linux-kernel - [PATCH 0/3] extern inline native_save

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Message-Id: <20180601165550.90053-1-ndesaulniers@google.com>
Date:   Fri,  1 Jun 2018 09:55:47 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     akpm@...ux-foundation.org, ard.biesheuvel@...aro.org,
        aryabinin@...tuozzo.com, akataria@...are.com,
        boris.ostrovsky@...cle.com, brijesh.singh@....com,
        caoj.fnst@...fujitsu.com, gregkh@...uxfoundation.org,
        hpa@...or.com, jan.kiszka@...mens.com,
        jarkko.sakkinen@...ux.intel.com, jgross@...e.com,
        jpoimboe@...hat.com, kirill.shutemov@...ux.intel.com,
        mingo@...hat.com, mjg59@...gle.com, mka@...omium.org,
        ndesaulniers@...gle.com, pombredanne@...b.com, rostedt@...dmis.org,
        tglx@...utronix.de, thomas.lendacky@....com, tweek@...gle.com
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, virtualization@...ts.linux-foundation.org
Subject: [PATCH 0/3] extern inline native_save_fl for paravirt

paravirt depends on a custom calling convention (callee saved), but
expects this from a static inline function that it then forces to be
outlined. This is problematic because different compilers or flags can
then add a stack guard that violates the calling conventions.

Uses extern inline with the out-of-line definition in assembly to
prevent compilers from adding stack guards to the outlined version.

Other parts of the codebase overwrite KBUILD_CFLAGS, which is *extremely
problematic* for extern inline, as the sematics are completely the
opposite depending on what C standard is used.
http://blahg.josefsipek.net/?p=529

Nick Desaulniers (3):
  efi: use -std=gnu89 for proper extern inline semantics
  x86/build: use -std=gnu89 for proper extern inline semantics
  x86: paravirt: make native_save_fl extern inline

 arch/x86/boot/compressed/Makefile     |  2 +-
 arch/x86/include/asm/irqflags.h       |  2 +-
 arch/x86/kernel/Makefile              |  1 +
 arch/x86/kernel/irqflags.S            | 26 ++++++++++++++++++++++++++
 drivers/firmware/efi/libstub/Makefile |  2 +-
 5 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 arch/x86/kernel/irqflags.S

-- 
2.17.0.921.gf22659ad46-goog