fs rewrite stage 2: inodes + root directory (block-based, persistent)

- fs.asm: a real block filesystem on the persistent block device - superblock,
  block/inode bitmaps, a 32-entry inode table (type, size, 8 direct block
  pointers -> files up to 2 KiB), and a root directory of 16-byte entries.
  Metadata cached in WRAMX; one-block data cache streams file/dir blocks.
- same syscall interface (open/getb/putb/list/remove) -> tools unchanged;
  ls now enumerates until flist() runs out (16 files, was hardcoded 8).
- old 8-slot WRAM FS removed; cart RAM partitioned: process banks 0-7, disk 8-11.
- two register-clobber bugs fixed: alloc_block/alloc_inode returned the
  bitmap-block number (write_bitmap clobbers C); db_use loaded the wrong block
  on a transition (db_flush->write_block clobbers C) -> multi-block files broke.
- verified: 10+ files, multi-block (300-byte) files, delete, and persistence
  across reboots. Debug 'blk' disk tool retained (fill/peek).
- README: document the block filesystem.

1 files changed, 9 insertions, 1 deletions

diff --git a/c/libc.s b/c/libc.s
index 5b81dca..c245bbd 100644
--- a/c/libc.s
+++ b/c/libc.s
@@ -200,7 +200,7 @@ _reap:
 	rst	#0x30
 	ret
 
-	.globl _bfill, _bpeek
+	.globl _bfill, _bpeek, _bpeek2
 	;; void bfill(unsigned char block /*A*/, unsigned char byte /*E*/)
 _bfill:
 	ld	b, a
@@ -210,6 +210,14 @@ _bfill:
 	;; unsigned char bpeek(unsigned char block /*A*/) -> A
 _bpeek:
 	ld	b, a
+	ld	e, #0
 	ld	c, #24			; SYS_BPEEK
 	rst	#0x30
 	ret
+	;; unsigned char bpeek2(unsigned char block /*A*/, unsigned char off /*E*/) -> A
+_bpeek2:
+	ld	b, a
+	ld	c, #24			; SYS_BPEEK (off already in E)
+	rst	#0x30
+	ret
+