From c03461ec8ccff18f0928abe6d6acb777ce0c1314 Mon Sep 17 00:00:00 2001
From: mortimer <mortimer@openbsd.org>
Date: Sun, 12 Aug 2018 17:15:10 +0000
Subject: [PATCH] Add retguard macros for arm64 asm and apply them in the
 straightforward cases in kernel and libc. ok deraadt@

---
 lib/libc/arch/aarch64/gen/byte_swap_2.S  |  4 ++-
 lib/libc/arch/aarch64/gen/byte_swap_4.S  |  4 ++-
 lib/libc/arch/aarch64/sys/Ovfork.S       |  4 ++-
 lib/libc/arch/aarch64/sys/brk.S          |  4 ++-
 lib/libc/arch/aarch64/sys/cerror.S       |  4 ++-
 lib/libc/arch/aarch64/sys/sbrk.S         |  4 ++-
 lib/libc/arch/aarch64/sys/sigpending.S   |  4 ++-
 lib/libc/arch/aarch64/sys/sigprocmask.S  |  4 ++-
 lib/libc/arch/aarch64/sys/sigsuspend.S   |  4 ++-
 lib/libc/arch/aarch64/sys/tfork_thread.S |  4 ++-
 sys/arch/arm64/arm64/copy.S              | 14 ++++++++-
 sys/arch/arm64/arm64/copystr.S           |  6 +++-
 sys/arch/arm64/arm64/cpufunc_asm.S       | 28 +++++++++++++++--
 sys/arch/arm64/arm64/support.S           |  6 +++-
 sys/arch/arm64/include/asm.h             | 40 +++++++++++++++++++++++-
 15 files changed, 118 insertions(+), 16 deletions(-)

diff --git a/lib/libc/arch/aarch64/gen/byte_swap_2.S b/lib/libc/arch/aarch64/gen/byte_swap_2.S
index 5bd951ee8a4..76b7db58c5c 100644
--- a/lib/libc/arch/aarch64/gen/byte_swap_2.S
+++ b/lib/libc/arch/aarch64/gen/byte_swap_2.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: byte_swap_2.S,v 1.1 2017/01/11 18:09:24 patrick Exp $	*/
+/*	$OpenBSD: byte_swap_2.S,v 1.2 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: byte_swap_2.S,v 1.3 2003/04/05 23:08:51 bjh21 Exp $	*/
 
 /*-
@@ -36,7 +36,9 @@ _ENTRY(_C_LABEL(__bswap16))
 _ENTRY(_C_LABEL(ntohs))
 _ENTRY(_C_LABEL(htons))
 _PROF_PROLOGUE
+	RETGUARD_SETUP(__bswap16, x15)
 	and     w8, w0, #0xffff
         ubfx    w0, w0, #8, #8
 	bfi     w0, w8, #8, #16
+	RETGUARD_CHECK(__bswap16, x15)
 	ret
diff --git a/lib/libc/arch/aarch64/gen/byte_swap_4.S b/lib/libc/arch/aarch64/gen/byte_swap_4.S
index 6d9119b2230..dfc3db40d29 100644
--- a/lib/libc/arch/aarch64/gen/byte_swap_4.S
+++ b/lib/libc/arch/aarch64/gen/byte_swap_4.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: byte_swap_4.S,v 1.1 2017/01/11 18:09:24 patrick Exp $	*/
+/*	$OpenBSD: byte_swap_4.S,v 1.2 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: byte_swap_4.S,v 1.2 2003/04/05 23:08:51 bjh21 Exp $	*/
 
