[xen staging] xen/efi: Handle cases where file didn't come from ESP

[patchbot@xxxxxxx]

commit 196cdc097ff1603f2a7b4d9d165313073fdf5a75
Author:     Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
AuthorDate: Thu Jun 26 14:58:10 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jun 26 14:58:10 2025 +0200

    xen/efi: Handle cases where file didn't come from ESP
    
    A boot loader can load files from outside ESP.
    In these cases device could be not provided or path could
    be something not supported.
    In these cases allows to boot anyway, all information
    could be provided using UKI or using other boot loader
    features.
    
    Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
    Acked-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/common/efi/boot.c | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 1a9b4e7dae..9306dc8953 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -443,6 +443,18 @@ static EFI_FILE_HANDLE __init get_parent_handle(const 
EFI_LOADED_IMAGE *loaded_i
     CHAR16 *pathend, *ptr;
     EFI_STATUS ret;
 
+    /*
+     * In some cases the image could not come from a specific device.
+     * For instance this can happen if Xen was loaded using GRUB2 "linux"
+     * command.
+     */
+    *leaf = NULL;
+    if ( !loaded_image->DeviceHandle )
+    {
+        PrintStr(L"Xen image loaded without providing a device\r\n");
+        return NULL;
+    }
+
     do {
         EFI_FILE_IO_INTERFACE *fio;
 
@@ -466,7 +478,15 @@ static EFI_FILE_HANDLE __init get_parent_handle(const 
EFI_LOADED_IMAGE *loaded_i
 
         if ( DevicePathType(dp) != MEDIA_DEVICE_PATH ||
              DevicePathSubType(dp) != MEDIA_FILEPATH_DP )
-            blexit(L"Unsupported device path component");
+        {
+            /*
+             * The image could come from an unsupported device.
+             * For instance this can happen if Xen was loaded using GRUB2
+             * "chainloader" command and the file was not from ESP.
+             */
+            PrintStr(L"Unsupported device path component\r\n");
+            return NULL;
+        }
 
         if ( *buffer )
         {
@@ -772,8 +792,11 @@ static bool __init read_file(EFI_FILE_HANDLE dir_handle, 
CHAR16 *name,
 
     if ( !name )
         PrintErrMesg(L"No filename", EFI_OUT_OF_RESOURCES);
-    ret = dir_handle->Open(dir_handle, &FileHandle, name,
-                           EFI_FILE_MODE_READ, 0);
+    if ( dir_handle )
+        ret = dir_handle->Open(dir_handle, &FileHandle, name,
+                               EFI_FILE_MODE_READ, 0);
+    else
+        ret = EFI_NOT_FOUND;
     if ( file == &cfg && ret == EFI_NOT_FOUND )
         return false;
     if ( EFI_ERROR(ret) )
@@ -1404,7 +1427,7 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE 
ImageHandle,
         /* Read and parse the config file. */
         if ( read_section(loaded_image, L"config", &cfg, NULL) )
             PrintStr(L"Using builtin config file\r\n");
-        else if ( !cfg_file_name )
+        else if ( !cfg_file_name && file_name )
         {
             CHAR16 *tail;
 
@@ -1515,7 +1538,8 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE 
ImageHandle,
         efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
         cfg.addr = 0;
 
-        dir_handle->Close(dir_handle);
+        if ( dir_handle )
+            dir_handle->Close(dir_handle);
 
         if ( gop && !base_video )
         {
--
generated by git-patchbot for /home/xen/git/xen.git#staging