Re: [PATCH v2 2/2] docs/devel: tvg-plugins: add execlog plugin description

[Alexandre IOOSS]

On 6/22/21 10:48 AM, Alex Bennée wrote:
> Alexandre Iooss<erdnaxe@crans.org>  writes:
> > [...]
> > +
> > +The execlog tool traces executed instructions with memory access. It can be 
> > used
> > +for debugging and security analysis purposes.
> We should probably mention that this will generate a lot of output.
> Running the admittedly memory heavy softmmu memory test:
>
>    ./aarch64-softmmu/qemu-system-aarch64 -D test.out -d plugin \
>      -plugin contrib/plugins/libexeclog.so  \
>      -cpu max -serial mon:stdio -M virt \
>      -display none -semihosting-config chardev=serial0 \
>      -kernel ./tests/tcg/aarch64-softmmu/memory
>
> generates a 8.6Gb text file. I suspect once this is merged you might
> want to look at options to target the instrumentation at areas of
> specific interest or abbreviate information.

Yes! In my downstream version I am triggering the beginning and the end 
of trace acquisition by matching two virtual addresses of GPIO device 
access. This works in my case because I'm also using the same GPIO for 
triggering an oscilloscope, but maybe we would like to upstream 
something more generic.

I'm still thinking about this (maybe for a later patch) but I believe it 
would be nice to have the following:
 - If no argument is given to the plugin, log everything.
 - Allow the user to specify either a memory address, an instruction 
virtual address or an opcode that would start the acquisition.
 - Same to stop the acquisition.

This would look like this to start/stop acquisition using GPIO PA8 on 
STM32VLDISCOVERY:

  ./arm-softmmu/qemu-system-arm -M stm32vldiscovery \
    -kernel ./firmware.elf -d plugin \
    -plugin libexeclog.so,arg=mem:1073809424,arg=mem:1073809424

I would like to hear other users opinion on this, because I fear I might 
implement something too specific.

Thanks,
-- Alexandre

OpenPGP_signature
Description: OpenPGP digital signature