From b081609ec2de1cc4d306831ad0b9d4bfa5545d4e Mon Sep 17 00:00:00 2001
From: maxv <maxv@NetBSD.org>
Date: Fri, 8 Nov 2019 12:36:10 +0000
Subject: [PATCH] Exclude the PTE space from KCSAN, since there the same VA can
 point to different PAs.

---
 sys/arch/amd64/include/csan.h | 11 ++++++++++-
 sys/kern/subr_csan.c          |  6 ++++--
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/sys/arch/amd64/include/csan.h b/sys/arch/amd64/include/csan.h
index 4ab99ee2d17e..1817bc8fc7cd 100644
--- a/sys/arch/amd64/include/csan.h
+++ b/sys/arch/amd64/include/csan.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: csan.h,v 1.2 2019/11/06 06:57:22 maxv Exp $	*/
+/*	$NetBSD: csan.h,v 1.3 2019/11/08 12:36:11 maxv Exp $	*/
 
 /*
  * Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -30,8 +30,17 @@
  */
 
 #include <sys/ksyms.h>
+#include <uvm/uvm.h>
+#include <amd64/pmap.h>
 #include <x86/cpufunc.h>
 
+static inline bool
+kcsan_md_unsupported(vaddr_t addr)
+{
+	return (addr >= (vaddr_t)PTE_BASE &&
+	    addr < ((vaddr_t)PTE_BASE + NBPD_L4));
+}
+
 static inline bool
 kcsan_md_is_avail(void)
 {
diff --git a/sys/kern/subr_csan.c b/sys/kern/subr_csan.c
index e9814f3c8b06..a869469e221f 100644
--- a/sys/kern/subr_csan.c
+++ b/sys/kern/subr_csan.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: subr_csan.c,v 1.2 2019/11/06 06:57:22 maxv Exp $	*/
+/*	$NetBSD: subr_csan.c,v 1.3 2019/11/08 12:36:10 maxv Exp $	*/
 
 /*
  * Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_csan.c,v 1.2 2019/11/06 06:57:22 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_csan.c,v 1.3 2019/11/08 12:36:10 maxv Exp $");
 
 #include "opt_kcsan.h"
 
@@ -136,6 +136,8 @@ kcsan_access(uintptr_t addr, size_t size, bool write, bool atomic, uintptr_t pc)
 
 	if (__predict_false(!kcsan_enabled))
 		return;
+	if (__predict_false(kcsan_md_unsupported((vaddr_t)addr)))
+		return;
 
 	new.addr = addr;
 	new.size = size;