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