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      1 //===- DWARFDataExtractor.h -------------------------------------*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_DEBUGINFO_DWARF_DWARFDATAEXTRACTOR_H
     10 #define LLVM_DEBUGINFO_DWARF_DWARFDATAEXTRACTOR_H
     11 
     12 #include "llvm/BinaryFormat/Dwarf.h"
     13 #include "llvm/DebugInfo/DWARF/DWARFSection.h"
     14 #include "llvm/Support/DataExtractor.h"
     15 
     16 namespace llvm {
     17 class DWARFObject;
     18 
     19 /// A DataExtractor (typically for an in-memory copy of an object-file section)
     20 /// plus a relocation map for that section, if there is one.
     21 class DWARFDataExtractor : public DataExtractor {
     22   const DWARFObject *Obj = nullptr;
     23   const DWARFSection *Section = nullptr;
     24 
     25 public:
     26   /// Constructor for the normal case of extracting data from a DWARF section.
     27   /// The DWARFSection's lifetime must be at least as long as the extractor's.
     28   DWARFDataExtractor(const DWARFObject &Obj, const DWARFSection &Section,
     29                      bool IsLittleEndian, uint8_t AddressSize)
     30       : DataExtractor(Section.Data, IsLittleEndian, AddressSize), Obj(&Obj),
     31         Section(&Section) {}
     32 
     33   /// Constructor for cases when there are no relocations.
     34   DWARFDataExtractor(StringRef Data, bool IsLittleEndian, uint8_t AddressSize)
     35     : DataExtractor(Data, IsLittleEndian, AddressSize) {}
     36   DWARFDataExtractor(ArrayRef<uint8_t> Data, bool IsLittleEndian,
     37                      uint8_t AddressSize)
     38       : DataExtractor(
     39             StringRef(reinterpret_cast<const char *>(Data.data()), Data.size()),
     40             IsLittleEndian, AddressSize) {}
     41 
     42   /// Truncating constructor
     43   DWARFDataExtractor(const DWARFDataExtractor &Other, size_t Length)
     44       : DataExtractor(Other.getData().substr(0, Length), Other.isLittleEndian(),
     45                       Other.getAddressSize()),
     46         Obj(Other.Obj), Section(Other.Section) {}
     47 
     48   /// Extracts the DWARF "initial length" field, which can either be a 32-bit
     49   /// value smaller than 0xfffffff0, or the value 0xffffffff followed by a
     50   /// 64-bit length. Returns the actual length, and the DWARF format which is
     51   /// encoded in the field. In case of errors, it returns {0, DWARF32} and
     52   /// leaves the offset unchanged.
     53   std::pair<uint64_t, dwarf::DwarfFormat>
     54   getInitialLength(uint64_t *Off, Error *Err = nullptr) const;
     55 
     56   std::pair<uint64_t, dwarf::DwarfFormat> getInitialLength(Cursor &C) const {
     57     return getInitialLength(&getOffset(C), &getError(C));
     58   }
     59 
     60   /// Extracts a value and applies a relocation to the result if
     61   /// one exists for the given offset.
     62   uint64_t getRelocatedValue(uint32_t Size, uint64_t *Off,
     63                              uint64_t *SectionIndex = nullptr,
     64                              Error *Err = nullptr) const;
     65   uint64_t getRelocatedValue(Cursor &C, uint32_t Size,
     66                              uint64_t *SectionIndex = nullptr) const {
     67     return getRelocatedValue(Size, &getOffset(C), SectionIndex, &getError(C));
     68   }
     69 
     70   /// Extracts an address-sized value and applies a relocation to the result if
     71   /// one exists for the given offset.
     72   uint64_t getRelocatedAddress(uint64_t *Off, uint64_t *SecIx = nullptr) const {
     73     return getRelocatedValue(getAddressSize(), Off, SecIx);
     74   }
     75   uint64_t getRelocatedAddress(Cursor &C, uint64_t *SecIx = nullptr) const {
     76     return getRelocatedValue(getAddressSize(), &getOffset(C), SecIx,
     77                              &getError(C));
     78   }
     79 
     80   /// Extracts a DWARF-encoded pointer in \p Offset using \p Encoding.
     81   /// There is a DWARF encoding that uses a PC-relative adjustment.
     82   /// For these values, \p AbsPosOffset is used to fix them, which should
     83   /// reflect the absolute address of this pointer.
     84   Optional<uint64_t> getEncodedPointer(uint64_t *Offset, uint8_t Encoding,
     85                                        uint64_t AbsPosOffset = 0) const;
     86 };
     87 
     88 } // end namespace llvm
     89 
     90 #endif // LLVM_DEBUGINFO_DWARF_DWARFDATAEXTRACTOR_H
     91