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| author | user <user@clank> | 2026-07-16 00:37:09 +0200 |
|---|---|---|
| committer | user <user@clank> | 2026-07-16 00:37:09 +0200 |
| commit | 2538b138946128cc5ff473e14ba9bde564aef2e9 (patch) | |
| tree | 26b9680b11c2c22b05154ed5166923d0e3fa8d97 /src | |
| parent | wip: sys_read + serial console shell (read-store bug under investigation) (diff) | |
| download | gbos-2538b138946128cc5ff473e14ba9bde564aef2e9.tar.gz gbos-2538b138946128cc5ff473e14ba9bde564aef2e9.tar.xz gbos-2538b138946128cc5ff473e14ba9bde564aef2e9.zip | |
shell working: fix syscall ABI (trap clobbers HL) + document
- root cause of the read/echo corruption: SyscallTrap uses HL to index the
dispatch table, so HL is clobbered across a syscall; the shell then wrote its
buffer pointer's garbage into the $0000-$7FFF MBC register region, corrupting
the mapper. fix: userland saves HL around sys_read (push/pop).
- shell now runs commands end to end: $ hello -> hello world!, $ worker ->
worker!, $ foo -> ?
- README: document that syscalls clobber BC/DE/HL (return in A, B for wait);
add read + shell to the syscall table.
Diffstat (limited to 'src')
| -rw-r--r-- | src/programs.asm | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/src/programs.asm b/src/programs.asm index df2b98d..d4ae89f 100644 --- a/src/programs.asm +++ b/src/programs.asm @@ -59,8 +59,10 @@ ProgSh: ; read a line into SH_LINEBUF, echoing as we go ld hl, SH_LINEBUF .rd + push hl ; syscalls clobber HL (trap uses it to dispatch) ld c, SYS_READ rst $30 ; A = input byte + pop hl cp $0D jr z, .eol cp $0A @@ -70,7 +72,9 @@ ProgSh: ld [$FF01], a ; echo the char straight to serial ld a, $81 ld [$FF02], a - jr .rd + ld a, l + cp LOW(SH_LINEBUF) + SH_MAXLINE - 1 + jr c, .rd ; keep reading unless the buffer is full .eol ld [hl], 0 ; NUL-terminate |