kernel+sh: real anonymous pipes (concurrent, streaming, SIGPIPE)

Replace the shell's temp-file pipe hack with proper in-kernel FIFOs.

Kernel (src/pipe.asm, new):
- A small pool of bounded ring buffers (PIPE_MAX=2, 64 B each) with
  writers/readers refcounts. Pipe fds are $F0+idx*2 (read) / +1 (write);
  $FF stays "console".
- SYS_PIPE allocates one (writers=readers=1) and returns the read fd
  (write = read+1). getb/putb/close dispatch pipe fds here; sys_exit drops
  the refcounts held as PROC_STDIN/PROC_STDOUT.
- Blocking with SchedYield, which is the flow control: read blocks while
  empty with a writer (EOF once writers hit 0), write blocks while full
  with a reader, and if the last reader is gone the writer is killed
  (SIGPIPE -> exit 141). Cooperative-scheduler friendly.

Shell (c/sh.c):
- run_pipeline(): split on '|', make a pipe between adjacent stages, and
  fork ALL stages concurrently (no wait between), wiring stdin/stdout;
  then wait for all. Per-stage >/< still honored; orphaned pipe ends are
  closed on a lookup miss so EOF/EPIPE propagate.
- Drop the __pipe temp file and its 2 KB / serialized limits.

libc: pipe(). New c/ptest.c exercises the FIFO (write, read back, EOF).

Now works (old version couldn't): multi-stage a|b|c; streaming beyond 2 KB
(count 120 | wc = 3372 bytes through a 64 B buffer); early-exit SIGPIPE
(count 200 | true kills count instead of hanging/overflowing a file).

1 files changed, 8 insertions, 1 deletions

diff --git a/include/gbos.inc b/include/gbos.inc
index 9b44b33..aca92e3 100644
--- a/include/gbos.inc
+++ b/include/gbos.inc
@@ -125,7 +125,8 @@ DEF SYS_BPEEK   EQU 24   ; [debug] read a disk block      (B=block, E=off -> A)
 DEF SYS_MKDIR   EQU 25   ; make a directory               (DE=path -> A=0/$FF)
 DEF SYS_CHDIR   EQU 26   ; change directory               (DE=path -> A=0/$FF)
 DEF SYS_OPENDIR EQU 27   ; point ls at a directory        (DE=path -> A=0/$FF)
-DEF SYS_MAX     EQU 28
+DEF SYS_PIPE    EQU 28   ; make a pipe                    (-> A=read fd; write=A+1)
+DEF SYS_MAX     EQU 29
 ; SYS_KILL (9) is now implemented (B=pid -> A=0/$FF; pid 1 is immortal)
 ; (SYS_OPEN=4 / SYS_CLOSE=5 are now implemented by the filesystem)
 
@@ -179,6 +180,11 @@ DEF OF_MODE  EQU 2
 DEF OF_POS   EQU 3
 DEF OF_SIZE  EQU 5
 
+; anonymous pipes
+DEF PIPE_MAX     EQU 2      ; concurrent pipes
+DEF PIPE_BUFSZ   EQU 64     ; ring buffer bytes per pipe
+DEF PIPE_FD_BASE EQU $F0    ; pipe fds: $F0+idx*2 (read), +1 (write); $FF=console
+
 ; -----------------------------------------------------------------------------
 ; Program table indices (see programs.asm). exec() takes one of these in B.
 ; -----------------------------------------------------------------------------
@@ -204,5 +210,6 @@ DEF PROG_SPIN   EQU 18
 DEF PROG_BLK    EQU 19
 DEF PROG_MKDIR  EQU 20
 DEF PROG_COUNT  EQU 21
+DEF PROG_PTEST  EQU 22
 
     ENDC