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Subject[PATCH v6(RESEND) 0/4] make sigaltstack() compatible with swapcontext()
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It is absolutely unclear what happened with my patch series,
but it is neither applied nor rejected. So here's the re-send.

The following patches make it possible to use swapcontext()
in a sighandler that works on sigaltstack.
The approach is inspired by Andy Lutomirski's suggestion that
sigaltstack should disarm itself after saving into uc_stack:
https://lkml.org/lkml/2016/2/1/594

I add the SS_AUTODISARM flag that does exactly that.
On sighandler exit, the sigaltstack is restored from uc_stack.
Another possible name could be SS_ONESHOT, but, since it gets
always re-enabled, I choose SS_AUTODISARM.

Change since v5:
- Fix description of patch 4/4

Change since v4:
- Implement this Andy Lutomirski's suggestion:
https://lkml.org/lkml/2016/3/6/158
that allows the run-time probing of the existence of the
flags added in the future.

[PATCH 1/4] [Cleanup] x86: signal: unify the sigaltstack check with
A clean-up patch that unifies x86's sigaltstack handling with
other arches.
[PATCH 2/4] sigaltstack: preparations for adding new SS_xxx flags
Andy's suggested changes
[PATCH 3/4] sigaltstack: implement SS_AUTODISARM flag
This patch implements SS_AUTODISARM flag
[PATCH 4/4] selftests: Add test for
This patch adds the selftest code for new functionality

CC: linux-kernel@vger.kernel.org
CC: linux-api@vger.kernel.org
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Shuah Khan <shuahkh@osg.samsung.com>
CC: Ingo Molnar <mingo@redhat.com>

Diffstat:
arch/x86/kernel/signal.c | 23 +--
include/linux/sched.h | 8 +
include/linux/signal.h | 4
include/uapi/linux/signal.h | 7 +
kernel/fork.c | 2
kernel/signal.c | 26 ++--
tools/testing/selftests/Makefile | 1
tools/testing/selftests/sigaltstack/Makefile | 8 +
tools/testing/selftests/sigaltstack/sas.c | 156 +++++++++++++++++++++++++++
9 files changed, 208 insertions(+), 27 deletions(-)

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