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