linux-kernel - [PATCH 3.16 29/76] x86/retpoline/xen: Convert Xen hypercall indirect jumps

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Message-ID: <lsq.1520823972.542837140@decadent.org.uk>
Date:   Mon, 12 Mar 2018 03:06:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Ingo Molnar" <mingo@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>, gnomes@...rguk.ukuu.org.uk,
        "Juergen Gross" <jgross@...e.com>,
        "Andy Lutomirski" <luto@...capital.net>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Josh Poimboeuf" <jpoimboe@...hat.com>,
        "Arjan van de Ven" <arjan@...ux.intel.com>,
        "Rik van Riel" <riel@...hat.com>,
        "Kees Cook" <keescook@...gle.com>,
        "Dave Hansen" <dave.hansen@...el.com>,
        "Greg Kroah-Hartman" <gregkh@...ux-foundation.org>,
        "Jiri Kosina" <jikos@...nel.org>,
        "David Woodhouse" <dwmw@...zon.co.uk>, thomas.lendacky@....com,
        "Paul Turner" <pjt@...gle.com>, "Andi Kleen" <ak@...ux.intel.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Tim Chen" <tim.c.chen@...ux.intel.com>
Subject: [PATCH 3.16 29/76] x86/retpoline/xen: Convert Xen hypercall
 indirect jumps

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

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

From: David Woodhouse <dwmw@...zon.co.uk>

commit ea08816d5b185ab3d09e95e393f265af54560350 upstream.

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
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/include/asm/xen/hypercall.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- 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>
@@ -215,9 +216,9 @@ 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();