[PATCH v4 0/2] make sigaltstack() compatible with swapcontext()

From: Stas Sergeev
Date: Mon Feb 29 2016 - 16:30:03 EST

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:

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.

[PATCH 1/2] sigaltstack: implement SS_AUTODISARM flag
This patch implements SS_AUTODISARM flag
[PATCH 2/2] selftests: Add test for sigaltstack(SS_AUTODISARM)
This patch adds the selftest code for new functionality

CC: linux-kernel@xxxxxxxxxxxxxxx
CC: linux-api@xxxxxxxxxxxxxxx
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Oleg Nesterov <oleg@xxxxxxxxxx>
CC: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>

include/linux/sched.h | 8 +
include/linux/signal.h | 4
include/uapi/linux/signal.h | 3
kernel/fork.c | 2
kernel/signal.c | 23 ++--
tools/testing/selftests/Makefile | 1
tools/testing/selftests/sigaltstack/Makefile | 8 +
tools/testing/selftests/sigaltstack/sas.c | 151 +++++++++++++++++++++++++++
8 files changed, 187 insertions(+), 13 deletions(-)