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serenity/Kernel/Syscalls/select.cpp
Andreas Kling d96a44a738 Kernel: Avoid transient kmalloc heap allocations in sys$select() 
Dynamic Vector allocations in sys$select() were showing up in the
full-system profile and since there will never be more than FD_SETSIZE
file descriptors to worry about, we can confidently add enough inline
capacity to this Vector that it never has to kmalloc.

To compensate for the increased stack usage, reduce the size of the
FDInfo struct while we're here. :^)
2021-03-03 20:37:23 +01:00

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9.4 KiB
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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.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, 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 COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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 <AK/ScopeGuard.h>
#include <AK/Time.h>
#include <Kernel/Debug.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/Process.h>
namespace Kernel {
KResultOr<int> Process::sys$select(Userspace<const Syscall::SC_select_params*> user_params)
{
REQUIRE_PROMISE(stdio);
Syscall::SC_select_params params {};
if (!copy_from_user(&params, user_params))
return EFAULT;
if (params.nfds < 0)
return EINVAL;
Thread::BlockTimeout timeout;
if (params.timeout) {
Optional<Time> timeout_time = copy_time_from_user(params.timeout);
if (!timeout_time.has_value())
return EFAULT;
timeout = Thread::BlockTimeout(false, &timeout_time.value());
}
auto current_thread = Thread::current();
u32 previous_signal_mask = 0;
if (params.sigmask) {
sigset_t sigmask_copy;
if (!copy_from_user(&sigmask_copy, params.sigmask))
return EFAULT;
previous_signal_mask = current_thread->update_signal_mask(sigmask_copy);
}
ScopeGuard rollback_signal_mask([&]() {
if (params.sigmask)
current_thread->update_signal_mask(previous_signal_mask);
});
fd_set fds_read, fds_write, fds_except;
if (params.readfds && !copy_from_user(&fds_read, params.readfds))
return EFAULT;
if (params.writefds && !copy_from_user(&fds_write, params.writefds))
return EFAULT;
if (params.exceptfds && !copy_from_user(&fds_except, params.exceptfds))
return EFAULT;
Thread::SelectBlocker::FDVector fds_info;
Vector<int, FD_SETSIZE> fds;
for (int fd = 0; fd < params.nfds; fd++) {
u32 block_flags = (u32)Thread::FileBlocker::BlockFlags::None;
if (params.readfds && FD_ISSET(fd, &fds_read))
block_flags |= (u32)Thread::FileBlocker::BlockFlags::Read;
if (params.writefds && FD_ISSET(fd, &fds_write))
block_flags |= (u32)Thread::FileBlocker::BlockFlags::Write;
if (params.exceptfds && FD_ISSET(fd, &fds_except))
block_flags |= (u32)Thread::FileBlocker::BlockFlags::Exception;
if (block_flags == (u32)Thread::FileBlocker::BlockFlags::None)
continue;
auto description = file_description(fd);
if (!description) {
dbgln("sys$select: Bad fd number {}", fd);
return EBADF;
}
fds_info.append({ description.release_nonnull(), (Thread::FileBlocker::BlockFlags)block_flags });
fds.append(fd);
}
if constexpr (IO_DEBUG || POLL_SELECT_DEBUG)
dbgln("selecting on {} fds, timeout={}", fds_info.size(), params.timeout);
if (current_thread->block<Thread::SelectBlocker>(timeout, fds_info).was_interrupted()) {
dbgln_if(POLL_SELECT_DEBUG, "select was interrupted");
return EINTR;
}
if (params.readfds)
FD_ZERO(&fds_read);
if (params.writefds)
FD_ZERO(&fds_write);
if (params.exceptfds)
FD_ZERO(&fds_except);
int marked_fd_count = 0;
for (size_t i = 0; i < fds_info.size(); i++) {
auto& fd_entry = fds_info[i];
if (fd_entry.unblocked_flags == Thread::FileBlocker::BlockFlags::None)
continue;
if (params.readfds && ((u32)fd_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::Read)) {
FD_SET(fds[i], &fds_read);
marked_fd_count++;
}
