/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005, David Xu <davidxu@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "namespace.h"
#include <sys/param.h>
#include <sys/auxv.h>
#include <sys/elf.h>
#include <sys/signalvar.h>
#include <sys/syscall.h>
#include <signal.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <pthread_np.h>
#include "un-namespace.h"
#include "libc_private.h"

#include "libc_private.h"
#include "thr_private.h"

/* #define DEBUG_SIGNAL */
#ifdef DEBUG_SIGNAL
#define DBG_MSG         stdout_debug
#else
#define DBG_MSG(x...)
#endif

struct usigaction {
        struct sigaction sigact;
        struct urwlock   lock;
};

static struct usigaction _thr_sigact[_SIG_MAXSIG];

static inline struct usigaction *
__libc_sigaction_slot(int signo)
{

        return (&_thr_sigact[signo - 1]);
}

static void thr_sighandler(int, siginfo_t *, void *);
static void handle_signal(struct sigaction *, int, siginfo_t *, ucontext_t *);
static void check_deferred_signal(struct pthread *);
static void check_suspend(struct pthread *);
static void check_cancel(struct pthread *curthread, ucontext_t *ucp);

int     _sigtimedwait(const sigset_t *set, siginfo_t *info,
        const struct timespec * timeout);
int     _sigwaitinfo(const sigset_t *set, siginfo_t *info);
int     _sigwait(const sigset_t *set, int *sig);
int     _setcontext(const ucontext_t *);
int     _swapcontext(ucontext_t *, const ucontext_t *);

static const sigset_t _thr_deferset={{
        0xffffffff & ~(_SIG_BIT(SIGBUS)|_SIG_BIT(SIGILL)|_SIG_BIT(SIGFPE)|
        _SIG_BIT(SIGSEGV)|_SIG_BIT(SIGTRAP)|_SIG_BIT(SIGSYS)),
        0xffffffff,
        0xffffffff,
        0xffffffff}};

static const sigset_t _thr_maskset={{
        0xffffffff,
        0xffffffff,
        0xffffffff,
        0xffffffff}};

static void
thr_signal_block_slow(struct pthread *curthread)
{
        if (curthread->sigblock > 0) {
                curthread->sigblock++;
                return;
        }
        __sys_sigprocmask(SIG_BLOCK, &_thr_maskset, &curthread->sigmask);
        curthread->sigblock++;
}

static void
thr_signal_unblock_slow(struct pthread *curthread)
{
        if (--curthread->sigblock == 0)
                __sys_sigprocmask(SIG_SETMASK, &curthread->sigmask, NULL);
}

static void
thr_signal_block_fast(struct pthread *curthread)
{
        atomic_add_32(&curthread->fsigblock, SIGFASTBLOCK_INC);
}

static void
thr_signal_unblock_fast(struct pthread *curthread)
{
        uint32_t oldval;

        oldval = atomic_fetchadd_32(&curthread->fsigblock, -SIGFASTBLOCK_INC);
        if (oldval == (SIGFASTBLOCK_PEND | SIGFASTBLOCK_INC))
                __sys_sigfastblock(SIGFASTBLOCK_UNBLOCK, NULL);
}

static bool fast_sigblock;

void
_thr_signal_block(struct pthread *curthread)
{
        if (fast_sigblock)
                thr_signal_block_fast(curthread);
        else
                thr_signal_block_slow(curthread);
}

void
_thr_signal_unblock(struct pthread *curthread)
{
        if (fast_sigblock)
                thr_signal_unblock_fast(curthread);
        else
                thr_signal_unblock_slow(curthread);
}

void
_thr_signal_block_check_fast(void)
{
        int bsdflags, error;

        error = elf_aux_info(AT_BSDFLAGS, &bsdflags, sizeof(bsdflags));
        if (error != 0)
                return;
        fast_sigblock = (bsdflags & ELF_BSDF_SIGFASTBLK) != 0;
}

void
_thr_signal_block_setup(struct pthread *curthread)
{
        if (!fast_sigblock)
                return;
        __sys_sigfastblock(SIGFASTBLOCK_SETPTR, &curthread->fsigblock);
}

