linux-kernel - [tip:perf/urgent] tools headers: Restore READ

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] [day] [month] [year] [list]

Message-ID: <tip-4d3b57da1593c66835d8e3a757e4751b35493fb8@git.kernel.org>
Date:   Sun, 15 Apr 2018 23:41:33 -0700
From:   tip-bot for Mark Rutland <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     acme@...hat.com, lizhijian@...fujitsu.com, mingo@...nel.org,
        mark.rutland@....com, tglx@...utronix.de, hpa@...or.com,
        linux-kernel@...r.kernel.org, sandipan@...ux.vnet.ibm.com
Subject: [tip:perf/urgent] tools headers: Restore READ_ONCE() C++
 compatibility

Commit-ID:  4d3b57da1593c66835d8e3a757e4751b35493fb8
Gitweb:     https://git.kernel.org/tip/4d3b57da1593c66835d8e3a757e4751b35493fb8
Author:     Mark Rutland <mark.rutland@....com>
AuthorDate: Wed, 4 Apr 2018 17:34:45 +0100
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 12 Apr 2018 09:30:09 -0300

tools headers: Restore READ_ONCE() C++ compatibility

Our userspace <linux/compiler.h> defines READ_ONCE() in a way that clang
doesn't like, as we have an anonymous union in which neither field is
initialized.

WRITE_ONCE() is fine since it initializes the __val field. For
READ_ONCE() we can keep clang and GCC happy with a dummy initialization
of the __c field, so let's do that.

At the same time, let's split READ_ONCE() and WRITE_ONCE() over several
lines for legibility, as we do in the in-kernel <linux/compiler.h>.

Reported-by: Li Zhijian <lizhijian@...fujitsu.com>
Reported-by: Sandipan Das <sandipan@...ux.vnet.ibm.com>
Tested-by: Sandipan Das <sandipan@...ux.vnet.ibm.com>
Signed-off-by: Mark Rutland <mark.rutland@....com>
Fixes: 6aa7de059173a986 ("locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()")
Link: http://lkml.kernel.org/r/20180404163445.16492-1-mark.rutland@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/include/linux/compiler.h | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 04e32f965ad7..1827c2f973f9 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -151,11 +151,21 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
  * required ordering.
  */
 
-#define READ_ONCE(x) \
-	({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
-
-#define WRITE_ONCE(x, val) \
-	({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
+#define READ_ONCE(x)					\
+({							\
+	union { typeof(x) __val; char __c[1]; } __u =	\
+		{ .__c = { 0 } };			\
+	__read_once_size(&(x), __u.__c, sizeof(x));	\
+	__u.__val;					\
+})
+
+#define WRITE_ONCE(x, val)				\
+({							\
+	union { typeof(x) __val; char __c[1]; } __u =	\
+		{ .__val = (val) }; 			\
+	__write_once_size(&(x), __u.__c, sizeof(x));	\
+	__u.__val;					\
+})
 
 
 #ifndef __fallthrough