[wim] Always process .wim image file last

The order of input files is undefined on a UEFI system, which could
potentially lead to a situation in which a file automatically
extracted from a .wim image takes priority over a file provided
explicitly.

This issue has not arisen in practice since wimboot is almost always
loaded by iPXE, and iPXE happens to preserve the order of downloaded
files within the virtual filesystem.

Fix by deferring processing of the .wim file until after all other
input files have been read.

Modify the automated test script to place the .wim download in between
two files that are both required for the test to pass.

Signed-off-by: Michael Brown <mbrown@fensystems.co.uk>

src/efifile.c

@@ -145,6 +145,7 @@ void efi_extract ( EFI_HANDLE handle ) {
 		CHAR16 name[ VDISK_NAME_LEN + 1 /* WNUL */ ];
 	} __attribute__ (( packed )) info;
 	char name[ VDISK_NAME_LEN + 1 /* NUL */ ];
+	struct vdisk_file *wim = NULL;
 	struct vdisk_file *vfile;
 	EFI_FILE_PROTOCOL *root;
 	EFI_FILE_PROTOCOL *file;
@@ -212,17 +213,22 @@ void efi_extract ( EFI_HANDLE handle ) {
 		} else if ( wcscasecmp ( ( wname + ( wcslen ( wname ) - 4 ) ),
 					 L".wim" ) == 0 ) {
 			DBG ( "...found WIM file %ls\n", wname );
-			vdisk_patch_file ( vfile, patch_wim );
-			if ( ( ! bootmgfw ) &&
-			     ( bootmgfw = wim_add_file ( vfile, cmdline_index,
-							 bootmgfw_path,
-							 efi_bootarch() ) ) ) {
-				DBG ( "...extracted %ls\n", bootmgfw_path );
-			}
-			wim_add_files ( vfile, cmdline_index, efi_wim_paths );
+			wim = vfile;
 		}
 	}
 
+	/* Process WIM image */
+	if ( wim ) {
+		vdisk_patch_file ( wim, patch_wim );
+		if ( ( ! bootmgfw ) &&
+		     ( bootmgfw = wim_add_file ( wim, cmdline_index,
+						 bootmgfw_path,
+						 efi_bootarch() ) ) ) {
+			DBG ( "...extracted %ls\n", bootmgfw_path );
+		}
+		wim_add_files ( wim, cmdline_index, efi_wim_paths );
+	}
+
 	/* Check that we have a boot file */
 	if ( ! bootmgfw ) {
 		die ( "FATAL: no %ls or bootmgfw.efi found\n",

src/main.c

@@ -77,6 +77,9 @@ static const wchar_t *wim_paths[] = {
 /** bootmgr.exe file */
 static struct vdisk_file *bootmgr;
 
+/** WIM image file */
+static struct vdisk_file *bootwim;
+
 /** Minimal length of embedded bootmgr.exe */
 #define BOOTMGR_MIN_LEN 16384
 
@@ -364,14 +367,7 @@ static int add_file ( const char *name, void *data, size_t len ) {
 	} else if ( strcasecmp ( ( name + strlen ( name ) - 4 ),
 				 ".wim" ) == 0 ) {
 		DBG ( "...found WIM file %s\n", name );
-		vdisk_patch_file ( file, patch_wim );
-		if ( ( ! bootmgr ) &&
-		     ( bootmgr = wim_add_file ( file, cmdline_index,
-						bootmgr_path,
-						L"bootmgr.exe" ) ) ) {
-			DBG ( "...extracted bootmgr.exe\n" );
-		}
-		wim_add_files ( file, cmdline_index, wim_paths );
+		bootwim = file;
 	}
 
 	return 0;
@@ -447,6 +443,18 @@ int main ( void ) {
 	if ( cpio_extract ( initrd, initrd_len, add_file ) != 0 )
 		die ( "FATAL: could not extract initrd files\n" );
 
+	/* Process WIM image */
+	if ( bootwim ) {
+		vdisk_patch_file ( bootwim, patch_wim );
+		if ( ( ! bootmgr ) &&
+		     ( bootmgr = wim_add_file ( bootwim, cmdline_index,
+						bootmgr_path,
+						L"bootmgr.exe" ) ) ) {
+			DBG ( "...extracted bootmgr.exe\n" );
+		}
+		wim_add_files ( bootwim, cmdline_index, wim_paths );
+	}
+
 	/* Add INT 13 drive */
 	callback.drive = initialise_int13();
 

test/testwimboot

@@ -59,6 +59,7 @@ def ipxe_script(uuid, version, arch, bootmgr, bcd, bootsdi, bootargs):
     #!ipxe
     kernel ../wimboot {bootargs}
     initrd -n qr.txt qr-{uuid}.txt qr.txt
+    initrd ../images/{version}/{arch}/sources/boot.wim boot.wim
     initrd ../winpeshl.ini winpeshl.ini
     """).lstrip()
     if bootmgr:
@@ -74,7 +75,6 @@ def ipxe_script(uuid, version, arch, bootmgr, bcd, bootsdi, bootargs):
         initrd ../images/{version}/{arch}/boot/boot.sdi boot.sdi
         """).lstrip()
     script += textwrap.dedent(f"""
-    initrd ../images/{version}/{arch}/sources/boot.wim boot.wim
     boot
     """).lstrip()
     return script