From fc6f690727aac2b5c9bd368f9b13188fb0ba36a7 Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Thu, 16 Jul 2026 13:07:28 +0200
Subject: fs: reject open()/read() on a directory (EISDIR)

open() now checks the target's inode type: opening a directory as a file
returns $FE (EISDIR) instead of a valid fd, so 'cat docs' no longer streams the
raw directory block as bytes. cat reports 'is a directory'; wc/head/save treat
any invalid fd (>3) as an open failure. (ls is unaffected - it uses the
structural opendir/list path, not open/getb.)
---
 src/fs.asm | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'src/fs.asm')

diff --git a/src/fs.asm b/src/fs.asm
index d543b0f..a4ad77e 100644
--- a/src/fs.asm
+++ b/src/fs.asm
@@ -678,6 +678,13 @@ sys_open::
     ld [wFsDir], a
     call dir_find               ; A = target inode or 0
     ld [wFsInode], a
+    or a
+    jr z, .notdir               ; doesn't exist yet: no type to check
+    call inode_ptr
+    ld a, [hl]                  ; I_TYPE
+    cp IT_DIR
+    jr z, .isdir                ; can't open a directory as a file
+.notdir
     ld a, [wFsMode]
     or a
     jr nz, .write
@@ -730,6 +737,9 @@ sys_open::
     ld a, c
     cp OF_MAX
     jr c, .ofl
+.isdir
+    ld a, $FE                   ; EISDIR: is a directory
+    ret
 .fail
     ld a, $FF
     ret
-- 
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