updated zig version

.asm-lsp.toml

@@ -0,0 +1,21 @@
+[default_config]
+version = "0.10.0"
+assembler = "nasm"
+instruction_set = "x86/x86-64"
+
+[default_config.opts]
+compiler = "zig"
+compile_flags_txt = [
+  "cc",
+  "-x",
+  "assembler-with-cpp",
+  "-g",
+  "-Wall",
+  "-Wextra",
+  "-pedantic",
+  "-pedantic-errors",
+  "-std=c2y",
+  "-mllvm --x86-asm-syntax=intel",
+]
+diagnostics = true
+default_diagnostics = false

.gitignore

@@ -1,2 +1,3 @@
 zig-out
 .zig-cache
+.kate-swp

README.md

@@ -0,0 +1,33 @@
+an operating system made in nasm assembly and (in the future) zig, using the zig build system.
+this project is based on [this video series](https://www.youtube.com/playlist?list=PLFjM7v6KGMpiH2G-kT781ByCNC_0pKpPN) by [nanobyte](https://www.youtube.com/@nanobyte-dev)
+
+# HOWTO
+
+## dependencies
+
+this project requires the nasm assembler, mtools for floppy disk generation and zig to build.
+this project uses qemu as the default emulator, but this is optional
+
+## building
+
+```bash
+git clone https://dario48.site/git/Dario48/zos.git
+cd zos
+zig build
+```
+
+## running
+
+- with the default emulator
+
+```bash
+cd zos
+zig build run
+```
+
+- with a different emulator
+
+```bash
+cd zos
+emulator_cmd zig-out/bin/main_floppy.img
+```

build.zig

@@ -18,16 +18,40 @@ pub fn build(b: *std.Build) void {
     var floppy = createFloppy(b, "main_floppy.img");
     floppy.run = formatFloppyFat12(b, floppy);
 
+    var installToFloppy = installImgToFloppy(b, floppy, initramfs, &.{
+        NamedFile{ .file = .{ .runFile = kernel }, .name = "::kernel.bin" },
+        NamedFile{ .file = .{ .simpleFile = b.path("src/reference_implementations/test.txt") }, .name = "::test.txt" },
+    });
+
     const img_install = b.addInstallBinFile(floppy.obj, "main_floppy.img");
-    img_install.step.dependOn(&installImgToFloppy(b, floppy, initramfs, kernel).step);
+    img_install.step.dependOn(&installToFloppy);
 
     b.getInstallStep().dependOn(&img_install.step);
 
+    const target = b.standardTargetOptions(.{});
+    const fat_reference_mod = b.createModule(.{
+        .root_source_file = b.path("src/reference_implementations/fat.zig"),
+        .target = target,
+        .link_libc = true,
+    });
+
     const run = b.addSystemCommand(&.{ "qemu-system-i386", "-fda" });
-    run.addFileArg(b.path("zig-out/bin/initramfs.img"));
+    run.addFileArg(floppy.obj);
 
     const run_step = b.step("run", "run the os in qemu");
     run_step.dependOn(&run.step);
+
+    const fat_reference = b.addExecutable(.{
+        .root_module = fat_reference_mod,
+        .name = "fat_reference_implementation",
+        .use_lld = false,
+        .use_llvm = false,
+    });
+
+    const fat_install = b.addInstallArtifact(fat_reference, .{});
+
+    const build_references = b.step("references", "build the reference implementations");
+    build_references.dependOn(&fat_install.step);
 }
 
 const AddNasmFilesOptions = struct {
@@ -43,6 +67,11 @@ const NasmFile = struct {
 
 const Floppydisk = NasmFile;
 
+const NamedFile = struct {
+    file: union(enum) { runFile: NasmFile, simpleFile: std.Build.LazyPath },
+    name: []const u8,
+};
+
 fn createFloppy(b: *std.Build, name: []const u8) Floppydisk {
     const dd = b.addSystemCommand(&.{ "dd", "if=/dev/zero" });
     const Floppy = dd.addPrefixedOutputFileArg("of=", name);
@@ -63,7 +92,7 @@ fn formatFloppyFat12(b: *std.Build, floppy: Floppydisk) *std.Build.Step.Run {
     return mkfs;
 }
 