 /*-
@@ -36,5 +36,7 @@ _ENTRY(_C_LABEL(__bswap32))
 _ENTRY(_C_LABEL(ntohl))
 _ENTRY(_C_LABEL(htonl))
 _PROF_PROLOGUE
+	RETGUARD_SETUP(__bswap32, x15)
 	rev	w0, w0
+	RETGUARD_CHECK(__bswap32, x15)
 	ret
diff --git a/lib/libc/arch/aarch64/sys/Ovfork.S b/lib/libc/arch/aarch64/sys/Ovfork.S
index 3dd82683ac7..db40fb8b118 100644
--- a/lib/libc/arch/aarch64/sys/Ovfork.S
+++ b/lib/libc/arch/aarch64/sys/Ovfork.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: Ovfork.S,v 1.3 2017/11/22 20:36:02 kettenis Exp $	*/
+/*	$OpenBSD: Ovfork.S,v 1.4 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: Ovfork.S,v 1.6 2003/08/07 16:42:03 agc Exp $	*/
 
 /*-
@@ -35,9 +35,11 @@
 #include "SYS.h"
 
 SYSENTRY_HIDDEN(vfork)
+	RETGUARD_SETUP(vfork, x15)
 	mov	x2, x30
 	SYSTRAP(vfork)
 	bcs	CERROR
 	mov	x30, x2
+	RETGUARD_CHECK(vfork, x15)
 	ret
 SYSCALL_END_HIDDEN(vfork)
diff --git a/lib/libc/arch/aarch64/sys/brk.S b/lib/libc/arch/aarch64/sys/brk.S
index af0e31de410..574c615afb9 100644
--- a/lib/libc/arch/aarch64/sys/brk.S
+++ b/lib/libc/arch/aarch64/sys/brk.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: brk.S,v 1.4 2017/11/22 20:36:02 kettenis Exp $	*/
+/*	$OpenBSD: brk.S,v 1.5 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: brk.S,v 1.7 2003/12/26 11:23:44 martin Exp $	*/
 
 /*-
@@ -48,6 +48,7 @@ __minbrk:
  * Change the data segment size
  */
 ENTRY(brk)
+	RETGUARD_SETUP(brk, x15)
 #ifdef __PIC__
 	/* Setup the GOT */
 	adrp	x3, :got:__minbrk
@@ -81,6 +82,7 @@ ENTRY(brk)
 
 	/* Return 0 for success */
 	mov	x0, #0x00000000
+	RETGUARD_CHECK(brk, x15)
 	ret
 
 	.align	3
diff --git a/lib/libc/arch/aarch64/sys/cerror.S b/lib/libc/arch/aarch64/sys/cerror.S
index 4ef8359f63f..e12dcf44062 100644
--- a/lib/libc/arch/aarch64/sys/cerror.S
+++ b/lib/libc/arch/aarch64/sys/cerror.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cerror.S,v 1.4 2017/03/19 00:29:02 guenther Exp $	*/
+/*	$OpenBSD: cerror.S,v 1.5 2018/08/12 17:15:10 mortimer Exp $	*/
 /*-
  * Copyright (c) 2014 Andrew Turner
  * All rights reserved.
@@ -32,8 +32,10 @@
 #define TCB_OFFSET_ERRNO	(-12)
 
 _ENTRY(CERROR)
+	RETGUARD_SETUP(CERROR, x15)
 	mrs	x1, tpidr_el0
 	str	w0, [x1, #TCB_OFFSET_ERRNO]
 	movn	x0, #0
+	RETGUARD_CHECK(CERROR, x15)
 	ret
 END(CERROR)
diff --git a/lib/libc/arch/aarch64/sys/sbrk.S b/lib/libc/arch/aarch64/sys/sbrk.S
index 75b25a73c57..1e3bd836832 100644
--- a/lib/libc/arch/aarch64/sys/sbrk.S
+++ b/lib/libc/arch/aarch64/sys/sbrk.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sbrk.S,v 1.3 2017/11/22 20:36:02 kettenis Exp $	*/
+/*	$OpenBSD: sbrk.S,v 1.4 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: sbrk.S,v 1.7 2003/08/07 16:42:05 agc Exp $	*/
 
 /*-
@@ -49,6 +49,7 @@ __curbrk:
  * Change the data segment size
  */
 ENTRY(sbrk)
+	RETGUARD_SETUP(sbrk, x15)
 #ifdef __PIC__
 	/* Setup the GOT */
 	adrp	x3, :got:__curbrk
@@ -71,6 +72,7 @@ ENTRY(sbrk)
 	str	x1, [x2]
 
