diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-06-05 13:15:32 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-06-05 13:15:32 -0700 |
commit | c3c55a07203947f72afa50a3218460b27307c47d (patch) | |
tree | de3a2f8adbb3bea4bba1df0f709b0d6c1f4e87b7 /Documentation/arm | |
parent | 046f153343e33dcad1be7f6249ea6ff1c6fd9b58 (diff) | |
parent | 74bcc2499291d38b6253f9dbd6af33a195222208 (diff) |
Merge branch 'arm64-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next
Pull ARM64 EFI update from Peter Anvin:
"By agreement with the ARM64 EFI maintainers, we have agreed to make
-tip the upstream for all EFI patches. That is why this patchset
comes from me :)
This patchset enables EFI stub support for ARM64, like we already have
on x86"
* 'arm64-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
arm64: efi: only attempt efi map setup if booting via EFI
efi/arm64: ignore dtb= when UEFI SecureBoot is enabled
doc: arm64: add description of EFI stub support
arm64: efi: add EFI stub
doc: arm: add UEFI support documentation
arm64: add EFI runtime services
efi: Add shared FDT related functions for ARM/ARM64
arm64: Add function to create identity mappings
efi: add helper function to get UEFI params from FDT
doc: efi-stub.txt updates for ARM
lib: add fdt_empty_tree.c
Diffstat (limited to 'Documentation/arm')
-rw-r--r-- | Documentation/arm/00-INDEX | 2 | ||||
-rw-r--r-- | Documentation/arm/uefi.txt | 64 |
2 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index a94090cc785d..3b08bc2b04cf 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX @@ -46,5 +46,7 @@ swp_emulation - 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. diff --git a/Documentation/arm/uefi.txt b/Documentation/arm/uefi.txt new file mode 100644 index 000000000000..d60030a1b909 --- /dev/null +++ b/Documentation/arm/uefi.txt @@ -0,0 +1,64 @@ +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. |