys_progname::
+    ld hl, NameTable
+.l
+    ld a, [hl]
+    or a
+    jr z, .none
+    ld a, l
+    ld [wPnStart], a
+    ld a, h
+    ld [wPnStart+1], a
+.sk
+    ld a, [hl+]
+    or a
+    jr nz, .sk                  ; HL now at the id byte
+    ld a, [hl]
+    cp b
+    jr z, .match
+    inc hl                      ; skip id -> next entry
+    jr .l
+.match
+    ld a, [wPnStart]
+    ld l, a
+    ld a, [wPnStart+1]
+    ld h, a
+    ld b, 8
+.cp
+    ld a, [hl+]
+    ld [de], a
+    inc de
+    or a
+    jr z, .done
+    dec b
+    jr nz, .cp
+.done
+    ret
+.none
+    ld a, $3F                   ; '?'
+    ld [de], a
+    inc de
+    xor a
+    ld [de], a
+    ret