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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.
124 lines
4.2 KiB
C++
124 lines
4.2 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 <AK/ScopeGuard.h>
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#include <AK/Time.h>
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#include <Kernel/Debug.h>
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#include <Kernel/FileSystem/OpenFileDescription.h>
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#include <Kernel/Process.h>
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namespace Kernel {
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using BlockFlags = Thread::FileBlocker::BlockFlags;
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ErrorOr<FlatPtr> Process::sys$poll(Userspace<const Syscall::SC_poll_params*> user_params)
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{
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VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
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TRY(require_promise(Pledge::stdio));
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auto params = TRY(copy_typed_from_user(user_params));
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if (params.nfds >= OpenFileDescriptions::max_open())
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return ENOBUFS;
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Thread::BlockTimeout timeout;
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if (params.timeout) {
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auto timeout_time = TRY(copy_time_from_user(params.timeout));
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timeout = Thread::BlockTimeout(false, &timeout_time);
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}
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sigset_t sigmask = {};
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if (params.sigmask)
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TRY(copy_from_user(&sigmask, params.sigmask));
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Vector<pollfd, FD_SETSIZE> fds_copy;
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if (params.nfds > 0) {
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Checked<size_t> nfds_checked = sizeof(pollfd);
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nfds_checked *= params.nfds;
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if (nfds_checked.has_overflow())
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return EFAULT;
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TRY(fds_copy.try_resize(params.nfds));
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TRY(copy_from_user(fds_copy.data(), ¶ms.fds[0], nfds_checked.value()));
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}
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Thread::SelectBlocker::FDVector fds_info;
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for (size_t i = 0; i < params.nfds; i++) {
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auto& pfd = fds_copy[i];
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auto description = TRY(fds().open_file_description(pfd.fd));
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BlockFlags block_flags = BlockFlags::Exception; // always want POLLERR, POLLHUP, POLLNVAL
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if (pfd.events & POLLIN)
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block_flags |= BlockFlags::Read;
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if (pfd.events & POLLOUT)
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block_flags |= BlockFlags::Write;
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if (pfd.events & POLLPRI)
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block_flags |= BlockFlags::ReadPriority;
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if (pfd.events & POLLWRBAND)
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block_flags |= BlockFlags::WritePriority;
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TRY(fds_info.try_append({ move(description), block_flags }));
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}
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auto* current_thread = Thread::current();
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u32 previous_signal_mask = 0;
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if (params.sigmask)
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previous_signal_mask = current_thread->update_signal_mask(sigmask);
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ScopeGuard rollback_signal_mask([&]() {
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if (params.sigmask)
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current_thread->update_signal_mask(previous_signal_mask);
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});
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if constexpr (IO_DEBUG || POLL_SELECT_DEBUG)
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dbgln("polling on {} fds, timeout={}", fds_info.size(), params.timeout);
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if (current_thread->block<Thread::SelectBlocker>(timeout, fds_info).was_interrupted())
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return EINTR;
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int fds_with_revents = 0;
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for (unsigned i = 0; i < params.nfds; ++i) {
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auto& pfd = fds_copy[i];
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auto& fds_entry = fds_info[i];
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pfd.revents = 0;
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if (fds_entry.unblocked_flags == BlockFlags::None)
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continue;
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if (has_any_flag(fds_entry.unblocked_flags, BlockFlags::Exception)) {
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::ReadHangUp))
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pfd.revents |= POLLRDHUP;
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::WriteError))
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pfd.revents |= POLLERR;
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::WriteHangUp))
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pfd.revents |= POLLNVAL;
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} else {
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::Read)) {
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VERIFY(pfd.events & POLLIN);
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pfd.revents |= POLLIN;
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}
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::ReadPriority)) {
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VERIFY(pfd.events & POLLPRI);
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pfd.revents |= POLLPRI;
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}
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::Write)) {
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VERIFY(pfd.events & POLLOUT);
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pfd.revents |= POLLOUT;
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}
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if (has_flag(fds_entry.unblocked_flags, BlockFlags::WritePriority)) {
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VERIFY(pfd.events & POLLWRBAND);
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pfd.revents |= POLLWRBAND;
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}
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}
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if (pfd.revents)
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fds_with_revents++;
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}
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if (params.nfds > 0)
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TRY(copy_to_user(¶ms.fds[0], fds_copy.data(), params.nfds * sizeof(pollfd)));
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return fds_with_revents;
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}
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}
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