linux-kernel - Re: [PATCH] kselftest/arm64: bti: force static linking

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Message-ID: <YoDQY/0i9BrEIEO8@arm.com>
Date:   Sun, 15 May 2022 11:05:23 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Andre Przywara <andre.przywara@....com>
Cc:     Will Deacon <will@...nel.org>, Shuah Khan <shuah@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Brown <broonie@...nel.org>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kselftest/arm64: bti: force static linking

On Wed, May 11, 2022 at 06:21:29PM +0100, Andre Przywara wrote:
> The "bti" selftests are built with -nostdlib, which apparently
> automatically creates a statically linked binary, which is what we want
> and need for BTI (to avoid interactions with the dynamic linker).
> 
> However this is not true when building a PIE binary, which some
> toolchains (Ubuntu) configure as the default.
> When compiling btitest with such a toolchain, it will create a
> dynamically linked binary, which will probably fail some tests, as the
> dynamic linker might not support BTI:
> ===================
> TAP version 13
> 1..18
> not ok 1 nohint_func/call_using_br_x0
> not ok 2 nohint_func/call_using_br_x16
> not ok 3 nohint_func/call_using_blr
> ....
> ===================
> 
> To make sure we create static binaries, add an explicit -static on the
> linker command line. This forces static linking even if the toolchain
> defaults to PIE builds, and fixes btitest runs on BTI enabled machines.
> 
> Signed-off-by: Andre Przywara <andre.przywara@....com>

Does this need to go in as a fix (cc stable, fixes tag)?

-- 
Catalin