pipe: PIPE_MAX 2->4 (5-stage pipelines) + fix cross-yield byte corruption

2026-07-16T23:11:11Z

Bump PIPE_MAX to 4 so a|b|c|d|e (4 pipes) works. This stays within the single-byte buffer-offset math (idx*64+pos <= 3*64+63 = 255) and the fd space ($F0..$F7, clear of $FF console). The bump exposed a data-corruption bug that also affected the 2-pipe case (just invisibly - a wc-only test can't see mangled bytes): pipe_write kept the byte-to-write in the SHARED wPipeByte global across its SchedYield (buffer full), so a concurrent pipe op clobbered it and the writer then stored the wrong byte. Now the byte is held in D across the yield, and pipe_bufptr no longer clobbers D; pipe_read/pipe_write also push their idx across SchedYield rather than assume the yield preserves registers. Verified: count N | cat now streams EXACT content (no 'linn'/'llne' corruption); count 60 | cat | cat | wc = 60 180 1671; 5-stage count 4 | cat | cat | cat | cat prints line 1..4; SIGPIPE (count 200|true) and count 100|wc still fine, no hangs.

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

2026-07-16T23:04:16Z

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).

gbos.git/src/pipe.asm, branch master

pipe: PIPE_MAX 2->4 (5-stage pipelines) + fix cross-yield byte corruption

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