[coreboot-announce] SerialICE - Qemu based x86 firmware debugger

Stefan Reinauer stepan at coresystems.de
Sat Jun 6 20:35:05 CEST 2009

Dear x86 hardware and low-level software developers and enthusiasts!

coresystems GmbH is proud to release the first version of our
"Integrated Circuit Emulator over Serial", short SerialICE.

This piece of software consists of two parts:

- a serial console "rom shell" compiled with romcc, with minimal
footprint. (Due to romcc the image is still 128k because it did not fit
in 64k but this can be optimized later)
- a patch to Qemu 0.10.4, which adds a new "SerialICE" machine.

Short description:

SerialICE is a BIOS/Firmware debugging tool. It allows you to run and
observe BIOS images (such as coreboot®: http://www.coreboot.org/)
written for real hardware in Qemu (http://www.nongnu.org/qemu) for
debugging purposes. Thanks to Qemu's compelling feature set, it's also
possible to debug this BIOS code with GNU GDB.

SerialICE can be downloaded from

With "qemu -m serialice -serialice /dev/ttyS0 -L
path-to-your-bios.bin-dir -hda /dev/zero" you can run an arbitrary BIOS
binary written for your target hardware in Qemu, thus logging all IO and
memory accesses. Those operations will additionally be transmitted to
the target system's shell and are executed there, while their results
are submitted back to Qemu.

Operations sent to the target:
- memory reads/writes (some of them)
- IO reads/writes
- MSR reads/writes
- CPUID calls (the bios code path might rely on this)

Note: The code is very experimental and still buggy, but it was already
useful in some debugging scenarios we had and was able to reveil
information that would normally only be available with a hardware
debugger of the price of a new car. Don't expect SerialICE to completely
replace a ICE/JTAG/ITP device, but it might just work for your case, as
it did for us.

The code needs minimal board/chipset specific setup in order to have
serial console operational for communication with Qemu. See mainboard/*
for an example.  This release contains demo code for two mainboards with
Intel® CPUs. Also, some hardware accesses have to be caught in the Qemu
code (hw/serialice.c) in order to prevent the system from locking up
(ie. by disabling the serial console).

Known issues:
- The code is ugly, and the Qemu part is light years from a state where
integration would be possible.
- infrastructure for compiling with gcc + xmmstack is there, but it
still fails with some odd assembler errors. This should push the
SerialICE rom shell clearly below 64k again.
- microcode updates from within emulated ROM code will fail.
- some rarely used calls of cpuid will not give the correct information
(those using two registers for input)

Special thanks go to
* Alex Graf for listening to my odd ideas while embedded world and
supporting this project from early on.
* Paul Brook for helping me find the last bug that prevented surviving
all of RAM initialization on one board.
* Patrick Georgi for Development and Testing.
* Ron Minnich for advice and encouragement.
* Eric Biederman for romcc

Comments and patches are of course very welcome!

Best regards,

Stefan Reinauer

coresystems GmbH • Brahmsstr. 16 • D-79104 Freiburg i. Br.
      Tel.: +49 761 7668825 • Fax: +49 761 7664613
Email: info at coresystems.dehttp://www.coresystems.de/
Registergericht: Amtsgericht Freiburg • HRB 7656
Geschäftsführer: Stefan Reinauer • Ust-IdNr.: DE245674866

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