initramfs -> bootloader, kernel can now be loaded, FAT can now be looked
at throug reference implementation
This commit is contained in:
parent
c7ec508dba
commit
e1926aec8a
5 changed files with 495 additions and 316 deletions
83
build.zig
83
build.zig
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@ -1,12 +1,13 @@
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const std = @import("std");
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const std = @import("std");
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const LazyPath = std.Build.LazyPath;
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// Although this function looks imperative, note that its job is to
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// Although this function looks imperative, note that its job is to
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// declaratively construct a build graph that will be executed by an external
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// declaratively construct a build graph that will be executed by an external
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// runner.
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// runner.
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pub fn build(b: *std.Build) void {
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pub fn build(b: *std.Build) void {
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const initramfs = addNasmFiles(b, AddNasmFilesOptions{
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const bootloader = addNasmFiles(b, AddNasmFilesOptions{
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.filename = "src/initramfs.asm",
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.filename = "src/bootloader.asm",
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.outputname = "initramfs.bin",
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.outputname = "bootloader.bin",
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.flags = &.{"-f bin"},
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.flags = &.{"-f bin"},
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});
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});
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const kernel = addNasmFiles(b, AddNasmFilesOptions{
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const kernel = addNasmFiles(b, AddNasmFilesOptions{
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@ -15,16 +16,16 @@ pub fn build(b: *std.Build) void {
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.flags = &.{"-f bin"},
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.flags = &.{"-f bin"},
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});
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});
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var floppy = createFloppy(b, "main_floppy.img");
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const floppy = createFloppy(b, "main_floppy.img");
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floppy.run = formatFloppyFat12(b, floppy);
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formatFloppyFat12(b, floppy);
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var installToFloppy = installImgToFloppy(b, floppy, initramfs, &.{
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var installToFloppy = installImgToFloppy(b, floppy, bootloader, &.{
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NamedFile{ .file = .{ .runFile = kernel }, .name = "::kernel.bin" },
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NamedFile{ .file = kernel, .name = "::kernel.bin" },
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NamedFile{ .file = .{ .simpleFile = b.path("src/reference_implementations/test.txt") }, .name = "::test.txt" },
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NamedFile{ .file = b.path("src/reference_implementations/test.txt"), .name = "::test.txt" },
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});
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});
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const img_install = b.addInstallBinFile(floppy.obj, "main_floppy.img");
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const img_install = b.addInstallBinFile(floppy, "main_floppy.img");
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img_install.step.dependOn(&installToFloppy);
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img_install.step.dependOn(&installToFloppy.step);
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b.getInstallStep().dependOn(&img_install.step);
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b.getInstallStep().dependOn(&img_install.step);
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@ -35,8 +36,7 @@ pub fn build(b: *std.Build) void {
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.link_libc = true,
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.link_libc = true,
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});
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});
