linux-kernel - [PATCH 0/4] x86/srso: Reduce overhead of the mitigation

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Date:   Mon, 21 Aug 2023 12:27:19 +0100
From:   Andrew Cooper <andrew.cooper3@...rix.com>
To:     LKML <linux-kernel@...r.kernel.org>
CC:     Andrew Cooper <andrew.cooper3@...rix.com>, <x86@...nel.org>,
        "Borislav Petkov" <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Babu Moger <babu.moger@....com>, <David.Kaplan@....com>,
        Nikolay Borisov <nik.borisov@...e.com>,
        <gregkh@...uxfoundation.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 0/4] x86/srso: Reduce overhead of the mitigation

The main point of this series is patch 4 to remove one taken branch from every
function return.  Everything else is cleanup.

Patch 3 has an issue that sadly may invalidate this as a technique.  Patch 4
needs some objtool whispering to fix.

Based on x86/urgent but I suspect this may want rebasing around other fixes in
flight.

Andrew Cooper (4):
  x86/srso: Rename srso_alias_*() to srso_fam19_*()
  x86/srso: Rename fam17 SRSO infrastructure to srso_fam17_*()
  x86/ret-thunk: Support CALL-ing to the ret-thunk
  x86/srso: Use CALL-based return thunks to reduce overhead

 arch/x86/include/asm/nospec-branch.h |  9 ++--
 arch/x86/kernel/alternative.c        |  4 +-
 arch/x86/kernel/cpu/bugs.c           |  9 ++--
 arch/x86/kernel/ftrace.c             |  8 +--
 arch/x86/kernel/static_call.c        | 10 ++--
 arch/x86/kernel/vmlinux.lds.S        | 10 ++--
 arch/x86/lib/retpoline.S             | 75 ++++++++++++----------------
 arch/x86/net/bpf_jit_comp.c          |  5 +-
 8 files changed, 67 insertions(+), 63 deletions(-)


base-commit: 6405b72e8d17bd1875a56ae52d23ec3cd51b9d66
-- 
2.30.2