Messages in this thread | | | Date | Wed, 27 Jan 2021 17:26:51 -0600 | From | Josh Poimboeuf <> | Subject | Re: [RFC PATCH 12/17] gcc-plugins: objtool: Add plugin to detect switch table on arm64 |
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On Wed, Jan 27, 2021 at 02:15:57PM -0800, Nick Desaulniers wrote: > > 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).
The problem is being able to detect switch statement jump table vectors.
For a given indirect branch (due to a switch statement), what are all the corresponding jump targets?
We would need the compiler to annotate that information somehow.
> Distributions (like Android, CrOS) wont be able to use such a feature as > is.
Would a Clang plugin be out of the question?
-- Josh
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