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.

4 files changed, 47 insertions, 0 deletions

diff --git a/c/gbos.h b/c/gbos.h
index fa926fd..5f22a5a 100644
--- a/c/gbos.h
+++ b/c/gbos.h
@@ -38,4 +38,7 @@ unsigned char wait(void);
 void          setin(unsigned char fd);      /* redirect stdin  ($FF=console) */
 void          setout(unsigned char fd);     /* redirect stdout ($FF=console) */
 unsigned char lookup(const char *name);     /* command name -> program id    */
+unsigned char kill(unsigned char pid);      /* terminate a pid (1 is immortal)*/
+unsigned char psget(unsigned char slot, unsigned char *buf); /* {pid,state,prog}*/
+void          progname(unsigned char id, char *buf);         /* id -> name     */
 #endif
diff --git a/c/kill.c b/c/kill.c
new file mode 100644
index 0000000..e524627
--- /dev/null
+++ b/c/kill.c
@@ -0,0 +1,10 @@
+#include "gbos.h"
+/* kill <pid>: terminate a process (pid 1 is immortal). */
+void main(void) {
+    char *argv[4];
+    unsigned char argc = argv_parse(argv, 4);
+    unsigned char pid;
+    if (argc < 1) { puts("usage: kill <pid>"); nl(); return; }
+    pid = atou(argv[0]);
+    if (kill(pid)) { puts("kill: no such pid (or immortal)"); nl(); }
+}
diff --git a/c/libc.s b/c/libc.s
index 857a16d..bcc8199 100644
--- a/c/libc.s
+++ b/c/libc.s
@@ -167,3 +167,23 @@ _lookup:
 	ld	c, #19			; SYS_LOOKUP
 	rst	#0x30
 	ret
+
+	.globl _kill, _psget, _progname
+	;; unsigned char kill(unsigned char pid /*A*/) -> A (0 ok, $FF fail)
+_kill:
+	ld	b, a
+	ld	c, #9			; SYS_KILL
+	rst	#0x30
+	ret
+	;; unsigned char psget(unsigned char slot /*A*/, unsigned char *buf /*DE*/) -> A
+_psget:
+	ld	b, a
+	ld	c, #20			; SYS_PS
+	rst	#0x30
+	ret
+	;; void progname(unsigned char id /*A*/, char *buf /*DE*/)
+_progname:
+	ld	b, a
+	ld	c, #21			; SYS_PROGNAME
+	rst	#0x30
+	ret
diff --git a/c/ps.c b/c/ps.c
new file mode 100644
index 0000000..7bfc0de
--- /dev/null
+++ b/c/ps.c
@@ -0,0 +1,14 @@
+#include "gbos.h"
+/* ps: list live processes (pid, state, command). */
+void main(void) {
+    unsigned char i, buf[3];
+    char name[9];
+    for (i = 0; i < 8; i++) {
+        if (psget(i, buf)) {              /* buf = {pid, state, prog} */
+            putu(buf[0]); putc(' ');
+            putc("-RrBZ"[buf[1]]); putc(' ');
+            progname(buf[2], name);
+            puts(name); nl();
+        }
+    }
+}