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Julius Werner e0058e89ab arm64: Reimplement mmu_disable() in assembly
Disabling the MMU with proper cache behavior is a bit tricky on ARM64:
you can flush the cache first and then disable the MMU (like we have
been doing), but then you run the risk of having new cache lines
allocated in the tiny window between the two, which may or may not
become a problem when those get flushed at a later point (on some
platforms certain memory regions "go away" at certain points in a way
that makes the CPU very unhappy if it ever issues a write cycle to
them again afterwards).

The obvious alternative is to first disable the MMU and then flush the
cache, ensuring that every memory access after the flush already has the
non-cacheable attribute. But we can't just flip the order around in the
C code that we have because then those accesses in the tiny window
in-between will go straight to memory, so loads may yield the wrong
result or stores may get overwritten again by the later cache flush.

In the end, this all shouldn't really be a problem because we can do
both operations purely from registers without doing any explicit memory
accesses in-between. We just have to reimplement the function in
assembly to make sure the compiler doesn't insert any stack accesses at
the wrong points.

Change-Id: Ic552960c91400dadae6f130b2521a696eeb4c0b1
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/27238
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2018-06-26 23:59:18 +00:00
3rdparty 3rdparty/libgfxinit: Update submodule pointer 2018-06-08 03:27:23 +00:00
Documentation Documentation: Add cavium SoC and mainboard 2018-06-19 18:09:04 +00:00
configs configs: add PC Engines apu2 sample configuration 2018-05-19 16:55:56 +00:00
payloads libpayload: cheza - fix config for chromium chroot build 2018-06-22 13:11:06 +00:00
src arm64: Reimplement mmu_disable() in assembly 2018-06-26 23:59:18 +00:00
util util/crossgcc: Allow building a new gcc against new binutils with -D 2018-06-26 20:58:01 +00:00
.checkpatch.conf .checkpatch.conf: Ignore CORRUPTED_PATCH lint 2017-10-29 10:11:58 +00:00
.clang-format clang-format: Update .clang-format to be compliant with linux kernel coding style 2018-04-23 09:26:08 +00:00
.gitignore Documentation: Add support for building with Sphinx 2018-04-26 12:25:03 +00:00
.gitmodules
.gitreview
COPYING
MAINTAINERS MAINTAINERS: change second PC Engines maintainer 2018-03-21 18:25:49 +00:00
Makefile Makefile: Add filelist to help 2018-01-29 15:35:11 +00:00
Makefile.inc Kconfig: Add new config for OVERRIDE_DEVICETREE 2018-06-25 17:40:28 +00:00
README README: Update requirements 2017-06-27 17:04:32 +00:00
gnat.adc
toolchain.inc Introduce bootblock self-decompression 2018-05-22 02:44:14 +00:00

README

-------------------------------------------------------------------------------
coreboot README
-------------------------------------------------------------------------------

coreboot is a Free Software project aimed at replacing the proprietary BIOS
(firmware) found in most computers.  coreboot performs a little bit of
hardware initialization and then executes additional boot logic, called a
payload.

With the separation of hardware initialization and later boot logic,
coreboot can scale from specialized applications that run directly
firmware, run operating systems in flash, load custom
bootloaders, or implement firmware standards, like PC BIOS services or
UEFI. This allows for systems to only include the features necessary
in the target application, reducing the amount of code and flash space
required.

coreboot was formerly known as LinuxBIOS.


Payloads
--------

After the basic initialization of the hardware has been performed, any
desired "payload" can be started by coreboot.

See https://www.coreboot.org/Payloads for a list of supported payloads.


Supported Hardware
------------------

coreboot supports a wide range of chipsets, devices, and mainboards.

For details please consult:

 * https://www.coreboot.org/Supported_Motherboards
 * https://www.coreboot.org/Supported_Chipsets_and_Devices


Build Requirements
------------------

 * make
 * gcc / g++
   Because Linux distribution compilers tend to use lots of patches. coreboot
   does lots of "unusual" things in its build system, some of which break due
   to those patches, sometimes by gcc aborting, sometimes - and that's worse -
   by generating broken object code.
   Two options: use our toolchain (eg. make crosstools-i386) or enable the
   ANY_TOOLCHAIN Kconfig option if you're feeling lucky (no support in this
   case).
 * iasl (for targets with ACPI support)
 * pkg-config
 * libssl-dev (openssl)

Optional:

 * doxygen (for generating/viewing documentation)
 * gdb (for better debugging facilities on some targets)
 * ncurses (for 'make menuconfig' and 'make nconfig')
 * flex and bison (for regenerating parsers)


Building coreboot
-----------------

Please consult https://www.coreboot.org/Build_HOWTO for details.


Testing coreboot Without Modifying Your Hardware
------------------------------------------------

If you want to test coreboot without any risks before you really decide
to use it on your hardware, you can use the QEMU system emulator to run
coreboot virtually in QEMU.

Please see https://www.coreboot.org/QEMU for details.


Website and Mailing List
------------------------

Further details on the project, a FAQ, many HOWTOs, news, development
guidelines and more can be found on the coreboot website:

  https://www.coreboot.org

You can contact us directly on the coreboot mailing list:

  https://www.coreboot.org/Mailinglist


Copyright and License
---------------------

The copyright on coreboot is owned by quite a large number of individual
developers and companies. Please check the individual source files for details.

coreboot is licensed under the terms of the GNU General Public License (GPL).
Some files are licensed under the "GPL (version 2, or any later version)",
and some files are licensed under the "GPL, version 2". For some parts, which
were derived from other projects, other (GPL-compatible) licenses may apply.
Please check the individual source files for details.

This makes the resulting coreboot images licensed under the GPL, version 2.