1 //===-- MCExternalSymbolizer.cpp - External symbolizer --------------------===//
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/MCDisassembler/MCExternalSymbolizer.h"
11 #include "llvm/MC/MCContext.h"
12 #include "llvm/MC/MCExpr.h"
13 #include "llvm/MC/MCInst.h"
14 #include "llvm/Support/raw_ostream.h"
15 #include <cstring>
16
17 using namespace llvm;
18
19 namespace llvm {
20 class Triple;
21 }
22
23 // This function tries to add a symbolic operand in place of the immediate
24 // Value in the MCInst. The immediate Value has had any PC adjustment made by
25 // the caller. If the instruction is a branch instruction then IsBranch is true,
26 // else false. If the getOpInfo() function was set as part of the
27 // setupForSymbolicDisassembly() call then that function is called to get any
28 // symbolic information at the Address for this instruction. If that returns
29 // non-zero then the symbolic information it returns is used to create an MCExpr
30 // and that is added as an operand to the MCInst. If getOpInfo() returns zero
31 // and IsBranch is true then a symbol look up for Value is done and if a symbol
32 // is found an MCExpr is created with that, else an MCExpr with Value is
33 // created. This function returns true if it adds an operand to the MCInst and
34 // false otherwise.
tryAddingSymbolicOperand(MCInst & MI,raw_ostream & cStream,int64_t Value,uint64_t Address,bool IsBranch,uint64_t Offset,uint64_t InstSize)35 bool MCExternalSymbolizer::tryAddingSymbolicOperand(MCInst &MI,
36 raw_ostream &cStream,
37 int64_t Value,
38 uint64_t Address,
39 bool IsBranch,
40 uint64_t Offset,
41 uint64_t InstSize) {
42 struct LLVMOpInfo1 SymbolicOp;
43 std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1));
44 SymbolicOp.Value = Value;
45
46 if (!GetOpInfo ||
47 !GetOpInfo(DisInfo, Address, Offset, InstSize, 1, &SymbolicOp)) {
48 // Clear SymbolicOp.Value from above and also all other fields.
49 std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1));
50
51 // At this point, GetOpInfo() did not find any relocation information about
52 // this operand and we are left to use the SymbolLookUp() call back to guess
53 // if the Value is the address of a symbol. In the case this is a branch
54 // that always makes sense to guess. But in the case of an immediate it is
55 // a bit more questionable if it is an address of a symbol or some other
56 // reference. So if the immediate Value comes from a width of 1 byte,
57 // InstSize, we will not guess it is an address of a symbol. Because in
58 // object files assembled starting at address 0 this usually leads to
59 // incorrect symbolication.
60 if (!SymbolLookUp || (InstSize == 1 && !IsBranch))
61 return false;
62
63 uint64_t ReferenceType;
64 if (IsBranch)
65 ReferenceType = LLVMDisassembler_ReferenceType_In_Branch;
66 else
67 ReferenceType = LLVMDisassembler_ReferenceType_InOut_None;
68 const char *ReferenceName;
69 const char *Name = SymbolLookUp(DisInfo, Value, &ReferenceType, Address,
70 &ReferenceName);
71 if (Name) {
72 SymbolicOp.AddSymbol.Name = Name;
73 SymbolicOp.AddSymbol.Present = true;
74 // If Name is a C++ symbol name put the human readable name in a comment.
75 if(ReferenceType == LLVMDisassembler_ReferenceType_DeMangled_Name)
76 cStream << ReferenceName;
77 }
78 // For branches always create an MCExpr so it gets printed as hex address.
