qcore_unix.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// Copyright (C) 2016 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:default
 
#include <QtCore/private/qglobal_p.h>
#include <QtCore/qbasicatomic.h>
#include "qcore_unix_p.h"
 
#include <stdlib.h>
 
#ifdef __GLIBC__
#  include <sys/syscall.h>
#  include <pthread.h>
#  include <unistd.h>
#endif
 
#ifdef Q_OS_DARWIN
#include <mach/mach_time.h>
#endif
 
QT_BEGIN_NAMESPACE
 
void qt_ignore_sigpipe() noexcept // noexcept: sigaction(2) is not a Posix Cancellation Point
{
    // Set to ignore SIGPIPE once only.
    Q_CONSTINIT static QBasicAtomicInt atom = Q_BASIC_ATOMIC_INITIALIZER(0);
    if (!atom.loadRelaxed()) {
        // More than one thread could turn off SIGPIPE at the same time
        // But that's acceptable because they all would be doing the same
        // action
        struct sigaction noaction = {};
        noaction.sa_handler = SIG_IGN;
        ::sigaction(SIGPIPE, &noaction, nullptr);
        atom.storeRelaxed(1);
    }
}
 
QByteArray qt_readlink(const char *path)
{
#ifndef PATH_MAX
    // suitably large value that won't consume too much memory
#  define PATH_MAX  1024*1024
#endif
 
    QByteArray buf(256, Qt::Uninitialized);
 
    ssize_t len = ::readlink(path, buf.data(), buf.size());
    while (len == buf.size()) {
        // readlink(2) will fill our buffer and not necessarily terminate with NUL;
        if (buf.size() >= PATH_MAX) {
            errno = ENAMETOOLONG;
            return QByteArray();
        }
 
        // double the size and try again
        buf.resize(buf.size() * 2);
        len = ::readlink(path, buf.data(), buf.size());
    }
 
    if (len == -1)
        return QByteArray();
 
    buf.resize(len);
    return buf;
}
 
#if defined(Q_PROCESSOR_X86_32) && defined(__GLIBC__)
#  if !__GLIBC_PREREQ(2, 22)
// glibc prior to release 2.22 had a bug that suppresses the third argument to
// open() / open64() / openat(), causing file creation with O_TMPFILE to have
// the wrong permissions. So we bypass the glibc implementation and go straight
// for the syscall. See
// https://sourceware.org/git/?p=glibc.git;a=commit;h=65f6f938cd562a614a68e15d0581a34b177ec29d
int qt_open64(const char *pathname, int flags, mode_t mode)
{
    return syscall(SYS_open, pathname, flags | O_LARGEFILE, mode);
}
#  endif
#endif
 
#ifndef QT_BOOTSTRAPPED
 
#if QT_CONFIG(poll_pollts)
#  define ppoll pollts
#endif
 
[[maybe_unused]]
static inline int timespecToMillisecs(const struct timespec *ts)
{
    using namespace std::chrono;
    if (!ts)
        return -1;
    auto ms = ceil<milliseconds>(timespecToChrono<nanoseconds>(*ts));
    return int(ms.count());
}
 
// defined in qpoll.cpp
int qt_poll(struct pollfd *fds, nfds_t nfds, const struct timespec *timeout_ts);
 
static inline int qt_ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *timeout_ts)
{
#if QT_CONFIG(poll_ppoll) || QT_CONFIG(poll_pollts)
    return ::ppoll(fds, nfds, timeout_ts, nullptr);
#elif QT_CONFIG(poll_poll)
    return ::poll(fds, nfds, timespecToMillisecs(timeout_ts));
#elif QT_CONFIG(poll_select)
    return qt_poll(fds, nfds, timeout_ts);
#else
    // configure.json reports an error when everything is not available
#endif
}
 
 
/*!
    \internal
 
    Behaves as close to POSIX poll(2) as practical but may be implemented
    using select(2) where necessary. In that case, returns -1 and sets errno
    to EINVAL if passed any descriptor greater than or equal to FD_SETSIZE.
*/
int qt_safe_poll(struct pollfd *fds, nfds_t nfds, QDeadlineTimer deadline)
{
    if (deadline.isForever()) {
        // no timeout -> block forever
        int ret;
        QT_EINTR_LOOP(ret, qt_ppoll(fds, nfds, nullptr));
        return ret;
    }
 
    using namespace std::chrono;
    nanoseconds remaining = deadline.remainingTimeAsDuration();
    // loop and recalculate the timeout as needed
    do {
        timespec ts = durationToTimespec(remaining);
        const int ret = qt_ppoll(fds, nfds, &ts);
        if (ret != -1 || errno != EINTR)
            return ret;
        remaining = deadline.remainingTimeAsDuration();
    } while (remaining > 0ns);
 
    return 0;
}
 
#endif // QT_BOOTSTRAPPED
 
QT_END_NAMESPACE