Create a GPT disk image

Cargo.lock

@@ -14,6 +14,12 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 
+[[package]]
+name = "build_const"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39092a32794787acd8525ee150305ff051b0aa6cc2abaf193924f5ab05425f39"
+
 [[package]]
 name = "byteorder"
 version = "1.4.2"
@@ -39,11 +45,21 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "crc"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d663548de7f5cca343f1e0a48d14dcfb0e9eb4e079ec58883b7251539fa10aeb"
+dependencies = [
+ "build_const",
+]
+
 [[package]]
 name = "disk_image"
 version = "0.1.0"
 dependencies = [
  "fatfs",
+ "gpt",
 ]
 
 [[package]]
@@ -58,6 +74,29 @@ dependencies = [
  "log",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "gpt"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a30b0e3659ffee31427c4aaa68c1e5115c8c86ba71ff11da5a16e5b70f3471d"
+dependencies = [
+ "bitflags",
+ "crc",
+ "log",
+ "uuid",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.86"
@@ -107,6 +146,15 @@ dependencies = [
 name = "uefi_app"
 version = "0.1.0"
 
+[[package]]
+name = "uuid"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bc5cf98d8186244414c848017f0e2676b3fcb46807f6668a97dfe67359a3c4b7"
+dependencies = [
+ "getrandom",
+]
+
 [[package]]
 name = "wasi"
 version = "0.10.0+wasi-snapshot-preview1"

disk_image/Cargo.toml

@@ -8,3 +8,4 @@ edition = "2018"
 
 [dependencies]
 fatfs = "0.3.5"
+gpt = "2.0.0"

disk_image/src/main.rs

@@ -1,4 +1,9 @@
-use std::{fs, io, path::Path};
+use std::{
+    convert::TryFrom,
+    fs::{self, File},
+    io::{self, Seek},
+    path::Path,
+};
 
 fn main() {
     println!("Hello, world!");
@@ -34,3 +39,50 @@ fn create_fat_filesystem(fat_path: &Path, efi_file: &Path) {
     bootx64.truncate().unwrap();
     io::copy(&mut fs::File::open(&efi_file).unwrap(), &mut bootx64).unwrap();
 }
+
+fn create_gpt_disk(disk_path: &Path, fat_image: &Path) {
+    // create new file
+    let mut disk = fs::OpenOptions::new()
+        .create(true)
+        .truncate(true)
+        .read(true)
+        .write(true)
+        .open(&disk_path)
+        .unwrap();
+
+    // set file size
+    let partition_size: u64 = fs::metadata(&fat_image).unwrap().len();
+    let disk_size = partition_size + 1024 * 64; // for GPT headers
+    disk.set_len(disk_size).unwrap();
+
+    // create a protective MBR at LBA0 so that disk is not considered
+    // unformatted on BIOS systems
+    let mbr = gpt::mbr::ProtectiveMBR::with_lb_size(
+        u32::try_from((disk_size / 512) - 1).unwrap_or(0xFF_FF_FF_FF),
+    );
+    mbr.overwrite_lba0(&mut disk).unwrap();
+
+    // create new GPT structure
+    let block_size = gpt::disk::LogicalBlockSize::Lb512;
+    let mut gpt = gpt::GptConfig::new()
+        .writable(true)
+        .initialized(false)
+        .logical_block_size(block_size)
+        .create_from_device(Box::new(&mut disk), None)
+        .unwrap();
+    gpt.update_partitions(Default::default()).unwrap();
+
+    // add new EFI system partition and get its byte offset in the file
+    let partition_id = gpt
+        .add_partition("boot", partition_size, gpt::partition_types::EFI, 0)
+        .unwrap();
+    let partition = gpt.partitions().get(&partition_id).unwrap();
+    let start_offset = partition.bytes_start(block_size).unwrap();
+
+    // close the GPT structure and write out changes
+    gpt.write().unwrap();
+
+    // place the FAT filesystem in the newly created partition
+    disk.seek(io::SeekFrom::Start(start_offset)).unwrap();
+    io::copy(&mut File::open(&fat_image).unwrap(), &mut disk).unwrap();
+}