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      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 }
    136