-fn installImgToFloppy(b: *std.Build, floppy: Floppydisk, bootloader: NasmFile, kernel: NasmFile) *std.Build.Step.Run {
+fn installImgToFloppy(b: *std.Build, floppy: Floppydisk, bootloader: NasmFile, additional_files: []const NamedFile) std.Build.Step {
     const dd = b.addSystemCommand(&.{"dd"});
     dd.addPrefixedFileArg("if=", bootloader.obj);
     dd.addPrefixedFileArg("of=", floppy.obj);
@@ -71,14 +100,22 @@ fn installImgToFloppy(b: *std.Build, floppy: Floppydisk, bootloader: NasmFile, k
     dd.step.dependOn(&floppy.run.step);
     dd.step.dependOn(&bootloader.run.step);
 
+    var mcopy_step = std.Build.Step.init(.{ .name = "mcopy", .owner = b, .id = .custom });
+    mcopy_step.dependOn(&dd.step);
+    for (additional_files) |f| {
         const mcopy = b.addSystemCommand(&.{"mcopy"});
         mcopy.addPrefixedFileArg("-i", floppy.obj);
-    mcopy.addFileArg(kernel.obj);
-    mcopy.addArg("::kernel.bin");
-    mcopy.step.dependOn(&dd.step);
-    mcopy.step.dependOn(&kernel.run.step);
-
-    return mcopy;
+        switch (f.file) {
+            .runFile => |file| {
+                mcopy.addFileArg(file.obj);
+                mcopy_step.dependOn(&file.run.step);
+            },
+            .simpleFile => |file| mcopy.addFileArg(file),
+        }
+        mcopy.addArg(f.name);
+        mcopy_step.dependOn(&mcopy.step);
+    }
+    return mcopy_step;
 }
 
 // adapted from https://codeberg.org/raddari/zig-nasm-lib.git

build.zig.zon

@@ -28,7 +28,7 @@
 
     // Tracks the earliest Zig version that the package considers to be a
     // supported use case.
-    .minimum_zig_version = "0.14.1",
+    .minimum_zig_version = "0.15.0",
 
     // This field is optional.
     // Each dependency must either provide a `url` and `hash`, or a `path`.

src/initramfs.asm

@@ -2,8 +2,40 @@
 org 0x7C00
 bits 16
 
+
 %define ENDL 0x0D, 0x0A
 
+;
+; FAT12 Header
+;
+jmp short start
+nop
+
+bdb_oem:					db "mkfs.fat"
+bdb_bytes_per_sector:		dw 512
+bdb_sectors_per_cluster:	db 1
+bdb_reserved_sectors:		dw 1
+bdb_fat_count:				db 2
+bdb_dir_entries_count:		dw 0E0h
+bdb_total_sectors:			dw 2880
+bdb_media_descriptor_type:	db 0F0h
+bdb_sectors_per_fat:		dw 9
+bdb_sectors_per_track:		dw 18
+bdb_heads:					dw 2
+bdb_hidden_sectors:			dd 0
+bdb_large_sector_count:		dd 0
+
+; Extended boot record
+ebr_drive_number:			db 0
+							db 0
+ebr_signature:				db 29h
+ebr_volume_id:				db 68h, 6Fh, 6Dh, 6Fh
+ebr_volume_laber:			db 'zos disk   '
+ebr_system_id:				db 'FAT12   '
+
+
+
+
 start:
 	jmp main
 
@@ -47,16 +79,139 @@ main:
 	mov ss, ax
 	mov sp, 0x7C00	; stack grows downward from where we are loaded in memory
 
-	; print the hello world
-	mov si, msg_hello
+	mov si, msg_startup
 	call echo
 
+	mov si, msg_reading_from_disk
+	call echo
+	mov [ebr_drive_number], dl
+
+	mov ax, 1								; second sector from disk
+	mov cl, 1								; 1 sector to read
+	mov bx, 0x7E00							; data should be after the bootloader
+	call disk_read
+
+	cli
+	hlt
+
+; errors
+
+floppy_error:
+	mov si, msg_read_failed
+	call echo
+	jmp .wait_and_reboot
+
+.wait_and_reboot:
+	mov ah, 0
+	int 16h
+	
+	jmp 0FFFFh:0							; jump to start of bios, should reboot
+
 	hlt
 
