llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp

   1 //===- DWARFDataExtractor.cpp ---------------------------------------------===//
   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 #include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
  10 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
  11
  12 using namespace llvm;
  13
  14 std::pair<uint64_t, dwarf::DwarfFormat>
  15 DWARFDataExtractor::getInitialLength(uint64_t *Off, Error *Err) const {
  16   ErrorAsOutParameter ErrAsOut(Err);
  17   if (Err && *Err)
  18     return {0, dwarf::DWARF32};
  19
  20   Cursor C(*Off);
  21   uint64_t Length = getRelocatedValue(C, 4);
  22   dwarf::DwarfFormat Format = dwarf::DWARF32;
  23   if (Length == dwarf::DW_LENGTH_DWARF64) {
  24     Length = getRelocatedValue(C, 8);
  25     Format = dwarf::DWARF64;
  26   } else if (Length >= dwarf::DW_LENGTH_lo_reserved) {
  27     cantFail(C.takeError());
  28     if (Err)
  29       *Err = createStringError(
  30           errc::invalid_argument,
  31           "unsupported reserved unit length of value 0x%8.8" PRIx64, Length);
  32     return {0, dwarf::DWARF32};
  33   }
  34
  35   if (C) {
  36     *Off = C.tell();
  37     return {Length, Format};
  38   }
  39   if (Err)
  40     *Err = C.takeError();
  41   else
  42     consumeError(C.takeError());
  43   return {0, dwarf::DWARF32};
  44 }
  45
  46 uint64_t DWARFDataExtractor::getRelocatedValue(uint32_t Size, uint64_t *Off,
  47                                                uint64_t *SecNdx,
  48                                                Error *Err) const {
  49   if (SecNdx)
  50     *SecNdx = object::SectionedAddress::UndefSection;
  51   if (!Section)
  52     return getUnsigned(Off, Size, Err);
  53
  54   ErrorAsOutParameter ErrAsOut(Err);
  55   Optional<RelocAddrEntry> E = Obj->find(*Section, *Off);
  56   uint64_t LocData = getUnsigned(Off, Size, Err);
  57   if (!E || (Err && *Err))
  58     return LocData;
  59   if (SecNdx)
  60     *SecNdx = E->SectionIndex;
  61
  62   uint64_t R =
  63       object::resolveRelocation(E->Resolver, E->Reloc, E->SymbolValue, LocData);
  64   if (E->Reloc2)
  65     R = object::resolveRelocation(E->Resolver, *E->Reloc2, E->SymbolValue2, R);
  66   return R;
  67 }
  68
  69 Optional<uint64_t>
  70 DWARFDataExtractor::getEncodedPointer(uint64_t *Offset, uint8_t Encoding,
  71                                       uint64_t PCRelOffset) const {
  72   if (Encoding == dwarf::DW_EH_PE_omit)
  73     return None;
  74
  75   uint64_t Result = 0;
  76   uint64_t OldOffset = *Offset;
  77   // First get value
  78   switch (Encoding & 0x0F) {
  79   case dwarf::DW_EH_PE_absptr:
  80     switch (getAddressSize()) {
  81     case 2:
  82     case 4:
  83     case 8:
  84       Result = getUnsigned(Offset, getAddressSize());
  85       break;
  86     default:
  87       return None;
  88     }
  89     break;
  90   case dwarf::DW_EH_PE_uleb128:
  91     Result = getULEB128(Offset);
  92     break;
  93   case dwarf::DW_EH_PE_sleb128:
  94     Result = getSLEB128(Offset);
  95     break;
  96   case dwarf::DW_EH_PE_udata2:
  97     Result = getUnsigned(Offset, 2);
  98     break;
  99   case dwarf::DW_EH_PE_udata4:
 100     Result = getUnsigned(Offset, 4);
 101     break;
 102   case dwarf::DW_EH_PE_udata8:
 103     Result = getUnsigned(Offset, 8);
 104     break;
 105   case dwarf::DW_EH_PE_sdata2:
 106     Result = getSigned(Offset, 2);
 107     break;
 108   case dwarf::DW_EH_PE_sdata4:
 109     Result = SignExtend64<32>(getRelocatedValue(4, Offset));
 110     break;
 111   case dwarf::DW_EH_PE_sdata8:
 112     Result = getRelocatedValue(8, Offset);
 113     break;
 114   default:
 115     return None;
 116   }
 117   // Then add relative offset, if required
 118   switch (Encoding & 0x70) {
 119   case dwarf::DW_EH_PE_absptr:
 120     // do nothing
 121     break;
 122   case dwarf::DW_EH_PE_pcrel:
 123     Result += PCRelOffset;
 124     break;
 125   case dwarf::DW_EH_PE_datarel:
 126   case dwarf::DW_EH_PE_textrel:
 127   case dwarf::DW_EH_PE_funcrel:
 128   case dwarf::DW_EH_PE_aligned:
 129   default:
 130     *Offset = OldOffset;
 131     return None;
 132   }
 133
 134   return Result;
 135 }