efi_loader: Implement FileLoad2 for initramfs loading
Following kernel's proposal for an arch-agnostic initrd loading
mechanism [1] let's implement the U-boot counterpart.
This new approach has a number of advantages compared to what we did up
to now. The file is loaded into memory only when requested limiting the
area of TOCTOU attacks. Users will be allowed to place the initramfs
file on any u-boot accessible partition instead of just the ESP one.
Finally this is an attempt of a generic interface across architectures
in the linux kernel so it makes sense to support that.
The file location is intentionally only supported as a config option
argument(CONFIG_EFI_INITRD_FILESPEC), in an effort to enhance security.
Although U-boot is not responsible for verifying the integrity of the
initramfs, we can enhance the offered security by only accepting a
built-in option, which will be naturally verified by UEFI Secure Boot.
This can easily change in the future if needed and configure that via ENV
or UEFI variable.
[1] https://lore.kernel.org/linux-efi/20200207202637.GA3464906@rani.riverdale.lan/T/#m4a25eb33112fab7a22faa0fd65d4d663209af32f
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/efi_load_initrd.h b/include/efi_load_initrd.h
new file mode 100644
index 0000000..478ae80
--- /dev/null
+++ b/include/efi_load_initrd.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2020, Linaro Limited
+ */
+
+#if !defined _EFI_LOAD_INITRD_H_
+#define _EFI_LOAD_INITRD_H_
+
+#include <efi.h>
+#include <efi_api.h>
+
+/*
+ * Vendor GUID used by Linux to identify the handle with the
+ * EFI_LOAD_FILE2_PROTOCOL and load an initial ramdisk.
+ */
+#define EFI_INITRD_MEDIA_GUID \
+ EFI_GUID(0x5568e427, 0x68fc, 0x4f3d, \
+ 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68)
+
+struct efi_initrd_dp {
+ struct efi_device_path_vendor vendor;
+ struct efi_device_path end;
+} __packed;
+
+#endif