79 else if (IsBranch) {
80 SymbolicOp.Value = Value;
81 }
82 if(ReferenceType == LLVMDisassembler_ReferenceType_Out_SymbolStub)
83 cStream << "symbol stub for: " << ReferenceName;
84 else if(ReferenceType == LLVMDisassembler_ReferenceType_Out_Objc_Message)
85 cStream << "Objc message: " << ReferenceName;
86 if (!Name && !IsBranch)
87 return false;
88 }
89
90 const MCExpr *Add = nullptr;
91 if (SymbolicOp.AddSymbol.Present) {
92 if (SymbolicOp.AddSymbol.Name) {
93 StringRef Name(SymbolicOp.AddSymbol.Name);
94 MCSymbol *Sym = Ctx.getOrCreateSymbol(Name);
95 Add = MCSymbolRefExpr::create(Sym, Ctx);
96 } else {
97 Add = MCConstantExpr::create((int)SymbolicOp.AddSymbol.Value, Ctx);
98 }
99 }
100
101 const MCExpr *Sub = nullptr;
102 if (SymbolicOp.SubtractSymbol.Present) {
103 if (SymbolicOp.SubtractSymbol.Name) {
104 StringRef Name(SymbolicOp.SubtractSymbol.Name);
105 MCSymbol *Sym = Ctx.getOrCreateSymbol(Name);
106 Sub = MCSymbolRefExpr::create(Sym, Ctx);
107 } else {
108 Sub = MCConstantExpr::create((int)SymbolicOp.SubtractSymbol.Value, Ctx);
109 }
110 }
111
112 const MCExpr *Off = nullptr;
113 if (SymbolicOp.Value != 0)
114 Off = MCConstantExpr::create(SymbolicOp.Value, Ctx);
115
116 const MCExpr *Expr;
117 if (Sub) {
118 const MCExpr *LHS;
119 if (Add)
120 LHS = MCBinaryExpr::createSub(Add, Sub, Ctx);
121 else
122 LHS = MCUnaryExpr::createMinus(Sub, Ctx);
123 if (Off)
124 Expr = MCBinaryExpr::createAdd(LHS, Off, Ctx);
125 else
126 Expr = LHS;
127 } else if (Add) {
128 if (Off)
129 Expr = MCBinaryExpr::createAdd(Add, Off, Ctx);
130 else
131 Expr = Add;
132 } else {
133 if (Off)
134 Expr = Off;
135 else
136 Expr = MCConstantExpr::create(0, Ctx);
137 }
138
139 Expr = RelInfo->createExprForCAPIVariantKind(Expr, SymbolicOp.VariantKind);
140 if (!Expr)
141 return false;
142
143 MI.addOperand(MCOperand::createExpr(Expr));
144 return true;
145 }
146
147 // This function tries to add a comment as to what is being referenced by a load
148 // instruction with the base register that is the Pc. These can often be values
149 // in a literal pool near the Address of the instruction. The Address of the
150 // instruction and its immediate Value are used as a possible literal pool entry.
151 // The SymbolLookUp call back will return the name of a symbol referenced by the
152 // literal pool's entry if the referenced address is that of a symbol. Or it
153 // will return a pointer to a literal 'C' string if the referenced address of
154 // the literal pool's entry is an address into a section with C string literals.
155 // Or if the reference is to an Objective-C data structure it will return a
156 // specific reference type for it and a string.
tryAddingPcLoadReferenceComment(raw_ostream & cStream,int64_t Value,uint64_t Address)157 void MCExternalSymbolizer::tryAddingPcLoadReferenceComment(raw_ostream &cStream,
158 int64_t Value,
159 uint64_t Address) {
160 if (SymbolLookUp) {
161 uint64_t ReferenceType = LLVMDisassembler_ReferenceType_In_PCrel_Load;
162 const char *ReferenceName;
163 (void)SymbolLookUp(DisInfo, Value, &ReferenceType, Address, &ReferenceName);
164 if(ReferenceType == LLVMDisassembler_ReferenceType_Out_LitPool_SymAddr)
165 cStream << "literal pool symbol address: " << ReferenceName;
166 else if(ReferenceType ==
167 LLVMDisassembler_ReferenceType_Out_LitPool_CstrAddr) {
168 cStream << "literal pool for: \"";
169 cStream.write_escaped(ReferenceName);
170 cStream << "\"";
171 }
172 else if(ReferenceType ==
173 LLVMDisassembler_ReferenceType_Out_Objc_CFString_Ref)
174 cStream << "Objc cfstring ref: @\"" << ReferenceName << "\"";
175 else if(ReferenceType ==
176 LLVMDisassembler_ReferenceType_Out_Objc_Message)
177 cStream << "Objc message: " << ReferenceName;
178 else if(ReferenceType ==
179 LLVMDisassembler_ReferenceType_Out_Objc_Message_Ref)
180 cStream << "Objc message ref: " << ReferenceName;
181 else if(ReferenceType ==
182 LLVMDisassembler_ReferenceType_Out_Objc_Selector_Ref)
183 cStream << "Objc selector ref: " << ReferenceName;
184 else if(ReferenceType ==
185 LLVMDisassembler_ReferenceType_Out_Objc_Class_Ref)
186 cStream << "Objc class ref: " << ReferenceName;
187 }
188 }
189
190 namespace llvm {
createMCSymbolizer(const Triple & TT,LLVMOpInfoCallback GetOpInfo,LLVMSymbolLookupCallback SymbolLookUp,void * DisInfo,MCContext * Ctx,std::unique_ptr<MCRelocationInfo> && RelInfo)191 MCSymbolizer *createMCSymbolizer(const Triple &TT, LLVMOpInfoCallback GetOpInfo,
192 LLVMSymbolLookupCallback SymbolLookUp,
193 void *DisInfo, MCContext *Ctx,
194 std::unique_ptr<MCRelocationInfo> &&RelInfo) {
195 assert(Ctx && "No MCContext given for symbolic disassembly");
196
197 return new MCExternalSymbolizer(*Ctx, std::move(RelInfo), GetOpInfo,
198 SymbolLookUp, DisInfo);
199 }
200 }
201