1 //===-- lib/MC/MCObjectSymbolizer.cpp -------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "llvm/MC/MCObjectSymbolizer.h"
11 #include "llvm/ADT/SmallString.h"
12 #include "llvm/MC/MCContext.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/MC/MCInst.h"
15 #include "llvm/MC/MCRelocationInfo.h"
16 #include "llvm/MC/MCSymbol.h"
17 #include "llvm/Object/MachO.h"
18 #include "llvm/Object/ELF.h"
19 #include "llvm/Support/raw_ostream.h"
20 #include <algorithm>
21
22 using namespace llvm;
23 using namespace object;
24
25 //===- MCMachObjectSymbolizer ---------------------------------------------===//
26
27 namespace {
28 class MCMachObjectSymbolizer : public MCObjectSymbolizer {
29 public:
MCMachObjectSymbolizer(MCContext & Ctx,OwningPtr<MCRelocationInfo> & RelInfo,const object::MachOObjectFile * MachOOF)30 MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
31 const object::MachOObjectFile *MachOOF)
32 : MCObjectSymbolizer(Ctx, RelInfo, MachOOF)
33 {}
34
tryAddingPcLoadReferenceComment(raw_ostream & cStream,int64_t Value,uint64_t Address)35 void tryAddingPcLoadReferenceComment(raw_ostream &cStream,
36 int64_t Value, uint64_t Address) {
37 AddrToRelocMap::iterator RI = AddrToReloc.find(Address);
38 if (RI != AddrToReloc.end()) {
39 const MCExpr *RelExpr = RelInfo->createExprForRelocation(RI->second);
40 if (!RelExpr || RelExpr->EvaluateAsAbsolute(Value) == false)
41 return;
42 }
43 uint64_t Addr = Value;
44 SortedSectionList::const_iterator SI = findSectionContaining(Addr);
45 if (SI != SortedSections.end()) {
46 const SectionRef &S = *SI;
47 StringRef Name; S.getName(Name);
48 uint64_t SAddr; S.getAddress(SAddr);
49 if (Name == "__cstring") {
50 StringRef Contents;
51 S.getContents(Contents);
52 Contents = Contents.substr(Addr - SAddr);
53 cStream << " ## literal pool for: "
54 << Contents.substr(0, Contents.find_first_of(0));
55 }
56 }
57 }
58 };
59 } // End unnamed namespace
60
61 //===- MCObjectSymbolizer -------------------------------------------------===//
62
MCObjectSymbolizer(MCContext & Ctx,OwningPtr<MCRelocationInfo> & RelInfo,const ObjectFile * Obj)63 MCObjectSymbolizer::MCObjectSymbolizer(MCContext &Ctx,
64 OwningPtr<MCRelocationInfo> &RelInfo,
65 const ObjectFile *Obj)
66 : MCSymbolizer(Ctx, RelInfo), Obj(Obj), SortedSections(), AddrToReloc() {
67 error_code ec;
68 for (section_iterator SI = Obj->begin_sections(),
69 SE = Obj->end_sections();
70 SI != SE;
71 SI.increment(ec)) {
72 if (ec) break;
73
74 section_iterator RelSecI = SI->getRelocatedSection();
75 if (RelSecI == Obj->end_sections())
76 continue;
77
78 uint64_t StartAddr; RelSecI->getAddress(StartAddr);
79 uint64_t Size; RelSecI->getSize(Size);
80 bool RequiredForExec; RelSecI->isRequiredForExecution(RequiredForExec);
81 if (RequiredForExec == false || Size == 0)
82 continue;
83 insertSection(*SI);
84 for (relocation_iterator RI = SI->begin_relocations(),
85 RE = SI->end_relocations();
86 RI != RE;
87 RI.increment(ec)) {
88 if (ec) break;
89 // FIXME: libObject is inconsistent regarding error handling. The
90 // overwhelming majority of methods always return object_error::success,
91 // and assert for simple errors.. Here, ELFObjectFile::getRelocationOffset
92 // asserts when the file type isn't ET_REL.
93 // This workaround handles x86-64 elf, the only one that has a relocinfo.
94 uint64_t Offset;
95 if (Obj->isELF()) {
96 const ELF64LEObjectFile *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj);
97 if (ELFObj == 0)
98 break;
99 if (ELFObj->getElfHeader()->e_type == ELF::ET_REL) {
100 RI->getOffset(Offset);
101 Offset += StartAddr;
102 } else {
103 RI->getAddress(Offset);
104 }
105 } else {
106 RI->getOffset(Offset);
107 Offset += StartAddr;
108 }
109 // At a specific address, only keep the first relocation.