 	/* Return old curbrk value */
+	RETGUARD_CHECK(sbrk, x15)
 	ret
 
 	.align	3
diff --git a/lib/libc/arch/aarch64/sys/sigpending.S b/lib/libc/arch/aarch64/sys/sigpending.S
index 076473b1ccb..c532274f79c 100644
--- a/lib/libc/arch/aarch64/sys/sigpending.S
+++ b/lib/libc/arch/aarch64/sys/sigpending.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sigpending.S,v 1.2 2017/02/23 22:50:07 patrick Exp $	*/
+/*	$OpenBSD: sigpending.S,v 1.3 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: sigpending.S,v 1.5 2003/08/07 16:42:05 agc Exp $	*/
 
 /*-
@@ -35,10 +35,12 @@
 #include "SYS.h"
 
 SYSENTRY(sigpending)
+	RETGUARD_SETUP(sigpending, x15)
 	mov	x2, x0
 	SYSTRAP(sigpending)
 	bcs	CERROR
 	str	w0, [x2]
 	mov	x0, #0
+	RETGUARD_CHECK(sigpending, x15)
 	ret
 SYSCALL_END(sigpending)
diff --git a/lib/libc/arch/aarch64/sys/sigprocmask.S b/lib/libc/arch/aarch64/sys/sigprocmask.S
index 7a9ea688f14..a07ef23ae9f 100644
--- a/lib/libc/arch/aarch64/sys/sigprocmask.S
+++ b/lib/libc/arch/aarch64/sys/sigprocmask.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sigprocmask.S,v 1.2 2017/02/22 22:18:51 patrick Exp $	*/
+/*	$OpenBSD: sigprocmask.S,v 1.3 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: sigprocmask.S,v 1.5 2003/08/07 16:42:05 agc Exp $	*/
 
 /*-
@@ -35,6 +35,7 @@
 #include "SYS.h"
 
 SYSENTRY_HIDDEN(sigprocmask)
+	RETGUARD_SETUP(sigprocmask, x15)
 	cbz	x1, 1f
 	ldr	w1, [x1]
 	b	2f
@@ -49,5 +50,6 @@ SYSENTRY_HIDDEN(sigprocmask)
 	str	w0, [x2]
 1:
 	mov	x0, #0x00000000
+	RETGUARD_CHECK(sigprocmask, x15)
 	ret
 SYSCALL_END_HIDDEN(sigprocmask)
diff --git a/lib/libc/arch/aarch64/sys/sigsuspend.S b/lib/libc/arch/aarch64/sys/sigsuspend.S
index 9be04da1525..d28d0377af6 100644
--- a/lib/libc/arch/aarch64/sys/sigsuspend.S
+++ b/lib/libc/arch/aarch64/sys/sigsuspend.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sigsuspend.S,v 1.1 2017/01/11 18:09:24 patrick Exp $	*/
+/*	$OpenBSD: sigsuspend.S,v 1.2 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: sigsuspend.S,v 1.6 2003/08/07 16:42:05 agc Exp $	*/
 
 /*-
@@ -35,9 +35,11 @@
 #include "SYS.h"
 
 SYSENTRY_HIDDEN(sigsuspend)
+	RETGUARD_SETUP(sigsuspend, x15)
 	ldr	w0, [x0]
 	SYSTRAP(sigsuspend)
 	bcs	CERROR
 	mov	x0, #0
+	RETGUARD_CHECK(sigsuspend, x15)
 	ret
 SYSCALL_END_HIDDEN(sigsuspend)
diff --git a/lib/libc/arch/aarch64/sys/tfork_thread.S b/lib/libc/arch/aarch64/sys/tfork_thread.S
index 5dda781adc2..6e515c32b24 100644
--- a/lib/libc/arch/aarch64/sys/tfork_thread.S
+++ b/lib/libc/arch/aarch64/sys/tfork_thread.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: tfork_thread.S,v 1.2 2017/02/20 08:42:46 patrick Exp $ */
+/* $OpenBSD: tfork_thread.S,v 1.3 2018/08/12 17:15:10 mortimer Exp $ */
 /*
  * Copyright (c) 2005 Dale Rahn <drahn@openbsd.org>
  *
@@ -24,11 +24,13 @@
  */
 
