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Diffstat (limited to '')
| -rw-r--r-- | README.md | 56 |
1 files changed, 26 insertions, 30 deletions
@@ -294,42 +294,38 @@ $ ps ## Filesystem -> **Being rewritten** into a persistent block-based FS. Stage 1 landed: a block -> device (`src/blk.asm`) over battery-backed cart RAM (banks 8–11, 256-byte -> blocks) read/written through a WRAM bounce buffer — so only two routines touch -> cart-RAM banking, and (crucially) they never touch the stack while the disk -> bank is mapped over the process's `$A000` window. Data survives power-off via -> the emulator's `.sav`. The 8-slot WRAM filesystem below still backs the tools -> until stages 2–3 (inodes + directories) replace it. +A small **block-based, persistent filesystem** on battery-backed cart RAM +(`src/blk.asm` + `src/fs.asm`). Layout on the 32 KiB "disk" (256-byte blocks): +``` +block 0 superblock (magic + version) +block 1 bitmaps (free blocks + free inodes) +blocks 2-3 inode table (32 inodes x 16 B: type, size, 8 direct block ptrs) +blocks 4.. data blocks +``` -A tiny **RAM filesystem** lives in **WRAMX (`$D000-$DFFF`, 4 KiB)** — always -mapped in DMG mode and simultaneously accessible with a process's `$A000` data -bank, so the kernel copies between file and process memory with no bounce -buffer. 8 fixed slots of 512 bytes: `name[8]` + `len[2]` + `data[502]`. Seeded -with a `readme` at boot. - -Syscalls: `open` (4), `close` (5), `getb` (12), `putb` (13, byte in `E`), -`list` (14), `remove` (15). Libc: `open`/`close`/`fgetc`/`fputc`/`flist`/ -`fremove` (`c/libc.s`). +- **Inodes + a root directory.** A directory is a file of 16-byte entries + (inode# + name). Files are up to **2 KiB** (8 direct blocks); up to **16** + entries in the root, **32** inodes. +- **Bounce buffer.** Only `read_block`/`write_block` touch cart-RAM banking; + everything else works on WRAM buffers. The bitmap + inode table are cached in + WRAMX; data/dir blocks stream through a one-block cache. +- **Persistent.** Formats on first boot (magic/version check), then survives + power-off via the emulator's `.sav`. +- Same syscalls as before (`open`/`getb`/`putb`/`list`/`remove`) so the tools + (`cat`/`ls`/`save`/`rm`/`wc`/`head`) are unchanged. ``` $ save notes -gbos has a filesystem now +gbos has a real filesystem now $ cat notes -gbos has a filesystem now -$ wc notes -1 5 26 +gbos has a real filesystem now $ ls -readme notes -$ rm notes +$ wc notes # survives a reboot +1 5 31 ``` -> **ABI note:** the syscall trap indexes its jump table with `A`, so syscall -> args go in `B`/`DE`/`E` (never `A`) and results come back in `A`. That's why -> `putb` takes its byte in `E`. - ## Roadmap - [x] `fork`: copy parent's 8 KiB RAM bank → free bank, child returns 0 @@ -348,10 +344,10 @@ $ rm notes - [x] per-process stdin/stdout routing (`KGetc`/`KPutc`, `setin`/`setout`) - [ ] more tools (`rev`, `grep`, `tail`), true concurrent pipes - [~] persistent filesystem rewrite (block-based, cart SRAM), directories: - - [x] **stage 1**: block device (`blk.asm`) — read_block/write_block via a WRAM - bounce buffer, format-on-first-boot, **persists across reboots** (`.sav`) - - [ ] stage 2: inodes + flat root dir (variable-size files); port cat/ls/save - - [ ] stage 3: directories, path resolution, per-process cwd, `cd`/`mkdir` + - [x] **stage 1**: block device (`blk.asm`) via a WRAM bounce buffer + - [x] **stage 2**: inodes + root directory; variable-size files (<=2 KiB), + bitmap allocators; 16 files / 32 inodes; persists across reboots + - [ ] stage 3: nested directories, path resolution, per-process cwd, `cd`/`mkdir` - [ ] Preemptive scheduling: real context save in `TimerISR` → `hSwitchTo` - [ ] Use the `$D000-$DFFF` u-area (SVBK) for per-process kernel state / kstack - [ ] `brk`/heap allocator inside the task bank (heap up, stack down, collision = ENOMEM) |