linux-kernel - [tip:x86/pti] x86/retpoline: Remove compile time warning

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Date:   Sun, 14 Jan 2018 13:33:43 -0800
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     luto@...capital.net, jikos@...nel.org, riel@...hat.com,
        mingo@...nel.org, keescook@...gle.com, jpoimboe@...hat.com,
        hpa@...or.com, gregkh@...ux-foundation.org,
        tim.c.chen@...ux.intel.com, torvalds@...ux-foundation.org,
        peterz@...radead.org, dave.hansen@...el.com, ak@...ux.intel.com,
        dwmw@...zon.co.uk, linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: [tip:x86/pti] x86/retpoline: Remove compile time warning

Commit-ID:  b8b9ce4b5aec8de9e23cabb0a26b78641f9ab1d6
Gitweb:     https://git.kernel.org/tip/b8b9ce4b5aec8de9e23cabb0a26b78641f9ab1d6
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Sun, 14 Jan 2018 22:13:29 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 14 Jan 2018 22:29:36 +0100

x86/retpoline: Remove compile time warning

Remove the compile time warning when CONFIG_RETPOLINE=y and the compiler
does not have retpoline support. Linus rationale for this is:

  It's wrong because it will just make people turn off RETPOLINE, and the
  asm updates - and return stack clearing - that are independent of the
  compiler are likely the most important parts because they are likely the
  ones easiest to target.

  And it's annoying because most people won't be able to do anything about
  it. The number of people building their own compiler? Very small. So if
  their distro hasn't got a compiler yet (and pretty much nobody does), the
  warning is just annoying crap.

  It is already properly reported as part of the sysfs interface. The
  compile-time warning only encourages bad things.

Fixes: 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
Requested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: gnomes@...rguk.ukuu.org.uk
Cc: Rik van Riel <riel@...hat.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: thomas.lendacky@....com
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Jiri Kosina <jikos@...nel.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Kees Cook <keescook@...gle.com>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...ux-foundation.org>
Link: https://lkml.kernel.org/r/CA+55aFzWgquv4i6Mab6bASqYXg3ErV3XDFEYf=GEcCDQg5uAtw@mail.gmail.com
---
 arch/x86/Makefile | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 974c618..504b1a4 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -240,8 +240,6 @@ ifdef CONFIG_RETPOLINE
     RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
     ifneq ($(RETPOLINE_CFLAGS),)
         KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
-    else
-        $(warning CONFIG_RETPOLINE=y, but not supported by the compiler. Toolchain update recommended.)
     endif
 endif