 ENTRY(__tfork_thread)
+	RETGUARD_SETUP(__tfork_thread, x15)
 	SYSTRAP(__tfork)
 	bcs	CERROR
 
 	/* check if we are parent or child */
 	cbz	x0, 1f
+	RETGUARD_CHECK(__tfork_thread, x15)
 	ret
 
 1:
diff --git a/sys/arch/arm64/arm64/copy.S b/sys/arch/arm64/arm64/copy.S
index af9f015ec08..4ced221e81f 100644
--- a/sys/arch/arm64/arm64/copy.S
+++ b/sys/arch/arm64/arm64/copy.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: copy.S,v 1.4 2017/12/30 10:20:34 kettenis Exp $ */
+/* $OpenBSD: copy.S,v 1.5 2018/08/12 17:15:10 mortimer Exp $ */
 /*
  * Copyright (c) 2015 Dale Rahn <drahn@dalerahn.com>
  * Copyright (c) 2014 Patrick Wildt <patrick@blueri.se>
@@ -34,8 +34,10 @@
  * XXX should this assert that address spaces are correct for each address?
  */
 ENTRY(copyin)
+	RETGUARD_SETUP(copy, x15)
 	cbnz	x2, 1f
 	mov	x0, 0
+	RETGUARD_CHECK(copy, x15)
 	ret
 1:
 	mrs	x3, tpidr_el1			// load cpuinfo
@@ -53,11 +55,13 @@ ENTRY(copyin)
 
 	str	x4, [x3, #(PCB_ONFAULT)]	// clear handler
 	mov	x0, xzr
+	RETGUARD_CHECK(copy, x15)
 	ret
 
 .Lcopyfault:
 	mov	x0, #EFAULT
 	ldr	x4, [x3, #(PCB_ONFAULT)]
+	RETGUARD_CHECK(copy, x15)
 	ret
 
 /*
@@ -69,6 +73,7 @@ ENTRY(copyin)
  * XXX should this assert that address spaces are correct for each address?
  */
 ENTRY(copyin32)
+	RETGUARD_SETUP(copy, x15)
 	mrs	x3, tpidr_el1			// load cpuinfo
 	ldr	x3, [x3, #(CI_CURPCB)]
 	ldr	x4, [x3, #(PCB_ONFAULT)]
@@ -80,6 +85,7 @@ ENTRY(copyin32)
 
 	str	x4, [x3, #(PCB_ONFAULT)]	// clear handler
 	mov	x0, xzr
+	RETGUARD_CHECK(copy, x15)
 	ret
 
 /*
@@ -93,8 +99,10 @@ ENTRY(copyin32)
  */
 
 ENTRY(copyout)
+	RETGUARD_SETUP(copy, x15)
 	cbnz	x2, 1f
 	mov	x0, 0
+	RETGUARD_CHECK(copy, x15)
 	ret
 1:
 	mrs	x3, tpidr_el1			// load cpuinfo
@@ -112,6 +120,7 @@ ENTRY(copyout)
 
 	str	x4, [x3, #(PCB_ONFAULT)]	// clear handler
 	mov	x0, xzr
+	RETGUARD_CHECK(copy, x15)
 	ret
 
