Re: [PATCH v2 3/3] Add inject plugin and x86_64 target for the inject plugin

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 12/6/24 17:02, Rowan Hart wrote:
>>> +++ b/tests/tcg/plugins/inject.c
>>
>> Could we find a better name?
> 
> For sure, maybe "hypercalls.c" since that's really what it's mostly about.
> 

Sounds good.

>>> @@ -0,0 +1,206 @@
>>> +/*
>>> + * Copyright (C) 2024, Rowan Hart <rowanbhart@gmail.com>
>>> + *
>>> + * License: GNU GPL, version 2 or later.
>>> + *   See the COPYING file in the top-level directory.
>>> + */
>>
>> We can add a comment here about what the plugin is doing.
> 
> Will do!
> 
>> One challenge with picking a random value, is how to ensure this pattern has no other meaning for all architectures? I'm not sure we can find a single pattern of bytes that works for all arch, even though that would be definitely stylish :).
>>
>> In more, it seems that we are reinventing the syscall interface, while we already have it. But as the current instrumentation only works for user-mode, having a specific hypercall interface might be worth it for plugins, so system mode could benefit from it too.
>>
>> The work done here could serve later to define a proper interface.
> 
> 
> I'll see what I can do about this. SIMICS supports many architectures and has a
> "magic instruction" interface[0] (basically hypercalls) and has these
> instructions defined per-architecture in a way that at minimum there are 12
> values available which work on every architecture the simulator supports. QEMU
> supports more architectures than SIMICS but I think we could start there and
> follow a similar approach.
> 
> [0]:
> https://intel.github.io/tsffs/simics/simics-user-guide/breakpoints.html#Magic-Breakpoints
> 

Looks like a good model to reuse if we want to implement something similar.

> -Rowan