src: Remove variable length arrays

Variable length arrays were a feature added in C99 that allows the
length of an array to be determined at runtime. Eg.

	int sum(size_t n) {
		int arr[n];

This adds a small amount of runtime overhead, but is also very
dangerous, since it allows use of an unlimited amount of stack memory,
potentially leading to stack overflow. This is only worsened in
coreboot, which often has very little stack space to begin with. Citing
concerns like this, all instances of VLA's were recently removed from the
Linux kernel. In the immortal words of Linus Torvalds [0],

    AND USING VLA'S IS ACTIVELY STUPID! It generates much more code, and
    much _slower_ code (and more fragile code), than just using a fixed
    key size would have done. [...] Anyway, some of these are definitely
    easy to just fix, and using VLA's is actively bad not just for
    security worries, but simply because VLA's are a really horribly bad
    idea in general in the kernel.

This patch follows suit and zaps all VLA's in coreboot. Some of the
existing VLA's are accidental ones, and all but one can be replaced with
small fixed-size buffers. The single tricky exception is in the SPI
controller interface, which will require a rewrite of old drivers
to remove [1].


Change-Id: I7d9d1ddadbf1cee5f695165bbe3f0effb7bd32b9
Signed-off-by: Jacob Garber <>
Tested-by: build bot (Jenkins) <>
Reviewed-by: Patrick Georgi <>
12 files changed
tree: 761b138ce45fface88f8babba31d48bff43203d5
  1. 3rdparty/
  2. configs/
  3. Documentation/
  4. payloads/
  5. src/
  6. util/
  7. .checkpatch.conf
  8. .clang-format
  9. .gitignore
  10. .gitmodules
  11. .gitreview
  14. gnat.adc
  16. Makefile

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.


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

See for a list of supported payloads.

Supported Hardware

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

For details please consult:

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)


  • 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 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 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:

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.