[PATCH 4/4] signals/sigaltstack: Change SS_AUTODISARM to (1U << 31)

Subsystems: kernel selftest framework, the rest

STALE3795d

2 messages, 2 authors, 2016-05-07 · open the first message on its own page

[PATCH 4/4] signals/sigaltstack: Change SS_AUTODISARM to (1U << 31)

From: Andy Lutomirski <luto@kernel.org>
Date: 2016-05-03 17:32:28 

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 <redacted>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Aleksa Sarai <redacted>
Cc: Amanieu d'Antras <redacted>
Cc: Andrea Arcangeli <redacted>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <redacted>
Cc: Denys Vlasenko <redacted>
Cc: Eric W. Biederman <redacted>
Cc: Frederic Weisbecker <redacted>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Heinrich Schuchardt <redacted>
Cc: Jason Low <redacted>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Konstantin Khlebnikov <redacted>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Moore <redacted>
Cc: Pavel Emelyanov <redacted>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Sasha Levin <redacted>
Cc: Shuah Khan <redacted>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <redacted>
Cc: Vladimir Davydov <redacted>
Cc: linux-api@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.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

Re: [PATCH 4/4] signals/sigaltstack: Change SS_AUTODISARM to (1U << 31)

From: Stas Sergeev <hidden>
Date: 2016-05-07 15:16:39 

03.05.2016 20:31, Andy Lutomirski пишет:
quoted hunk
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 <redacted>
Cc: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Cc: Aleksa Sarai <cyphar-gVpy/LI/lHzQT0dZR+AlfA@public.gmane.org>
Cc: Amanieu d'Antras <redacted>
Cc: Andrea Arcangeli <redacted>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Andy Lutomirski <redacted>
Cc: Borislav Petkov <redacted>
Cc: Brian Gerst <redacted>
Cc: Denys Vlasenko <redacted>
Cc: Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Cc: Frederic Weisbecker <redacted>
Cc: H. Peter Anvin <redacted>
Cc: Heinrich Schuchardt <redacted>
Cc: Jason Low <redacted>
Cc: Josh Triplett <redacted>
Cc: Konstantin Khlebnikov <redacted>
Cc: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Oleg Nesterov <redacted>
Cc: Palmer Dabbelt <redacted>
Cc: Paul Moore <redacted>
Cc: Pavel Emelyanov <redacted>
Cc: Peter Zijlstra <redacted>
Cc: Richard Weinberger <richard-/L3Ra7n9ekc@public.gmane.org>
Cc: Sasha Levin <redacted>
Cc: Shuah Khan <redacted>
Cc: Tejun Heo <redacted>
Cc: Thomas Gleixner <redacted>
Cc: Vladimir Davydov <redacted>
Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Andy Lutomirski <redacted>
---
  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 */
And what if we are out of 32 bits for storing both mode and flags? :)
Well, yes, very unlikely, but I did it that way exactly so that
we can eventually promote to 64bit variable.
Doesn't matter at all, of course. Let it be any way you like.
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