arm64: Print a char to UART early in exception handler

Over time our printk() seems to acquire more and more features... which
is nice, but it also makes it a little less robust when something goes
wrong. If the wrong global is trampled by some buffer overflow, it
suddenly doesn't print anymore. It would be nice to have at least some
way to tell that we triggered a real exception in that case.

With this patch, arm64 exceptions will print a '!' straight to the UART
before trying any of the more fancy printk() stuff. It's not much but it
should tell the difference between an exception and a hang and hopefully
help someone dig in the right direction sooner. This violates loglevels
(which is part of the point), but presumably when you have a fatal
exception you shouldn't care about that anymore.

Change-Id: I3b08ab86beaee55263786011caa5588d93bbc720
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37465
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed
tree: f5bba103398af605ce15435f012f9331c8cf5b7d
  1. .checkpatch.conf
  2. .clang-format
  3. .editorconfig
  4. .gitignore
  5. .gitmodules
  6. .gitreview
  7. 3rdparty/
  8. AUTHORS
  9. COPYING
  10. Documentation/
  11. LICENSES/
  12. MAINTAINERS
  13. Makefile
  14. Makefile.inc
  15. README.md
  16. configs/
  17. gnat.adc
  18. payloads/
  19. src/
  20. toolchain.inc
  21. util/
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:

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.