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Date: Mon, 5 Feb 2024 08:21:47 -0800
From: Kees Cook <keescook@chromium.org>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>
Subject: Re: [PATCH 1/2] Compiler Attributes: Add __uninitialized macro
Message-ID: <202402050818.B11CFAD2B@keescook>
References: <20240205154844.3757121-1-hca@linux.ibm.com>
 <20240205154844.3757121-2-hca@linux.ibm.com>
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On Mon, Feb 05, 2024 at 04:48:43PM +0100, Heiko Carstens wrote:
> With INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO enabled the kernel will
> be compiled with -ftrivial-auto-var-init=<...> which causes initialization
> of stack variables at function entry time.
> 
> In order to avoid the performance impact that comes with this users can use
> the "uninitialized" attribute to prevent such initialization.
> 
> Therefore provide the __uninitialized macro which can be used for cases
> where INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO is enabled, but only
> selected variables should not be initialized.
> 
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Thanks! We had something similar a while back with syscall entry:
efa90c11f62e ("stack: Constrain and fix stack offset randomization with Clang builds")

Acked-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook