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authorkamil <kamil@NetBSD.org>2018-05-30 17:48:13 +0000
committerkamil <kamil@NetBSD.org>2018-05-30 17:48:13 +0000
commit9128e3119d85146df2a0960362103d312b5f72ae (patch)
treeb12d087b7ba43b5d89c3fe54d7cae9e5a8f4626c /tests/kernel
parentca6ad33a9855119a058a070fb46daeaeb6f91155 (diff)
Add a comment for the workaround in trigger_bus()
Explain PROT_READ|PROT_WRITE.
Diffstat (limited to 'tests/kernel')
-rw-r--r--tests/kernel/h_segv.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/tests/kernel/h_segv.c b/tests/kernel/h_segv.c
index 44a7efec637..c34208beb4a 100644
--- a/tests/kernel/h_segv.c
+++ b/tests/kernel/h_segv.c
@@ -1,4 +1,4 @@
-/* $NetBSD: h_segv.c,v 1.6 2018/05/30 17:31:34 kamil Exp $ */
+/* $NetBSD: h_segv.c,v 1.7 2018/05/30 17:48:13 kamil Exp $ */
/*-
* Copyright (c) 2017 The NetBSD Foundation, Inc.
@@ -29,7 +29,7 @@
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
-__RCSID("$NetBSD: h_segv.c,v 1.6 2018/05/30 17:31:34 kamil Exp $");
+__RCSID("$NetBSD: h_segv.c,v 1.7 2018/05/30 17:48:13 kamil Exp $");
#include <sys/types.h>
#include <sys/mman.h>
@@ -119,7 +119,12 @@ trigger_bus(void)
if (fp == NULL)
err(EXIT_FAILURE, "tmpfile");
- /* Map an empty file with mmap(2) to a pointer. */
+ /*
+ * Map an empty file with mmap(2) to a pointer.
+ *
+ * PROT_READ handles read-modify-write sequences emitted for
+ * certain combinations of CPUs and compilers (e.g. Alpha AXP).
+ */
p = mmap(0, 1, PROT_READ|PROT_WRITE, MAP_PRIVATE, fileno(fp), 0);
if (p == MAP_FAILED)
err(EXIT_FAILURE, "mmap");