linux-kernel - Re: [PATCH 7/9] arm64/build: Warn on orphan section placement

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Message-ID: <202003171558.7E1D46AED6@keescook>
Date:   Tue, 17 Mar 2020 16:01:16 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Will Deacon <will@...nel.org>
Cc:     Borislav Petkov <bp@...e.de>, "H.J. Lu" <hjl.tools@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <masahiroy@...nel.org>, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/9] arm64/build: Warn on orphan section placement

On Tue, Mar 17, 2020 at 09:56:14PM +0000, Will Deacon wrote:
> On Thu, Feb 27, 2020 at 04:22:42PM -0800, Kees Cook wrote:
> > We don't want to depend on the linker's orphan section placement
> > heuristics as these can vary between linkers, and may change between
> > versions. All sections need to be explicitly named in the linker
> > script.
> > 
> > Explicitly include debug sections when they're present. Add .eh_frame*
> > to discard as it seems that these are still generated even though
> > -fno-asynchronous-unwind-tables is being specified. Add .plt and
> > .data.rel.ro to discards as they are not actually used. Add .got.plt
> > to the image as it does appear to be mapped near .data. Finally enable
> > orphan section warnings.
> 
> Hmm, I don't understand what .got.plt is doing here. Please can you
> elaborate?

I didn't track it down, but it seems to have been present (and merged
into the kernel .data) for a while now. I can try to track this down if
you want?

-- 
Kees Cook