Re: [RFC PATCH 12/17] gcc-plugins: objtool: Add plugin to detect switch table on arm64
From: Josh Poimboeuf <hidden>
Date: 2021-01-27 23:29:49
Also in:
linux-efi, linux-hardening, lkml
On Wed, Jan 27, 2021 at 02:15:57PM -0800, Nick Desaulniers wrote:
quoted
From: Raphael Gault <redacted> 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 <redacted> [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 <redacted>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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel