c43001eb14
C strict aliasing rules state that it is undefined behaviour to access
any pointer using another pointer of a different type (with several small
exceptions). Eg.
uint64_t x = 3;
uint16_t y = *((uint16_t *)&x); // undefined behaviour
From an architectural point of view there is often nothing wrong with
pointer aliasing - the problem is that since it is undefined behaviour,
the compiler will often use this as a cop-out to perform unintended or
unsafe optimizations. The "safe" way to perfom the above assignment is
to cast the pointers to a uint8_t * first (which is allowed to alias
anything), and then work on a byte level:
*((uint8_t *)&y) = *((uint8_t *)&x);
*((uint8_t *)&y + 1) = *((uint8_t *)&x + 1);
Horribly ugly, but there you go. Anyway, in an attempt to follow these
strict aliasing rules, the ReadMEM() function in SB800 does the above
operation when reading a uint16_t. While perfectly fine, however, it
doesn't have to - all calls to ReadMEM() that read a uint16_t are passed
a uint16_t pointer, so there are no strict aliasing violations to worry
about (the WriteMEM() function is exactly similar). The problem is that
using this unnecessary workaround generates almost 50 false positive
warnings in Coverity. Rather than manually ignore them one-by-one, let's
just remove the workaround entirely. As a side note, this change makes
ReadMEM() and WriteMEM() now match their definitions in the SB900 code.
Change-Id: Ia7e3a1eff88b855a05b33c7dafba16ed23784e43
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34783
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
|
||
|---|---|---|
| 3rdparty | ||
| Documentation | ||
| configs | ||
| payloads | ||
| src | ||
| util | ||
| .checkpatch.conf | ||
| .clang-format | ||
| .gitignore | ||
| .gitmodules | ||
| .gitreview | ||
| AUTHORS | ||
| COPYING | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc | ||
| README.md | ||
| gnat.adc | ||
| toolchain.inc | ||
README.md
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_TOOLCHAINKconfig 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 menuconfigandmake 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:
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.