110 if (AddrToReloc.find(Offset) == AddrToReloc.end())
111 AddrToReloc[Offset] = *RI;
112 }
113 }
114 }
115
116 bool MCObjectSymbolizer::
tryAddingSymbolicOperand(MCInst & MI,raw_ostream & cStream,int64_t Value,uint64_t Address,bool IsBranch,uint64_t Offset,uint64_t InstSize)117 tryAddingSymbolicOperand(MCInst &MI, raw_ostream &cStream,
118 int64_t Value, uint64_t Address, bool IsBranch,
119 uint64_t Offset, uint64_t InstSize) {
120 AddrToRelocMap::iterator RI = AddrToReloc.find(Address + Offset);
121 if (RI != AddrToReloc.end()) {
122 if (const MCExpr *RelExpr = RelInfo->createExprForRelocation(RI->second)) {
123 MI.addOperand(MCOperand::CreateExpr(RelExpr));
124 return true;
125 }
126 // Only try to create a symbol+offset expression if there is no relocation.
127 return false;
128 }
129
130 // Interpret Value as a branch target.
131 if (IsBranch == false)
132 return false;
133 uint64_t UValue = Value;
134 // FIXME: map instead of looping each time?
135 error_code ec;
136 for (symbol_iterator SI = Obj->begin_symbols(),
137 SE = Obj->end_symbols();
138 SI != SE;
139 SI.increment(ec)) {
140 if (ec) break;
141 uint64_t SymAddr; SI->getAddress(SymAddr);
142 uint64_t SymSize; SI->getSize(SymSize);
143 StringRef SymName; SI->getName(SymName);
144 SymbolRef::Type SymType; SI->getType(SymType);
145 if (SymAddr == UnknownAddressOrSize || SymSize == UnknownAddressOrSize
146 || SymName.empty() || SymType != SymbolRef::ST_Function)
147 continue;
148
149 if ( SymAddr == UValue ||
150 (SymAddr <= UValue && SymAddr + SymSize > UValue)) {
151 MCSymbol *Sym = Ctx.GetOrCreateSymbol(SymName);
152 const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
153 if (SymAddr != UValue) {
154 const MCExpr *Off = MCConstantExpr::Create(UValue - SymAddr, Ctx);
155 Expr = MCBinaryExpr::CreateAdd(Expr, Off, Ctx);
156 }
157 MI.addOperand(MCOperand::CreateExpr(Expr));
158 return true;
159 }
160 }
161 return false;
162 }
163
164 void MCObjectSymbolizer::
tryAddingPcLoadReferenceComment(raw_ostream & cStream,int64_t Value,uint64_t Address)165 tryAddingPcLoadReferenceComment(raw_ostream &cStream,
166 int64_t Value, uint64_t Address) {
167 }
168
169 MCObjectSymbolizer *
createObjectSymbolizer(MCContext & Ctx,OwningPtr<MCRelocationInfo> & RelInfo,const ObjectFile * Obj)170 MCObjectSymbolizer::createObjectSymbolizer(MCContext &Ctx,
171 OwningPtr<MCRelocationInfo> &RelInfo,
172 const ObjectFile *Obj) {
173 if (const MachOObjectFile *MachOOF = dyn_cast<MachOObjectFile>(Obj)) {
174 return new MCMachObjectSymbolizer(Ctx, RelInfo, MachOOF);
175 }
176 return new MCObjectSymbolizer(Ctx, RelInfo, Obj);
177 }
178
179 // SortedSections implementation.
180
SectionStartsBefore(const SectionRef & S,uint64_t Addr)181 static bool SectionStartsBefore(const SectionRef &S, uint64_t Addr) {
182 uint64_t SAddr; S.getAddress(SAddr);
183 return SAddr < Addr;
184 }
185
186 MCObjectSymbolizer::SortedSectionList::const_iterator
findSectionContaining(uint64_t Addr) const187 MCObjectSymbolizer::findSectionContaining(uint64_t Addr) const {
188 SortedSectionList::const_iterator
189 EndIt = SortedSections.end(),
190 It = std::lower_bound(SortedSections.begin(), EndIt,
191 Addr, SectionStartsBefore);
192 if (It == EndIt)
193 return It;
194 uint64_t SAddr; It->getAddress(SAddr);
195 uint64_t SSize; It->getSize(SSize);
196 if (Addr >= SAddr + SSize)
197 return EndIt;
198 return It;
199 }
200
insertSection(SectionRef Sec)201 void MCObjectSymbolizer::insertSection(SectionRef Sec) {
202 uint64_t SAddr; Sec.getAddress(SAddr);
203 uint64_t SSize; Sec.getSize(SSize);
204 SortedSectionList::iterator It = std::lower_bound(SortedSections.begin(),
205 SortedSections.end(),
206 SAddr,
207 SectionStartsBefore);
208 if (It != SortedSections.end()) {
209 uint64_t FoundSAddr; It->getAddress(FoundSAddr);
210 if (FoundSAddr < SAddr + SSize)
211 llvm_unreachable("Inserting overlapping sections");
212 }
213 SortedSections.insert(It, Sec);
214 }
215