74 lines
2.7 KiB
C++
74 lines
2.7 KiB
C++
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//===- FileHeaderReader.cpp - XRay File Header Reader --------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/XRay/FileHeaderReader.h"
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namespace llvm {
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namespace xray {
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// Populates the FileHeader reference by reading the first 32 bytes of the file.
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Expected<XRayFileHeader> readBinaryFormatHeader(DataExtractor &HeaderExtractor,
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uint64_t &OffsetPtr) {
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// FIXME: Maybe deduce whether the data is little or big-endian using some
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// magic bytes in the beginning of the file?
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// First 32 bytes of the file will always be the header. We assume a certain
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// format here:
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//
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// (2) uint16 : version
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// (2) uint16 : type
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// (4) uint32 : bitfield
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// (8) uint64 : cycle frequency
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// (16) - : padding
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XRayFileHeader FileHeader;
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auto PreReadOffset = OffsetPtr;
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FileHeader.Version = HeaderExtractor.getU16(&OffsetPtr);
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if (OffsetPtr == PreReadOffset)
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return createStringError(
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std::make_error_code(std::errc::invalid_argument),
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"Failed reading version from file header at offset %" PRId64 ".",
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OffsetPtr);
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PreReadOffset = OffsetPtr;
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FileHeader.Type = HeaderExtractor.getU16(&OffsetPtr);
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if (OffsetPtr == PreReadOffset)
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return createStringError(
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std::make_error_code(std::errc::invalid_argument),
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"Failed reading file type from file header at offset %" PRId64 ".",
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OffsetPtr);
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PreReadOffset = OffsetPtr;
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uint32_t Bitfield = HeaderExtractor.getU32(&OffsetPtr);
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if (OffsetPtr == PreReadOffset)
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return createStringError(
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std::make_error_code(std::errc::invalid_argument),
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"Failed reading flag bits from file header at offset %" PRId64 ".",
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OffsetPtr);
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FileHeader.ConstantTSC = Bitfield & 1uL;
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FileHeader.NonstopTSC = Bitfield & 1uL << 1;
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PreReadOffset = OffsetPtr;
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FileHeader.CycleFrequency = HeaderExtractor.getU64(&OffsetPtr);
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if (OffsetPtr == PreReadOffset)
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return createStringError(
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std::make_error_code(std::errc::invalid_argument),
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"Failed reading cycle frequency from file header at offset %" PRId64
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".",
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OffsetPtr);
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std::memcpy(&FileHeader.FreeFormData,
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HeaderExtractor.getData().bytes_begin() + OffsetPtr, 16);
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// Manually advance the offset pointer 16 bytes, after getting a raw memcpy
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// from the underlying data.
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OffsetPtr += 16;
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return std::move(FileHeader);
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}
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} // namespace xray
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} // namespace llvm
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