commit 2be6a19907a081b3489323b6bc3cb6cee478f169
parent 563bbf8e88826492dedd0b6e728264a214ff8d95
Author: Sylvia Ivory <git@sivory.net>
Date: Tue, 10 Mar 2026 14:48:40 -0700
Move MBR into separate file
Diffstat:
4 files changed, 155 insertions(+), 148 deletions(-)
diff --git a/pi/fs/fat.zig b/pi/fs/fat.zig
@@ -10,153 +10,6 @@ pub const Error =
pub const Sector = vfs.Sector;
pub const Disk = vfs.Disk;
-pub const MasterBootRecord = packed struct(Sector) {
- // 446 bytes
- // Zig doesn't allow arrays in packed
- // u8[446]
- boot_code: u3568,
- pte1: PartitionTableEntry,
- pte2: PartitionTableEntry,
- pte3: PartitionTableEntry,
- pte4: PartitionTableEntry,
- // 0xAA55
- signature: u16,
-
- const Self = @This();
-
- pub fn get_partition(self: *const Self, n: u2) *const PartitionTableEntry {
- return switch (n) {
- 0 => &self.pte1,
- 1 => &self.pte2,
- 2 => &self.pte3,
- 3 => &self.pte4,
- };
- }
-
- pub fn is_valid(self: *const Self) bool {
- return self.signature == 0xAA55;
- }
-
- pub fn debug_print(self: *const Self, w: *std.io.Writer) !void {
- var boot_code: [446]u8 = undefined;
- std.mem.writeInt(u3568, &boot_code, self.boot_code, .little);
- const crc32 = std.hash.Crc32.hash(&boot_code);
-
- try w.print(
- \\bootcode crc32 = 0x{X}
- \\signature = 0x{X}
- \\
- , .{
- crc32,
- self.signature,
- });
-
- // Copy to proper alignment
- var pte = self.pte1;
- try w.print("Partition 1:\n", .{});
- try pte.debug_print(w);
-
- pte = self.pte2;
- try w.print("Partition 2:\n", .{});
- try pte.debug_print(w);
-
- pte = self.pte3;
- try w.print("Partition 3:\n", .{});
- try pte.debug_print(w);
-
- pte = self.pte4;
- try w.print("Partition 4:\n", .{});
- try pte.debug_print(w);
- }
-};
-
-pub const PartitionTableEntry = packed struct(u128) {
- pub const Status = packed struct(u8) {
- _reserved: u7,
- bootable: bool,
- };
-
- status: Status,
- chs_start: u24,
- partition_type: u8,
- chs_end: u24,
- first_lba: u32,
- number_sectors: u32,
-
- const Self = @This();
-
- pub fn is_fat32(self: *const Self) bool {
- return self.partition_type == 0x0B or self.partition_type == 0x0C;
- }
-
- pub fn is_empty(self: *const Self) bool {
- return std.mem.allEqual(u8, @ptrCast(self), 0x00);
- }
-
- pub fn partition_type_str(self: *const Self) []const u8 {
- return switch (self.partition_type) {
- 0x00 => "Empty",
- 0x01 => "FAT12 - CHS",
- 0x04 => "FAT16 - 16-32 MB - CHS",
- 0x05 => "Microsoft Extended - CHS",
- 0x06 => "FAT16 - 32 MB-2 GB - CHS",
- 0x07 => "NTFS",
- 0x0B => "FAT32 - CHS",
- 0x0C => "FAT32 - LBA",
- 0x0E => "FAT16 - 32 MB-2 GB - LBA",
- 0x0F => "Microsoft Extended - LBA",
- 0x11 => "Hidden FAT12 - CHS",
- 0x14 => "Hidden FAT16 - 16-32 MB - CHS",
- 0x16 => "Hidden FAT16 - 32 MB-2 GB - CHS",
- 0x1b => "Hidden FAT32 - CHS",
