svn commit: r287960 - in head/sys/arm64: arm64 include

[Konstantin Belousov]

Author: kib
Date: Fri Sep 18 16:52:18 2015
New Revision: 287960
URL: https://svnweb.freebsd.org/changeset/base/287960

Log:
  Clear exclusive monitors when handling data aborts, the monitors are
  in unknown state per spec.
  
  Reviewed by:	andrew (previous version)
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D3668

Modified:
  head/sys/arm64/arm64/trap.c
  head/sys/arm64/include/cpufunc.h

Modified: head/sys/arm64/arm64/trap.c
==============================================================================
--- head/sys/arm64/arm64/trap.c	Fri Sep 18 13:44:15 2015	(r287959)
+++ head/sys/arm64/arm64/trap.c	Fri Sep 18 16:52:18 2015	(r287960)
@@ -155,6 +155,13 @@ data_abort(struct trapframe *frame, uint
 	uint64_t far;
 	int error, sig, ucode;
 
+	/*
+	 * According to the ARMv8-A rev. A.g, B2.10.5 "Load-Exclusive
+	 * and Store-Exclusive instruction usage restrictions", state
+	 * of the exclusive monitors after data abort exception is unknown.
+	 */
+	clrex();
+
 #ifdef KDB
 	if (kdb_active) {
 		kdb_reenter();

Modified: head/sys/arm64/include/cpufunc.h
==============================================================================
--- head/sys/arm64/include/cpufunc.h	Fri Sep 18 13:44:15 2015	(r287959)
+++ head/sys/arm64/include/cpufunc.h	Fri Sep 18 16:52:18 2015	(r287960)
@@ -108,6 +108,17 @@ get_mpidr(void)
 	return (mpidr);
 }
 
+static __inline void
+clrex(void)
+{
+
+	/*
+	 * Ensure compiler barrier, otherwise the monitor clear might
+	 * occur too late for us ?
+	 */
+	__asm __volatile("clrex" : : : "memory");
+}
+
 #define	cpu_nullop()			arm64_nullop()
 #define	cpufunc_nullop()		arm64_nullop()
 #define	cpu_setttb(a)			arm64_setttb(a)