linux-kernel - Re: [PATCH v2 16/28] init: lto: fix PREL32 relocations

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Message-ID: <202009031541.40B54A2E51@keescook>
Date:   Thu, 3 Sep 2020 15:41:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v2 16/28] init: lto: fix PREL32 relocations

On Thu, Sep 03, 2020 at 01:30:41PM -0700, 'Sami Tolvanen' via Clang Built Linux wrote:
> With LTO, the compiler can rename static functions to avoid global
> naming collisions. As initcall functions are typically static,
> renaming can break references to them in inline assembly. This
> change adds a global stub with a stable name for each initcall to
> fix the issue when PREL32 relocations are used.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

This was a Delight(tm) to get right. Thanks for finding the right magic
here. :)

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook