linux-kernel - [PATCH 3.2 076/104] x86/retpoline: Remove the esp/rsp thunk

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Date:   Mon, 12 Mar 2018 03:03:34 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Dave Hansen" <dave.hansen@...el.com>,
        "Josh Poimboeuf" <jpoimboe@...hat.com>,
        "Andy Lutomirski" <luto@...capital.net>,
        "Kees Cook" <keescook@...gle.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Paul Turner" <pjt@...gle.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Waiman Long" <longman@...hat.com>,
        "David Woodhouse" <dwmw@...zon.co.uk>,
        "Andi Kleen" <ak@...ux.intel.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Greg Kroah-Hartman" <gregkh@...ux-foundation.org>,
        "Jiri Kosina" <jikos@...nel.org>,
        "Tom Lendacky" <thomas.lendacky@....com>,
        "Arjan van de Ven" <arjan@...ux.intel.com>,
        "Tim Chen" <tim.c.chen@...ux.intel.com>,
        "Jeff Law" <law@...hat.com>
Subject: [PATCH 3.2 076/104] x86/retpoline: Remove the esp/rsp thunk

3.2.101-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Waiman Long <longman@...hat.com>

commit 1df37383a8aeabb9b418698f0bcdffea01f4b1b2 upstream.

It doesn't make sense to have an indirect call thunk with esp/rsp as
retpoline code won't work correctly with the stack pointer register.
Removing it will help compiler writers to catch error in case such
a thunk call is emitted incorrectly.

Fixes: 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
Suggested-by: Jeff Law <law@...hat.com>
Signed-off-by: Waiman Long <longman@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: David Woodhouse <dwmw@...zon.co.uk>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Kees Cook <keescook@...gle.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
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: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...ux-foundation.org>
Cc: Paul Turner <pjt@...gle.com>
Link: https://lkml.kernel.org/r/1516658974-27852-1-git-send-email-longman@redhat.com
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/lib/retpoline-export.c | 1 -
 arch/x86/lib/retpoline.S        | 1 -
 2 files changed, 2 deletions(-)

--- a/arch/x86/lib/retpoline-export.c
+++ b/arch/x86/lib/retpoline-export.c
@@ -22,5 +22,4 @@ INDIRECT_THUNK(dx)
 INDIRECT_THUNK(si)
 INDIRECT_THUNK(di)
 INDIRECT_THUNK(bp)
-INDIRECT_THUNK(sp)
 #endif /* CONFIG_RETPOLINE */
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -35,7 +35,6 @@ GENERATE_THUNK(_ASM_DX)
 GENERATE_THUNK(_ASM_SI)
 GENERATE_THUNK(_ASM_DI)
 GENERATE_THUNK(_ASM_BP)
-GENERATE_THUNK(_ASM_SP)
 #ifdef CONFIG_64BIT
 GENERATE_THUNK(r8)
 GENERATE_THUNK(r9)