[PATCH v5 06/17] efi_loader: bootmgr: add booting from removable media

Thu May 5 14:05:04 CEST 2022

> Date: Fri, 29 Apr 2022 19:03:22 +0200
> From: Heinrich Schuchardt <xypron.glpk at gmx.de>
> 
> On 4/28/22 10:09, Masahisa Kojima wrote:
> > From: AKASHI Takahiro <takahiro.akashi at linaro.org>
> >
> > 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 74522c898b35
> > ("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 at linaro.org>
> > Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
> > ---
> > Changes in v5:
> > - add default file name definition for SANDBOX to avoid build error
> >
> > Changes from original version:
> > - create new include file "efi_default_filename.h" to
> >    avoid conflict with config_distro_bootcmd.h
> > - modify the target pointer of efi_free_pool(), expand_media_path() should
> >    only free the pointer allocated by efi_dp_from_file() function.
> >   include/config_distro_bootcmd.h | 14 +--------
> >   include/efi_default_filename.h  | 33 ++++++++++++++++++++++
> >   lib/efi_loader/efi_bootmgr.c    | 50 ++++++++++++++++++++++++++++++++-
> >   3 files changed, 83 insertions(+), 14 deletions(-)
> >   create mode 100644 include/efi_default_filename.h
> >
> > diff --git a/include/config_distro_bootcmd.h b/include/config_distro_bootcmd.h
> > index c55023889c..6a3110f27b 100644
> > --- a/include/config_distro_bootcmd.h
> > +++ b/include/config_distro_bootcmd.h
> > @@ -91,19 +91,7 @@
> >   #endif
> >
> >   #ifdef CONFIG_EFI_LOADER
> > -#if defined(CONFIG_ARM64)
> > -#define BOOTEFI_NAME "bootaa64.efi"
> > -#elif defined(CONFIG_ARM)
> > -#define BOOTEFI_NAME "bootarm.efi"
> > -#elif defined(CONFIG_X86_RUN_32BIT)
> > -#define BOOTEFI_NAME "bootia32.efi"
> > -#elif defined(CONFIG_X86_RUN_64BIT)
> > -#define BOOTEFI_NAME "bootx64.efi"
> > -#elif defined(CONFIG_ARCH_RV32I)
> > -#define BOOTEFI_NAME "bootriscv32.efi"
> > -#elif defined(CONFIG_ARCH_RV64I)
> > -#define BOOTEFI_NAME "bootriscv64.efi"
> > -#endif
> > +#include <efi_default_filename.h>
> >   #endif
> >
> >   #ifdef BOOTEFI_NAME
> > diff --git a/include/efi_default_filename.h b/include/efi_default_filename.h
> > new file mode 100644
> > index 0000000000..cb2ef9e131
> > --- /dev/null
> > +++ b/include/efi_default_filename.h
> > @@ -0,0 +1,33 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/*
> > + * Default boot file name when none is present in the FilePath.
> > + * This is defined in the UEFI specification.
> > + *
> > + * Copyright (c) 2022, Linaro Limited
> > + */
> > +#ifndef _EFI_DEFAULT_FILENAME_H
> > +#define _EFI_DEFAULT_FILENAME_H
> > +
> > +#if defined(CONFIG_ARM64)
> > +#define BOOTEFI_NAME "BOOTAA64.EFI"
> > +#elif defined(CONFIG_ARM)
> > +#define BOOTEFI_NAME "BOOTARM.EFI"
> > +#elif defined(CONFIG_X86_64)
> > +#define BOOTEFI_NAME "BOOTX64.EFI"
> > +#elif defined(CONFIG_X86)
> > +#define BOOTEFI_NAME "BOOTIA32.EFI"
> > +#elif defined(CONFIG_ARCH_RV32I)
> > +#define BOOTEFI_NAME "BOOTRISCV32.EFI"
> > +#elif defined(CONFIG_ARCH_RV64I)
> > +#define BOOTEFI_NAME "BOOTRISCV64.EFI"
> > +#elif defined(CONFIG_SANDBOX)
> > +/*
> > + * SANDBOX is not defined in UEFI specification, but
> > + * this definition avoids build failure for SANDBOX.
> > + */
> > +#define BOOTEFI_NAME "BOOTSANDBOX.EFI"
> 
> The sandbox should boot the default binary for the host architecture:
> 
> #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

Maybe sanbox is special, but using the host architecture for actual
boards makes no sense.  I see this has made its way into master
already, but when I cross-build for apple_m1_defconfig on an amd64
machine I end up with:

    $ strings ./lib/efi_loader/efi_bootmgr.o | grep BOOT
    /EFI/BOOT/BOOTX64.EFI

The original diff that used CONFIG_ARM64, CONFIG_ARM, etc, did this
right.