void
pthread_signals_block_np(void)
{
        struct pthread *curthread;

        curthread = _get_curthread();
        _thr_signal_block(curthread);
}

void
pthread_signals_unblock_np(void)
{
        struct pthread *curthread;

        curthread = _get_curthread();
        _thr_signal_unblock(curthread);
}

int
_thr_send_sig(struct pthread *thread, int sig)
{
        return thr_kill(thread->tid, sig);
}

static inline void
remove_thr_signals(sigset_t *set)
{
        if (SIGISMEMBER(*set, SIGCANCEL))
                SIGDELSET(*set, SIGCANCEL);
}

static const sigset_t *
thr_remove_thr_signals(const sigset_t *set, sigset_t *newset)
{
        *newset = *set;
        remove_thr_signals(newset);
        return (newset);
}

static void
sigcancel_handler(int sig __unused, siginfo_t *info __unused, ucontext_t *ucp)
{
        struct pthread *curthread = _get_curthread();
        int err;

        if (THR_IN_CRITICAL(curthread))
                return;
        err = errno;
        check_suspend(curthread);
        check_cancel(curthread, ucp);
        errno = err;
}

typedef void (*ohandler)(int sig, int code, struct sigcontext *scp,
    char *addr, __sighandler_t *catcher);

/*
 * The signal handler wrapper is entered with all signal masked.
 */
static void
thr_sighandler(int sig, siginfo_t *info, void *_ucp)
{
        struct pthread *curthread;
        ucontext_t *ucp;
        struct sigaction act;
        struct usigaction *usa;
        int err;

        err = errno;
        curthread = _get_curthread();
        ucp = _ucp;
        usa = __libc_sigaction_slot(sig);
        _thr_rwl_rdlock(&usa->lock);
        act = usa->sigact;
        _thr_rwl_unlock(&usa->lock);
        errno = err;
        curthread->deferred_run = 0;

        /*
         * if a thread is in critical region, for example it holds low level locks,
         * try to defer the signal processing, however if the signal is synchronous
         * signal, it means a bad thing has happened, this is a programming error,
         * resuming fault point can not help anything (normally causes deadloop),
         * so here we let user code handle it immediately.
         */
        if (THR_IN_CRITICAL(curthread) && SIGISMEMBER(_thr_deferset, sig)) {
                memcpy(&curthread->deferred_sigact, &act, sizeof(struct sigaction));
                memcpy(&curthread->deferred_siginfo, info, sizeof(siginfo_t));
                curthread->deferred_sigmask = ucp->uc_sigmask;
                /* mask all signals, we will restore it later. */
                ucp->uc_sigmask = _thr_deferset;
                return;
        }

        handle_signal(&act, sig, info, ucp);
}

static void
handle_signal(struct sigaction *actp, int sig, siginfo_t *info, ucontext_t *ucp)
{
        struct pthread *curthread = _get_curthread();
        __siginfohandler_t *sigfunc;
        int cancel_point;
        int cancel_async;
        int cancel_enable;
        int in_sigsuspend;
        int err;

        /* add previous level mask */
        SIGSETOR(actp->sa_mask, ucp->uc_sigmask);

        /* add this signal's mask */
        if (!(actp->sa_flags & SA_NODEFER))
                SIGADDSET(actp->sa_mask, sig);

        in_sigsuspend = curthread->in_sigsuspend;
        curthread->in_sigsuspend = 0;

        /*
         * If thread is in deferred cancellation mode, disable cancellation
         * in signal handler.
         * If user signal handler calls a cancellation point function, e.g,
         * it calls write() to write data to file, because write() is a
         * cancellation point, the thread is immediately cancelled if 
         * cancellation is pending, to avoid this problem while thread is in
         * deferring mode, cancellation is temporarily disabled.
         */
        cancel_point = curthread->cancel_point;
        cancel_async = curthread->cancel_async;
        cancel_enable = curthread->cancel_enable;
        curthread->cancel_point = 0;
        if (!cancel_async)
                curthread->cancel_enable = 0;

        /* restore correct mask before calling user handler */
        __sys_sigprocmask(SIG_SETMASK, &actp->sa_mask, NULL);

        sigfunc = actp->sa_sigaction;

