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Julius Werner a7902edf56 chromeos: Reverse FMAP signature constant to avoid having it in .rodata
Even though coreboot always hardcodes the FMAP offset, the same is not
possible for all other tools that manipulate ROM images. Some need to
manually find the FMAP by searching for it's magic number (ASCII
"__FMAP__"). If we do something like 'memcmp(fmap_buffer, "__FMAP__",
...) in coreboot code, it has the unfortunate side effect that the
compiler will output that very same magic number as a constant in the
.rodata section to compare against. Other tools may mistake this for the
"real" FMAP location and get confused.

This patch reverses the constant defined in coreboot and changes the
only use of it correspondingly. It is not impossible but extremely
unlikely (at the current state of the art) that any compiler would be
clever enough to understand this pattern and optimize it back to a
straight memcmp() (GCC 4.9 definitely doesn't), so it should solve the
problem at least for another few years/decades.

BRANCH=veyron
BUG=chromium:447051
TEST=Made sure the new binaries actually contain "__PAMF__" in their
.rodata. Booted Pinky. Independently corrupted both the first and the
last byte of the FMAP signature with a hex editor and confirmed that
signature check fails in both cases.

Change-Id: I314b5e7e4d78352f409e73a3ed0e71d1b56fe774
Signed-off-by: Stefan Reinauer <reinauer@chromium.org>
Original-Commit-Id: 1359d2d4502eb34a043dffab35cf4a5b033ed65a
Original-Change-Id: I725652ef2a77f7f99884b46498428c3d68cd0945
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/240723
Original-Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/9562
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2015-04-13 12:22:55 +02:00
3rdparty@2bc495fd31 3rdparty: Update submodule to get Tegra 132 binaries 2015-03-07 17:50:58 +01:00
documentation documentation: define downstream data consumption rules 2015-04-07 00:20:13 +02:00
payloads serial: Combine Tegra and Rockchip UARTs to generic 8250_mmio32 2015-04-10 07:50:21 +02:00
src chromeos: Reverse FMAP signature constant to avoid having it in .rodata 2015-04-13 12:22:55 +02:00
util util/bimgtool: Add verification mode 2015-04-10 12:03:35 +02:00
.gitignore .gitignore: add the doxygen directory. 2014-12-14 23:30:45 +01:00
.gitmodules nvidia/cbootimage: avoid upstream's build system 2014-10-02 10:26:58 +02:00
.gitreview add .gitreview 2012-11-01 23:13:39 +01:00
COPYING
Makefile build system: run linker scripts through the preprocessor 2015-04-06 19:14:00 +02:00
Makefile.inc Makefile.inc: Only add `-Wno-unused-but-set-variable` for GCC 2015-04-08 15:42:37 +02:00
README
toolchain.inc mips: mips, not mipsel 2015-03-29 22:38:57 +02:00

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

 * gcc / g++
 * make

Optional:

 * doxygen (for generating/viewing documentation)
 * iasl (for targets with ACPI support)
 * gdb (for better debugging facilities on some targets)
 * ncurses (for 'make menuconfig')
 * 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.