test: Create minimal PE binary for testing

Buffered UKI readers fail if the binary being read is not a valid PE
binary. To fix tests, create a minimal PE binary

Assisted-By: Claude Code (Opus)
Signed-off-by: Pragyan Poudyal <pragyanpoudyal41999@gmail.com>

Author: Johan-Liebert1

crates/lib/src/kernel.rs

@@ -168,6 +168,7 @@ fn find_uki_path(root: &Dir) -> Result<Option<Utf8PathBuf>> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use bootc_utils::create_minimal_pe;
     use cap_std_ext::{cap_std, cap_tempfile, dirext::CapStdExtDirExt};
 
     #[test]
@@ -209,7 +210,7 @@ mod tests {
     fn test_find_kernel_uki() -> Result<()> {
         let tempdir = cap_tempfile::tempdir(cap_std::ambient_authority())?;
         tempdir.create_dir_all("boot/EFI/Linux")?;
-        tempdir.atomic_write("boot/EFI/Linux/fedora-6.12.0.efi", b"fake uki")?;
+        tempdir.atomic_write("boot/EFI/Linux/fedora-6.12.0.efi", &create_minimal_pe())?;
 
         let kernel_internal = find_kernel(&tempdir)?.expect("should find kernel");
         assert_eq!(kernel_internal.kernel.version, "fedora-6.12.0");
@@ -233,7 +234,7 @@ mod tests {
             b"fake kernel",
         )?;
         tempdir.create_dir_all("boot/EFI/Linux")?;
-        tempdir.atomic_write("boot/EFI/Linux/fedora-6.12.0.efi", b"fake uki")?;
+        tempdir.atomic_write("boot/EFI/Linux/fedora-6.12.0.efi", &create_minimal_pe())?;
 
         let kernel_internal = find_kernel(&tempdir)?.expect("should find kernel");
         // UKI should take precedence
@@ -246,9 +247,9 @@ mod tests {
     fn test_find_uki_path_sorted() -> Result<()> {
         let tempdir = cap_tempfile::tempdir(cap_std::ambient_authority())?;
         tempdir.create_dir_all("boot/EFI/Linux")?;
-        tempdir.atomic_write("boot/EFI/Linux/zzz.efi", b"fake uki")?;
-        tempdir.atomic_write("boot/EFI/Linux/aaa.efi", b"fake uki")?;
-        tempdir.atomic_write("boot/EFI/Linux/mmm.efi", b"fake uki")?;
+        tempdir.atomic_write("boot/EFI/Linux/zzz.efi", &create_minimal_pe())?;
+        tempdir.atomic_write("boot/EFI/Linux/aaa.efi", &create_minimal_pe())?;
+        tempdir.atomic_write("boot/EFI/Linux/mmm.efi", &create_minimal_pe())?;
 
         // Should return first in sorted order
         let path = find_uki_path(&tempdir)?.expect("should find uki");

crates/lib/src/ukify.rs

@@ -124,6 +124,8 @@ pub(crate) async fn build_ukify(
 
 #[cfg(test)]
 mod tests {
+    use bootc_utils::create_minimal_pe;
+
     use super::*;
     use std::fs;
 
@@ -148,7 +150,11 @@ mod tests {
 
         // Create a UKI structure
         fs::create_dir_all(tempdir.path().join("boot/EFI/Linux")).unwrap();
-        fs::write(tempdir.path().join("boot/EFI/Linux/test.efi"), b"fake uki").unwrap();
+        fs::write(
+            tempdir.path().join("boot/EFI/Linux/test.efi"),
+            &create_minimal_pe(),
+        )
+        .unwrap();
 
         let result = build_ukify(path, &[], &[], false, None).await;
         assert!(result.is_err());

crates/utils/src/lib.rs

@@ -18,6 +18,8 @@ mod timestamp;
 pub use timestamp::*;
 mod tracing_util;
 pub use tracing_util::*;
+mod uki;
+pub use uki::*;
 
 /// The name of our binary
 pub const NAME: &str = "bootc";

crates/utils/src/uki.rs

@@ -0,0 +1,48 @@
+/// Create a minimal valid PE file for testing UKI parsing
+pub fn create_minimal_pe() -> Vec<u8> {
+    let mut pe = Vec::new();
+    let section_data_offset = 0x200u32; // Standard section alignment
+    let section_data = b"quiet splash"; // Sample cmdline content
+
+    // DOS header (64 bytes)
+    pe.extend_from_slice(b"MZ"); // e_magic
+    pe.extend_from_slice(&[0u8; 58]); // DOS header padding
+    pe.extend_from_slice(&0x80u32.to_le_bytes()); // e_lfanew (offset to PE header)
+
+    // DOS stub padding to reach offset 0x80
+    pe.resize(0x80, 0);
+
+    // PE header (4 bytes)
+    pe.extend_from_slice(b"PE\0\0");
+
+    // COFF header (20 bytes)
+    pe.extend_from_slice(&0x8664u16.to_le_bytes()); // machine (x64)
+    pe.extend_from_slice(&1u16.to_le_bytes()); // number of sections
+    pe.extend_from_slice(&0u32.to_le_bytes()); // timestamp
+    pe.extend_from_slice(&0u32.to_le_bytes()); // pointer to symbol table
+    pe.extend_from_slice(&0u32.to_le_bytes()); // number of symbols
+    pe.extend_from_slice(&0xF0u16.to_le_bytes()); // size of optional header
+    pe.extend_from_slice(&0x2022u16.to_le_bytes()); // characteristics
+
+    // Optional header (240 bytes for PE32+)
+    pe.extend_from_slice(&0x020Bu16.to_le_bytes()); // magic (PE32+)
+    pe.extend_from_slice(&[0u8; 0xF0 - 2]); // rest of optional header filled with zeros
+
+    // Section header (40 bytes)
+    let mut section_header = [0u8; 40];
+    section_header[..8].copy_from_slice(b".cmdline"); // name
+    section_header[8..12].copy_from_slice(&(section_data.len() as u32).to_le_bytes()); // virtual_size
+    section_header[12..16].copy_from_slice(&0x1000u32.to_le_bytes()); // virtual_address
+    section_header[16..20].copy_from_slice(&(section_data.len() as u32).to_le_bytes()); // size_of_raw_data
+    section_header[20..24].copy_from_slice(&section_data_offset.to_le_bytes()); // pointer_to_raw_data
+    section_header[36..40].copy_from_slice(&0x40000040u32.to_le_bytes()); // characteristics (readable)
+    pe.extend_from_slice(&section_header);
+
+    // Pad to section data offset
+    pe.resize(section_data_offset as usize, 0);
+
+    // Section data
+    pe.extend_from_slice(section_data);
+
+    pe
+}