        /*
         * We have already reset cancellation point flags, so if user's code
         * longjmp()s out of its signal handler, wish its jmpbuf was set
         * outside of a cancellation point, in most cases, this would be
         * true.  However, there is no way to save cancel_enable in jmpbuf,
         * so after setjmps() returns once more, the user code may need to
         * re-set cancel_enable flag by calling pthread_setcancelstate().
         */
        if ((actp->sa_flags & SA_SIGINFO) != 0) {
                sigfunc(sig, info, ucp);
        } else {
                ((ohandler)sigfunc)(sig, info->si_code,
                    (struct sigcontext *)ucp, info->si_addr,
                    (__sighandler_t *)sigfunc);
        }
        err = errno;

        curthread->in_sigsuspend = in_sigsuspend;
        curthread->cancel_point = cancel_point;
        curthread->cancel_enable = cancel_enable;

        SIGDELSET(ucp->uc_sigmask, SIGCANCEL);

        /* reschedule cancellation */
        check_cancel(curthread, ucp);
        errno = err;
}

void
_thr_ast(struct pthread *curthread)
{

        if (!THR_IN_CRITICAL(curthread)) {
                check_deferred_signal(curthread);
                check_suspend(curthread);
                check_cancel(curthread, NULL);
        }
}

/* reschedule cancellation */
static void
check_cancel(struct pthread *curthread, ucontext_t *ucp)
{

        if (__predict_true(!curthread->cancel_pending ||
            !curthread->cancel_enable || curthread->no_cancel))
                return;

        /*
         * Otherwise, we are in defer mode, and we are at
         * cancel point, tell kernel to not block the current
         * thread on next cancelable system call.
         * 
         * There are three cases we should call thr_wake() to
         * turn on TDP_WAKEUP or send SIGCANCEL in kernel:
         * 1) we are going to call a cancelable system call,
         *    non-zero cancel_point means we are already in
         *    cancelable state, next system call is cancelable.
         * 2) because _thr_ast() may be called by
         *    THR_CRITICAL_LEAVE() which is used by rtld rwlock
         *    and any libthr internal locks, when rtld rwlock
         *    is used, it is mostly caused by an unresolved PLT.
         *    Those routines may clear the TDP_WAKEUP flag by
         *    invoking some system calls, in those cases, we
         *    also should reenable the flag.
         * 3) thread is in sigsuspend(), and the syscall insists
         *    on getting a signal before it agrees to return.
         */
        if (curthread->cancel_point) {
                if (curthread->in_sigsuspend) {
                        if (ucp != NULL) {
                                SIGADDSET(ucp->uc_sigmask, SIGCANCEL);
                                curthread->unblock_sigcancel = 1;
                        }
                        _thr_send_sig(curthread, SIGCANCEL);
                } else
                        thr_wake(curthread->tid);
        } else if (curthread->cancel_async) {
                /*
                 * asynchronous cancellation mode, act upon
                 * immediately.
                 */
                _pthread_exit_mask(PTHREAD_CANCELED, ucp != NULL ?
                    &ucp->uc_sigmask : NULL);
        }
}

static void
check_deferred_signal(struct pthread *curthread)
{
        ucontext_t *uc;
        struct sigaction act;
        siginfo_t info;
        int uc_len;

        if (__predict_true(curthread->deferred_siginfo.si_signo == 0 ||
            curthread->deferred_run))
                return;

        curthread->deferred_run = 1;
        uc_len = __getcontextx_size();
        uc = alloca(uc_len);
        getcontext(uc);
        if (curthread->deferred_siginfo.si_signo == 0) {
                curthread->deferred_run = 0;
                return;
        }
        __fillcontextx2((char *)uc);
        act = curthread->deferred_sigact;
        uc->uc_sigmask = curthread->deferred_sigmask;
        memcpy(&info, &curthread->deferred_siginfo, sizeof(siginfo_t));
        /* remove signal */
        curthread->deferred_siginfo.si_signo = 0;
        handle_signal(&act, info.si_signo, &info, uc);
        syscall(SYS_sigreturn, uc);
}

static void
check_suspend(struct pthread *curthread)
{
        uint32_t cycle;

        if (__predict_true((curthread->flags & (THR_FLAGS_NEED_SUSPEND |
            THR_FLAGS_SUSPENDED)) != THR_FLAGS_NEED_SUSPEND))
                return;
        if (curthread == _single_thread)
                return;
        if (curthread->force_exit)
                return;