if (params.writefds && ((u32)fd_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::Write)) {
FD_SET(fds[i], &fds_write);
marked_fd_count++;
}
if (params.exceptfds && ((u32)fd_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::Exception)) {
FD_SET(fds[i], &fds_except);
marked_fd_count++;
}
}
if (params.readfds && !copy_to_user(params.readfds, &fds_read))
return EFAULT;
if (params.writefds && !copy_to_user(params.writefds, &fds_write))
return EFAULT;
if (params.exceptfds && !copy_to_user(params.exceptfds, &fds_except))
return EFAULT;
return marked_fd_count;
}
KResultOr<int> Process::sys$poll(Userspace<const Syscall::SC_poll_params*> user_params)
{
REQUIRE_PROMISE(stdio);
Syscall::SC_poll_params params;
if (!copy_from_user(&params, user_params))
return EFAULT;
if (params.nfds >= m_max_open_file_descriptors)
return ENOBUFS;
Thread::BlockTimeout timeout;
if (params.timeout) {
auto timeout_time = copy_time_from_user(params.timeout);
if (!timeout_time.has_value())
return EFAULT;
timeout = Thread::BlockTimeout(false, &timeout_time.value());
}
sigset_t sigmask = {};
if (params.sigmask && !copy_from_user(&sigmask, params.sigmask))
return EFAULT;
Vector<pollfd> fds_copy;
if (params.nfds > 0) {
Checked nfds_checked = sizeof(pollfd);
nfds_checked *= params.nfds;
if (nfds_checked.has_overflow())
return EFAULT;
fds_copy.resize(params.nfds);
if (!copy_from_user(fds_copy.data(), &params.fds[0], nfds_checked.value()))
return EFAULT;
}
Thread::SelectBlocker::FDVector fds_info;
for (size_t i = 0; i < params.nfds; i++) {
auto& pfd = fds_copy[i];
auto description = file_description(pfd.fd);
if (!description) {
dbgln("sys$poll: Bad fd number {}", pfd.fd);
return EBADF;
}
u32 block_flags = (u32)Thread::FileBlocker::BlockFlags::Exception; // always want POLLERR, POLLHUP, POLLNVAL
if (pfd.events & POLLIN)
block_flags |= (u32)Thread::FileBlocker::BlockFlags::Read;
if (pfd.events & POLLOUT)
block_flags |= (u32)Thread::FileBlocker::BlockFlags::Write;
if (pfd.events & POLLPRI)
block_flags |= (u32)Thread::FileBlocker::BlockFlags::ReadPriority;
fds_info.append({ description.release_nonnull(), (Thread::FileBlocker::BlockFlags)block_flags });
}
auto current_thread = Thread::current();
u32 previous_signal_mask = 0;
if (params.sigmask)
previous_signal_mask = current_thread->update_signal_mask(sigmask);
ScopeGuard rollback_signal_mask([&]() {
if (params.sigmask)
current_thread->update_signal_mask(previous_signal_mask);
});
if constexpr (IO_DEBUG || POLL_SELECT_DEBUG)
dbgln("polling on {} fds, timeout={}", fds_info.size(), params.timeout);
if (current_thread->block<Thread::SelectBlocker>(timeout, fds_info).was_interrupted())
return EINTR;
int fds_with_revents = 0;
for (unsigned i = 0; i < params.nfds; ++i) {
auto& pfd = fds_copy[i];
auto& fds_entry = fds_info[i];
pfd.revents = 0;
if (fds_entry.unblocked_flags == Thread::FileBlocker::BlockFlags::None)
continue;
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::Exception) {
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::ReadHangUp)
pfd.revents |= POLLRDHUP;
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::WriteError)
pfd.revents |= POLLERR;
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::WriteHangUp)
pfd.revents |= POLLNVAL;
} else {
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::Read) {
VERIFY(pfd.events & POLLIN);
pfd.revents |= POLLIN;
}
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::ReadPriority) {
VERIFY(pfd.events & POLLPRI);
pfd.revents |= POLLPRI;
}
if ((u32)fds_entry.unblocked_flags & (u32)Thread::FileBlocker::BlockFlags::Write) {
VERIFY(pfd.events & POLLOUT);
pfd.revents |= POLLOUT;
}
}
if (pfd.revents)
fds_with_revents++;
}
if (params.nfds > 0 && !copy_to_user(&params.fds[0], fds_copy.data(), params.nfds * sizeof(pollfd)))
return EFAULT;
return fds_with_revents;
}
}
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