linux-kernel - [PATCH 2/6] s390: add optimized array_index_mask

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1517986811-27819-3-git-send-email-schwidefsky@de.ibm.com>
Date:   Wed,  7 Feb 2018 08:00:07 +0100
From:   Martin Schwidefsky <schwidefsky@...ibm.com>
To:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jon Masters <jcm@...hat.com>,
        Marcus Meissner <meissner@...e.de>,
        Jiri Kosina <jkosina@...e.cz>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Pavel Machek <pavel@....cz>,
        David Woodhouse <dwmw2@...radead.org>
Subject: [PATCH 2/6] s390: add optimized array_index_mask_nospec

Add an optimized version of the array_index_mask_nospec function for
s390 based on a compare and a subtract with borrow.

Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
---
 arch/s390/include/asm/barrier.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
index 1043260..f9eddbc 100644
--- a/arch/s390/include/asm/barrier.h
+++ b/arch/s390/include/asm/barrier.h
@@ -49,6 +49,30 @@ do {									\
 #define __smp_mb__before_atomic()	barrier()
 #define __smp_mb__after_atomic()	barrier()
 
+/**
+ * array_index_mask_nospec - generate a mask for array_idx() that is
+ * ~0UL when the bounds check succeeds and 0 otherwise
+ * @index: array element index
+ * @size: number of elements in array
+ */
+#define array_index_mask_nospec array_index_mask_nospec
+static inline unsigned long array_index_mask_nospec(unsigned long index,
+						    unsigned long size)
+{
+	unsigned long mask;
+
+	if (__builtin_constant_p(size) && size > 0) {
+		asm("	clgr	%2,%1\n"
+		    "	slbgr	%0,%0\n"
+		    :"=d" (mask) : "d" (size-1), "d" (index) :"cc");
+		return mask;
+	}
+	asm("	clgr	%1,%2\n"
+	    "	slbgr	%0,%0\n"
+	    :"=d" (mask) : "d" (size), "d" (index) :"cc");
+	return ~mask;
+}
+
 #include <asm-generic/barrier.h>
 
 #endif /* __ASM_BARRIER_H */
-- 
2.7.4