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const run = b.addSystemCommand(&.{ "qemu-system-i386", "-fda" });
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const run = b.addSystemCommand(&.{ "qemu-system-i386", "-fda", "zig-out/bin/main_floppy.img" });
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run.addFileArg(floppy.obj);
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const run_step = b.step("run", "run the os in qemu");
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const run_step = b.step("run", "run the os in qemu");
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run_step.dependOn(&run.step);
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run_step.dependOn(&run.step);
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@ -60,66 +60,45 @@ const AddNasmFilesOptions = struct {
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flags: []const []const u8 = &.{},
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flags: []const []const u8 = &.{},
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};
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};
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const NasmFile = struct {
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run: *std.Build.Step.Run,
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obj: std.Build.LazyPath,
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};
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const Floppydisk = NasmFile;
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const NamedFile = struct {
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const NamedFile = struct {
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file: union(enum) { runFile: NasmFile, simpleFile: std.Build.LazyPath },
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file: std.Build.LazyPath,
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name: []const u8,
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name: []const u8,
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};
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};
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fn createFloppy(b: *std.Build, name: []const u8) Floppydisk {
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fn createFloppy(b: *std.Build, name: []const u8) LazyPath {
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const dd = b.addSystemCommand(&.{ "dd", "if=/dev/zero" });
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const dd = b.addSystemCommand(&.{ "dd", "if=/dev/zero" });
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const Floppy = dd.addPrefixedOutputFileArg("of=", name);
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const Floppy = dd.addPrefixedOutputFileArg("of=", name);
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dd.has_side_effects = true;
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dd.addArgs(&.{ "bs=512", "count=2880" });
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dd.addArgs(&.{ "bs=512", "count=2880" });
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return Floppydisk{
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return Floppy;
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.run = dd,
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.obj = Floppy,
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};
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}
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}
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fn formatFloppyFat12(b: *std.Build, floppy: Floppydisk) *std.Build.Step.Run {
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fn formatFloppyFat12(b: *std.Build, floppy: LazyPath) void {
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const mkfs = b.addSystemCommand(&.{ "mkfs.fat", "-F12", "-nNBOS" });
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const mkfs = b.addSystemCommand(&.{ "mkfs.fat", "-F12", "-nNBOS" });
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mkfs.addFileArg(floppy.obj);
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mkfs.addFileArg(floppy);
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mkfs.step.dependOn(&floppy.run.step);
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return mkfs;
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}
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}
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fn installImgToFloppy(b: *std.Build, floppy: Floppydisk, bootloader: NasmFile, additional_files: []const NamedFile) std.Build.Step {
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fn installImgToFloppy(b: *std.Build, floppy: LazyPath, bootloader: LazyPath, additional_files: []const NamedFile) *std.Build.Step.Run {
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const dd = b.addSystemCommand(&.{"dd"});
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const dd = b.addSystemCommand(&.{"dd"});
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dd.addPrefixedFileArg("if=", bootloader.obj);
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dd.addPrefixedFileArg("if=", bootloader);
