serenity/Kernel/Syscalls/pipe.cpp

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <Kernel/FileSystem/FIFO.h>
#include <Kernel/Process.h>

namespace Kernel {

ErrorOr<FlatPtr> Process::sys$pipe(int pipefd[2], int flags)
{
    VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
    TRY(require_promise(Pledge::stdio));
    auto open_count = fds().with_shared([](auto& fds) { return fds.open_count(); });
    if (open_count + 2 > OpenFileDescriptions::max_open())
        return EMFILE;
    // Reject flags other than O_CLOEXEC, O_NONBLOCK
    if ((flags & (O_CLOEXEC | O_NONBLOCK)) != flags)
        return EINVAL;

    u32 fd_flags = (flags & O_CLOEXEC) ? FD_CLOEXEC : 0;
    auto fifo = TRY(FIFO::try_create(uid()));

    ScopedDescriptionAllocation reader_fd_allocation;
    ScopedDescriptionAllocation writer_fd_allocation;

    TRY(m_fds.with_exclusive([&](auto& fds) -> ErrorOr<void> {
        reader_fd_allocation = TRY(fds.allocate());
        writer_fd_allocation = TRY(fds.allocate());
        return {};
    }));

    auto reader_description = TRY(fifo->open_direction(FIFO::Direction::Reader));
    auto writer_description = TRY(fifo->open_direction(FIFO::Direction::Writer));

    reader_description->set_readable(true);
    writer_description->set_writable(true);
    if (flags & O_NONBLOCK) {
        reader_description->set_blocking(false);
        writer_description->set_blocking(false);
    }

    TRY(m_fds.with_exclusive([&](auto& fds) -> ErrorOr<void> {
        fds[reader_fd_allocation.fd].set(move(reader_description), fd_flags);
        fds[writer_fd_allocation.fd].set(move(writer_description), fd_flags);
        return {};
    }));

    TRY(copy_to_user(&pipefd[0], &reader_fd_allocation.fd));
    TRY(copy_to_user(&pipefd[1], &writer_fd_allocation.fd));
    return 0;
}

}