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[PATCH 3/4] signals/sigaltstack: Report current flag bits in sigaltstack()

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  [PATCH 3/4] signals/sigaltstack: Report current flag bits in sigaltstack() Andy Lutomirski <luto@kernel.org> - 2016-05-03 19:40 +0200
    Re: [PATCH 3/4] signals/sigaltstack: Report current flag bits in  sigaltstack() Ingo Molnar <mingo@kernel.org> - 2016-05-04 08:40 +0200
    [tip:core/signals] signals/sigaltstack: Report current flag bits in  sigaltstack() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-05-04 09:20 +0200

#1393645 — [PATCH 3/4] signals/sigaltstack: Report current flag bits in sigaltstack()

sigaltstack()'s reported previous state uses a somewhat odd
convention, but the concept of flag bits is new, and we can do the
flag bits sensibly.  Specifically, let's just report them directly.

This will allow saving and restoring the sigaltstack state using
sigaltstack() to work correctly.

Signed-off-by: Stas Sergeev <stsp@list.ru>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Amanieu d'Antras <amanieu@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: linux-api@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 kernel/signal.c                           |  3 ++-
 tools/testing/selftests/sigaltstack/sas.c | 19 ++++++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index bf97ea5775ae..ab122a2cee41 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3099,7 +3099,8 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 
 	oss.ss_sp = (void __user *) current->sas_ss_sp;
 	oss.ss_size = current->sas_ss_size;
-	oss.ss_flags = sas_ss_flags(sp);
+	oss.ss_flags = sas_ss_flags(sp) |
+		(current->sas_ss_flags & SS_FLAG_BITS);
 
 	if (uss) {
 		void __user *ss_sp;
diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index a98c3ef8141f..4280d0699792 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -113,6 +113,19 @@ int main(void)
 		perror("mmap()");
 		return EXIT_FAILURE;
 	}
+
+	err = sigaltstack(NULL, &stk);
+	if (err) {
+		perror("[FAIL]\tsigaltstack()");
+		exit(EXIT_FAILURE);
+	}
+	if (stk.ss_flags == SS_DISABLE) {
+		printf("[OK]\tInitial sigaltstack state was SS_DISABLE\n");
+	} else {
+		printf("[FAIL]\tInitial sigaltstack state was %i; should have been SS_DISABLE\n", stk.ss_flags);
+		return EXIT_FAILURE;
+	}
+
 	stk.ss_sp = sstack;
 	stk.ss_size = SIGSTKSZ;
 	stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
@@ -151,12 +164,12 @@ int main(void)
 		perror("[FAIL]\tsigaltstack()");
 		exit(EXIT_FAILURE);
 	}
-	if (stk.ss_flags != 0) {
-		printf("[FAIL]\tss_flags=%i, should be 0\n",
+	if (stk.ss_flags != SS_AUTODISARM) {
+		printf("[FAIL]\tss_flags=%i, should be SS_AUTODISARM\n",
 				stk.ss_flags);
 		exit(EXIT_FAILURE);
 	}
-	printf("[OK]\tsigaltstack is enabled after signal\n");
+	printf("[OK]\tsigaltstack is still SS_AUTODISARM after signal\n");
 
 	printf("[OK]\tTest passed\n");
 	return 0;
-- 
2.5.5

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#1394020 — Re: [PATCH 3/4] signals/sigaltstack: Report current flag bits in sigaltstack()

* Andy Lutomirski <luto@kernel.org> wrote:

> sigaltstack()'s reported previous state uses a somewhat odd
> convention, but the concept of flag bits is new, and we can do the
> flag bits sensibly.  Specifically, let's just report them directly.
> 
> This will allow saving and restoring the sigaltstack state using
> sigaltstack() to work correctly.
> 
> Signed-off-by: Stas Sergeev <stsp@list.ru>

This SOB seems stray as well, so I've removed it too.

Thanks,

	Ingo

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#1394036 — [tip:core/signals] signals/sigaltstack: Report current flag bits in sigaltstack()

Commit-ID:  0318bc8a919ded355eaa5078689924a15c1bf52a
Gitweb:     http://git.kernel.org/tip/0318bc8a919ded355eaa5078689924a15c1bf52a
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Tue, 3 May 2016 10:31:51 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 4 May 2016 08:34:14 +0200

signals/sigaltstack: Report current flag bits in sigaltstack()

sigaltstack()'s reported previous state uses a somewhat odd
convention, but the concept of flag bits is new, and we can do the
flag bits sensibly.  Specifically, let's just report them directly.

This will allow saving and restoring the sigaltstack state using
sigaltstack() to work correctly.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Amanieu d'Antras <amanieu@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Stas Sergeev <stsp@list.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: linux-api@vger.kernel.org
Link: http://lkml.kernel.org/r/94b291ec9fd47741a9264851e316e158ded0b00d.1462296606.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/signal.c                           |  3 ++-
 tools/testing/selftests/sigaltstack/sas.c | 19 ++++++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index bf97ea5..ab122a2 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3099,7 +3099,8 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 
 	oss.ss_sp = (void __user *) current->sas_ss_sp;
 	oss.ss_size = current->sas_ss_size;
-	oss.ss_flags = sas_ss_flags(sp);
+	oss.ss_flags = sas_ss_flags(sp) |
+		(current->sas_ss_flags & SS_FLAG_BITS);
 
 	if (uss) {
 		void __user *ss_sp;
diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index a98c3ef..4280d06 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -113,6 +113,19 @@ int main(void)
 		perror("mmap()");
 		return EXIT_FAILURE;
 	}
+
+	err = sigaltstack(NULL, &stk);
+	if (err) {
+		perror("[FAIL]\tsigaltstack()");
+		exit(EXIT_FAILURE);
+	}
+	if (stk.ss_flags == SS_DISABLE) {
+		printf("[OK]\tInitial sigaltstack state was SS_DISABLE\n");
+	} else {
+		printf("[FAIL]\tInitial sigaltstack state was %i; should have been SS_DISABLE\n", stk.ss_flags);
+		return EXIT_FAILURE;
+	}
+
 	stk.ss_sp = sstack;
 	stk.ss_size = SIGSTKSZ;
 	stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
@@ -151,12 +164,12 @@ int main(void)
 		perror("[FAIL]\tsigaltstack()");
 		exit(EXIT_FAILURE);
 	}
-	if (stk.ss_flags != 0) {
-		printf("[FAIL]\tss_flags=%i, should be 0\n",
+	if (stk.ss_flags != SS_AUTODISARM) {
+		printf("[FAIL]\tss_flags=%i, should be SS_AUTODISARM\n",
 				stk.ss_flags);
 		exit(EXIT_FAILURE);
 	}
-	printf("[OK]\tsigaltstack is enabled after signal\n");
+	printf("[OK]\tsigaltstack is still SS_AUTODISARM after signal\n");
 
 	printf("[OK]\tTest passed\n");
 	return 0;

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