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Date:   Wed, 27 Jan 2021 14:15:57 -0800
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Subject: Re: [RFC PATCH 12/17] gcc-plugins: objtool: Add plugin to detect
 switch table on arm64
From:   Nick Desaulniers <ndesaulniers@google.com>
To:     jthierry@redhat.com
Cc:     ardb@kernel.org, broonie@kernel.org, catalin.marinas@arm.com,
        jpoimboe@redhat.com, keescook@chromium.org,
        linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org,
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        mark.rutland@arm.com, masahiroy@kernel.org,
        michal.lkml@markovi.net, peterz@infradead.org,
        raphael.gault@arm.com, will@kernel.org,
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> From: Raphael Gault <raphael.gault@arm.com>
> 
> This plugins comes into play before the final 2 RTL passes of GCC and
> detects switch-tables that are to be outputed in the ELF and writes
> information in an ".discard.switch_table_info" section which will be
> used by objtool.
> 
> Signed-off-by: Raphael Gault <raphael.gault@arm.com>
> [J.T.: Change section name to store switch table information,
>        Make plugin Kconfig be selected rather than opt-in by user,
>        Add a relocation in the switch_table_info that points to
>        the jump operation itself]
> Signed-off-by: Julien Thierry <jthierry@redhat.com>

Rather than tightly couple this feature to a particular toolchain via
plugin, it might be nice to consider what features could be spec'ed out
for toolchains to implement (perhaps via a -f flag).

Distributions (like Android, CrOS) wont be able to use such a feature as
is.