| 1 | // Copyright (C) 2016 The Qt Company Ltd. |
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| 2 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 3 | |
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| 4 | #include "qv4compilationunitmapper_p.h" |
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| 5 | |
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| 6 | #include <private/qcore_unix_p.h> |
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| 7 | #include <private/qv4compileddata_p.h> |
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| 8 | |
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| 9 | #include <QtCore/qscopeguard.h> |
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| 10 | #include <QtCore/qdatetime.h> |
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| 11 | |
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| 12 | #include <functional> |
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| 13 | #include <sys/mman.h> |
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| 14 | |
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| 15 | QT_BEGIN_NAMESPACE |
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| 16 | |
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| 17 | using namespace QV4; |
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| 18 | |
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| 19 | CompiledData::Unit *CompilationUnitMapper::open(const QString &cacheFileName, const QDateTime &sourceTimeStamp, QString *errorString) |
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| 20 | { |
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| 21 | close(); |
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| 22 | |
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| 23 | int fd = qt_safe_open(pathname: QFile::encodeName(fileName: cacheFileName).constData(), O_RDONLY); |
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| 24 | if (fd == -1) { |
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| 25 | *errorString = qt_error_string(errno); |
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| 26 | return nullptr; |
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| 27 | } |
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| 28 | |
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| 29 | auto cleanup = qScopeGuard(f: [fd]{ |
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| 30 | qt_safe_close(fd) ; |
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| 31 | }); |
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| 32 | |
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| 33 | CompiledData::Unit ; |
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| 34 | qint64 bytesRead = qt_safe_read(fd, data: reinterpret_cast<char *>(&header), maxlen: sizeof(header)); |
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| 35 | |
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| 36 | if (bytesRead != sizeof(header)) { |
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| 37 | *errorString = QStringLiteral("File too small for the header fields" ); |
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| 38 | return nullptr; |
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| 39 | } |
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| 40 | |
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| 41 | if (!header.verifyHeader(expectedSourceTimeStamp: sourceTimeStamp, errorString)) |
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| 42 | return nullptr; |
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| 43 | |
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| 44 | // Data structure and qt version matched, so now we can access the rest of the file safely. |
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| 45 | |
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| 46 | length = static_cast<size_t>(lseek(fd: fd, offset: 0, SEEK_END)); |
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| 47 | /* Error out early on file corruption. We assume we can read header.unitSize bytes |
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| 48 | later (even before verifying the checksum), potentially causing out-of-bound |
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| 49 | reads |
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| 50 | Also, no need to wait until checksum verification if we know beforehand |
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| 51 | that the cached unit is bogus |
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| 52 | */ |
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| 53 | if (length != header.unitSize) { |
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| 54 | *errorString = QStringLiteral("Potential file corruption, file too small" ); |
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| 55 | return nullptr; |
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| 56 | } |
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| 57 | |
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| 58 | void *ptr = mmap(addr: nullptr, len: length, PROT_READ, MAP_SHARED, fd: fd, /*offset*/0); |
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| 59 | if (ptr == MAP_FAILED) { |
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| 60 | *errorString = qt_error_string(errno); |
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| 61 | return nullptr; |
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| 62 | } |
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| 63 | dataPtr = ptr; |
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| 64 | |
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| 65 | return reinterpret_cast<CompiledData::Unit*>(dataPtr); |
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| 66 | } |
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| 67 | |
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| 68 | void CompilationUnitMapper::close() |
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| 69 | { |
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| 70 | // Do not unmap the data here. |
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| 71 | if (dataPtr != nullptr) { |
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| 72 | // Do not unmap cache files that are built with the StaticData flag. That's the majority of |
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| 73 | // them and it's necessary to benefit from the QString literal optimization. There might |
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| 74 | // still be QString instances around that point into that memory area. The memory is backed |
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| 75 | // on the disk, so the kernel is free to release the pages and all that remains is the |
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| 76 | // address space allocation. |
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| 77 | if (!(reinterpret_cast<CompiledData::Unit*>(dataPtr)->flags & CompiledData::Unit::StaticData)) |
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| 78 | munmap(addr: dataPtr, len: length); |
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| 79 | } |
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| 80 | dataPtr = nullptr; |
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| 81 | } |
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| 82 | |
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| 83 | QT_END_NAMESPACE |
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| 84 | |
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