 /*
@@ -123,8 +132,10 @@ ENTRY(copyout)
  */
 
 ENTRY(kcopy)
+	RETGUARD_SETUP(copy, x15)
 	cbnz	x2, 1f
 	mov	x0, 0
+	RETGUARD_CHECK(copy, x15)
 	ret
 1:
 	mrs	x3, tpidr_el1			// load cpuinfo
@@ -141,4 +152,5 @@ ENTRY(kcopy)
 
 	str	x4, [x3, #(PCB_ONFAULT)]	// clear handler
 	mov	x0, xzr
+	RETGUARD_CHECK(copy, x15)
 	ret
diff --git a/sys/arch/arm64/arm64/copystr.S b/sys/arch/arm64/arm64/copystr.S
index 3c13b3a2a24..6273584b6ef 100644
--- a/sys/arch/arm64/arm64/copystr.S
+++ b/sys/arch/arm64/arm64/copystr.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: copystr.S,v 1.3 2017/02/15 21:39:50 patrick Exp $ */
+/* $OpenBSD: copystr.S,v 1.4 2018/08/12 17:15:10 mortimer Exp $ */
 /*
  * Copyright (c) 2015 Dale Rahn <drahn@dalerahn.com>
  * Copyright (c) 2014 Patrick Wildt <patrick@blueri.se>
@@ -35,6 +35,7 @@
  * Copy string from x0 to x1
  */
 ENTRY(copystr)
+	RETGUARD_SETUP(copystr, x15)
 	mrs	x6, tpidr_el1			// load curcpu
 	ldr	x6, [x6, #(CI_CURPCB)]
 	ldr	x5, [x6, #(PCB_ONFAULT)]
@@ -65,6 +66,7 @@ ENTRY(copystr)
 	str	x8, [x3]
 2:
 	str	x5, [x6, #(PCB_ONFAULT)]
+	RETGUARD_CHECK(copystr, x15)
 	ret
 
 /*
@@ -76,6 +78,7 @@ ENTRY(copystr)
  * Copy string from user space to kernel space
  */
 ENTRY(copyinstr)
+	RETGUARD_SETUP(copystr, x15)
 	mrs	x6, tpidr_el1			// load curcpu
 	ldr	x6, [x6, #(CI_CURPCB)]
 	ldr	x5, [x6, #(PCB_ONFAULT)]
@@ -104,6 +107,7 @@ ENTRY(copyinstr)
  * Copy string from kernel space to user space
  */
 ENTRY(copyoutstr)
+	RETGUARD_SETUP(copystr, x15)
 	mrs	x6, tpidr_el1			// load curcpu
 	ldr	x6, [x6, #(CI_CURPCB)]
 	ldr	x5, [x6, #(PCB_ONFAULT)]
diff --git a/sys/arch/arm64/arm64/cpufunc_asm.S b/sys/arch/arm64/arm64/cpufunc_asm.S
index 94a127df330..44c5272a48c 100644
--- a/sys/arch/arm64/arm64/cpufunc_asm.S
+++ b/sys/arch/arm64/arm64/cpufunc_asm.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: cpufunc_asm.S,v 1.4 2018/01/10 23:27:18 kettenis Exp $ */
+/* $OpenBSD: cpufunc_asm.S,v 1.5 2018/08/12 17:15:10 mortimer Exp $ */
 /*-
  * Copyright (c) 2014 Robin Randhawa
  * Copyright (c) 2015 The FreeBSD Foundation
@@ -71,7 +71,6 @@
 .if \ic != 0
 	isb
 .endif
-	ret
 .endm
 
 /*
@@ -79,44 +78,54 @@
  */
 
 ENTRY(cpu_setttb)
+	RETGUARD_SETUP(cpu_setttb, x15)
 	mrs	x2, ttbr1_el1
 	bfi	x2, x0, #48, #16
 	msr	ttbr1_el1, x2
 	isb
 	msr	ttbr0_el1, x1
 	isb
+	RETGUARD_CHECK(cpu_setttb, x15)
 	ret
 END(cpu_setttb)
 
 ENTRY(cpu_tlb_flush)
+	RETGUARD_SETUP(cpu_tlb_flush, x15)
 	dsb	ishst
 	tlbi	vmalle1is
 	dsb	ish
 	isb
+	RETGUARD_CHECK(cpu_tlb_flush, x15)
 	ret
 END(cpu_tlb_flush)
 
