Add MBR parser

Cargo.toml

@@ -3,10 +3,6 @@ name = "cuteloader"
 version = "0.1.0"
 edition = "2021"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[dependencies]
-
 
 # panic behaviour
 

src/read_mbr.rs

@@ -0,0 +1,79 @@
+use x86_64::instructions::port::Port;
+
+#[derive(Debug)]
+struct PartitionEntry {
+ bootable: u8,
+ start_chs: [u8; 3],
+ partition_type: u8,
+ end_chs: [u8; 3],
+ start_lba: u32,
+ size_sectors: u32,
+}
+
+impl PartitionEntry {
+ fn new(buffer: &[u8]) -> Self {
+ Self {
+ bootable: buffer[0],
+ start_chs: [buffer[1], buffer[2], buffer[3]],
+ partition_type: buffer[4],
+ end_chs: [buffer[5], buffer[6], buffer[7]],
+ start_lba: u32::from_le_bytes([
+ buffer[8],
+ buffer[9],
+ buffer[10],
+ buffer[11],
+ ]),
+ size_sectors: u32::from_le_bytes([
+ buffer[12],
+ buffer[13],
+ buffer[14],
+ buffer[15],
+ ]),
+ }
+ }
+}
+
+fn read_disk_sector(buffer: &mut [u8], sector: u32) {
+ let ah = 0x02; // AH = 2 (Read sector)
+ let al = buffer.len() as u8;
+ let ch = (sector >> 8) as u8;
+ let cl = (sector & 0xFF) as u8;
+ let dh = 0; // DH = 0 (Head number)
+ let dl = 0x80; // DL = 0x80 (Drive number: 0x80 for first hard disk)
+
+ unsafe {
+ asm!(
+ "int 0x13",
+ in("ah") ah,
+ in("al") al,
+ in("ch") ch,
+ in("cl") cl,
+ in("dh") dh,
+ in("dl") dl,
+ inout("rcx") buffer.len() => _,
+ inout("rdi") buffer.as_mut_ptr() => _,
+ );
+ }
+}
+
+fn fetch_bootable_partitions(sector: u32) {
+ let mut mbr_buffer: [u8; 512] = [0; 512];
+ read_disk_sector(&mut mbr_buffer, sector);
+
+ let mut partition_entries: Vec<PartitionEntry> = Vec::new();
+ let mut bootable_parts: Vec<PartitionEntry> = Vec::new();
+ for i in 0..4 {
+ let offset = 446 + i * 16;
+ let entry_buffer = &mbr_buffer[offset..offset + 16];
+ let partition_entry = PartitionEntry::new(entry_buffer);
+ partition_entries.push(partition_entry);
+ }
+
+ for (i, entry) in partition_entries.iter().enumerate() {
+ if entry.bootable == 0x80 {
+ bootable_parts.push(entry)
+ }
+ }
+
+ bootable_parts
+}