[xen staging] efi: Support using Shim's LoadImage protocol

[patchbot@xxxxxxx]

commit 59a1d6d3ea1ea147c9bcd1a9b0b94378ce67ce6f
Author:     Gerald Elder-Vass <gerald.elder-vass@xxxxxxxxx>
AuthorDate: Fri Sep 5 12:10:18 2025 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Sep 5 23:45:38 2025 +0100

    efi: Support using Shim's LoadImage protocol
    
    The existing Verify functionality of the Shim lock protocol is
    deprecated and will be removed, the alternative it to use the LoadImage
    interface to perform the verification.
    
    When the loading is successful we won't be using the newly loaded image
    (as of yet) so we must then immediately unload the image to clean up.
    
    If the LoadImage protocol isn't available then fall back to the Shim
    Lock (Verify) interface.
    
    Log when the kernel is not verified and fail if this occurs
    when secure boot mode is enabled.
    
    Signed-off-by: Gerald Elder-Vass <gerald.elder-vass@xxxxxxxxx>
    Acked-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/efi/boot.c | 63 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 55 insertions(+), 8 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index ccbfc401f7..b86c83d334 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -38,6 +38,8 @@
   { 0xf2fd1544U, 0x9794, 0x4a2c, {0x99, 0x2e, 0xe5, 0xbb, 0xcf, 0x20, 0xe3, 
0x94} }
 #define SHIM_LOCK_PROTOCOL_GUID \
   { 0x605dab50U, 0xe046, 0x4300, {0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 
0x23} }
+#define SHIM_IMAGE_LOADER_GUID \
+  { 0x1f492041U, 0xfadb, 0x4e59, {0x9e, 0x57, 0x7c, 0xaf, 0xe7, 0x3a, 0x55, 
0xab} }
 #define APPLE_PROPERTIES_PROTOCOL_GUID \
   { 0x91bd12feU, 0xf6c3, 0x44fb, {0xa5, 0xb7, 0x51, 0x22, 0xab, 0x30, 0x3a, 
0xe0} }
 #define EFI_SYSTEM_RESOURCE_TABLE_GUID    \
@@ -70,6 +72,13 @@ typedef struct {
     EFI_SHIM_LOCK_VERIFY Verify;
 } EFI_SHIM_LOCK_PROTOCOL;
 
+typedef struct _SHIM_IMAGE_LOADER {
+    EFI_IMAGE_LOAD LoadImage;
+    EFI_IMAGE_START StartImage;
+    EFI_EXIT Exit;
+    EFI_IMAGE_UNLOAD UnloadImage;
+} SHIM_IMAGE_LOADER;
+
 struct _EFI_APPLE_PROPERTIES;
 
 typedef EFI_STATUS
@@ -1047,6 +1056,50 @@ static UINTN __init 
efi_find_gop_mode(EFI_GRAPHICS_OUTPUT_PROTOCOL *gop,
     return gop_mode;
 }
 
+static void __init efi_verify_kernel(EFI_HANDLE ImageHandle)
+{
+    static EFI_GUID __initdata shim_image_guid = SHIM_IMAGE_LOADER_GUID;
+    static EFI_GUID __initdata shim_lock_guid = SHIM_LOCK_PROTOCOL_GUID;
+    SHIM_IMAGE_LOADER *shim_loader;
+    EFI_HANDLE loaded_kernel;
+    EFI_SHIM_LOCK_PROTOCOL *shim_lock;
+    EFI_STATUS status;
+    bool verified = false;
+
+    /* Look for SHIM_IMAGE_LOADER first. */
+    if ( !EFI_ERROR(efi_bs->LocateProtocol(&shim_image_guid, NULL,
+                                           (void **)&shim_loader)) )
+    {
+        status = shim_loader->LoadImage(false, ImageHandle, NULL,
+                                        (void *)kernel.ptr, kernel.size,
+                                        &loaded_kernel);
+        if ( !EFI_ERROR(status) )
+            verified = true;
+
+        /*
+         * Always unload the image.  We only needed LoadImage() to perform
+         * verification anyway, and in the case of a failure there may still
+         * be cleanup needing to be performed.
+         */
+        shim_loader->UnloadImage(loaded_kernel);
+    }
+
+    /* Otherwise, fall back to SHIM_LOCK. */
+    if ( !verified &&
+         !EFI_ERROR(efi_bs->LocateProtocol(&shim_lock_guid, NULL,
+                                           (void **)&shim_lock)) &&
+         !EFI_ERROR(shim_lock->Verify(kernel.ptr, kernel.size)) )
+        verified = true;
+
+    if ( !verified )
+    {
+        PrintStr(L"Kernel was not verified\n");
+
+        if ( efi_secure_boot )
+            blexit(L"Refusing to boot unverified kernel with UEFI SecureBoot 
enabled");
+    }
+}
+
 static void __init efi_tables(void)
 {
     unsigned int i;
@@ -1334,13 +1387,11 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE 
ImageHandle,
                                       EFI_SYSTEM_TABLE *SystemTable)
 {
     static EFI_GUID __initdata loaded_image_guid = LOADED_IMAGE_PROTOCOL;
-    static EFI_GUID __initdata shim_lock_guid = SHIM_LOCK_PROTOCOL_GUID;
     EFI_LOADED_IMAGE *loaded_image;
     EFI_STATUS status;
     unsigned int i;
     CHAR16 *file_name, *cfg_file_name = NULL, *options = NULL;
     UINTN gop_mode = ~0;
-    EFI_SHIM_LOCK_PROTOCOL *shim_lock;
     EFI_GRAPHICS_OUTPUT_PROTOCOL *gop = NULL;
     union string section = { NULL }, name;
     bool base_video = false;
@@ -1591,12 +1642,8 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE 
ImageHandle,
      * device tree through the efi_check_dt_boot function, in this stage
      * verify it.
      */
-    if ( kernel.ptr &&
-         !kernel_verified &&
-         !EFI_ERROR(efi_bs->LocateProtocol(&shim_lock_guid, NULL,
-                                           (void **)&shim_lock)) &&
-         (status = shim_lock->Verify(kernel.ptr, kernel.size)) != EFI_SUCCESS )
-        PrintErrMesg(L"Dom0 kernel image could not be verified", status);
+    if ( kernel.ptr && !kernel_verified )
+        efi_verify_kernel(ImageHandle);
 
     efi_arch_edd();
 
--
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