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dd.addPrefixedFileArg("of=", floppy.obj);
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dd.addPrefixedFileArg("of=", floppy);
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dd.addArg("conv=notrunc");
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dd.addArg("conv=notrunc");
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dd.step.dependOn(&floppy.run.step);
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dd.step.dependOn(&bootloader.run.step);
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var mcopy_step = std.Build.Step.init(.{ .name = "mcopy", .owner = b, .id = .custom });
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var last_step = dd;
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mcopy_step.dependOn(&dd.step);
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for (additional_files) |f| {
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for (additional_files) |f| {
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const mcopy = b.addSystemCommand(&.{"mcopy"});
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const mcopy = b.addSystemCommand(&.{"mcopy"});
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mcopy.addPrefixedFileArg("-i", floppy.obj);
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mcopy.addPrefixedFileArg("-i", floppy);
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switch (f.file) {
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mcopy.addFileArg(f.file);
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.runFile => |file| {
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mcopy.addFileArg(file.obj);
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mcopy_step.dependOn(&file.run.step);
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},
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.simpleFile => |file| mcopy.addFileArg(file),
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}
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mcopy.addArg(f.name);
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mcopy.addArg(f.name);
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mcopy_step.dependOn(&mcopy.step);
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mcopy.step.dependOn(&last_step.step);
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last_step = mcopy;
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}
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}
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return mcopy_step;
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return last_step;
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}
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}
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// adapted from https://codeberg.org/raddari/zig-nasm-lib.git
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// adapted from https://codeberg.org/raddari/zig-nasm-lib.git
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fn addNasmFiles(b: *std.Build, options: AddNasmFilesOptions) NasmFile {
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fn addNasmFiles(b: *std.Build, options: AddNasmFilesOptions) LazyPath {
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std.debug.assert(!std.fs.path.isAbsolute(options.filename));
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std.debug.assert(!std.fs.path.isAbsolute(options.filename));
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const src_file = b.path(options.filename);
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const src_file = b.path(options.filename);
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const output = options.outputname orelse b.fmt("{s}.o", .{std.mem.sliceTo(options.filename, '.')});
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const output = options.outputname orelse b.fmt("{s}.o", .{std.mem.sliceTo(options.filename, '.')});
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@ -129,9 +108,7 @@ fn addNasmFiles(b: *std.Build, options: AddNasmFilesOptions) NasmFile {
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nasm.addPrefixedDirectoryArg("-i", b.path("src"));
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nasm.addPrefixedDirectoryArg("-i", b.path("src"));
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const obj = nasm.addPrefixedOutputFileArg("-o", output);
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const obj = nasm.addPrefixedOutputFileArg("-o", output);
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nasm.addFileArg(src_file);
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nasm.addFileArg(src_file);
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nasm.has_side_effects = true;
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return .{
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return obj;
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.run = nasm,
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.obj = obj,
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};
