linux-kernel - Re: [PATCH] kbuild: Remove CONFIG_DEBUG_SECTION

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Date:   Fri, 8 Apr 2022 21:14:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Sam Ravnborg <sam@...nborg.org>, X86 ML <x86@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Changbin Du <changbin.du@...il.com>
Subject: Re: [PATCH] kbuild: Remove CONFIG_DEBUG_SECTION_MISMATCH

On Sat, Apr 09, 2022 at 03:29:21AM +0900, Masahiro Yamada wrote:
> Is [2] caused by dead code that was not optimized out
> due to the unusual inlining decisions by the compiler ?

The complaint is due to SMAP validation; objtool will scream if there's
a CALL in between STAC/CLAC. The thinking is that since they open a
security window, we want tight code between them. We also very much
don't want tracing and other funnies to happen there. As such, any CALL
is dis-allowed.

This weird option is having us upgrade quite a few 'inline' to
'__always_inline'.