[PATCH 6/8 v2] efi_loader: Replace config option with EFI variable for initrd loading

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

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 the EFI application is launched through the bootmgr, we'll try to
match the BootCurrent value to an Initrd#### EFI variable.
e.g Boot0000 -> Initrd0000, Boot0010 -> Initrd0010 etc.

The Initrd#### EFI variable is expected to include the full file path,
i.e 'mmc 0:1 initrd'.  If the file is found, we'll install the
appropriate protocol so the kernel's efi-stub can use it and load our 
initrd. If the file is not found the kernel will still try to load an 
initrd parsing the kernel cmdline, since the protocol won't be installed.

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. So we can base the whole boot flow on the Boot####
and Initrd#### paired values.

Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
---
 cmd/bootefi.c                    | 13 +++++
 include/efi_loader.h             |  2 +-
 lib/efi_loader/Kconfig           | 13 ++---
 lib/efi_loader/efi_load_initrd.c | 93 ++++++++++----------------------
 4 files changed, 46 insertions(+), 75 deletions(-)

diff --git a/cmd/bootefi.c b/cmd/bootefi.c
index fdf909f8da2c..0234b0df2258 100644
--- a/cmd/bootefi.c
+++ b/cmd/bootefi.c
@@ -377,6 +377,19 @@ static int do_efibootmgr(void)
 		return CMD_RET_FAILURE;
 	}
 
+	/* efi_exit() will delete all protocols and the handle itself on exit */
+	if (IS_ENABLED(CONFIG_EFI_LOAD_FILE2_INITRD)) {
+		ret = efi_initrd_register(&handle);
+		/* Just warn the user. If the installation fails, the kernel
+		 * either load an initrd specificied in the cmdline or fail
+		 * to boot.
+		 * If we decide to fail the command here we need to uninstall
+		 * the protocols efi_bootmgr_load() installed
+		 */
+		if (ret != EFI_SUCCESS)
+			log_warning("EFI boot manager: Failed to install Loadfile2 for initrd\n");
+	}
+
 	ret = do_bootefi_exec(handle, load_options);
 
 	if (ret != EFI_SUCCESS)
diff --git a/include/efi_loader.h b/include/efi_loader.h
index af30dbafab77..000cc942e31c 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -422,7 +422,7 @@ efi_status_t efi_gop_register(void);
 efi_status_t efi_net_register(void);
 /* Called by bootefi to make the watchdog available */
 efi_status_t efi_watchdog_register(void);
-efi_status_t efi_initrd_register(void);
+efi_status_t efi_initrd_register(efi_handle_t *initrd_handle);
 /* Called by bootefi to make SMBIOS tables available */
 /**
  * efi_acpi_register() - write out ACPI tables
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index dd8b93bd3c5a..96b5934a221d 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -212,14 +212,11 @@ config EFI_LOAD_FILE2_INITRD
 	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
-	help
-	  Full path of the initramfs file, e.g. mmc 0:2 initramfs.cpio.gz.
+	  initrd=<ramdisk> will stop working. The protocol will only be
+	  installed if bootmgr is used and the file is found on the defined
+	  path. A boot entry of Boot0001 will try to match Initrd0001 and use
+	  it. Initrd EFI variable format should be '<dev> <part> <filename>'
+	  i.e 'mmc 0:1 boot/initrd'
 
 config EFI_SECURE_BOOT
 	bool "Enable EFI secure boot support"
diff --git a/lib/efi_loader/efi_load_initrd.c b/lib/efi_loader/efi_load_initrd.c
index 4ec55d70979d..6289957c97bc 100644
--- a/lib/efi_loader/efi_load_initrd.c
+++ b/lib/efi_loader/efi_load_initrd.c
@@ -5,7 +5,9 @@
 
 #include <common.h>
 #include <efi_loader.h>
+#include <efi_helper.h>
 #include <efi_load_initrd.h>
+#include <efi_variable.h>
 #include <fs.h>
 #include <malloc.h>
 #include <mapmem.h>
@@ -43,40 +45,7 @@ static const struct efi_initrd_dp dp = {
 };
 
 /**
- * get_file_size() - retrieve the size of initramfs, set efi status on error
- *
- * @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
- *
- * Return:			size of file
- */
-static loff_t get_file_size(const char *dev, const char *part, const char *file,
-			    efi_status_t *status)
-{
-	loff_t sz = 0;
-	int ret;
-
-	ret = fs_set_blk_dev(dev, part, FS_TYPE_ANY);
-	if (ret) {
-		*status = EFI_NO_MEDIA;
-		goto out;
-	}
-
-	ret = fs_size(file, &sz);
-	if (ret) {
-		sz = 0;
-		*status = EFI_NOT_FOUND;
-		goto out;
-	}
-
-out:
-	return sz;
-}
-
-/**
- * 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.
@@ -96,21 +65,15 @@ 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 load_file_info info;
+	char initrd[] = "Initrd";
 
 	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;
@@ -128,24 +91,11 @@ efi_load_file2_initrd(struct efi_load_file_protocol *this,
 		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)
-		goto out;
-	part = strsep(&pos, " ");
-	if (!part)
-		goto out;
-	file = strsep(&pos, " ");
-	if (!file)
+	status = efi_get_fp_from_var(initrd, &info);
+	if (status != EFI_SUCCESS)
 		goto out;
 
-	file_sz = get_file_size(dev, part, file, &status);
+	file_sz = get_file_size(&info, &status);
 	if (!file_sz)
 		goto out;
 
@@ -153,23 +103,25 @@ efi_load_file2_initrd(struct efi_load_file_protocol *this,
 		status = EFI_BUFFER_TOO_SMALL;
 		*buffer_size = file_sz;
 	} else {
-		ret = fs_set_blk_dev(dev, part, FS_TYPE_ANY);
+		ret = fs_set_blk_dev(info.dev, info.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)
+		ret = fs_read(info.filename, map_to_sysmem(buffer), 0,
+			      *buffer_size, &read_sz);
+		if (ret || read_sz != file_sz) {
+			status = EFI_DEVICE_ERROR;
 			goto out;
+		}
 		*buffer_size = read_sz;
 
 		status = EFI_SUCCESS;
 	}
 
 out:
-	free(filespec);
 	return EFI_EXIT(status);
 }
 
@@ -183,13 +135,22 @@ out:
  *
  * Return:	status code
  */
-efi_status_t efi_initrd_register(void)
+efi_status_t efi_initrd_register(efi_handle_t *efi_initrd_handle)
 {
-	efi_handle_t efi_initrd_handle = NULL;
 	efi_status_t ret;
+	struct load_file_info info;
+	char initrd[] = "Initrd";
+
+	ret = efi_get_fp_from_var(initrd, &info);
+	/*
+	 * Don't fail here. If we don't install the protocol the efi-stub will
+	 * try to load and initrd parsing the kernel cmdline
+	 */
+	if (ret != EFI_SUCCESS)
+		return EFI_SUCCESS;
 
 	ret = EFI_CALL(efi_install_multiple_protocol_interfaces
-		       (&efi_initrd_handle,
+		       (efi_initrd_handle,
 			/* initramfs */
 			&efi_guid_device_path, &dp,
 			/* LOAD_FILE2 */
-- 
2.30.0