        /* 
         * Blocks SIGCANCEL which other threads must send.
         */
        _thr_signal_block(curthread);

        /*
         * Increase critical_count, here we don't use THR_LOCK/UNLOCK
         * because we are leaf code, we don't want to recursively call
         * ourself.
         */
        curthread->critical_count++;
        THR_UMUTEX_LOCK(curthread, &(curthread)->lock);
        while ((curthread->flags & THR_FLAGS_NEED_SUSPEND) != 0) {
                curthread->cycle++;
                cycle = curthread->cycle;

                /* Wake the thread suspending us. */
                _thr_umtx_wake(&curthread->cycle, INT_MAX, 0);

                /*
                 * if we are from pthread_exit, we don't want to
                 * suspend, just go and die.
                 */
                if (curthread->state == PS_DEAD)
                        break;
                curthread->flags |= THR_FLAGS_SUSPENDED;
                THR_UMUTEX_UNLOCK(curthread, &(curthread)->lock);
                _thr_umtx_wait_uint(&curthread->cycle, cycle, NULL, 0);
                THR_UMUTEX_LOCK(curthread, &(curthread)->lock);
        }
        THR_UMUTEX_UNLOCK(curthread, &(curthread)->lock);
        curthread->critical_count--;

        _thr_signal_unblock(curthread);
}

void
_thr_signal_init(int dlopened)
{
        struct sigaction act, nact, oact;
        struct usigaction *usa;
        sigset_t oldset;
        int sig, error;

        if (dlopened) {
                __sys_sigprocmask(SIG_SETMASK, &_thr_maskset, &oldset);
                for (sig = 1; sig <= _SIG_MAXSIG; sig++) {
                        if (sig == SIGCANCEL)
                                continue;
                        error = __sys_sigaction(sig, NULL, &oact);
                        if (error == -1 || oact.sa_handler == SIG_DFL ||
                            oact.sa_handler == SIG_IGN)
                                continue;
                        usa = __libc_sigaction_slot(sig);
                        usa->sigact = oact;
                        nact = oact;
                        remove_thr_signals(&usa->sigact.sa_mask);
                        nact.sa_flags &= ~SA_NODEFER;
                        nact.sa_flags |= SA_SIGINFO;
                        nact.sa_sigaction = thr_sighandler;
                        nact.sa_mask = _thr_maskset;
                        (void)__sys_sigaction(sig, &nact, NULL);
                }
                __sys_sigprocmask(SIG_SETMASK, &oldset, NULL);
        }

        /* Install SIGCANCEL handler. */
        SIGFILLSET(act.sa_mask);
        act.sa_flags = SA_SIGINFO;
        act.sa_sigaction = (__siginfohandler_t *)&sigcancel_handler;
        __sys_sigaction(SIGCANCEL, &act, NULL);

        /* Unblock SIGCANCEL */
        SIGEMPTYSET(act.sa_mask);
        SIGADDSET(act.sa_mask, SIGCANCEL);
        __sys_sigprocmask(SIG_UNBLOCK, &act.sa_mask, NULL);
}

void
_thr_sigact_unload(struct dl_phdr_info *phdr_info __unused)
{
#if 0
        struct pthread *curthread = _get_curthread();
        struct urwlock *rwlp;
        struct sigaction *actp;
        struct usigaction *usa;
        struct sigaction kact;
        void (*handler)(int);
        int sig;
 
