efi/libstub: Make initrd file loader configurable

Loading an initrd passed via the kernel command line is deprecated: it
is limited to files that reside in the same volume as the one the kernel
itself was loaded from, and we have more flexible ways to achieve the
same. So make it configurable so new architectures can decide not to
enable it.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/Kconfig

@@ -124,6 +124,17 @@ config EFI_ARMSTUB_DTB_LOADER
 	  functionality for bootloaders that do not have such support
 	  this option is necessary.
 
+config EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER
+	bool "Enable the command line initrd loader"
+	depends on EFI_GENERIC_STUB
+	default y
+	help
+	  Select this config option to add support for the initrd= command
+	  line parameter, allowing an initrd that resides on the same volume
+	  as the kernel image to be loaded into memory.
+
+	  This method is deprecated.
+
 config EFI_BOOTLOADER_CONTROL
 	tristate "EFI Bootloader Control"
 	depends on EFI_VARS

drivers/firmware/efi/libstub/efistub.h

@@ -651,15 +651,35 @@ efi_status_t efi_parse_options(char const *cmdline);
 efi_status_t efi_setup_gop(struct screen_info *si, efi_guid_t *proto,
 			   unsigned long size);
 
-efi_status_t efi_load_dtb(efi_loaded_image_t *image,
+efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
+				  const efi_char16_t *optstr,
+				  int optstr_size,
+				  unsigned long soft_limit,
+				  unsigned long hard_limit,
 				  unsigned long *load_addr,
 				  unsigned long *load_size);
 
-efi_status_t efi_load_initrd(efi_loaded_image_t *image,
+
+static inline efi_status_t efi_load_dtb(efi_loaded_image_t *image,
+					unsigned long *load_addr,
+					unsigned long *load_size)
+{
+	return handle_cmdline_files(image, L"dtb=", sizeof(L"dtb=") - 2,
+				    ULONG_MAX, ULONG_MAX, load_addr, load_size);
+}
+
+static inline efi_status_t efi_load_initrd(efi_loaded_image_t *image,
 					   unsigned long *load_addr,
 					   unsigned long *load_size,
 					   unsigned long soft_limit,
-			     unsigned long hard_limit);
+					   unsigned long hard_limit)
+{
+	if (!IS_ENABLED(CONFIG_EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER))
+		return EFI_SUCCESS;
+
+	return handle_cmdline_files(image, L"initrd=", sizeof(L"initrd=") - 2,
+				    soft_limit, hard_limit, load_addr, load_size);
+}
 
 efi_status_t efi_load_initrd_dev_path(unsigned long *load_addr,
 				      unsigned long *load_size,

drivers/firmware/efi/libstub/file.c

@@ -121,7 +121,7 @@ static int find_file_option(const efi_char16_t *cmdline, int cmdline_len,
  * We only support loading a file from the same filesystem as
  * the kernel image.
  */
-static efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
+efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
 				  const efi_char16_t *optstr,
 				  int optstr_size,
 				  unsigned long soft_limit,
@@ -239,21 +239,3 @@ static efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
 	efi_free(alloc_size, alloc_addr);
 	return status;
 }
-
-efi_status_t efi_load_dtb(efi_loaded_image_t *image,
-			  unsigned long *load_addr,
-			  unsigned long *load_size)
-{
-	return handle_cmdline_files(image, L"dtb=", sizeof(L"dtb=") - 2,
-				    ULONG_MAX, ULONG_MAX, load_addr, load_size);
-}
-
-efi_status_t efi_load_initrd(efi_loaded_image_t *image,
-			     unsigned long *load_addr,
-			     unsigned long *load_size,
-			     unsigned long soft_limit,
-			     unsigned long hard_limit)
-{
-	return handle_cmdline_files(image, L"initrd=", sizeof(L"initrd=") - 2,
-				    soft_limit, hard_limit, load_addr, load_size);
-}