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[RFC,v1,02/26] stackdepot: prevent Clang from optimizing away stackdepot_memcmp()

Message ID 20191018094304.37056-3-glider@google.com (mailing list archive)
State New, archived
Headers show
Series Add KernelMemorySanitizer infrastructure | expand

Commit Message

Alexander Potapenko Oct. 18, 2019, 9:42 a.m. UTC 
Clang may replace stackdepot_memcmp() with a call to instrumented bcmp(),
which is exactly what we wanted to avoid creating stackdepot_memcmp().
Add a compiler barrier() to prevent optimizations.

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: linux-mm@kvack.org
---

Change-Id: I4495b617b15c0ab003a61c1f0d54d0026fa8b144
---
 lib/stackdepot.c | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 0d00d2ac0c4b..785839298e08 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -163,6 +163,11 @@  int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
 			unsigned int n)
 {
 	for ( ; n-- ; u1++, u2++) {
+		/*
+		 * Prevent Clang from replacing this function with a bcmp()
+		 * call.
+		 */
+		barrier();
 		if (*u1 != *u2)
 			return 1;
 	}