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}
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}
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381
src/bootloader.asm
Normal file
381
src/bootloader.asm
Normal file
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@ -0,0 +1,381 @@
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; vim: ft=nasm
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org 0x7C00
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bits 16
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%define ENDL 0x0D, 0x0A
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;
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; FAT12 Header
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;
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jmp short start
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nop
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bdb_oem: db "mkfs.fat" ; 8 bytes
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bdb_bytes_per_sector: dw 512
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bdb_sectors_per_cluster: db 1
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bdb_reserved_sectors: dw 1
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bdb_fat_count: db 2
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bdb_dir_entries_count: dw 0E0h
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bdb_total_sectors: dw 2880 ; 2880 * 512 = 1.44MB
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bdb_media_descriptor_type: db 0F0h ; F0 = 3.5" floppy disk
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bdb_sectors_per_fat: dw 9 ; 9 sectors/fat
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bdb_sectors_per_track: dw 18
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bdb_heads: dw 2
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bdb_hidden_sectors: dd 0
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bdb_large_sector_count: dd 0
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; Extended boot record
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ebr_drive_number: db 0 ; 0x00 floppy, 0x80 hdd, useless
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db 0 ; reserved
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ebr_signature: db 29h
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ebr_volume_id: db 68h, 6Fh, 6Dh, 6Fh ; serial number, value doesn't matter
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ebr_volume_label: db 'zos disk' ; 11 bytes, padded with spaces
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ebr_system_id: db 'FAT12 ' ; 8 bytes
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start:
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; setup data segments
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mov ax, 0 ; use ax as and intermediary as we can't write to es/ds directly
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mov ds, ax
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mov es, ax
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; setup stack
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mov ss, ax
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mov sp, 0x7C00 ; stack grows downward from where we are loaded in memory
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; some BIOS start us at 07C00:0000 instead of 0000:07C0, make sure we are in the right place
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push es
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push word .after
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retf
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.after:
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mov [ebr_drive_number], dl
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mov si, msg_loading
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call echo
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; read drive parameters (you never know)
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push es
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mov ah, 08h
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int 13h
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jc floppy_error
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pop es
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and cl, 0x3F ; remove top 2 bites
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xor ch, ch
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mov [bdb_sectors_per_track], cx ; sectors count
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inc dh
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mov [bdb_heads], dh ; head count
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; read FAT root directory
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; compute LBA of root directory = reserved + fats * sectors_per_fat
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mov ax, [bdb_sectors_per_fat]
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mov bl, [bdb_fat_count]
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xor bh, bh
