Aaron Durbin dd6fa93ded x86: prepare cache-as-ram to allow multiple stages
In order to do a verification of romstage on x86 one needs to
run verstage which verifies romstage (and the memory init code).
However, x86 doesn't have SRAM like every other modern SoC so
managing the cache-as-ram region is especially critical.

First move all of the "shared" objects to the beginning of
the .car.data section. This change then ensures that each stage
using car.ld to link has the same consistent view of the addresses
of these fixed-sized objects in cache-as-ram. The CAR_GLOBALs can
be unique per stage. However, these variables are expected to have
a value of zero at the start of each stage. In order to allow a
stage to provide those semantics outside of the initial cache-as-arm
setup routine add _car_global_start and _car_global_end symbols.
Those symbols can be used to clear the CAR_GLOBALs for that stage.

Note that the timestamp region can't be moved out similarly to the
pre-ram cbmem console because the object storage of the timestamp
cache is used *after* cache-as-ram is torn down to indicate if the
cache should be used or not. Therefore, that timestamp needs to
migrated to ram. A logic change in src/lib/timestamp.c could
alleviate this requirement, but that task wasn't tackled in this
patch.

BUG=chrome-os-partner:44827
BRANCH=None
TEST=Built and booted glados.

Change-Id: I15e9f6b0c632ee5a2369da0709535d6cb0d94f61
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11740
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2015-09-30 06:53:55 +00:00
2012-11-01 23:13:39 +01:00
2006-08-12 22:03:36 +00:00

-------------------------------------------------------------------------------
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 http://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:

 * http://www.coreboot.org/Supported_Motherboards
 * http://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)

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 http://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 http://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:

  http://www.coreboot.org

You can contact us directly on the coreboot mailing list:

  http://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.

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