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/DWARFObject.h"
  11 #include "llvm/DebugInfo/DWARF/DWARFRelocMap.h"
  12 #include "llvm/Support/Errc.h"
  13
  14 using namespace llvm;
  15
  16 std::pair<uint64_t, dwarf::DwarfFormat>
  17 DWARFDataExtractor::getInitialLength(uint64_t *Off, Error *Err) const {
  18   ErrorAsOutParameter ErrAsOut(Err);
  19   if (Err && *Err)
  20     return {0, dwarf::DWARF32};
  21
  22   Cursor C(*Off);
  23   uint64_t Length = getRelocatedValue(C, 4);
  24   dwarf::DwarfFormat Format = dwarf::DWARF32;
  25   if (Length == dwarf::DW_LENGTH_DWARF64) {
  26     Length = getRelocatedValue(C, 8);
  27     Format = dwarf::DWARF64;
  28   } else if (Length >= dwarf::DW_LENGTH_lo_reserved) {
  29     cantFail(C.takeError());
  30     if (Err)
  31       *Err = createStringError(
  32           errc::invalid_argument,
  33           "unsupported reserved unit length of value 0x%8.8" PRIx64, Length);
  34     return {0, dwarf::DWARF32};
  35   }
  36
  37   if (C) {
  38     *Off = C.tell();
  39     return {Length, Format};
  40   }
  41   if (Err)
  42     *Err = C.takeError();
  43   else
  44     consumeError(C.takeError());
  45   return {0, dwarf::DWARF32};
  46 }
  47
  48 uint64_t DWARFDataExtractor::getRelocatedValue(uint32_t Size, uint64_t *Off,
  49                                                uint64_t *SecNdx,
  50                                                Error *Err) const {
  51   if (SecNdx)
  52     *SecNdx = object::SectionedAddress::UndefSection;
  53   if (!Section)
  54     return getUnsigned(Off, Size, Err);
  55
  56   ErrorAsOutParameter ErrAsOut(Err);
  57   std::optional<RelocAddrEntry> E = Obj->find(*Section, *Off);
  58   uint64_t LocData = getUnsigned(Off, Size, Err);
  59   if (!E || (Err && *Err))
  60     return LocData;
  61   if (SecNdx)
  62     *SecNdx = E->SectionIndex;
  63
  64   uint64_t R =
  65       object::resolveRelocation(E->Resolver, E->Reloc, E->SymbolValue, LocData);
  66   if (E->Reloc2)
  67     R = object::resolveRelocation(E->Resolver, *E->Reloc2, E->SymbolValue2, R);
  68   return R;
  69 }
  70
  71 std::optional<uint64_t>
  72 DWARFDataExtractor::getEncodedPointer(uint64_t *Offset, uint8_t Encoding,
  73                                       uint64_t PCRelOffset) const {
  74   if (Encoding == dwarf::DW_EH_PE_omit)
  75     return std::nullopt;
  76
  77   uint64_t Result = 0;
  78   uint64_t OldOffset = *Offset;
  79   // First get value
  80   switch (Encoding & 0x0F) {
  81   case dwarf::DW_EH_PE_absptr:
  82     switch (getAddressSize()) {
  83     case 2:
  84     case 4:
  85     case 8:
  86       Result = getUnsigned(Offset, getAddressSize());
  87       break;
  88     default:
  89       return std::nullopt;
  90     }
  91     break;
  92   case dwarf::DW_EH_PE_uleb128:
  93     Result = getULEB128(Offset);
  94     break;
  95   case dwarf::DW_EH_PE_sleb128:
  96     Result = getSLEB128(Offset);
  97     break;
  98   case dwarf::DW_EH_PE_udata2:
  99     Result = getUnsigned(Offset, 2);
 100     break;
 101   case dwarf::DW_EH_PE_udata4:
 102     Result = getUnsigned(Offset, 4);
 103     break;
 104   case dwarf::DW_EH_PE_udata8:
 105     Result = getUnsigned(Offset, 8);
 106     break;
 107   case dwarf::DW_EH_PE_sdata2:
 108     Result = getSigned(Offset, 2);
 109     break;
 110   case dwarf::DW_EH_PE_sdata4:
 111     Result = SignExtend64<32>(getRelocatedValue(4, Offset));
 112     break;
 113   case dwarf::DW_EH_PE_sdata8:
 114     Result = getRelocatedValue(8, Offset);
 115     break;
 116   default:
 117     return std::nullopt;
 118   }
 119   // Then add relative offset, if required
 120   switch (Encoding & 0x70) {
 121   case dwarf::DW_EH_PE_absptr:
 122     // do nothing
 123     break;
 124   case dwarf::DW_EH_PE_pcrel:
 125     Result += PCRelOffset;
 126     break;
 127   case dwarf::DW_EH_PE_datarel:
 128   case dwarf::DW_EH_PE_textrel:
 129   case dwarf::DW_EH_PE_funcrel:
 130   case dwarf::DW_EH_PE_aligned:
 131   default:
 132     *Offset = OldOffset;
 133     return std::nullopt;
 134   }
 135
 136   return Result;
 137 }