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Re: [PATCH v2 2/2] docs/devel: tvg-plugins: add execlog plugin descripti
From: |
Alex Bennée |
Subject: |
Re: [PATCH v2 2/2] docs/devel: tvg-plugins: add execlog plugin description |
Date: |
Tue, 22 Jun 2021 11:37:07 +0100 |
User-agent: |
mu4e 1.5.13; emacs 28.0.50 |
Alexandre IOOSS <erdnaxe@crans.org> writes:
> [[PGP Signed Part:Undecided]]
> 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.
Sounds reasonable to me.
> 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 quite like the formats you can use for -dfilter, for example:
0x1000+0x100,0x2100-0x100,0x3000..0x3100
it might even be worth exposing qemu_set_dfilter_ranges as a helper
function to plugins to avoid copy and paste.
So what would your above command trigger? A write to 1073809424 would
start the trace and the next write to the same address would stop it?
> I would like to hear other users opinion on this, because I fear I
> might implement something too specific.
>
> Thanks,
> -- Alexandre
>
> [[End of PGP Signed Part]]
--
Alex Bennée
Re: [PATCH v2 2/2] docs/devel: tvg-plugins: add execlog plugin description, Alex Bennée, 2021/06/22
Re: [PATCH v2 0/2] execlog TCG plugin to log instructions, Alexandre IOOSS, 2021/06/18