        _thr_signal_block(curthread);
        for (sig = 1; sig <= _SIG_MAXSIG; sig++) {
                usa = __libc_sigaction_slot(sig);
                actp = &usa->sigact;
retry:
                handler = actp->sa_handler;
                if (handler != SIG_DFL && handler != SIG_IGN &&
                    __elf_phdr_match_addr(phdr_info, handler)) {
                        rwlp = &usa->lock;
                        _thr_rwl_wrlock(rwlp);
                        if (handler != actp->sa_handler) {
                                _thr_rwl_unlock(rwlp);
                                goto retry;
                        }
                        actp->sa_handler = SIG_DFL;
                        actp->sa_flags = SA_SIGINFO;
                        SIGEMPTYSET(actp->sa_mask);
                        if (__sys_sigaction(sig, NULL, &kact) == 0 &&
                                kact.sa_handler != SIG_DFL &&
                                kact.sa_handler != SIG_IGN)
                                __sys_sigaction(sig, actp, NULL);
                        _thr_rwl_unlock(rwlp);
                }
        }
        _thr_signal_unblock(curthread);
#endif
}

void
_thr_signal_prefork(void)
{
        int i;

        for (i = 1; i <= _SIG_MAXSIG; ++i)
                _thr_rwl_rdlock(&__libc_sigaction_slot(i)->lock);
}

void
_thr_signal_postfork(void)
{
        int i;

        for (i = 1; i <= _SIG_MAXSIG; ++i)
                _thr_rwl_unlock(&__libc_sigaction_slot(i)->lock);
}

void
_thr_signal_postfork_child(void)
{
        int i;

        for (i = 1; i <= _SIG_MAXSIG; ++i) {
                bzero(&__libc_sigaction_slot(i) -> lock,
                    sizeof(struct urwlock));
        }
}

void
_thr_signal_deinit(void)
{
}

int
__thr_sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
{
        struct sigaction newact, oldact, oldact2;
        sigset_t oldset;
        struct usigaction *usa;
        int ret, err;

        if (!_SIG_VALID(sig) || sig == SIGCANCEL) {
                errno = EINVAL;
                return (-1);
        }

        ret = 0;
        err = 0;
        usa = __libc_sigaction_slot(sig);

        __sys_sigprocmask(SIG_SETMASK, &_thr_maskset, &oldset);
        _thr_rwl_wrlock(&usa->lock);
 
        if (act != NULL) {
                oldact2 = usa->sigact;
                newact = *act;

                /*
                 * if a new sig handler is SIG_DFL or SIG_IGN,
                 * don't remove old handler from __libc_sigact[],
                 * so deferred signals still can use the handlers,
                 * multiple threads invoking sigaction itself is
                 * a race condition, so it is not a problem.
                 */
                if (newact.sa_handler != SIG_DFL &&
                    newact.sa_handler != SIG_IGN) {
                        usa->sigact = newact;
                        remove_thr_signals(&usa->sigact.sa_mask);
                        newact.sa_flags &= ~SA_NODEFER;
                        newact.sa_flags |= SA_SIGINFO;
                        newact.sa_sigaction = thr_sighandler;
                        newact.sa_mask = _thr_maskset; /* mask all signals */
                }
                ret = __sys_sigaction(sig, &newact, &oldact);
                if (ret == -1) {
                        err = errno;
                        usa->sigact = oldact2;
                }
        } else if (oact != NULL) {
                ret = __sys_sigaction(sig, NULL, &oldact);
                err = errno;
        }

        if (oldact.sa_handler != SIG_DFL && oldact.sa_handler != SIG_IGN) {
                if (act != NULL)
                        oldact = oldact2;
                else if (oact != NULL)
                        oldact = usa->sigact;
        }

        _thr_rwl_unlock(&usa->lock);
        __sys_sigprocmask(SIG_SETMASK, &oldset, NULL);

        if (ret == 0) {
                if (oact != NULL)
                        *oact = oldact;
        } else {
                errno = err;
        }
        return (ret);
}

int
__thr_sigprocmask(int how, const sigset_t *set, sigset_t *oset)
{
        const sigset_t *p = set;
        sigset_t newset;

        if (how != SIG_UNBLOCK) {
                if (set != NULL) {
                        newset = *set;
                        SIGDELSET(newset, SIGCANCEL);
                        p = &newset;
                }
        }
        return (__sys_sigprocmask(how, p, oset));
}

