linux-kernel - [tip:x86/pti] x86/retpoline/xen: Convert Xen hypercall indirect jumps

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Date:   Thu, 11 Jan 2018 15:25:55 -0800
From:   tip-bot for David Woodhouse <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tim.c.chen@...ux.intel.com, mingo@...nel.org, peterz@...radead.org,
        jpoimboe@...hat.com, hpa@...or.com, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, jgross@...e.com,
        arjan@...ux.intel.com, riel@...hat.com, dave.hansen@...el.com,
        jikos@...nel.org, pjt@...gle.com, ak@...ux.intel.com,
        keescook@...gle.com, dwmw@...zon.co.uk, luto@...capital.net,
        tglx@...utronix.de, gregkh@...ux-foundation.org
Subject: [tip:x86/pti] x86/retpoline/xen: Convert Xen hypercall indirect
 jumps

Commit-ID:  ea08816d5b185ab3d09e95e393f265af54560350
Gitweb:     https://git.kernel.org/tip/ea08816d5b185ab3d09e95e393f265af54560350
Author:     David Woodhouse <dwmw@...zon.co.uk>
AuthorDate: Thu, 11 Jan 2018 21:46:31 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 12 Jan 2018 00:14:31 +0100

x86/retpoline/xen: Convert Xen hypercall indirect jumps

Convert indirect call in Xen hypercall to use non-speculative sequence,
when CONFIG_RETPOLINE is enabled.

Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Arjan van de Ven <arjan@...ux.intel.com>
Acked-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Juergen Gross <jgross@...e.com>
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: 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: Kees Cook <keescook@...gle.com>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...ux-foundation.org>
Cc: Paul Turner <pjt@...gle.com>
Link: https://lkml.kernel.org/r/1515707194-20531-10-git-send-email-dwmw@amazon.co.uk

---
 arch/x86/include/asm/xen/hypercall.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index 7cb282e..bfd8826 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -44,6 +44,7 @@
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/smap.h>
+#include <asm/nospec-branch.h>
 
 #include <xen/interface/xen.h>
 #include <xen/interface/sched.h>
@@ -217,9 +218,9 @@ privcmd_call(unsigned call,
 	__HYPERCALL_5ARG(a1, a2, a3, a4, a5);
 
 	stac();
-	asm volatile("call *%[call]"
+	asm volatile(CALL_NOSPEC
 		     : __HYPERCALL_5PARAM
-		     : [call] "a" (&hypercall_page[call])
+		     : [thunk_target] "a" (&hypercall_page[call])
 		     : __HYPERCALL_CLOBBER5);
 	clac();