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mul bx ; ax = fats * sectors_per_fat
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add ax, [bdb_reserved_sectors] ; ax = LBA of root dir
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push ax
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; compute size of root directory = (32 * number_of_entries) / bytes_per_sector
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mov ax, [bdb_dir_entries_count]
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shl ax, 5 ; ax *= 32
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xor dx, dx
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div word [bdb_bytes_per_sector] ; number of sectors we need to read
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test dx, dx ; if != 0 add 1
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jz .root_dir_after
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inc ax ; divistion reminder != 0, add 1
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.root_dir_after:
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; read root dir
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mov cl, al ; cl = number of sectors to read = size of root directory
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pop ax ; ax = LBA of root directory
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mov dl, [ebr_drive_number] ; dl = drive number (as saved previously)
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mov bx, buffer ; es:bx = buffer
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call disk_read
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; search for kernel.bin
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xor bx, bx
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mov di, buffer
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.search_kernel:
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mov si, file_kernel_bin
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mov cx, 11 ; compare up to 11 characters
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push di
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repe cmpsb ; repe: repeat until cx = 0
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; cmpsb: compare ds:si to es:di, they are also incremented or decremented based on a flag
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pop di
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je .found_kernel
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add di, 32
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inc bx
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cmp bx, [bdb_dir_entries_count]
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jl .search_kernel
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; kernel not found
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jmp kernel_not_found_error
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.found_kernel:
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; di should point to the adress of the entry
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mov ax, [di + 26] ; first logical cluster (offset 26)
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mov [kernel_cluster], ax
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; load FAT from disk into memory
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mov ax, [bdb_reserved_sectors]
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mov bx, buffer
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mov cl, [bdb_sectors_per_fat]
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mov dl, [ebr_drive_number]
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call disk_read
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; read kernel and process FAT chain
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mov bx, KERNEL_LOAD_SEGMENT
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mov es, bx
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mov bx, KERNEL_LOAD_OFFSET
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.load_kernel_loop:
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; read next cluster
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mov ax, [kernel_cluster]
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add ax, 31 ; tmp hardcoding ; first cluster = (kernel_cluster - 2) * sectors_per_cluster + start_sector
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; start_sector = reserved + fats + root_directory_size = 1 + 18 + 134 = 33
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mov cl, 1
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mov dl, [ebr_drive_number]
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call disk_read
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; can overflow, risky!!!!
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add bx, [bdb_bytes_per_sector]
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; cumpute location of next cluster
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mov ax, [kernel_cluster]
