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efi_loader: bootmgr: add booting from removable media

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Under the current implementation, booting from removable media using
a architecture-specific default image name, say BOOTAA64.EFI, is
supported only in distro_bootcmd script. See the commit 74522c898b
("efi_loader: Add distro boot script for removable media").

This is, however, half-baked implementation because
1) UEFI specification requires this feature to be implemented as part
   of Boot Manager's responsibility:

  3 - Boot Manager
  3.5.1 Boot via the Simple File Protocol
  When booting via the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL, the FilePath will
  start with a device path that points to the device that implements the
  EFI_SIMPLE_FILE_SYSTEM_PROTOCOL or the EFI_BLOCK_IO_PROTOCOL. The next
  part of the FilePath may point to the file name, including
  subdirectories, which contain the bootable image. If the file name is
  a null device path, the file name must be generated from the rules
  defined below.
  ...
  3.5.1.1 Removable Media Boot Behavior
  To generate a file name when none is present in the FilePath, the
  firmware must append a default file name in the form
  \EFI\BOOT\BOOT{machine type short-name}.EFI ...

2) So (1) entails the hehavior that the user's preference of boot media
   order should be determined by Boot#### and BootOrder variables.

With this patch, the semantics mentioned above is fully implemented.
For example, if you want to boot the system from USB and SCSI in this
order,
* define Boot0001 which contains only a device path to the USB device
  (without any file path/name)
* define Boot0002 which contains only a device path to the SCSI device,
and
* set BootOrder to Boot0001:Boot0002

To avoid build error for sandbox, default file name "BOOTSANDBOX.efi"
is defined even if it is out of scope of UEFI specification.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
On sandbox use binary name corresponding to host architecture.
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
This commit is contained in:
AKASHI Takahiro 2022-04-28 17:09:39 +09:00 committed by Heinrich Schuchardt
parent d8465ffc01
commit 4e65ca00f3
2 changed files with 95 additions and 1 deletions
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45
include/efi_default_filename.h Normal file
View file

@ -0,0 +1,45 @@
/* SPDX-License-Identifier: GPL-2.0+ */
/*
* When a boot option does not provide a file path the EFI file to be
* booted is \EFI\BOOT\$(BOOTEFI_NAME).EFI. The architecture specific
* file name is defined in this include.
*
* Copyright (c) 2022, Heinrich Schuchardt <xypron.glpk@gmx.de>
*/
#ifndef _EFI_DEFAULT_FILENAME_H
#define _EFI_DEFAULT_FILENAME_H
#include <host_arch.h>
#undef BOOTEFI_NAME
#if HOST_ARCH == HOST_ARCH_X86_64
#define BOOTEFI_NAME "BOOTX64.EFI"
#endif
#if HOST_ARCH == HOST_ARCH_X86
#define BOOTEFI_NAME "BOOTIA32.EFI"
#endif
#if HOST_ARCH == HOST_ARCH_AARCH64
#define BOOTEFI_NAME "BOOTAA64.EFI"
#endif
#if HOST_ARCH == HOST_ARCH_ARM
#define BOOTEFI_NAME "BOOTARM.EFI"
#endif
#if HOST_ARCH == HOST_ARCH_RISCV32
#define BOOTEFI_NAME "BOOTRISCV32.EFI"
#endif
#if HOST_ARCH == HOST_ARCH_RISCV64
#define BOOTEFI_NAME "BOOTRISCV64.EFI"
#endif
#ifndef BOOTEFI_NAME
#error Unsupported UEFI architecture
#endif
#endif

51
lib/efi_loader/efi_bootmgr.c
View file

@ -11,6 +11,7 @@
#include <charset.h>
#include <log.h>
#include <malloc.h>
#include <efi_default_filename.h>
#include <efi_loader.h>
#include <efi_variable.h>
#include <asm/unaligned.h>
@ -30,6 +31,51 @@ static const struct efi_runtime_services *rs;
* should do normal or recovery boot.
*/
/**
* expand_media_path() - expand a device path for default file name
* @device_path: device path to check against
*
* If @device_path is a media or disk partition which houses a file
* system, this function returns a full device path which contains
* an architecture-specific default file name for removable media.
*
* Return: a newly allocated device path
*/
static
struct efi_device_path *expand_media_path(struct efi_device_path *device_path)
{
struct efi_device_path *dp, *full_path;
efi_handle_t handle;
efi_status_t ret;
if (!device_path)
return NULL;
/*
* If device_path is a (removable) media or partition which provides
* simple file system protocol, append a default file name to support
* booting from removable media.
*/
dp = device_path;
ret = EFI_CALL(efi_locate_device_path(
&efi_simple_file_system_protocol_guid,
&dp, &handle));
if (ret == EFI_SUCCESS) {
if (dp->type == DEVICE_PATH_TYPE_END) {
dp = efi_dp_from_file(NULL, 0,
"/EFI/BOOT/" BOOTEFI_NAME);
full_path = efi_dp_append(device_path, dp);
efi_free_pool(dp);
} else {
full_path = efi_dp_dup(device_path);
}
} else {
full_path = efi_dp_dup(device_path);
}
return full_path;
}
/**
* try_load_entry() - try to load image for boot option
*
@ -64,13 +110,16 @@ static efi_status_t try_load_entry(u16 n, efi_handle_t *handle,
}
if (lo.attributes & LOAD_OPTION_ACTIVE) {
struct efi_device_path *file_path;
u32 attributes;
log_debug("trying to load \"%ls\" from %pD\n", lo.label,
lo.file_path);
ret = EFI_CALL(efi_load_image(true, efi_root, lo.file_path,
file_path = expand_media_path(lo.file_path);
ret = EFI_CALL(efi_load_image(true, efi_root, file_path,
NULL, 0, handle));
efi_free_pool(file_path);
if (ret != EFI_SUCCESS) {
log_warning("Loading %ls '%ls' failed\n",
varname, lo.label);