 ENTRY(cpu_tlb_flush_asid)
+	RETGUARD_SETUP(cpu_tlb_flush_asid, x15)
 	dsb	ishst
 	tlbi	vae1is, x0
 	dsb	ish
 	isb
+	RETGUARD_CHECK(cpu_tlb_flush_asid, x15)
 	ret
 END(cpu_tlb_flush_asid)
 
 ENTRY(cpu_tlb_flush_all_asid)
+	RETGUARD_SETUP(cpu_tlb_flush_all_asid, x15)
 	dsb	ishst
 	tlbi	vaale1is, x0
 	dsb	ish
 	isb
+	RETGUARD_CHECK(cpu_tlb_flush_all_asid, x15)
 	ret
 END(cpu_tlb_flush_all_asid)
 
 ENTRY(cpu_tlb_flush_asid_all)
+	RETGUARD_SETUP(cpu_tlb_flush_asid_all, x15)
 	dsb	ishst
 	tlbi	aside1is, x0
 	dsb	ish
 	isb
+	RETGUARD_CHECK(cpu_tlb_flush_asid_all, x15)
 	ret
 END(cpu_tlb_flush_asid_all)
 
@@ -124,14 +133,20 @@ END(cpu_tlb_flush_asid_all)
  * void cpu_dcache_wb_range(vaddr_t, vsize_t)
  */
 ENTRY(cpu_dcache_wb_range)
+	RETGUARD_SETUP(cpu_dcache_wb_range, x15)
 	cache_handle_range	dcop = cvac
+	RETGUARD_CHECK(cpu_dcache_wb_range, x15)
+	ret
 END(cpu_dcache_wb_range)
 
 /*
  * void cpu_dcache_wbinv_range(vaddr_t, vsize_t)
  */
 ENTRY(cpu_dcache_wbinv_range)
+	RETGUARD_SETUP(cpu_dcache_wbinv_range, x15)
 	cache_handle_range	dcop = civac
+	RETGUARD_CHECK(cpu_dcache_wbinv_range, x15)
+	ret
 END(cpu_dcache_wbinv_range)
 
 /*
@@ -141,19 +156,28 @@ END(cpu_dcache_wbinv_range)
  * must use wb-inv of the entire cache.
  */
 ENTRY(cpu_dcache_inv_range)
+	RETGUARD_SETUP(cpu_dcache_inv_range, x15)
 	cache_handle_range	dcop = ivac
+	RETGUARD_CHECK(cpu_dcache_inv_range, x15)
+	ret
 END(cpu_dcache_inv_range)
 
 /*
  * void cpu_idcache_wbinv_range(vaddr_t, vsize_t)
  */
 ENTRY(cpu_idcache_wbinv_range)
+	RETGUARD_SETUP(cpu_idcache_wbinv_range, x15)
 	cache_handle_range	dcop = civac, ic = 1, icop = ivau
+	RETGUARD_CHECK(cpu_idcache_wbinv_range, x15)
+	ret
 END(cpu_idcache_wbinv_range)
 
 /*
  * void cpu_icache_sync_range(vaddr_t, vsize_t)
  */
 ENTRY(cpu_icache_sync_range)
+	RETGUARD_SETUP(cpu_icache_sync_range, x15)
 	cache_handle_range	dcop = cvau, ic = 1, icop = ivau
+	RETGUARD_CHECK(cpu_icache_sync_range, x15)
+	ret
 END(cpu_icache_sync_range)
diff --git a/sys/arch/arm64/arm64/support.S b/sys/arch/arm64/arm64/support.S
index ea0212b59ae..765327627ba 100644
--- a/sys/arch/arm64/arm64/support.S
+++ b/sys/arch/arm64/arm64/support.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: support.S,v 1.6 2017/08/09 03:06:55 jsg Exp $ */
+/* $OpenBSD: support.S,v 1.7 2018/08/12 17:15:10 mortimer Exp $ */
 /*-
  * Copyright (c) 2014 Andrew Turner
  * Copyright (c) 2014-2015 The FreeBSD Foundation
@@ -83,6 +83,7 @@ END(longjmp)
  * pagezero, simple implementation
  */
 ENTRY(pagezero_simple)
+	RETGUARD_SETUP(pagezero_simple, x15)
 	add	x1, x0, #PAGE_SIZE
 