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mov cx, 3
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mul cx
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mov cx, 2
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div cx ; ax = index of entry in FAT, dx = cluster mod 2
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mov si, buffer
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add si, ax
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mov ax, [ds:si] ; read entry from FAT table at index ax
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or dx, dx
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jz .even
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.odd:
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shr ax, 4
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jmp .next_cluster_after
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.even:
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and ax, 0x0FFF
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.next_cluster_after:
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cmp ax, 0x0FF8 ; end of chain
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jae .read_finish
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mov [kernel_cluster], ax
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jmp .load_kernel_loop
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.read_finish:
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; jump to kernel
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mov dl, [ebr_drive_number] ; boot device in dl
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mov ax, KERNEL_LOAD_SEGMENT ; set segment registers
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mov ds, ax
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mov es, ax
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jmp KERNEL_LOAD_SEGMENT:KERNEL_LOAD_OFFSET
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jmp wait_key_and_reboot ; should never happen
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cli
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hlt
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; errors
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floppy_error:
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mov si, msg_read_failed
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call echo
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jmp wait_key_and_reboot
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kernel_not_found_error:
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mov si, msg_kernel_not_found
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call echo
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||||||
|
jmp wait_key_and_reboot
|
||||||
|
|
||||||
|
wait_key_and_reboot:
|
||||||
|
mov ah, 0
|
||||||
|
int 16h ; wait for keypress
|
||||||
|
jmp 0FFFFh:0 ; jump to start of bios, should reboot
|
||||||
|
|
||||||
|
.halt:
|
||||||
|
cli ; disable interrupts, this way we shouldn't be able to get out of halt
|
||||||
|
hlt
|
||||||
|
|
||||||
|
|
||||||
|
;
|
||||||
|
; echo:
|
||||||
|
; print something to the screen
|
||||||
|
; - ds:si points to string
|
||||||
|
;
|
||||||
|
echo:
|
||||||
|
; save the registers we want to modify
|
||||||
|
push si
|
||||||
|
push ax
|
||||||
|
push bx
|
||||||
|
|
||||||
|
.loop:
|
||||||
|
lodsb ; load byte from ds:si to al
|
||||||
|
or al, al ; check if next char is null
|
||||||
|
jz .done
|
||||||
|
|
||||||
|
mov ah, 0x0E
|
||||||
|
mov bh, 0
|
||||||
|
int 0x10
|
||||||
|
|
||||||
|
jmp .loop
|
||||||
|
|
||||||
|
.done:
|
||||||
|
pop bx
|
||||||
|
pop ax
|
||||||
|
pop si
|
||||||
|
ret
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
|
;
|
||||||
|
; 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:
|
||||||
|
; all attempts exausted
|
||||||
|
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_loading: db 'starting zos', ENDL, 0
|
||||||
|
msg_read_failed: db 'error on floppy read', ENDL, 0
|
||||||
|
msg_kernel_not_found: db 'kernel.bin not found', ENDL, 0
|
||||||
|
file_kernel_bin: db 'KERNEL BIN'
|
||||||
|
kernel_cluster: dw 0
|
||||||
|
|
||||||
|
KERNEL_LOAD_SEGMENT equ 0x2000
|
||||||
|
KERNEL_LOAD_OFFSET equ 0
|
||||||
|
|
||||||
|
|
||||||
|
times 510-($-$$) db 0
|
||||||
|
dw 0AA55h
|
||||||
|
|
||||||
|
buffer:
|
||||||
|
|
@ -1,217 +0,0 @@
|
||||||
; vim: ft=nasm
|
|
||||||
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
|
|
||||||
|
|
||||||
;
|
|
||||||
; echo:
|
|
||||||
; print something to the screen
|
|
||||||
; - ds:si points to string
|
|
||||||
;
|
|
||||||
echo:
|
|
||||||
; save the registers we want to modify
|
|
||||||
push si
|
|
||||||
push ax
|
|
||||||
push bx
|
|
||||||
|
|
||||||
mov ah, 0xe
|
|
||||||
mov bh, 0
|
|
||||||
|
|
||||||
.loop:
|
|
||||||
lodsb ; load byte from ds:si to al
|
|
||||||
or al, al ; check if next char is null
|
|
||||||
jz .done
|
|
||||||
|
|
||||||
int 0x10
|
|
||||||
jmp .loop
|
|
||||||
|
|
||||||
.done:
|
|
||||||
pop bx
|
|
||||||
pop ax
|
|
||||||
pop si
|
|
||||||