__weak_reference(_thr_sigmask, pthread_sigmask);
__weak_reference(_thr_sigmask, _pthread_sigmask);

int
_thr_sigmask(int how, const sigset_t *set, sigset_t *oset)
{

        if (__thr_sigprocmask(how, set, oset))
                return (errno);
        return (0);
}

int
__thr_sigsuspend(const sigset_t *set)
{
        struct pthread *curthread;
        sigset_t newset;
        int ret, old;

        curthread = _get_curthread();

        old = curthread->in_sigsuspend;
        curthread->in_sigsuspend = 1;
        _thr_cancel_enter(curthread);
        ret = __sys_sigsuspend(thr_remove_thr_signals(set, &newset));
        _thr_cancel_leave(curthread, 1);
        curthread->in_sigsuspend = old;
        if (curthread->unblock_sigcancel) {
                curthread->unblock_sigcancel = 0;
                SIGEMPTYSET(newset);
                SIGADDSET(newset, SIGCANCEL);
                __sys_sigprocmask(SIG_UNBLOCK, &newset, NULL);
        }

        return (ret);
}

int
_sigtimedwait(const sigset_t *set, siginfo_t *info,
    const struct timespec *timeout)
{
        sigset_t newset;

        return (__sys_sigtimedwait(thr_remove_thr_signals(set, &newset), info,
            timeout));
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread got signal,
 *   it is not canceled.
 */
int
__thr_sigtimedwait(const sigset_t *set, siginfo_t *info,
    const struct timespec *timeout)
{
        struct pthread  *curthread = _get_curthread();
        sigset_t newset;
        int ret;

        _thr_cancel_enter(curthread);
        ret = __sys_sigtimedwait(thr_remove_thr_signals(set, &newset), info,
            timeout);
        _thr_cancel_leave(curthread, (ret == -1));
        return (ret);
}

int
_sigwaitinfo(const sigset_t *set, siginfo_t *info)
{
        sigset_t newset;

        return (__sys_sigwaitinfo(thr_remove_thr_signals(set, &newset), info));
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread got signal,
 *   it is not canceled.
 */ 
int
__thr_sigwaitinfo(const sigset_t *set, siginfo_t *info)
{
        struct pthread  *curthread = _get_curthread();
        sigset_t newset;
        int ret;

        _thr_cancel_enter(curthread);
        ret = __sys_sigwaitinfo(thr_remove_thr_signals(set, &newset), info);
        _thr_cancel_leave(curthread, ret == -1);
        return (ret);
}

int
_sigwait(const sigset_t *set, int *sig)
{
        sigset_t newset;

        return (__sys_sigwait(thr_remove_thr_signals(set, &newset), sig));
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread got signal,
 *   it is not canceled.
 */ 
int
__thr_sigwait(const sigset_t *set, int *sig)
{
        struct pthread  *curthread = _get_curthread();
        sigset_t newset;
        int ret;

        do {
                _thr_cancel_enter(curthread);
                ret = __sys_sigwait(thr_remove_thr_signals(set, &newset), sig);
                _thr_cancel_leave(curthread, (ret != 0));
        } while (ret == EINTR);
        return (ret);
}

int
__thr_setcontext(const ucontext_t *ucp)
{
        ucontext_t uc;

        if (ucp == NULL) {
                errno = EINVAL;
                return (-1);
        }
        if (!SIGISMEMBER(ucp->uc_sigmask, SIGCANCEL))
                return (__sys_setcontext(ucp));
        (void) memcpy(&uc, ucp, sizeof(uc));
        SIGDELSET(uc.uc_sigmask, SIGCANCEL);
        return (__sys_setcontext(&uc));
}

int
__thr_swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
{
        ucontext_t uc;

        if (oucp == NULL || ucp == NULL) {
                errno = EINVAL;
                return (-1);
        }
        if (SIGISMEMBER(ucp->uc_sigmask, SIGCANCEL)) {
                (void) memcpy(&uc, ucp, sizeof(uc));
                SIGDELSET(uc.uc_sigmask, SIGCANCEL);
                ucp = &uc;
        }
        return (__sys_swapcontext(oucp, ucp));
}