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 A = getUnsigned(Off, Size, Err);
57   if (!E || (Err && *Err))
58     return A;
59   if (SecNdx)
60     *SecNdx = E->SectionIndex;
61   uint64_t R = E->Resolver(E->Reloc, E->SymbolValue, A);
62   if (E->Reloc2)
63     R = E->Resolver(*E->Reloc2, E->SymbolValue2, R);
64   return R;
65 }
66 
67 Optional<uint64_t>
68 DWARFDataExtractor::getEncodedPointer(uint64_t *Offset, uint8_t Encoding,
69                                       uint64_t PCRelOffset) const {
70   if (Encoding == dwarf::DW_EH_PE_omit)
71     return None;
72 
73   uint64_t Result = 0;
74   uint64_t OldOffset = *Offset;
75   // First get value
76   switch (Encoding & 0x0F) {
77   case dwarf::DW_EH_PE_absptr:
78     switch (getAddressSize()) {
79     case 2:
80     case 4:
81     case 8:
82       Result = getUnsigned(Offset, getAddressSize());
83       break;
84     default:
85       return None;
86     }
87     break;
88   case dwarf::DW_EH_PE_uleb128:
89     Result = getULEB128(Offset);
90     break;
91   case dwarf::DW_EH_PE_sleb128:
92     Result = getSLEB128(Offset);
93     break;
94   case dwarf::DW_EH_PE_udata2:
95     Result = getUnsigned(Offset, 2);
96     break;
97   case dwarf::DW_EH_PE_udata4:
98     Result = getUnsigned(Offset, 4);
99     break;
100   case dwarf::DW_EH_PE_udata8:
101     Result = getUnsigned(Offset, 8);
102     break;
103   case dwarf::DW_EH_PE_sdata2:
104     Result = getSigned(Offset, 2);
105     break;
106   case dwarf::DW_EH_PE_sdata4:
107     Result = getSigned(Offset, 4);
108     break;
109   case dwarf::DW_EH_PE_sdata8:
110     Result = getSigned(Offset, 8);
111     break;
112   default:
113     return None;
114   }
115   // Then add relative offset, if required
116   switch (Encoding & 0x70) {
117   case dwarf::DW_EH_PE_absptr:
118     // do nothing
119     break;
120   case dwarf::DW_EH_PE_pcrel:
121     Result += PCRelOffset;
122     break;
123   case dwarf::DW_EH_PE_datarel:
124   case dwarf::DW_EH_PE_textrel:
125   case dwarf::DW_EH_PE_funcrel:
126   case dwarf::DW_EH_PE_aligned:
127   default:
128     *Offset = OldOffset;
129     return None;
130   }
131 
132   return Result;
133 }
134