ret
|
|
||||||
|
|
||||||
main:
|
|
||||||
|
|
||||||
; setup data segments
|
|
||||||
; use ax as and intermediary as we can't write to es/ds directly
|
|
||||||
mov ax, 0
|
|
||||||
mov ds, ax
|
|
||||||
mov es, ax
|
|
||||||
|
|
||||||
; setup stack
|
|
||||||
mov ss, ax
|
|
||||||
mov sp, 0x7C00 ; stack grows downward from where we are loaded in memory
|
|
||||||
|
|
||||||
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
|
|
||||||
|
|
||||||
|
|
||||||
;
|
|
||||||
; 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
|
|
||||||
|
|
@ -1,13 +1,18 @@
|
||||||
; vim: ft=nasm
|
; vim: ft=nasm
|
||||||
org 0x7C00
|
org 0x0
|
||||||
bits 16
|
bits 16
|
||||||
|
|
||||||
%define ENDL 0x0D, 0x0A
|
%define ENDL 0x0D, 0x0A
|
||||||
|
|
||||||
start:
|
start:
|
||||||
jmp main
|
; ; print hello world message
|
||||||
|
mov si, msg_hello
|
||||||
|
call echo
|
||||||
|
|
||||||
|
.halt:
|
||||||
|
cli
|
||||||
|
hlt
|
||||||
|
|
||||||
;
|
|
||||||
; echo:
|
; echo:
|
||||||
; print something to the screen
|
; print something to the screen
|
||||||
; - ds:si points to string
|
; - ds:si points to string
|
||||||
|
|
@ -35,28 +40,5 @@ echo:
|
||||||
pop si
|
pop si
|
||||||
ret
|
ret
|
||||||
|
|
||||||
main:
|
|
||||||
|
|
||||||
; setup data segments
|
|
||||||
; use ax as and intermediary as we can't write to es/ds directly
|
|
||||||
mov ax, 0
|
|
||||||
mov ds, ax
|
|
||||||
mov es, ax
|
|
||||||
|
|
||||||
; setup stack
|
|
||||||
mov ss, ax
|
|
||||||
mov sp, 0x7C00 ; stack grows downward from where we are loaded in memory
|
|
||||||
|
|
||||||
; print the hello world
|
|
||||||
mov si, msg_hello
|
|
||||||
call echo
|
|
||||||
|
|
||||||
hlt
|
|
||||||
|
|
||||||
.halt:
|
|
||||||
jmp .halt
|
|
||||||
|
|
||||||
msg_hello: db 'Hello, world!', ENDL, 0
|
msg_hello: db 'Hello, world!', ENDL, 0
|
||||||
|
|
||||||
times 510-($-$$) db 0
|
|
||||||
dw 0AA55h
|
|
||||||
|
|
|
||||||
|
|
@ -6,6 +6,10 @@ var buffer: [1024]u8 = undefined;
|
||||||
|
|
||||||
var g_Fat: []u8 = undefined;
|
var g_Fat: []u8 = undefined;
|
||||||
|
|
||||||
|
pub const std_options: std.Options = .{
|
||||||
|
.log_level = .info,
|
||||||
|
};
|
||||||
|
|
||||||
const BootSector = extern struct {
|
const BootSector = extern struct {
|
||||||
BootJumpInstruction: [3]u8 align(1),
|
BootJumpInstruction: [3]u8 align(1),
|
||||||
OemIdentifier: [8]u8 align(1),
|
OemIdentifier: [8]u8 align(1),
|
||||||
|
|
@ -49,10 +53,11 @@ const DirectoryEntry = extern struct {
|
||||||
};
|
};
|
||||||
|
|
||||||
var g_RootDirectory: []DirectoryEntry = undefined;
|
var g_RootDirectory: []DirectoryEntry = undefined;
|
||||||
|
var g_RootDirectoryEnd: u32 = undefined;
|
||||||
|
|
||||||
fn readStruct(reader: *std.fs.File.Reader, T: type) !T {
|
fn readStruct(reader: *std.fs.File.Reader, T: type) !T {
|
||||||
var ret: [@sizeOf(T)]u8 = undefined;
|
var ret: [@sizeOf(T)]u8 = undefined;
|
||||||
_ = try reader.*.read(&ret);
|
_ = try reader.*.readStreaming(&ret);
|
||||||
return @bitCast(ret);
|
return @bitCast(ret);
|
||||||
}
|
}
|
||||||
|
|
||||||
|
|
@ -61,13 +66,13 @@ fn readBootSector(disk: *std.fs.File) !void {
|
||||||
g_BootSector = try readStruct(&reader, BootSector);
|
g_BootSector = try readStruct(&reader, BootSector);
|
||||||
}
|
}
|
||||||
|
|
||||||
fn readSectors(disk: *std.fs.File, lba: u32, count: u32, bufferOut: *[]anyopaque) !void {
|
fn readSectors(disk: *std.fs.File, lba: u32, count: u32, bufferOut: *[]u8) !void {
|
||||||
const dest: []u8 = try std.heap.smp_allocator.alloc(u8, g_BootSector.BytesPerSector * count);
|
const dest: []u8 = try std.heap.smp_allocator.alloc(u8, g_BootSector.BytesPerSector * count);
|
||||||
defer std.heap.smp_allocator.free(dest);
|
defer std.heap.smp_allocator.free(dest);
|
||||||
var stream = disk.readerStreaming(&buffer);
|
try disk.seekTo(lba * g_BootSector.BytesPerSector);
|
||||||
try stream.seekTo(lba * g_BootSector.BytesPerSector);
|
var reader = disk.readerStreaming(&buffer);
|
||||||
if (try stream.readStreaming(dest) != g_BootSector.BytesPerSector * count) return Errors.ReadSectors;
|
if (try reader.readStreaming(dest) != g_BootSector.BytesPerSector * count) return Errors.ReadSectors;
|
||||||
@memcpy(@as(*[]u8, @ptrCast(bufferOut)).*, dest);
|
@memcpy(bufferOut.*, dest);
|
||||||
}
|
}
|
||||||
|
|
||||||
fn readFat(disk: *std.fs.File) !void {
|
fn readFat(disk: *std.fs.File) !void {
|
||||||
|
|
@ -76,42 +81,93 @@ fn readFat(disk: *std.fs.File) !void {
|
||||||
try readSectors(disk, g_BootSector.ReservedSectors, g_BootSector.SectorsPerFat, &g_Fat);
|
try readSectors(disk, g_BootSector.ReservedSectors, g_BootSector.SectorsPerFat, &g_Fat);
|
||||||
}
|
}
|
||||||
|
|
||||||
fn readRootDirectory(disk: std.fs.File) !void {
|
fn readRootDirectory(disk: *std.fs.File) !void {
|
||||||
const lba: u32 = g_BootSector.ReservedSectors + g_BootSector.SectorsPerFat + g_BootSector.FatCount;
|
const lba: u32 = g_BootSector.ReservedSectors + g_BootSector.SectorsPerFat * g_BootSector.FatCount;
|
||||||
const size: u32 = @sizeOf(DirectoryEntry) * g_BootSector.DirEntryCount;
|
const size: u32 = @sizeOf(DirectoryEntry) * g_BootSector.DirEntryCount;
