Commit 0318bc8a authored May 03, 2016 by Andy Lutomirski Committed by Ingo Molnar May 04, 2016

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>

parent 158b67b5

kernel/signal.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;

tools/testing/selftests/sigaltstack/sas.c

+16 −3

Original line number	Diff line number	Diff line
		@@ -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;