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 }
138