 1:
@@ -92,6 +93,7 @@ ENTRY(pagezero_simple)
 	stp	xzr, xzr, [x0], #0x10
 	cmp	x0, x1
 	b.ne	1b
+	RETGUARD_CHECK(pagezero_simple, x15)
 	ret
 
 END(pagezero_simple)
@@ -100,6 +102,7 @@ END(pagezero_simple)
  * pagezero, cache assisted
  */
 ENTRY(pagezero_cache)
+	RETGUARD_SETUP(pagezero_cache, x15)
 	add	x1, x0, #PAGE_SIZE
 
 	ldr	x2, =dczva_line_size
@@ -110,6 +113,7 @@ ENTRY(pagezero_cache)
 	add	x0, x0, x2
 	cmp	x0, x1
 	b.ne	1b
+	RETGUARD_CHECK(pagezero_cache, x15)
 	ret
 
 END(pagezero_cache)
diff --git a/sys/arch/arm64/include/asm.h b/sys/arch/arm64/include/asm.h
index 35c911f7cf5..f31386ea4d1 100644
--- a/sys/arch/arm64/include/asm.h
+++ b/sys/arch/arm64/include/asm.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: asm.h,v 1.3 2017/06/29 17:36:16 deraadt Exp $	*/
+/*	$OpenBSD: asm.h,v 1.4 2018/08/12 17:15:10 mortimer Exp $	*/
 /*	$NetBSD: asm.h,v 1.4 2001/07/16 05:43:32 matt Exp $	*/
 
 /*
@@ -82,6 +82,44 @@
 # define _PROF_PROLOGUE
 #endif
 
+#if defined(_RET_PROTECTOR)
+# define RETGUARD_SETUP(x, reg) \
+	RETGUARD_SYMBOL(x); \
+	adrp    reg, __CONCAT(__retguard_, x); \
+	ldr     reg, [reg, :lo12:__CONCAT(__retguard_, x)]; \
+	eor     reg, reg, x30
+# define RETGUARD_CHECK(x, reg) \
+	eor     reg, reg, x30; \
+	adrp    x9, __CONCAT(__retguard_, x); \
+	ldr     x9, [x9, :lo12:__CONCAT(__retguard_, x)]; \
+	subs    reg, reg, x9; \
+	cbz     reg, 66f; \
+	brk     #0x1; \
+66:
+# define RETGUARD_PUSH(reg) \
+	str     reg, [sp, #-16]!
+# define RETGUARD_POP(reg) \
+	ldr     reg, [sp, #16]!
+# define RETGUARD_SYMBOL(x) \
+	.ifndef __CONCAT(__retguard_, x); \
+	.hidden __CONCAT(__retguard_, x); \
+	.type   __CONCAT(__retguard_, x),@object; \
+	.pushsection .openbsd.randomdata.retguard,"aw",@progbits; \
+	.weak   __CONCAT(__retguard_, x); \
+	.p2align 3; \
+	__CONCAT(__retguard_, x): ; \
+	.xword 0; \
+	.size __CONCAT(__retguard_, x), 8; \
+	.popsection; \
+	.endif
+#else
+# define RETGUARD_SETUP(x, reg)
+# define RETGUARD_CHECK(x, reg)
+# define RETGUARD_PUSH(reg)
+# define RETGUARD_POP(reg)
+# define RETGUARD_SYMBOL(x)
+#endif
+
 #define	ENTRY(y)	_ENTRY(_C_LABEL(y)); _PROF_PROLOGUE
 #define	ENTRY_NP(y)	_ENTRY(_C_LABEL(y))
 #define	ASENTRY(y)	_ENTRY(_ASM_LABEL(y)); _PROF_PROLOGUE
-- 
2.20.1