Merge branch 'arm64-efi-for-linus' of...

	- SWP/SWPB emulation handler/logging description

tcm.txt

	- ARM Tightly Coupled Memory

uefi.txt

	- [U]EFI configuration and runtime services documentation

vlocks.txt

	- Voting locks, low-level mechanism relying on memory system atomic writes.

UEFI, the Unified Extensible Firmware Interface, is a specification

governing the behaviours of compatible firmware interfaces. It is

maintained by the UEFI Forum - http://www.uefi.org/.

UEFI is an evolution of its predecessor 'EFI', so the terms EFI and

UEFI are used somewhat interchangeably in this document and associated

source code. As a rule, anything new uses 'UEFI', whereas 'EFI' refers

to legacy code or specifications.

UEFI support in Linux

=====================

Booting on a platform with firmware compliant with the UEFI specification

makes it possible for the kernel to support additional features:

- UEFI Runtime Services

- Retrieving various configuration information through the standardised

  interface of UEFI configuration tables. (ACPI, SMBIOS, ...)

For actually enabling [U]EFI support, enable:

- CONFIG_EFI=y

- CONFIG_EFI_VARS=y or m

The implementation depends on receiving information about the UEFI environment

in a Flattened Device Tree (FDT) - so is only available with CONFIG_OF.

UEFI stub

=========

The "stub" is a feature that extends the Image/zImage into a valid UEFI

PE/COFF executable, including a loader application that makes it possible to

load the kernel directly from the UEFI shell, boot menu, or one of the

lightweight bootloaders like Gummiboot or rEFInd.

The kernel image built with stub support remains a valid kernel image for

booting in non-UEFI environments.

UEFI kernel support on ARM

==========================

UEFI kernel support on the ARM architectures (arm and arm64) is only available

when boot is performed through the stub.

When booting in UEFI mode, the stub deletes any memory nodes from a provided DT.

Instead, the kernel reads the UEFI memory map.

The stub populates the FDT /chosen node with (and the kernel scans for) the

following parameters:

________________________________________________________________________________

Name                      | Size   | Description

================================================================================

linux,uefi-system-table   | 64-bit | Physical address of the UEFI System Table.

--------------------------------------------------------------------------------

linux,uefi-mmap-start     | 64-bit | Physical address of the UEFI memory map,

                          |        | populated by the UEFI GetMemoryMap() call.

--------------------------------------------------------------------------------

linux,uefi-mmap-size      | 32-bit | Size in bytes of the UEFI memory map

                          |        | pointed to in previous entry.

--------------------------------------------------------------------------------

linux,uefi-mmap-desc-size | 32-bit | Size in bytes of each entry in the UEFI

                          |        | memory map.

--------------------------------------------------------------------------------

linux,uefi-mmap-desc-ver  | 32-bit | Version of the mmap descriptor format.

--------------------------------------------------------------------------------

linux,uefi-stub-kern-ver  | string | Copy of linux_banner from build.

--------------------------------------------------------------------------------

For verbose debug messages, specify 'uefi_debug' on the kernel command line.

Header notes:

- code0/code1 are responsible for branching to stext.

- when booting through EFI, code0/code1 are initially skipped.

  res5 is an offset to the PE header and the PE header has the EFI

  entry point (efi_stub_entry). When the stub has done its work, it

  jumps to code0 to resume the normal boot process.

The image must be placed at the specified offset (currently 0x80000)

from the start of the system RAM and called there. The start of the

			  The EFI Boot Stub

		     ---------------------------

On the x86 platform, a bzImage can masquerade as a PE/COFF image,

thereby convincing EFI firmware loaders to load it as an EFI

executable. The code that modifies the bzImage header, along with the

EFI-specific entry point that the firmware loader jumps to are

collectively known as the "EFI boot stub", and live in

On the x86 and ARM platforms, a kernel zImage/bzImage can masquerade

as a PE/COFF image, thereby convincing EFI firmware loaders to load

it as an EFI executable. The code that modifies the bzImage header,

along with the EFI-specific entry point that the firmware loader

jumps to are collectively known as the "EFI boot stub", and live in

arch/x86/boot/header.S and arch/x86/boot/compressed/eboot.c,

respectively.

respectively. For ARM the EFI stub is implemented in

arch/arm/boot/compressed/efi-header.S and

arch/arm/boot/compressed/efi-stub.c. EFI stub code that is shared

between architectures is in drivers/firmware/efi/efi-stub-helper.c.

For arm64, there is no compressed kernel support, so the Image itself

masquerades as a PE/COFF image and the EFI stub is linked into the

kernel. The arm64 EFI stub lives in arch/arm64/kernel/efi-entry.S

and arch/arm64/kernel/efi-stub.c.

By using the EFI boot stub it's possible to boot a Linux kernel

without the use of a conventional EFI boot loader, such as grub or

System Partition (ESP) and renamed with the extension ".efi". Without

the extension the EFI firmware loader will refuse to execute it. It's

not possible to execute bzImage.efi from the usual Linux file systems

because EFI firmware doesn't have support for them.

because EFI firmware doesn't have support for them. For ARM the

arch/arm/boot/zImage should be copied to the system partition, and it

may not need to be renamed. Similarly for arm64, arch/arm64/boot/Image

should be copied but not necessarily renamed.

**** Passing kernel parameters from the EFI shell

because the image we're executing is interpreted by the EFI shell,

which understands relative paths, whereas the rest of the command line

is passed to bzImage.efi.

**** The "dtb=" option

For the ARM and arm64 architectures, we also need to be able to provide a

device tree to the kernel. This is done with the "dtb=" command line option,

and is processed in the same manner as the "initrd=" option that is

described above.

	  This is useful if you cannot or don't want to change the

	  command-line options your boot loader passes to the kernel.

config EFI

	bool "UEFI runtime support"

	depends on OF && !CPU_BIG_ENDIAN

	select LIBFDT

	select UCS2_STRING

	select EFI_PARAMS_FROM_FDT

	default y

	help

	  This option provides support for runtime services provided

	  by UEFI firmware (such as non-volatile variables, realtime

          clock, and platform reset). A UEFI stub is also provided to

	  allow the kernel to be booted as an EFI application. This

	  is only useful on systems that have UEFI firmware.

endmenu

menu "Userspace binary formats"

source "drivers/Kconfig"

source "drivers/firmware/Kconfig"

source "fs/Kconfig"

source "arch/arm64/kvm/Kconfig"