efi_loader: Replace config option for initrd loading

Up to now we install EFI_LOAD_FILE2_PROTOCOL to load an initrd
unconditionally. Although we correctly return various EFI exit codes
depending on the file status (i.e EFI_NO_MEDIA, EFI_NOT_FOUND etc), the
kernel loader, only falls back to the cmdline interpreted initrd if the
protocol is not installed.

This creates a problem for EFI installers, since they won't be able to
load their own initrd and continue the installation. It also makes the
feature hard to use, since we can either have a single initrd or we have
to recompile u-boot if the filename changes.

So let's introduce a different logic that will decouple the initrd
path from the config option we currently have.
When defining a UEFI BootXXXX we can use the filepathlist and store
a file path pointing to our initrd. Specifically the EFI spec describes:

"The first element of the array is a device path that describes the device
and location of the Image for this load option. Other device paths may
optionally exist in the FilePathList, but their usage is OSV specific"

When the EFI application is launched through the bootmgr, we'll try to
interpret the extra device path. If that points to a file that exists on
our disk, we'll now install the load_file2 and the efi-stub will be able
to use it.

This opens up another path using U-Boot and defines a new boot flow.
A user will be able to control the kernel/initrd pairs without explicit
cmdline args or GRUB.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

3 files changed, 140 insertions, 98 deletions

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 634d3b1..0a41244 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -315,18 +315,13 @@ config EFI_TCG2_PROTOCOL_EVENTLOG_SIZE
 
 config EFI_LOAD_FILE2_INITRD
 	bool "EFI_FILE_LOAD2_PROTOCOL for Linux initial ramdisk"
-	default n
-	help
-	  Expose a EFI_FILE_LOAD2_PROTOCOL that the Linux UEFI stub can
-	  use to load the initial ramdisk. Once this is enabled using
-	  initrd=<ramdisk> will stop working.
-
-config EFI_INITRD_FILESPEC
-	string "initramfs path"
-	default "host 0:1 initrd"
-	depends on EFI_LOAD_FILE2_INITRD
+	default y
 	help
-	  Full path of the initramfs file, e.g. mmc 0:2 initramfs.cpio.gz.
+	  Linux v5.7 and later can make use of this option. If the boot option
+	  selected by the UEFI boot manager specifies an existing file to be used
+	  as initial RAM disk, a Linux specific Load File2 protocol will be
+	  installed and Linux 5.7+ will ignore any initrd=<ramdisk> command line
+	  argument.
 
 config EFI_SECURE_BOOT
 	bool "Enable EFI secure boot support"
diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
index 25f5ceb..46c8011 100644
--- a/lib/efi_loader/efi_bootmgr.c
+++ b/lib/efi_loader/efi_bootmgr.c
@@ -118,11 +118,13 @@ static efi_status_t try_load_entry(u16 n, efi_handle_t *handle,
 		ret = efi_set_variable_int(L"BootCurrent",
 					   &efi_global_variable_guid,
 					   attributes, sizeof(n), &n, false);
-		if (ret != EFI_SUCCESS) {
-			if (EFI_CALL(efi_unload_image(*handle))
-			    != EFI_SUCCESS)
-				log_err("Unloading image failed\n");
-			goto error;
+		if (ret != EFI_SUCCESS)
+			goto unload;
+		/* try to register load file2 for initrd's */
+		if (IS_ENABLED(CONFIG_EFI_LOAD_FILE2_INITRD)) {
+			ret = efi_initrd_register();
+			if (ret != EFI_SUCCESS)
+				goto unload;
 		}
 
 		log_info("Booting: %ls\n", lo.label);
@@ -147,6 +149,13 @@ error:
 	free(load_option);
 
 	return ret;
+
+unload:
+	if (EFI_CALL(efi_unload_image(*handle)) != EFI_SUCCESS)
+		log_err("Unloading image failed\n");
+	free(load_option);
+
+	return ret;
 }
 
 /**
diff --git a/lib/efi_loader/efi_load_initrd.c b/lib/efi_loader/efi_load_initrd.c
index b9ee883..e2a8063 100644
--- a/lib/efi_loader/efi_load_initrd.c
+++ b/lib/efi_loader/efi_load_initrd.c
@@ -3,9 +3,11 @@
  * Copyright (c) 2020, Linaro Limited
  */
 