 .halt:
+	cli										; disable interrupts, this way we shouldn't be able to get out of halt
+	hlt
 	jmp .halt
 
-msg_hello: db 'Hello, world!', ENDL, 0
+
+;
+; args: 
+;	ax = lba adress
+; return:
+; 	cx[0..5] = sector number
+; 	cx[6-15] = cilinder number
+; 	dh: head
+;
+lba_to_chs:
+	push ax
+	push dx
+
+	xor dx, dx								; clear dw
+	div word [bdb_sectors_per_track]		; ax = LBA / SectorsPerTrack
+											; dx = LBA % SectorsPerTrack
+
+	inc dx
+	mov cx, dx								; cx = sector
+
+	xor dx, dx								; clear dx
+	div word [bdb_heads]					; ax = (LBA / SectorsPerTrack) / Heads = cylinder
+	                                        ; dx = (LBA / SectorsPerTrack) % Heads = head
+	mov dh, dl
+	mov ch, al
+	shl ah, 6
+	or cl, ah								; put upper 2 bits of cylinder in CL
+
+	pop ax
+	mov dl, al
+	pop ax
+
+	ret
+
+
+;
+; args:
+;	ax = LBA adress
+;	cl = number of sectors to read
+;	dl = drive number
+;	es:bx = pointer to where to store the data
+;
+
+disk_read:
+	push ax
+	push bx
+	push cx
+	push dx
+	push di
+
+	push cx									; cx will be overridden
+	call lba_to_chs
+	pop ax									; al = number of sectors to read
+	mov ah, 02h
+	mov di, 3								; hoe many times to try
+
+.retry:
+	pusha
+	stc										; set carry flag
+	int 13h									; if no carry flag => it work
+
+	jnc .done
+
+	; read fail
+	popa
+	call disk_reset
+	dec di
+
+	test di, di
+	jnz .retry
+
+.fail:
+	jmp floppy_error
+
+.done:
+	popa
+	
+	pop di
+	pop dx
+	pop cx
+	pop bx
+	pop ax
+	ret
+
+; arg: dl = drive number
+
+disk_reset:
+	pusha
+	mov ah, 0
+	stc										; set carry
+	int 13h	
+	jc floppy_error
+	popa
+	ret
+
+msg_startup: 								db 'starting zos, please hold while we check for any problems', ENDL, 0
+msg_reading_from_disk:						db 'testing reading from disk', ENDL, 0
+msg_read_failed:							db 'error when trying to read from floppy', ENDL, 0
 
