Re: [PATCH v4 06/11] efi_loader: bootmgr: add booting from removable media

[Masahisa Kojima <masahisa.kojima@linaro.org>]

Hi Ilias,

On Thu, 31 Mar 2022 at 04:13, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> Hello Akashi-san,
>
> On Thu, Mar 24, 2022 at 10:54:38PM +0900, Masahisa Kojima wrote:
> > From: AKASHI Takahiro <takahiro.akashi@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
>
> Mark had some concerns wrt to this approach and from what I can tell this
> hasn't changed in this revision [1]. Can we use boot_targets and generate
> Boot#### with an empty FilePath as Mark suggested?  Or is the user expected to
> select that somehow from the menu?
>
> [1] https://lore.kernel.org/u-boot/d3cac2e5b37f96b5@bloch.sibelius.xs4all.nl/

My patch series tries to resolve the above issue to some extent
by a different approach.

The patch "[PATCH v4 10/11] bootmenu: add removable media entries" [*1]
enumerates the all (removable) medias supporting
EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.

Example bootmenu is as below.

    *** U-Boot Boot Menu ***

       UEFI BOOT0000 : mmc0:1
       UEFI BOOT0001 : mmc0:2
       UEFI BOOT0002 : debian
       UEFI BOOT0003 : nvme0:1
       UEFI BOOT0004 : ubuntu
       UEFI BOOT0005 : nvme0:2
       UEFI BOOT0006 : usb0:2

mmcX:X, usbX:X and nvmeX:X are the entries of the removable media
having device path without FilePath. They are automatically created
by the bootmenu and BOOT#### and BootOrder variables are updated.
They are also managed by the bootmenu, if the usb device is removed from
the system at the next boot, the BOOT#### variable is removed by bootmenu
and BootOrder is also updated.

[*1] https://lore.kernel.org/u-boot/20220324135443.1571-11-masahisa.kojima@linaro.org/

Thanks,
Masahisa Kojima

>
> Thanks
> /Ilias
> >
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
> > ---
> > 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  | 26 +++++++++++++++++
> >  lib/efi_loader/efi_bootmgr.c    | 50 ++++++++++++++++++++++++++++++++-
> >  3 files changed, 76 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 2f90929178..ef2c9f330e 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..de030d2692
> > --- /dev/null
> > +++ b/include/efi_default_filename.h
> > @@ -0,0 +1,26 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/*
> > + * Default boot file name when none is present in the FilePath.
> > + *
> > + * 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"
> > +#else
> > +#error Unsupported UEFI architecture
> > +#endif
> > +
> > +#endif
> > diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
> > index 8c04ecbdc8..22a4302aac 100644
> > --- a/lib/efi_loader/efi_bootmgr.c
> > +++ b/lib/efi_loader/efi_bootmgr.c
> > @@ -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 +31,50 @@ 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_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
> >   *
> > @@ -68,13 +113,16 @@ 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("%s: trying to load \"%ls\" from %pD\n",
> >                         __func__, 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);
> > --
> > 2.17.1
> >