1 //===- DWARFDebugAranges.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/DWARFDebugAranges.h"
10 #include "llvm/DebugInfo/DWARF/DWARFCompileUnit.h"
11 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
12 #include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
13 #include "llvm/Support/DataExtractor.h"
14 #include "llvm/Support/WithColor.h"
15 #include <algorithm>
16 #include <cassert>
17 #include <cstdint>
18 #include <set>
19 #include <vector>
20 
21 using namespace llvm;
22 
23 void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
24   if (!DebugArangesData.isValidOffset(0))
25     return;
26   uint64_t Offset = 0;
27   DWARFDebugArangeSet Set;
28 
29   while (DebugArangesData.isValidOffset(Offset)) {
30     if (Error E = Set.extract(DebugArangesData, &Offset)) {
31       WithColor::error() << toString(std::move(E)) << '\n';
32       return;
33     }
34     uint64_t CUOffset = Set.getCompileUnitDIEOffset();
35     for (const auto &Desc : Set.descriptors()) {
36       uint64_t LowPC = Desc.Address;
37       uint64_t HighPC = Desc.getEndAddress();
38       appendRange(CUOffset, LowPC, HighPC);
39     }
40     ParsedCUOffsets.insert(CUOffset);
41   }
42 }
43 
44 void DWARFDebugAranges::generate(DWARFContext *CTX) {
45   clear();
46   if (!CTX)
47     return;
48 
49   // Extract aranges from .debug_aranges section.
50   DataExtractor ArangesData(CTX->getDWARFObj().getArangesSection(),
51                             CTX->isLittleEndian(), 0);
52   extract(ArangesData);
53 
54   // Generate aranges from DIEs: even if .debug_aranges section is present,
55   // it may describe only a small subset of compilation units, so we need to
56   // manually build aranges for the rest of them.
57   for (const auto &CU : CTX->compile_units()) {
58     uint64_t CUOffset = CU->getOffset();
59     if (ParsedCUOffsets.insert(CUOffset).second) {
60       Expected<DWARFAddressRangesVector> CURanges = CU->collectAddressRanges();
61       if (!CURanges)
62         WithColor::error() << toString(CURanges.takeError()) << '\n';
63       else
64         for (const auto &R : *CURanges)
65           appendRange(CUOffset, R.LowPC, R.HighPC);
66     }
67   }
68 
69   construct();
70 }
71 
72 void DWARFDebugAranges::clear() {
73   Endpoints.clear();
74   Aranges.clear();
75   ParsedCUOffsets.clear();
76 }
77 
78 void DWARFDebugAranges::appendRange(uint64_t CUOffset, uint64_t LowPC,
79                                     uint64_t HighPC) {
80   if (LowPC >= HighPC)
81     return;
82   Endpoints.emplace_back(LowPC, CUOffset, true);
83   Endpoints.emplace_back(HighPC, CUOffset, false);
84 }
85 
86 void DWARFDebugAranges::construct() {
87   std::multiset<uint64_t> ValidCUs;  // Maintain the set of CUs describing
88                                      // a current address range.
89   llvm::sort(Endpoints);
90   uint64_t PrevAddress = -1ULL;
91   for (const auto &E : Endpoints) {
92     if (PrevAddress < E.Address && !ValidCUs.empty()) {
93       // If the address range between two endpoints is described by some
94       // CU, first try to extend the last range in Aranges. If we can't
95       // do it, start a new range.
96       if (!Aranges.empty() && Aranges.back().HighPC() == PrevAddress &&
97           ValidCUs.find(Aranges.back().CUOffset) != ValidCUs.end()) {
98         Aranges.back().setHighPC(E.Address);
99       } else {
100         Aranges.emplace_back(PrevAddress, E.Address, *ValidCUs.begin());
101       }
102     }
103     // Update the set of valid CUs.
104     if (E.IsRangeStart) {
105       ValidCUs.insert(E.CUOffset);
106     } else {
107       auto CUPos = ValidCUs.find(E.CUOffset);
108       assert(CUPos != ValidCUs.end());
109       ValidCUs.erase(CUPos);
110     }
111     PrevAddress = E.Address;
112   }
113   assert(ValidCUs.empty());
114 
115   // Endpoints are not needed now.
116   Endpoints.clear();
117   Endpoints.shrink_to_fit();
118 }
119 
120 uint64_t DWARFDebugAranges::findAddress(uint64_t Address) const {
121   RangeCollIterator It =
122       partition_point(Aranges, [=](Range R) { return R.HighPC() <= Address; });
123   if (It != Aranges.end() && It->LowPC <= Address)
124     return It->CUOffset;
125   return -1ULL;
126 }
127