[PATCH v2 2/2] xen/efi: Support loading initrd using GRUB2 LoadFile2 protocol

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

Allows to load Xen using "linux" and "initrd" GRUB2 commands.
This can be used with UKI to separate initrd in a different module
instead of bundling all together.
Bundling all together can be a problem with Secure Boot where
we need to sign the bundle making harder to change it.
As initrd content does not need to be signed for Secure Boot
bundling it force it to be signed too.

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
---
Changes since v1:
- attempt to use LoadFile2 protocol after embedded section.
---
 xen/common/efi/boot.c     | 71 ++++++++++++++++++++++++++++++++++++++-
 xen/include/efi/efidevp.h | 21 ++++++++++++
 2 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index b18af2f1f4..b6ce3a0257 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -850,6 +850,74 @@ static bool __init read_file(EFI_FILE_HANDLE dir_handle, 
CHAR16 *name,
     return true;
 }
 
+#pragma pack(1)
+typedef struct {
+    VENDOR_DEVICE_PATH              VenMediaNode;
+    EFI_DEVICE_PATH                 EndNode;
+} SINGLE_NODE_VENDOR_MEDIA_DEVPATH;
+#pragma pack()
+
+static bool __init initrd_load_file2(const CHAR16 *name, struct file *file)
+{
+    static const SINGLE_NODE_VENDOR_MEDIA_DEVPATH __initconst initrd_dev_path 
= {
+        {
+            {
+                MEDIA_DEVICE_PATH, MEDIA_VENDOR_DP, { sizeof 
(VENDOR_DEVICE_PATH) }
+            },
+            LINUX_EFI_INITRD_MEDIA_GUID
+        },
+        {
+            END_DEVICE_PATH_TYPE, END_ENTIRE_DEVICE_PATH_SUBTYPE,
+            { sizeof (EFI_DEVICE_PATH) }
+        }
+    };
+    static EFI_GUID __initdata lf2_proto_guid = EFI_LOAD_FILE2_PROTOCOL_GUID;
+    EFI_DEVICE_PATH *dp;
+    EFI_LOAD_FILE2_PROTOCOL *lf2;
+    EFI_HANDLE handle;
+    EFI_STATUS ret;
+    UINTN size;
+
+    dp = (EFI_DEVICE_PATH *)&initrd_dev_path;
+    ret = efi_bs->LocateDevicePath(&lf2_proto_guid, &dp, &handle);
+    if ( EFI_ERROR(ret) )
+    {
+        if ( ret == EFI_NOT_FOUND)
+            return false;
+        PrintErrMesg(L"Error getting file with LoadFile2 interface", ret);
+    }
+
+    ret = efi_bs->HandleProtocol(handle, &lf2_proto_guid, (void **)&lf2);
+    if ( EFI_ERROR(ret) )
+        PrintErrMesg(L"LoadFile2 file does not provide correct protocol", ret);
+
+    size = 0;
+    ret = lf2->LoadFile(lf2, dp, false, &size, NULL);
+    if ( ret != EFI_BUFFER_TOO_SMALL )
+        PrintErrMesg(L"Loading failed", ret);
+
+    file->addr = min(1UL << (32 + PAGE_SHIFT),
+                     HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START);
+    ret = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
+                                PFN_UP(size), &file->addr);
+    if ( EFI_ERROR(ret) )
+        PrintErrMesg(L"Allocation failed", ret);
+
+    file->need_to_free = true;
+    file->size = size;
+
+    ret = lf2->LoadFile(lf2, dp, false, &size, file->str);
+    if ( EFI_ERROR(ret) )
+    {
+        efi_bs->FreePages(file->addr, PFN_UP(size));
+        PrintErrMesg(L"Loading failed", ret);
+    }
+
+    efi_arch_handle_module(file, name, NULL);
+
+    return true;
+}
+
 static bool __init read_section(const EFI_LOADED_IMAGE *image,
                                 const CHAR16 *name, struct file *file,
                                 const char *options)
@@ -1493,7 +1561,8 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE 
ImageHandle,
             kernel_verified = true;
         }
 
-        if ( !read_section(loaded_image, L"ramdisk", &ramdisk, NULL) )
+        if ( !read_section(loaded_image, L"ramdisk", &ramdisk, NULL) &&
+             !initrd_load_file2(L"ramdisk", &ramdisk) )
         {
             name.s = get_value(&cfg, section.s, "ramdisk");
             if ( name.s )
diff --git a/xen/include/efi/efidevp.h b/xen/include/efi/efidevp.h
index beb5785a45..b240c15d2a 100644
--- a/xen/include/efi/efidevp.h
+++ b/xen/include/efi/efidevp.h
@@ -398,5 +398,26 @@ typedef union {
 
 } EFI_DEV_PATH_PTR;
 
+#define EFI_LOAD_FILE2_PROTOCOL_GUID \
+    { 0x4006c0c1, 0xfcb3, 0x403e, {0x99, 0x6d, 0x4a, 0x6c, 0x87, 0x24, 0xe0, 
0x6d } }
+
+typedef struct EFI_LOAD_FILE2_PROTOCOL EFI_LOAD_FILE2_PROTOCOL;
+
+typedef
+EFI_STATUS
+(EFIAPI *EFI_LOAD_FILE2)(
+    IN EFI_LOAD_FILE2_PROTOCOL      *This,
+    IN EFI_DEVICE_PATH              *FilePath,
+    IN BOOLEAN                      BootPolicy,
+    IN OUT UINTN                    *BufferSize,
+    IN VOID                         *Buffer OPTIONAL
+    );
+
+struct EFI_LOAD_FILE2_PROTOCOL {
+    EFI_LOAD_FILE2                  LoadFile;
+};
+
+#define LINUX_EFI_INITRD_MEDIA_GUID \
+    { 0x5568e427, 0x68fc, 0x4f3d, {0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 
0x68} }
 
 #endif
-- 
2.43.0