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Date: Fri, 12 Jun 2020 02:45:00 +0300
From: Alexander Popov <>
To: Kees Cook <>
Cc: Emese Revfy <>,
 Miguel Ojeda <>,
 Masahiro Yamada <>,
 Michal Marek <>,
 Andrew Morton <>,
 Masahiro Yamada <>,
 Thiago Jung Bauermann <>,
 Luis Chamberlain <>, Jessica Yu <>,
 Sven Schnelle <>, Iurii Zaikin <>,
 Catalin Marinas <>, Will Deacon <>,
 Vincenzo Frascino <>,
 Thomas Gleixner <>, Peter Collingbourne <>,
 Naohiro Aota <>, Alexander Monakov <>,
 Mathias Krause <>, PaX Team <>,
 Brad Spengler <>, Laura Abbott <>,
 Florian Weimer <>,,,,,,,
Subject: Re: [PATCH 2/5] gcc-plugins/stackleak: Use asm instrumentation to
 avoid useless register saving

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,

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