linux-kernel - [PATCH 4/4] signals/sigaltstack: Change SS

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Date:	Tue,  3 May 2016 10:31:52 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>, Stas Sergeev <stsp@...t.ru>,
	Al Viro <viro@...iv.linux.org.uk>,
	Aleksa Sarai <cyphar@...har.com>,
	Amanieu d'Antras <amanieu@...il.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Heinrich Schuchardt <xypron.glpk@....de>,
	Jason Low <jason.low2@...com>,
	Josh Triplett <josh@...htriplett.org>,
	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Paul Moore <pmoore@...hat.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Richard Weinberger <richard@....at>,
	Sasha Levin <sasha.levin@...cle.com>,
	Shuah Khan <shuahkh@....samsung.com>,
	Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vladimir Davydov <vdavydov@...allels.com>,
	linux-api@...r.kernel.org
Subject: [PATCH 4/4] signals/sigaltstack: Change SS_AUTODISARM to (1U << 31)

Using bit 4 divides the space of available bits strangely.  Use bit
31 instead so that we have a better chance of keeping flag and mode
bits separate in the long run.

Cc: Stas Sergeev <stsp@...t.ru>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Aleksa Sarai <cyphar@...har.com>
Cc: Amanieu d'Antras <amanieu@...il.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Heinrich Schuchardt <xypron.glpk@....de>
Cc: Jason Low <jason.low2@...com>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Palmer Dabbelt <palmer@...belt.com>
Cc: Paul Moore <pmoore@...hat.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Richard Weinberger <richard@....at>
Cc: Sasha Levin <sasha.levin@...cle.com>
Cc: Shuah Khan <shuahkh@....samsung.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vladimir Davydov <vdavydov@...allels.com>
Cc: linux-api@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 include/uapi/linux/signal.h               | 2 +-
 tools/testing/selftests/sigaltstack/sas.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/signal.h b/include/uapi/linux/signal.h
index 738826048af2..cd0804b6bfa2 100644
--- a/include/uapi/linux/signal.h
+++ b/include/uapi/linux/signal.h
@@ -8,7 +8,7 @@
 #define SS_DISABLE	2
 
 /* bit-flags */
-#define SS_AUTODISARM	(1 << 4)	/* disable sas during sighandling */
+#define SS_AUTODISARM	(1U << 31)	/* disable sas during sighandling */
 /* mask for all SS_xxx flags */
 #define SS_FLAG_BITS	SS_AUTODISARM
 
diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index 4280d0699792..1bb01258e559 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -18,7 +18,7 @@
 #include <errno.h>
 
 #ifndef SS_AUTODISARM
-#define SS_AUTODISARM  (1 << 4)
+#define SS_AUTODISARM  (1U << 31)
 #endif
 
 static void *sstack, *ustack;
-- 
2.5.5