+#define LOG_CATEGORY LOGC_EFI
 #include <common.h>
 #include <efi_loader.h>
 #include <efi_load_initrd.h>
+#include <efi_variable.h>
 #include <fs.h>
 #include <malloc.h>
 #include <mapmem.h>
@@ -23,57 +25,56 @@ static const struct efi_load_file_protocol efi_lf2_protocol = {
  * Device path defined by Linux to identify the handle providing the
  * EFI_LOAD_FILE2_PROTOCOL used for loading the initial ramdisk.
  */
-static const struct efi_initrd_dp dp = {
+static const struct efi_initrd_dp dp_lf2_handle = {
 	.vendor = {
 		{
 		   DEVICE_PATH_TYPE_MEDIA_DEVICE,
 		   DEVICE_PATH_SUB_TYPE_VENDOR_PATH,
-		   sizeof(dp.vendor),
+		   sizeof(dp_lf2_handle.vendor),
 		},
 		EFI_INITRD_MEDIA_GUID,
 	},
 	.end = {
 		DEVICE_PATH_TYPE_END,
 		DEVICE_PATH_SUB_TYPE_END,
-		sizeof(dp.end),
+		sizeof(dp_lf2_handle.end),
 	}
 };
 
+static efi_handle_t efi_initrd_handle;
+
 /**
- * get_file_size() - retrieve the size of initramfs, set efi status on error
+ * get_initrd_fp() - Get initrd device path from a FilePathList device path
  *
- * @dev:			device to read from, e.g. "mmc"
- * @part:			device partition, e.g. "0:1"
- * @file:			name of file
- * @status:			EFI exit code in case of failure
+ * @initrd_fp:	the final initrd filepath
  *
- * Return:			size of file
+ * Return:	status code. Caller must free initrd_fp
  */
-static loff_t get_file_size(const char *dev, const char *part, const char *file,
-			    efi_status_t *status)
+static efi_status_t get_initrd_fp(struct efi_device_path **initrd_fp)
 {
-	loff_t sz = 0;
-	int ret;
-
-	ret = fs_set_blk_dev(dev, part, FS_TYPE_ANY);
-	if (ret) {
-		*status = EFI_NO_MEDIA;
-		goto out;
-	}
+	const efi_guid_t lf2_initrd_guid = EFI_INITRD_MEDIA_GUID;
+	struct efi_device_path *dp = NULL;
 
-	ret = fs_size(file, &sz);
-	if (ret) {
-		sz = 0;
-		*status = EFI_NOT_FOUND;
-		goto out;
-	}
+	/*
+	 * if bootmgr is setup with and initrd, the device path will be
+	 * in the FilePathList[] of our load options in Boot####.
+	 * The first device path of the multi instance device path will
+	 * start with a VenMedia and the initrds will follow.
+	 *
+	 * If the device path is not found return EFI_INVALID_PARAMETER.
+	 * We can then use this specific return value and not install the
+	 * protocol, while allowing the boot to continue
+	 */
+	dp = efi_get_dp_from_boot(lf2_initrd_guid);
+	if (!dp)
+		return EFI_INVALID_PARAMETER;
 
-out:
-	return sz;
+	*initrd_fp = dp;
+	return EFI_SUCCESS;
 }
 
 /**
- * efi_load_file2initrd() - load initial RAM disk
+ * efi_load_file2_initrd() - load initial RAM disk
  *
  * This function implements the LoadFile service of the EFI_LOAD_FILE2_PROTOCOL
  * in order to load an initial RAM disk requested by the Linux kernel stub.
@@ -93,102 +94,125 @@ efi_load_file2_initrd(struct efi_load_file_protocol *this,
 		      struct efi_device_path *file_path, bool boot_policy,
 		      efi_uintn_t *buffer_size, void *buffer)
 {
-	char *filespec;
-	efi_status_t status = EFI_NOT_FOUND;
-	loff_t file_sz = 0, read_sz = 0;
-	char *dev, *part, *file;
-	char *pos;
-	int ret;
+	struct efi_device_path *initrd_fp = NULL;
+	efi_status_t ret = EFI_NOT_FOUND;
+	struct efi_file_handle *f = NULL;
+	efi_uintn_t bs;
 
 	EFI_ENTRY("%p, %p, %d, %p, %p", this, file_path, boot_policy,
 		  buffer_size, buffer);
 
-	filespec = strdup(CONFIG_EFI_INITRD_FILESPEC);
-	if (!filespec)
-		goto out;
-	pos = filespec;
-
 	if (!this || this != &efi_lf2_protocol ||
 	    !buffer_size) {
-		status = EFI_INVALID_PARAMETER;
+		ret = EFI_INVALID_PARAMETER;
 		goto out;
 	}
 
-	if (file_path->type != dp.end.type ||
-	    file_path->sub_type != dp.end.sub_type) {
-		status = EFI_INVALID_PARAMETER;
+	if (file_path->type != dp_lf2_handle.end.type ||
+	    file_path->sub_type != dp_lf2_handle.end.sub_type) {
+		ret = EFI_INVALID_PARAMETER;
 		goto out;
 	}
 
 	if (boot_policy) {
-		status = EFI_UNSUPPORTED;
+		ret = EFI_UNSUPPORTED;
 		goto out;
 	}
 
