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Date: Wed, 10 Jun 2020 13:03:27 -0700
From: Kees Cook <>
To: Alexander Popov <>
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 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?

Kees Cook

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