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-...@vger.kernel.org CC: Andy Lutomirski <l...@amacapital.net> CC: Oleg Nesterov <o...@redhat.com> CC: Shuah Khan <shua...@osg.samsung.com> CC: Ingo Molnar <mi...@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(-)
