* Stas Sergeev [off-list ref] [2016-03-01 00:29:03 +0300]:
The following patches make it possible to use swapcontext()
in a sighandler that works on sigaltstack.
i don't think that's possible, the (obsolete) userspace
*context functions cannot operate on kernel provided
ucontext_t structs, so they are not usable in signal
handlers.
at least not on most target archs.
so i don't understand how the tests can work portably.
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.
[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: <redacted>
CC: <redacted>
CC: Andy Lutomirski <redacted>
CC: Oleg Nesterov <redacted>
CC: Shuah Khan <redacted>
Diffstat:
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(-)
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