26504d84bb
Allow MappedFile to expose a byte range within an fd. It maps the page-aligned region required by mmap internally. Add ImmutableBytes as a small shared holder for either owned bytes or a mapped file. This lets cache code thread file-backed response bodies through without copying response data into anonymous memory. Cover non-page-aligned ranges, empty ranges, invalid ranges, and mapped ImmutableBytes in TestLibCoreMappedFile.
111 lines
3.4 KiB
C++
111 lines
3.4 KiB
C++
/*
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* Copyright (c) 2018-2021, Andreas Kling <andreas@ladybird.org>
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* Copyright (c) 2023, kleines Filmröllchen <filmroellchen@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/Checked.h>
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#include <AK/ScopeGuard.h>
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#include <LibCore/File.h>
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#include <LibCore/MappedFile.h>
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#include <LibCore/System.h>
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#include <sys/mman.h>
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namespace Core {
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ErrorOr<NonnullOwnPtr<MappedFile>> MappedFile::map(StringView path, Mode mode)
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{
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auto const file_mode = mode == Mode::ReadOnly ? O_RDONLY : O_RDWR;
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auto fd = TRY(Core::System::open(path, file_mode | O_CLOEXEC, 0));
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return map_from_fd_and_close(fd, path, mode);
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}
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ErrorOr<NonnullOwnPtr<MappedFile>> MappedFile::map_from_file(NonnullOwnPtr<Core::File> stream, StringView path)
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{
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return map_from_fd_and_close(stream->leak_fd(), path);
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}
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ErrorOr<NonnullOwnPtr<MappedFile>> MappedFile::map_from_fd_and_close(int fd, [[maybe_unused]] StringView path, Mode mode)
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{
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ArmedScopeGuard fd_close_guard = [fd] {
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(void)System::close(fd);
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};
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auto stat = TRY(Core::System::fstat(fd));
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if (stat.st_size < 0)
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return Error::from_errno(EINVAL);
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fd_close_guard.disarm();
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return map_from_fd_range_and_close(fd, path, 0, static_cast<size_t>(stat.st_size), mode);
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}
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ErrorOr<NonnullOwnPtr<MappedFile>> MappedFile::map_from_fd_range_and_close(int fd, [[maybe_unused]] StringView path, off_t offset, size_t size, Mode mode)
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{
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ScopeGuard fd_close_guard = [fd] {
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(void)System::close(fd);
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};
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if (offset < 0 || !AK::is_within_range<size_t>(offset))
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return Error::from_errno(EINVAL);
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auto stat = TRY(Core::System::fstat(fd));
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if (stat.st_size < 0 || !AK::is_within_range<size_t>(stat.st_size))
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return Error::from_errno(EINVAL);
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auto file_size = static_cast<size_t>(stat.st_size);
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auto requested_offset = static_cast<size_t>(offset);
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if (requested_offset > file_size || size > file_size - requested_offset)
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return Error::from_errno(EINVAL);
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int protection;
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int flags;
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switch (mode) {
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case Mode::ReadOnly:
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protection = PROT_READ;
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flags = MAP_SHARED;
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break;
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case Mode::ReadWrite:
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protection = PROT_READ | PROT_WRITE;
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// Don't map a read-write mapping shared as a precaution.
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flags = MAP_PRIVATE;
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break;
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}
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if (size == 0)
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return adopt_own(*new MappedFile(nullptr, 0, nullptr, 0, mode));
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auto page_aligned_offset = align_down_to(requested_offset, PAGE_SIZE);
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auto offset_in_mapping = requested_offset - page_aligned_offset;
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Checked<size_t> mapping_size = offset_in_mapping;
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mapping_size += size;
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if (mapping_size.has_overflow())
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return Error::from_errno(EOVERFLOW);
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auto* mapping = TRY(Core::System::mmap(nullptr, mapping_size.value(), protection, flags, fd, page_aligned_offset, 0, path));
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auto* data = reinterpret_cast<u8*>(mapping) + offset_in_mapping;
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return adopt_own(*new MappedFile(mapping, mapping_size.value(), data, size, mode));
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}
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MappedFile::MappedFile(void* mapping, size_t mapping_size, void* data, size_t size, Mode mode)
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: FixedMemoryStream(Bytes { data, size }, mode)
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, m_mapping(mapping)
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, m_mapping_size(mapping_size)
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, m_data(data)
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, m_size(size)
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{
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}
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MappedFile::~MappedFile()
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{
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if (!m_mapping)
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return;
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auto res = Core::System::munmap(m_mapping, m_mapping_size);
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if (res.is_error())
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dbgln("Failed to unmap MappedFile (@ {:p}): {}", m_mapping, res.error());
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}
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}
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