linux-hardening - Re: [PATCH v2] x86/stackprotector: Work around strict Clang TLS symbol requirements

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Message-ID: <202410141357.3B2A71A340@keescook>
Date: Mon, 14 Oct 2024 13:59:49 -0700
From: Kees Cook <kees@...nel.org>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: x86@...nel.org, llvm@...ts.linux.dev, linux-hardening@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>, stable@...r.kernel.org,
	Fangrui Song <i@...kray.me>, Brian Gerst <brgerst@...il.com>,
	Uros Bizjak <ubizjak@...il.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2] x86/stackprotector: Work around strict Clang TLS
 symbol requirements

On Wed, Oct 09, 2024 at 02:43:53PM +0200, Ard Biesheuvel wrote:
> However, if a non-TLS definition of the symbol in question is visible in
> the same compilation unit (which amounts to the whole of vmlinux if LTO
> is enabled), it will drop the per-CPU prefix and emit a load from a
> bogus address.

I take this to mean that x86 32-bit kernels built with the stack
protector and using Clang LTO will crash very quickly?

-- 
Kees Cook