54b9a4ec1e
Previously we would crash the process immediately when a promise violation was found during a syscall. This is error prone, as we don't unwind the stack. This means that in certain cases we can leak resources, like an OwnPtr / RefPtr tracked on the stack. Or even leak a lock acquired in a ScopeLockLocker. To remedy this situation we move the promise violation handling to the syscall handler, right before we return to user space. This allows the code to follow the normal unwind path, and grantees there is no longer any cleanup that needs to occur. The Process::require_promise() and Process::require_no_promises() functions were modified to return ErrorOr<void> so we enforce that the errors are always propagated by the caller.
138 lines
3.7 KiB
C++
138 lines
3.7 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <Kernel/API/POSIX/errno.h>
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#include <Kernel/Arch/x86/InterruptDisabler.h>
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#include <Kernel/Debug.h>
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#include <Kernel/Process.h>
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#include <Kernel/TTY/MasterPTY.h>
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#include <Kernel/TTY/PTYMultiplexer.h>
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#include <Kernel/TTY/SlavePTY.h>
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#include <LibC/signal_numbers.h>
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#include <LibC/sys/ioctl_numbers.h>
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namespace Kernel {
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ErrorOr<NonnullRefPtr<MasterPTY>> MasterPTY::try_create(unsigned int index)
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{
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auto pts_name = TRY(KString::formatted("/dev/pts/{}", index));
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auto tty_name = TRY(pts_name->try_clone());
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auto buffer = TRY(DoubleBuffer::try_create());
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auto master_pty = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) MasterPTY(index, move(buffer), move(pts_name))));
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auto slave_pty = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) SlavePTY(*master_pty, index, move(tty_name))));
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master_pty->m_slave = slave_pty;
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master_pty->after_inserting();
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slave_pty->after_inserting();
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return master_pty;
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}
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MasterPTY::MasterPTY(unsigned index, NonnullOwnPtr<DoubleBuffer> buffer, NonnullOwnPtr<KString> pts_name)
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: CharacterDevice(200, index)
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, m_index(index)
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, m_buffer(move(buffer))
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, m_pts_name(move(pts_name))
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{
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auto& process = Process::current();
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set_uid(process.uid());
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set_gid(process.gid());
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m_buffer->set_unblock_callback([this]() {
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if (m_slave)
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evaluate_block_conditions();
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});
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}
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MasterPTY::~MasterPTY()
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{
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dbgln_if(MASTERPTY_DEBUG, "~MasterPTY({})", m_index);
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PTYMultiplexer::the().notify_master_destroyed({}, m_index);
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}
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KString const& MasterPTY::pts_name() const
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{
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return *m_pts_name;
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}
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ErrorOr<size_t> MasterPTY::read(OpenFileDescription&, u64, UserOrKernelBuffer& buffer, size_t size)
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{
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if (!m_slave && m_buffer->is_empty())
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return 0;
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return m_buffer->read(buffer, size);
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}
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ErrorOr<size_t> MasterPTY::write(OpenFileDescription&, u64, const UserOrKernelBuffer& buffer, size_t size)
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{
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if (!m_slave)
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return EIO;
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m_slave->on_master_write(buffer, size);
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return size;
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}
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bool MasterPTY::can_read(const OpenFileDescription&, size_t) const
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{
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if (!m_slave)
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return true;
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return !m_buffer->is_empty();
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}
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bool MasterPTY::can_write(const OpenFileDescription&, size_t) const
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{
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return true;
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}
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void MasterPTY::notify_slave_closed(Badge<SlavePTY>)
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{
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dbgln_if(MASTERPTY_DEBUG, "MasterPTY({}): slave closed, my retains: {}, slave retains: {}", m_index, ref_count(), m_slave->ref_count());
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// +1 ref for my MasterPTY::m_slave
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// +1 ref for OpenFileDescription::m_device
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if (m_slave->ref_count() == 2)
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m_slave = nullptr;
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}
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ErrorOr<size_t> MasterPTY::on_slave_write(const UserOrKernelBuffer& data, size_t size)
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{
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if (m_closed)
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return EIO;
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return m_buffer->write(data, size);
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}
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bool MasterPTY::can_write_from_slave() const
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{
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if (m_closed)
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return true;
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return m_buffer->space_for_writing();
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}
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ErrorOr<void> MasterPTY::close()
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{
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InterruptDisabler disabler;
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// After the closing OpenFileDescription dies, slave is the only thing keeping me alive.
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// From this point, let's consider ourselves closed.
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m_closed = true;
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if (m_slave)
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m_slave->hang_up();
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return {};
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}
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ErrorOr<void> MasterPTY::ioctl(OpenFileDescription& description, unsigned request, Userspace<void*> arg)
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{
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TRY(Process::current().require_promise(Pledge::tty));
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if (!m_slave)
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return EIO;
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if (request == TIOCSWINSZ || request == TIOCGPGRP)
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return m_slave->ioctl(description, request, arg);
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return EINVAL;
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}
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ErrorOr<NonnullOwnPtr<KString>> MasterPTY::pseudo_path(const OpenFileDescription&) const
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{
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return KString::formatted("ptm:{}", m_pts_name);
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}
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}
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