|
||||||
const sectors: u32 = (size / g_BootSector.BytesPerSector);
|
var sectors: u32 = (size / g_BootSector.BytesPerSector);
|
||||||
if (@rem(size, g_BootSector.BytesPerSector > 0))
|
if (@rem(size, g_BootSector.BytesPerSector) > 0)
|
||||||
sectors += 1;
|
sectors += 1;
|
||||||
|
|
||||||
g_RootDirectory = try std.heap.smp_allocator.alloc(DirectoryEntry, sectors * g_BootSector.BytesPerSector);
|
g_RootDirectory = try std.heap.smp_allocator.alloc(DirectoryEntry, sectors * g_BootSector.BytesPerSector);
|
||||||
errdefer std.heap.smp_allocator.free(g_RootDirectory);
|
g_RootDirectoryEnd = lba + sectors;
|
||||||
try readSectors(disk, lba, sectors, &g_RootDirectory);
|
try readSectors(disk, lba, sectors, @ptrCast(&g_RootDirectory));
|
||||||
|
for (g_RootDirectory) |Entry| {
|
||||||
|
std.log.debug("Entry: {any}, Entry.Name: {s}", .{
|
||||||
|
Entry, Entry.Name,
|
||||||
|
});
|
||||||
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
fn findFile(name: []const u8) !*DirectoryEntry {
|
fn findFile(name: []const u8) !*DirectoryEntry {
|
||||||
for (g_RootDirectory, 0..) |Entry, i|
|
for (g_RootDirectory, 0..) |Entry, i| {
|
||||||
if (std.mem.eql(u8, Entry.Name, name))
|
std.log.debug("looking at {s}", .{Entry.Name});
|
||||||
|
if (std.mem.eql(u8, &Entry.Name, name))
|
||||||
return &g_RootDirectory[i];
|
return &g_RootDirectory[i];
|
||||||
|
}
|
||||||
return Errors.FileNotFound;
|
return Errors.FileNotFound;
|
||||||
}
|
}
|
||||||
|
|
||||||
|
fn readFile(file: *DirectoryEntry, disk: *std.fs.File, outputBuffer: *[]u8) !void {
|
||||||
|
var currentCluster: u16 = file.FirstClusterLow;
|
||||||
|
const offset = g_BootSector.SectorsPerCluster * g_BootSector.BytesPerSector;
|
||||||
|
var i: usize = 0;
|
||||||
|
|
||||||
|
while (currentCluster < 0x0FF8) {
|
||||||
|
std.log.debug("currentCluster: {}", .{currentCluster});
|
||||||
|
const lba: u32 = g_RootDirectoryEnd + (currentCluster -% 2) * g_BootSector.SectorsPerCluster;
|
||||||
|
var sizedOutput = outputBuffer.*[i .. i + offset];
|
||||||
|
try readSectors(disk, lba, g_BootSector.SectorsPerCluster, &sizedOutput);
|
||||||
|
std.log.debug("sizedOutput: {s}", .{sizedOutput});
|
||||||
|
i += offset;
|
||||||
|
|
||||||
|
const fatindex = currentCluster * 3 / 2;
|
||||||
|
|
||||||
|
std.log.debug("@as(u16, g_Fat[fatindex]): {}, g_Fat[fatindex]: {}", .{ @as(*align(1) u16, @ptrCast(&g_Fat[fatindex])).*, g_Fat[fatindex] });
|
||||||
|
if (@rem(currentCluster, 2) == 0) {
|
||||||
|
currentCluster = @as(*align(1) u16, @ptrCast(&g_Fat[fatindex])).* & 0x0FFF;
|
||||||
|
} else {
|
||||||
|
currentCluster = @as(*align(1) u16, @ptrCast(&g_Fat[fatindex])).* >> 4;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
pub fn main() !void {
|
pub fn main() !void {
|
||||||
if (std.os.argv.len < 3) {
|
var args = try std.process.argsWithAllocator(std.heap.smp_allocator);
|
||||||
|
defer args.deinit();
|
||||||
|
if (args.inner.count < 3) {
|
||||||
std.log.err("syntax: {s} <disk image> <file name>", .{std.os.argv[0]});
|
std.log.err("syntax: {s} <disk image> <file name>", .{std.os.argv[0]});
|
||||||
return Errors.InvalidSyntax;
|
return Errors.InvalidSyntax;
|
||||||
}
|
}
|
||||||
|
|
||||||
var disk = try std.fs.cwd().openFileZ(std.os.argv[1], .{ .mode = .read_only });
|
_ = args.skip();
|
||||||
|
|
||||||
|
var disk = try std.fs.cwd().openFileZ(args.next().?, .{ .mode = .read_only });
|
||||||
|
std.log.debug("opened disk {any}", .{disk});
|
||||||
|
|
||||||
_ = &disk;
|
|
||||||
try readBootSector(&disk);
|
try readBootSector(&disk);
|
||||||
|
std.log.debug("read BootSector from disk, {any}", .{g_BootSector});
|
||||||
|
|
||||||
try readFat(&disk);
|
try readFat(&disk);
|
||||||
defer std.heap.smp_allocator.free(g_Fat);
|
defer std.heap.smp_allocator.free(g_Fat);
|
||||||
|
std.log.debug("read file allocation table from disk, {any}", .{g_Fat});
|
||||||
|
|
||||||
try readRootDirectory(disk);
|
try readRootDirectory(&disk);
|
||||||
defer std.heap.smp_allocator.free(g_RootDirectory);
|
defer std.heap.smp_allocator.free(g_RootDirectory);
|
||||||
|
std.log.debug("read root directory from disk, {any}", .{g_RootDirectory});
|
||||||
|
|
||||||
const fileEntry = try findFile(std.os.argv[2]);
|
const fileEntry = try findFile(try std.fmt.allocPrint(std.heap.smp_allocator, "{s}", .{args.next().?}));
|
||||||
_ = fileEntry;
|
|
||||||
|
var fileBuffer = try std.heap.smp_allocator.alloc(u8, fileEntry.Size + g_BootSector.BytesPerSector);
|
||||||
|
@memset(fileBuffer, 0);
|
||||||
|
defer std.heap.smp_allocator.free(fileBuffer);
|
||||||
|
|
||||||
|
try readFile(fileEntry, &disk, &fileBuffer);
|
||||||
|
const stdout = std.fs.File.stdout();
|
||||||
|
defer stdout.close();
|
||||||
|
var writer = stdout.writer(&buffer);
|
||||||
|
try writer.interface.print("{s}\n", .{@as(*[:0]u8, @ptrCast(&fileBuffer)).*});
|
||||||
|
|
||||||
|
const newline = "\n";
|
||||||
|
_ = try std.posix.write(0, fileBuffer);
|
||||||
|
_ = try std.posix.write(0, newline);
|
||||||
}
|
}
|
||||||
|
|
|
||||||
Loading…
Add table
Add a link
Reference in a new issue