Daniel Samson
a64a01a6a9
Add a FAT12/16/32 filesystem the VFS mounts at /mnt/usb, reading and writing a USB stick through the block device. Verified end to end under QEMU: the fat server mounts the volume, the VFS routes /mnt/usb to it, and a client lists the root and reads a file (the ELF magic of /mnt/usb/system/kernel). - engine.zig: the FAT engine over a BlockDevice interface — mount (a bare FAT or, as QEMU's VVFAT and most real sticks present it, an MBR-partitioned disk), FAT chain walk (12/16/32), cluster allocation, directory traversal with long-name read, and file read / write / create. Host-tested against a RAM-backed FAT16 image (create, cluster-spanning write, mid-file overwrite, read-back, list). - on-disk.zig: the align(1) boot-sector / directory / long-name / FSInfo structs and the cluster-count FAT-type detection. - fat.zig: the server — wraps the .block device (a DMA bounce buffer) in a BlockDevice, mounts the FAT, serves the vfs-protocol as a backend, and mounts itself into the VFS at /mnt/usb. Spawned by init as a boot service. - runtime.block: the block-device client (geometry / read / write by physical address, so whole sectors never cross IPC). - Raise the kernel service-name registry (maximum_services) 8 -> 16: it is indexed directly by ServiceId, and fat = 8 was being rejected, so the fat server exited before registering. - VFS: an absolute path with no matching mount is now not-found rather than silently created in the flat ramfs — so /mnt/usb fails cleanly until mounted. Tests: fat-mount (the full stack: block -> FAT -> VFS mount -> list + file read) passes; host units cover the engine and on-disk structs; the vfs, shutdown, and USB regression suite stays green (10/10).
69 lines
2.4 KiB
Zig
69 lines
2.4 KiB
Zig
//! system/services/fat/fat-test — a client that proves the FAT mount end to end:
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//! it waits for the fat server to mount the USB volume at /mnt/usb, lists the
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//! root directory through the VFS (which routes /mnt/usb to the fat backend), and
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//! reads a known file off it. Shipped in the initial_ramdisk; the `fat-mount`
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//! kernel test spawns it alongside init.
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const std = @import("std");
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const runtime = @import("runtime");
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fn writeLine(comptime fmt: []const u8, arguments: anytype) void {
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var line: [128]u8 = undefined;
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_ = runtime.system.write(std.fmt.bufPrint(&line, fmt, arguments) catch return);
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}
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pub fn main(init: runtime.process.Init) void {
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_ = init;
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const unistd = @import("posix").unistd;
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// Wait for /mnt/usb to be mounted — the fat server races us at boot (it must
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// bring up the whole USB storage chain first).
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var dir: i32 = -1;
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var tries: u32 = 0;
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while (dir < 0 and tries < 1400) : (tries += 1) {
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dir = unistd.opendir("/mnt/usb");
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if (dir < 0) runtime.system.sleep(50);
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}
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if (dir < 0) {
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_ = runtime.system.write("fat-test: /mnt/usb never became available\n");
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return;
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}
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var count: u32 = 0;
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var entry: unistd.DirEntry = .{};
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while (unistd.readdir(dir, &entry)) {
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writeLine("fat-test: entry '{s}' kind={d} size={d}\n", .{ entry.name(), entry.kind, entry.size });
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count += 1;
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if (count > 32) break;
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}
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unistd.closedir(dir);
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writeLine("fat-test: listed {d} entries\n", .{count});
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// Read a known file off the boot volume through the mount (best effort): the
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// kernel image is an ELF, so its first bytes are the ELF magic.
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const fd = unistd.open("/mnt/usb/system/kernel", 0);
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if (fd >= 0) {
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var magic: [4]u8 = undefined;
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const n = unistd.read(fd, &magic);
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unistd.close(fd);
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if (n == 4 and magic[0] == 0x7F and magic[1] == 'E' and magic[2] == 'L' and magic[3] == 'F') {
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_ = runtime.system.write("fat-test: read /mnt/usb/system/kernel ELF magic ok\n");
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} else {
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writeLine("fat-test: /mnt/usb/system/kernel read {d} bytes (not ELF magic)\n", .{n});
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}
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}
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if (count > 0) {
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while (true) {
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_ = runtime.system.write("fat-test: ok\n");
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runtime.system.sleep(1000);
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}
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}
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_ = runtime.system.write("fat-test: root listing was empty\n");
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}
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pub const panic = runtime.panic;
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comptime {
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_ = &runtime.start._start;
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}
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