release/4.8.27/x86-retpoline-hyperv-convert-assembler-indirect-jumps.patch

From e70e5892b28c18f517f29ab6e83bd57705104b31 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw@amazon.co.uk>
Date: Thu, 11 Jan 2018 21:46:30 +0000
Subject: x86/retpoline/hyperv: Convert assembler indirect jumps

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

commit e70e5892b28c18f517f29ab6e83bd57705104b31 upstream.

Convert all indirect jumps in hyperv inline asm code to use non-speculative
sequences when CONFIG_RETPOLINE is enabled.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: thomas.lendacky@amd.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/1515707194-20531-9-git-send-email-dwmw@amazon.co.uk
[ backport to 4.9, hopefully correct, not tested... - gregkh ]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/hv/hv.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -31,6 +31,7 @@
 #include <linux/clockchips.h>
 #include <asm/hyperv.h>
 #include <asm/mshyperv.h>
+#include <asm/nospec-branch.h>
 #include "hyperv_vmbus.h"
 
 /* The one and only */
@@ -103,9 +104,10 @@ u64 hv_do_hypercall(u64 control, void *i
 		return (u64)ULLONG_MAX;
 
 	__asm__ __volatile__("mov %0, %%r8" : : "r" (output_address) : "r8");
-	__asm__ __volatile__("call *%3" : "=a" (hv_status) :
+	__asm__ __volatile__(CALL_NOSPEC :
+			     "=a" (hv_status) :
 			     "c" (control), "d" (input_address),
-			     "m" (hypercall_page));
+			     THUNK_TARGET(hypercall_page));
 
 	return hv_status;
 
@@ -123,11 +125,12 @@ u64 hv_do_hypercall(u64 control, void *i
 	if (!hypercall_page)
 		return (u64)ULLONG_MAX;
 
-	__asm__ __volatile__ ("call *%8" : "=d"(hv_status_hi),
+	__asm__ __volatile__ (CALL_NOSPEC : "=d"(hv_status_hi),
 			      "=a"(hv_status_lo) : "d" (control_hi),
 			      "a" (control_lo), "b" (input_address_hi),
 			      "c" (input_address_lo), "D"(output_address_hi),
-			      "S"(output_address_lo), "m" (hypercall_page));
+			      "S"(output_address_lo),
+			      THUNK_TARGET(hypercall_page));
 
 	return hv_status_lo | ((u64)hv_status_hi << 32);
 #endif /* !x86_64 */