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Kernel: Implement sigsuspend using a SignalBlocker

Browse source 
`sigsuspend` was previously implemented using a poll on an empty set of
file descriptors. However, this broke quite a few assumptions in
`SelectBlocker`, as it verifies at least one file descriptor to be
ready after waking up and as it relies on being notified by the file
descriptor.

A bare-bones `sigsuspend` may also be implemented by relying on any of
the `sigwait` functions, but as `sigsuspend` features several (currently
unimplemented) restrictions on how returns work, it is a syscall on its
own.
This commit is contained in:
Tim Schumacher 2022-05-13 13:15:45 +02:00 committed by Brian Gianforcaro
parent edbffb3c7a
commit cf0ad3715e
Notes: sideshowbarker 2024-07-17 09:35:21 +09:00 
Author: https://github.com/timschumi
Commit: https://github.com/SerenityOS/serenity/commit/cf0ad3715e
Pull-request: https://github.com/SerenityOS/serenity/pull/13971
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/bgianfo ✅
Reviewed-by: https://github.com/kleinesfilmroellchen
Reviewed-by: https://github.com/linusg
4 changed files with 28 additions and 1 deletions
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1
Kernel/API/Syscall.h
View file

@ -170,6 +170,7 @@ enum class NeedsBigProcessLock {
S(sigpending, NeedsBigProcessLock::Yes) \
S(sigprocmask, NeedsBigProcessLock::Yes) \
S(sigreturn, NeedsBigProcessLock::Yes) \
S(sigsuspend, NeedsBigProcessLock::Yes) \
S(sigtimedwait, NeedsBigProcessLock::Yes) \
S(socket, NeedsBigProcessLock::Yes) \
S(socketpair, NeedsBigProcessLock::Yes) \

1
Kernel/Process.h
View file

@ -334,6 +334,7 @@ public:
ErrorOr<FlatPtr> sys$sigaltstack(Userspace<stack_t const*> ss, Userspace<stack_t*> old_ss);
ErrorOr<FlatPtr> sys$sigprocmask(int how, Userspace<sigset_t const*> set, Userspace<sigset_t*> old_set);
ErrorOr<FlatPtr> sys$sigpending(Userspace<sigset_t*>);
ErrorOr<FlatPtr> sys$sigsuspend(Userspace<sigset_t const*>);
ErrorOr<FlatPtr> sys$sigtimedwait(Userspace<sigset_t const*>, Userspace<siginfo_t*>, Userspace<timespec const*>);
ErrorOr<FlatPtr> sys$getgroups(size_t, Userspace<gid_t*>);
ErrorOr<FlatPtr> sys$setgroups(size_t, Userspace<gid_t const*>);

24
Kernel/Syscalls/sigaction.cpp
View file

@ -326,4 +326,28 @@ ErrorOr<FlatPtr> Process::sys$sigtimedwait(Userspace<sigset_t const*> set, Users
return info_value.si_signo;
}
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigsuspend.html
ErrorOr<FlatPtr> Process::sys$sigsuspend(Userspace<sigset_t const*> mask)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
auto sigmask = TRY(copy_typed_from_user(mask));
auto* current_thread = Thread::current();
u32 previous_signal_mask = current_thread->update_signal_mask(sigmask);
ScopeGuard rollback_signal_mask([&]() {
current_thread->update_signal_mask(previous_signal_mask);
});
// TODO: Ensure that/check if we never return if the action is to terminate the process.
// TODO: Ensure that/check if we only return after an eventual signal-catching function returns.
Thread::BlockTimeout timeout = {};
siginfo_t siginfo = {};
if (current_thread->block<Thread::SignalBlocker>(timeout, ~sigmask, siginfo).was_interrupted())
return EINTR;
return 0;
}
}

3
Userland/Libraries/LibC/signal.cpp
View file

@ -175,7 +175,8 @@ void siglongjmp(jmp_buf env, int val)
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigsuspend.html
int sigsuspend(sigset_t const* set)
{
return pselect(0, nullptr, nullptr, nullptr, nullptr, set);
int rc = syscall(SC_sigsuspend, set);
__RETURN_WITH_ERRNO(rc, rc, -1);
}
// https://pubs.opengroup.org/onlinepubs/009604499/functions/sigwait.html