Re: [PATCH 2/5] gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving

Alexander Popov
2020-06-11T23:45:09Z

On 10.06.2020 23:03, Kees Cook wrote:
> On Wed, Jun 10, 2020 at 06:47:14PM +0300, Alexander Popov wrote:
>> On 09.06.2020 21:46, Kees Cook wrote:
>> The inline asm statement that is used for instrumentation is arch-specific.
>> Trying to add
>> asm volatile("call stackleak_track_stack")
>> in gcc plugin on aarch64 makes gcc break spectacularly.
>
> Ah! Thank you, that eluded my eyes. :)
>
>> I pass the target arch name to the plugin and check it explicitly to avoid that.
>>
>> Moreover, I'm going to create a gcc enhancement request for supporting
>> no_caller_saved_registers attribute on aarch64.
>
> For arm64 right now it looks like the plugin will just remain
> "inefficient" in these cleanup, as before, yes?

Yes, for arm64 the instrumentation didn't change in this patch series.
I checked the disasm and see the similar issue with useless register saving.

I'm going to add asm instrumentation for arm64 when (I hope) the
no_caller_saved_registers attribute becomes available for that platform.

Best regards,
Alexander