-	/*
-	 * expect a string with three space separated parts:
-	 *
-	 * * a block device type, e.g. "mmc"
-	 * * a device and partition identifier, e.g. "0:1"
-	 * * a file path on the block device, e.g. "/boot/initrd.cpio.gz"
-	 */
-	dev = strsep(&pos, " ");
-	if (!dev)
+	ret = get_initrd_fp(&initrd_fp);
+	if (ret != EFI_SUCCESS)
 		goto out;
-	part = strsep(&pos, " ");
-	if (!part)
-		goto out;
-	file = strsep(&pos, " ");
-	if (!file)
+
+	/* Open file */
+	f = efi_file_from_path(initrd_fp);
+	if (!f) {
+		log_err("Can't find initrd specified in Boot####\n");
+		ret = EFI_NOT_FOUND;
 		goto out;
+	}
 
-	file_sz = get_file_size(dev, part, file, &status);
-	if (!file_sz)
+	/* Get file size */
+	ret = efi_file_size(f, &bs);
+	if (ret != EFI_SUCCESS)
 		goto out;
 
-	if (!buffer || *buffer_size < file_sz) {
-		status = EFI_BUFFER_TOO_SMALL;
-		*buffer_size = file_sz;
+	if (!buffer || *buffer_size < bs) {
+		ret = EFI_BUFFER_TOO_SMALL;
+		*buffer_size = bs;
 	} else {
-		ret = fs_set_blk_dev(dev, part, FS_TYPE_ANY);
-		if (ret) {
-			status = EFI_NO_MEDIA;
-			goto out;
-		}
-
-		ret = fs_read(file, map_to_sysmem(buffer), 0, *buffer_size,
-			      &read_sz);
-		if (ret || read_sz != file_sz)
-			goto out;
-		*buffer_size = read_sz;
-
-		status = EFI_SUCCESS;
+		ret = EFI_CALL(f->read(f, &bs, (void *)(uintptr_t)buffer));
+		*buffer_size = bs;
+	}
+
+out:
+	efi_free_pool(initrd_fp);
+	if (f)
+		EFI_CALL(f->close(f));
+	return EFI_EXIT(ret);
+}
+
+/**
+ * check_initrd() - Determine if the file defined as an initrd in Boot####
+ *		    load_options device path is present
+ *
+ * Return:	status code
+ */
+static efi_status_t check_initrd(void)
+{
+	struct efi_device_path *initrd_fp = NULL;
+	struct efi_file_handle *f;
+	efi_status_t ret;
+
+	ret = get_initrd_fp(&initrd_fp);
+	if (ret != EFI_SUCCESS)
+		goto out;
+
+	/*
+	 * If the file is not found, but the file path is set, return an error
+	 * and trigger the bootmgr fallback
+	 */
+	f = efi_file_from_path(initrd_fp);
+	if (!f) {
+		log_err("Can't find initrd specified in Boot####\n");
+		ret = EFI_NOT_FOUND;
+		goto out;
 	}
 
+	EFI_CALL(f->close(f));
+
 out:
-	free(filespec);
-	return EFI_EXIT(status);
+	efi_free_pool(initrd_fp);
+	return ret;
 }
 
 /**
  * efi_initrd_register() - create handle for loading initial RAM disk
  *
  * This function creates a new handle and installs a Linux specific vendor
- * device path and an EFI_LOAD_FILE_2_PROTOCOL. Linux uses the device path
+ * device path and an EFI_LOAD_FILE2_PROTOCOL. Linux uses the device path
  * to identify the handle and then calls the LoadFile service of the
- * EFI_LOAD_FILE_2_PROTOCOL to read the initial RAM disk.
+ * EFI_LOAD_FILE2_PROTOCOL to read the initial RAM disk.
  *
  * Return:	status code
  */
 efi_status_t efi_initrd_register(void)
 {
-	efi_handle_t efi_initrd_handle = NULL;
 	efi_status_t ret;
 
+	/*
+	 * Allow the user to continue if Boot#### file path is not set for
+	 * an initrd
+	 */
+	ret = check_initrd();
+	if (ret == EFI_INVALID_PARAMETER)
+		return EFI_SUCCESS;
+	if (ret != EFI_SUCCESS)
+		return ret;
+
 	ret = EFI_CALL(efi_install_multiple_protocol_interfaces
 		       (&efi_initrd_handle,
 			/* initramfs */
-			&efi_guid_device_path, &dp,
+			&efi_guid_device_path, &dp_lf2_handle,
 			/* LOAD_FILE2 */
 			&efi_guid_load_file2_protocol,
 			(void *)&efi_lf2_protocol,
@@ -196,3 +220,17 @@ efi_status_t efi_initrd_register(void)
 
 	return ret;
 }
+
+/**
+ * efi_initrd_deregister() - delete the handle for loading initial RAM disk
+ *
+ * This will delete the handle containing the Linux specific vendor device
+ * path and EFI_LOAD_FILE2_PROTOCOL for loading an initrd
+ *
+ * Return:	status code
+ */
+void efi_initrd_deregister(void)
+{
+	efi_delete_handle(efi_initrd_handle);
+	efi_initrd_handle = NULL;
+}