0f5b2c69a4
Commit 5d9db883761a ("efi: Add support for a UEFI variable filesystem")
dated Oct 5, 2012, introduced a new efivarfs pseudo-filesystem to
replace the efivars sysfs interface that was used up to that point to
expose EFI variables to user space.
The main problem with the sysfs interface was that it only supported up
to 1024 bytes of payload per file, whereas the underlying variables
themselves are only bounded by a platform specific per-variable and
global limit that is typically much higher than 1024 bytes.
The deprecated sysfs interface is only enabled on x86 and Itanium, other
EFI enabled architectures only support the efivarfs pseudo-filesystem.
So let's finally rip off the band aid, and drop the old interface
entirely. This will make it easier to refactor and clean up the
underlying infrastructure that is shared between efivars, efivarfs and
efi-pstore, and is long overdue for a makeover.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
59 lines
1.8 KiB
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59 lines
1.8 KiB
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.. SPDX-License-Identifier: GPL-2.0
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General note on [U]EFI x86_64 support
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The nomenclature EFI and UEFI are used interchangeably in this document.
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Although the tools below are _not_ needed for building the kernel,
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the needed bootloader support and associated tools for x86_64 platforms
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with EFI firmware and specifications are listed below.
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1. UEFI specification: http://www.uefi.org
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2. Booting Linux kernel on UEFI x86_64 platform requires bootloader
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support. Elilo with x86_64 support can be used.
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3. x86_64 platform with EFI/UEFI firmware.
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Mechanics
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---------
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- Build the kernel with the following configuration::
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CONFIG_FB_EFI=y
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CONFIG_FRAMEBUFFER_CONSOLE=y
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If EFI runtime services are expected, the following configuration should
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be selected::
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CONFIG_EFI=y
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CONFIG_EFIVAR_FS=y or m # optional
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- Create a VFAT partition on the disk
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- Copy the following to the VFAT partition:
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elilo bootloader with x86_64 support, elilo configuration file,
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kernel image built in first step and corresponding
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initrd. Instructions on building elilo and its dependencies
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can be found in the elilo sourceforge project.
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- Boot to EFI shell and invoke elilo choosing the kernel image built
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in first step.
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- If some or all EFI runtime services don't work, you can try following
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kernel command line parameters to turn off some or all EFI runtime
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services.
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noefi
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turn off all EFI runtime services
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reboot_type=k
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turn off EFI reboot runtime service
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- If the EFI memory map has additional entries not in the E820 map,
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you can include those entries in the kernels memory map of available
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physical RAM by using the following kernel command line parameter.
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add_efi_memmap
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include EFI memory map of available physical RAM
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