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Re: Gold Linker Patch: Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715 and in some places called "spectre".
- From: Cary Coutant <ccoutant at gmail dot com>
- To: Sriraman Tallam <tmsriram at google dot com>
- Cc: binutils <binutils at sourceware dot org>, Chandler Carruth <chandlerc at google dot com>, Reid Kleckner <rnk at google dot com>, Eric Christopher <echristo at google dot com>, Rui Ueyama <ruiu at google dot com>, Brooks Moses <bmoses at google dot com>, Sidney Hummert <shummert at google dot com>, Xinliang David Li <davidxl at google dot com>
- Date: Thu, 4 Jan 2018 15:08:07 -0800
- Subject: Re: Gold Linker Patch: Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715 and in some places called "spectre".
- Authentication-results: sourceware.org; auth=none
- References: <CAAs8HmzJkLiGaUWf9czpNfEejM=uCP=zFvudADEuxsA2wHk+fQ@mail.gmail.com>
> * options.h (retpolineplt): New -z option to use retpoline PLT.
> * x86_64.cc (Output_data_plt_x86_64_retpoline): New class.
> (Target_x86_64<64>::do_make_data_plt): Create retpoline PLT when
> the option is used.
> * testsuite/Makefile.am (retpoline_plt_1.sh): New test.
> * testsuite/Makefile.in: Regenerate.
> * testsuite/retpoline_plt_1.sh: New test script.
> * testsuite/retpoline_plt_1.s: New test source.
This makes the -z bndplt and -z retpolineplt options mutually
exclusive. Please add a check in options.cc
(General_options::finalize) for this.
Will we be seeing an aarch64 patch along these same lines soon? As I
understand it, 64-bit ARM is susceptible to Spectre, but 32-bit ARM is
not (because 32-bit chips don't do any OOO execution). I haven't seen
a clear statement about other architectures like Sparc and PPC.
-cary