- 0x1c => "Hidden FAT32 - LBA",
- 0x1e => "Hidden FAT16 - 32 MB-2 GB - LBA",
- 0x42 => "Microsoft MBR - Dynamic Disk",
- 0x82 => "Solaris x86 OR Linux Swap",
- 0x83 => "Linux",
- 0x84 => "Hibernation",
- 0x85 => "Linux Extended",
- 0x86 => "NTFS Volume Set",
- 0x87 => "NTFS Volume Set",
- 0xa0 => "Hibernation",
- 0xa1 => "Hibernation",
- 0xa5 => "FreeBSD",
- 0xa6 => "OpenBSD",
- 0xa8 => "Mac OSX",
- 0xa9 => "NetBSD",
- 0xab => "Mac OSX Boot",
- 0xb7 => "BSDI",
- 0xb8 => "BSDI swap",
- 0xee => "EFI GPT Disk",
- 0xef => "EFI System Partition",
- 0xfb => "Vmware File System",
- 0xfc => "Vmware swap",
- else => "Unknown",
- };
- }
-
- pub fn debug_print(self: *const Self, w: *std.io.Writer) !void {
- try w.print(
- \\ bootable = {any}
- \\ chs_start = 0x{X}
- \\ partition_type = 0x{X} ({s})
- \\ chs_end = 0X{X}
- \\ lba_start = 0x{X}
- \\ number sectors = {d} ({B})
- \\
- , .{
- self.status.bootable,
- self.chs_start,
- self.partition_type,
- self.partition_type_str(),
- self.chs_end,
- self.first_lba,
- self.number_sectors,
- @as(u64, self.number_sectors) * 512,
- });
- }
-};
-
pub const Fat32BootSector = packed struct(Sector) {
// u8[3]
asm_code: u24,
diff --git a/pi/fs/mbr.zig b/pi/fs/mbr.zig
@@ -0,0 +1,153 @@
+const std = @import("std");
+
+pub const vfs = @import("./vfs.zig");
+
+pub const Sector = vfs.Sector;
+pub const Disk = vfs.Disk;
+
+pub const MasterBootRecord = packed struct(Sector) {
+ // 446 bytes
+ // Zig doesn't allow arrays in packed
+ // u8[446]
+ boot_code: u3568,
+ pte1: PartitionTableEntry,
+ pte2: PartitionTableEntry,
+ pte3: PartitionTableEntry,
+ pte4: PartitionTableEntry,
+ // 0xAA55
+ signature: u16,
+
+ const Self = @This();
+
+ pub fn get_partition(self: *const Self, n: u2) *const PartitionTableEntry {
+ return switch (n) {
+ 0 => &self.pte1,
+ 1 => &self.pte2,
+ 2 => &self.pte3,
+ 3 => &self.pte4,
+ };
+ }
+
+ pub fn is_valid(self: *const Self) bool {
+ return self.signature == 0xAA55;
+ }
+
+ pub fn debug_print(self: *const Self, w: *std.io.Writer) !void {
+ var boot_code: [446]u8 = undefined;
+ std.mem.writeInt(u3568, &boot_code, self.boot_code, .little);
+ const crc32 = std.hash.Crc32.hash(&boot_code);
+
+ try w.print(
+ \\bootcode crc32 = 0x{X}
+ \\signature = 0x{X}
+ \\
+ , .{
+ crc32,
+ self.signature,
+ });
+
+ // Copy to proper alignment
+ var pte = self.pte1;
+ try w.print("Partition 1:\n", .{});
+ try pte.debug_print(w);
+
+ pte = self.pte2;
+ try w.print("Partition 2:\n", .{});
+ try pte.debug_print(w);
+
+ pte = self.pte3;
+ try w.print("Partition 3:\n", .{});
+ try pte.debug_print(w);
+
+ pte = self.pte4;
+ try w.print("Partition 4:\n", .{});
+ try pte.debug_print(w);
+ }
+};
+
+pub const PartitionTableEntry = packed struct(u128) {
+ pub const Status = packed struct(u8) {
+ _reserved: u7,
+ bootable: bool,
+ };
+
+ status: Status,
+ chs_start: u24,
+ partition_type: u8,
+ chs_end: u24,
+ first_lba: u32,
+ number_sectors: u32,
+
+ const Self = @This();
+
+ pub fn is_fat32(self: *const Self) bool {
+ return self.partition_type == 0x0B or self.partition_type == 0x0C;
+ }
+
+ pub fn is_empty(self: *const Self) bool {
+ return std.mem.allEqual(u8, @ptrCast(self), 0x00);
+ }
+
+ pub fn partition_type_str(self: *const Self) []const u8 {
+ return switch (self.partition_type) {
+ 0x00 => "Empty",
+ 0x01 => "FAT12 - CHS",
+ 0x04 => "FAT16 - 16-32 MB - CHS",
+ 0x05 => "Microsoft Extended - CHS",
+ 0x06 => "FAT16 - 32 MB-2 GB - CHS",
+ 0x07 => "NTFS",
+ 0x0B => "FAT32 - CHS",
+ 0x0C => "FAT32 - LBA",
+ 0x0E => "FAT16 - 32 MB-2 GB - LBA",
+ 0x0F => "Microsoft Extended - LBA",
+ 0x11 => "Hidden FAT12 - CHS",
+ 0x14 => "Hidden FAT16 - 16-32 MB - CHS",
+ 0x16 => "Hidden FAT16 - 32 MB-2 GB - CHS",
+ 0x1b => "Hidden FAT32 - CHS",
+ 0x1c => "Hidden FAT32 - LBA",
+ 0x1e => "Hidden FAT16 - 32 MB-2 GB - LBA",
+ 0x42 => "Microsoft MBR - Dynamic Disk",
+ 0x82 => "Solaris x86 OR Linux Swap",
+ 0x83 => "Linux",
+ 0x84 => "Hibernation",
+ 0x85 => "Linux Extended",
+ 0x86 => "NTFS Volume Set",
+ 0x87 => "NTFS Volume Set",
+ 0xa0 => "Hibernation",
+ 0xa1 => "Hibernation",
+ 0xa5 => "FreeBSD",
+ 0xa6 => "OpenBSD",
+ 0xa8 => "Mac OSX",
+ 0xa9 => "NetBSD",
+ 0xab => "Mac OSX Boot",
+ 0xb7 => "BSDI",
+ 0xb8 => "BSDI swap",
+ 0xee => "EFI GPT Disk",
+ 0xef => "EFI System Partition",
+ 0xfb => "Vmware File System",
+ 0xfc => "Vmware swap",
+ else => "Unknown",
+ };
+ }
+
+ pub fn debug_print(self: *const Self, w: *std.io.Writer) !void {
+ try w.print(
+ \\ bootable = {any}
+ \\ chs_start = 0x{X}
+ \\ partition_type = 0x{X} ({s})
+ \\ chs_end = 0X{X}
+ \\ lba_start = 0x{X}
+ \\ number sectors = {d} ({B})
+ \\
+ , .{
+ self.status.bootable,
+ self.chs_start,
+ self.partition_type,
+ self.partition_type_str(),
+ self.chs_end,
+ self.first_lba,
+ self.number_sectors,
+ @as(u64, self.number_sectors) * 512,
+ });
+ }
+};
diff --git a/pi/root.zig b/pi/root.zig
@@ -29,6 +29,7 @@ pub const devices = struct {
pub const fs = struct {
pub const vfs = @import("./fs/vfs.zig");
pub const fat = @import("./fs/fat.zig");
+ pub const mbr = @import("./fs/mbr.zig");
pub const FatVFS = @import("./fs/fatvfs.zig");
};
diff --git a/programs/fs.zig b/programs/fs.zig
@@ -270,7 +270,7 @@ pub fn main() !void {
var vfs_disk = vfs.Disk.impl_by(&sd_card);
const vfs_fat = vfs.FileSystem.impl_by(&fat_vfs);
- const mbr: pi.fs.fat.MasterBootRecord = @bitCast(try vfs_disk.read_sector(0));
+ const mbr: pi.fs.mbr.MasterBootRecord = @bitCast(try vfs_disk.read_sector(0));
try mbr.debug_print(&uart.writer);