 times 510-($-$$) db 0
 dw 0AA55h

src/reference_implementations/fat.zig

@@ -0,0 +1,117 @@
+const std = @import("std");
+
+const Errors = error{ InvalidSyntax, ReadSectors, FileNotFound };
+
+var buffer: [1024]u8 = undefined;
+
+var g_Fat: []u8 = undefined;
+
+const BootSector = extern struct {
+    BootJumpInstruction: [3]u8 align(1),
+    OemIdentifier: [8]u8 align(1),
+    BytesPerSector: u16 align(1),
+    SectorsPerCluster: u8 align(1),
+    ReservedSectors: u16 align(1),
+    FatCount: u8 align(1),
+    DirEntryCount: u16 align(1),
+    TotalSectors: u16 align(1),
+    MediaDescriptorType: u8 align(1),
+    SectorsPerFat: u16 align(1),
+    SectorsPerTrack: u16 align(1),
+    Heads: u16 align(1),
+    HiddenSectors: u32 align(1),
+    LargeSectorCount: u32 align(1),
+
+    // ebr
+    DriveNumber: u8 align(1),
+    _Reserved: u8 align(1),
+    Signature: u8 align(1),
+    VolumeId: u32 align(1),
+    VolumeLaber: [11]u8 align(1),
+    SystemId: [8]u8 align(1),
+};
+
+var g_BootSector: BootSector = undefined;
+
+const DirectoryEntry = extern struct {
+    Name: [11]u8 align(1),
+    Attributes: u8 align(1),
+    _Reserved: u8 align(1),
+    CreatedTimeTenths: u8 align(1),
+    CreatedTime: u16 align(1),
+    CreatedDate: u16 align(1),
+    AccessedDate: u16 align(1),
+    FirstClusterHigh: u16 align(1),
+    ModifiedTime: u16 align(1),
+    ModifiedDate: u16 align(1),
+    FirstClusterLow: u16 align(1),
+    Size: u32 align(1),
+};
+
+var g_RootDirectory: []DirectoryEntry = undefined;
+
+fn readStruct(reader: *std.fs.File.Reader, T: type) !T {
+    var ret: [@sizeOf(T)]u8 = undefined;
+    _ = try reader.*.read(&ret);
+    return @bitCast(ret);
+}
+
+fn readBootSector(disk: *std.fs.File) !void {
+    var reader = disk.*.reader(&buffer);
+    g_BootSector = try readStruct(&reader, BootSector);
+}
+
+fn readSectors(disk: *std.fs.File, lba: u32, count: u32, bufferOut: *[]anyopaque) !void {
+    const dest: []u8 = try std.heap.smp_allocator.alloc(u8, g_BootSector.BytesPerSector * count);
+    defer std.heap.smp_allocator.free(dest);
+    var stream = disk.readerStreaming(&buffer);
+    try stream.seekTo(lba * g_BootSector.BytesPerSector);
+    if (try stream.readStreaming(dest) != g_BootSector.BytesPerSector * count) return Errors.ReadSectors;
+    @memcpy(@as(*[]u8, @ptrCast(bufferOut)).*, dest);
+}
+
+fn readFat(disk: *std.fs.File) !void {
+    g_Fat = try std.heap.smp_allocator.alloc(u8, g_BootSector.SectorsPerFat * g_BootSector.BytesPerSector);
+    errdefer std.heap.smp_allocator.free(g_Fat);
+    try readSectors(disk, g_BootSector.ReservedSectors, g_BootSector.SectorsPerFat, &g_Fat);
+}
+
+fn readRootDirectory(disk: std.fs.File) !void {
+    const lba: u32 = g_BootSector.ReservedSectors + g_BootSector.SectorsPerFat + g_BootSector.FatCount;
+    const size: u32 = @sizeOf(DirectoryEntry) * g_BootSector.DirEntryCount;
+    const sectors: u32 = (size / g_BootSector.BytesPerSector);
+    if (@rem(size, g_BootSector.BytesPerSector > 0))
+        sectors += 1;
+
+    g_RootDirectory = try std.heap.smp_allocator.alloc(DirectoryEntry, sectors * g_BootSector.BytesPerSector);
+    errdefer std.heap.smp_allocator.free(g_RootDirectory);
+    try readSectors(disk, lba, sectors, &g_RootDirectory);
+}
+
+fn findFile(name: []const u8) !*DirectoryEntry {
+    for (g_RootDirectory, 0..) |Entry, i|
+        if (std.mem.eql(u8, Entry.Name, name))
+            return &g_RootDirectory[i];
+    return Errors.FileNotFound;
+}
+
+pub fn main() !void {
+    if (std.os.argv.len < 3) {
+        std.log.err("syntax: {s} <disk image> <file name>", .{std.os.argv[0]});
+        return Errors.InvalidSyntax;
+    }
+
+    var disk = try std.fs.cwd().openFileZ(std.os.argv[1], .{ .mode = .read_only });
+
+    _ = &disk;
+    try readBootSector(&disk);
+
+    try readFat(&disk);
+    defer std.heap.smp_allocator.free(g_Fat);
+
+    try readRootDirectory(disk);
+    defer std.heap.smp_allocator.free(g_RootDirectory);
+
+    const fileEntry = try findFile(std.os.argv[2]);
+    _ = fileEntry;
+}

src/reference_implementations/test.txt

@@ -0,0 +1,3 @@
+testing file
+aabaacaadaaeaafaagaahaaiaajaakaalaamaanaaoaapaaqaaraasaataauaavaawaaxaayaaz
+tstngfl