1 //===-- MCExternalSymbolizer.cpp - External symbolizer --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/MC/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"
19 // This function tries to add a symbolic operand in place of the immediate
20 // Value in the MCInst. The immediate Value has had any PC adjustment made by
21 // the caller. If the instruction is a branch instruction then IsBranch is true,
22 // else false. If the getOpInfo() function was set as part of the
23 // setupForSymbolicDisassembly() call then that function is called to get any
24 // symbolic information at the Address for this instruction. If that returns
25 // non-zero then the symbolic information it returns is used to create an MCExpr
26 // and that is added as an operand to the MCInst. If getOpInfo() returns zero
27 // and IsBranch is true then a symbol look up for Value is done and if a symbol
28 // is found an MCExpr is created with that, else an MCExpr with Value is
29 // created. This function returns true if it adds an operand to the MCInst and
31 bool MCExternalSymbolizer::tryAddingSymbolicOperand(MCInst
&MI
,
38 struct LLVMOpInfo1 SymbolicOp
;
39 std::memset(&SymbolicOp
, '\0', sizeof(struct LLVMOpInfo1
));
40 SymbolicOp
.Value
= Value
;
43 !GetOpInfo(DisInfo
, Address
, Offset
, InstSize
, 1, &SymbolicOp
)) {
44 // Clear SymbolicOp.Value from above and also all other fields.
45 std::memset(&SymbolicOp
, '\0', sizeof(struct LLVMOpInfo1
));
47 // At this point, GetOpInfo() did not find any relocation information about
48 // this operand and we are left to use the SymbolLookUp() call back to guess
49 // if the Value is the address of a symbol. In the case this is a branch
50 // that always makes sense to guess. But in the case of an immediate it is
51 // a bit more questionable if it is an address of a symbol or some other
52 // reference. So if the immediate Value comes from a width of 1 byte,
53 // InstSize, we will not guess it is an address of a symbol. Because in
54 // object files assembled starting at address 0 this usually leads to
55 // incorrect symbolication.
56 if (!SymbolLookUp
|| (InstSize
== 1 && !IsBranch
))
59 uint64_t ReferenceType
;
61 ReferenceType
= LLVMDisassembler_ReferenceType_In_Branch
;
63 ReferenceType
= LLVMDisassembler_ReferenceType_InOut_None
;
64 const char *ReferenceName
;
65 const char *Name
= SymbolLookUp(DisInfo
, Value
, &ReferenceType
, Address
,
68 SymbolicOp
.AddSymbol
.Name
= Name
;
69 SymbolicOp
.AddSymbol
.Present
= true;
70 // If Name is a C++ symbol name put the human readable name in a comment.
71 if(ReferenceType
== LLVMDisassembler_ReferenceType_DeMangled_Name
)
72 cStream
<< ReferenceName
;
74 // For branches always create an MCExpr so it gets printed as hex address.
76 SymbolicOp
.Value
= Value
;
78 if(ReferenceType
== LLVMDisassembler_ReferenceType_Out_SymbolStub
)
79 cStream
<< "symbol stub for: " << ReferenceName
;
80 else if(ReferenceType
== LLVMDisassembler_ReferenceType_Out_Objc_Message
)
81 cStream
<< "Objc message: " << ReferenceName
;
82 if (!Name
&& !IsBranch
)
86 const MCExpr
*Add
= nullptr;
87 if (SymbolicOp
.AddSymbol
.Present
) {
88 if (SymbolicOp
.AddSymbol
.Name
) {
89 StringRef
Name(SymbolicOp
.AddSymbol
.Name
);
90 MCSymbol
*Sym
= Ctx
.GetOrCreateSymbol(Name
);
91 Add
= MCSymbolRefExpr::Create(Sym
, Ctx
);
93 Add
= MCConstantExpr::Create((int)SymbolicOp
.AddSymbol
.Value
, Ctx
);
97 const MCExpr
*Sub
= nullptr;
98 if (SymbolicOp
.SubtractSymbol
.Present
) {
99 if (SymbolicOp
.SubtractSymbol
.Name
) {
100 StringRef
Name(SymbolicOp
.SubtractSymbol
.Name
);
101 MCSymbol
*Sym
= Ctx
.GetOrCreateSymbol(Name
);
102 Sub
= MCSymbolRefExpr::Create(Sym
, Ctx
);
104 Sub
= MCConstantExpr::Create((int)SymbolicOp
.SubtractSymbol
.Value
, Ctx
);
108 const MCExpr
*Off
= nullptr;
109 if (SymbolicOp
.Value
!= 0)
110 Off
= MCConstantExpr::Create(SymbolicOp
.Value
, Ctx
);
116 LHS
= MCBinaryExpr::CreateSub(Add
, Sub
, Ctx
);
118 LHS
= MCUnaryExpr::CreateMinus(Sub
, Ctx
);
120 Expr
= MCBinaryExpr::CreateAdd(LHS
, Off
, Ctx
);
125 Expr
= MCBinaryExpr::CreateAdd(Add
, Off
, Ctx
);
132 Expr
= MCConstantExpr::Create(0, Ctx
);
135 Expr
= RelInfo
->createExprForCAPIVariantKind(Expr
, SymbolicOp
.VariantKind
);
139 MI
.addOperand(MCOperand::CreateExpr(Expr
));
143 // This function tries to add a comment as to what is being referenced by a load
144 // instruction with the base register that is the Pc. These can often be values
145 // in a literal pool near the Address of the instruction. The Address of the
146 // instruction and its immediate Value are used as a possible literal pool entry.
147 // The SymbolLookUp call back will return the name of a symbol referenced by the
148 // literal pool's entry if the referenced address is that of a symbol. Or it
149 // will return a pointer to a literal 'C' string if the referenced address of
150 // the literal pool's entry is an address into a section with C string literals.
151 // Or if the reference is to an Objective-C data structure it will return a
152 // specific reference type for it and a string.
153 void MCExternalSymbolizer::tryAddingPcLoadReferenceComment(raw_ostream
&cStream
,
157 uint64_t ReferenceType
= LLVMDisassembler_ReferenceType_In_PCrel_Load
;
158 const char *ReferenceName
;
159 (void)SymbolLookUp(DisInfo
, Value
, &ReferenceType
, Address
, &ReferenceName
);
160 if(ReferenceType
== LLVMDisassembler_ReferenceType_Out_LitPool_SymAddr
)
161 cStream
<< "literal pool symbol address: " << ReferenceName
;
162 else if(ReferenceType
==
163 LLVMDisassembler_ReferenceType_Out_LitPool_CstrAddr
) {
164 cStream
<< "literal pool for: \"";
165 cStream
.write_escaped(ReferenceName
);
168 else if(ReferenceType
==
169 LLVMDisassembler_ReferenceType_Out_Objc_CFString_Ref
)
170 cStream
<< "Objc cfstring ref: @\"" << ReferenceName
<< "\"";
171 else if(ReferenceType
==
172 LLVMDisassembler_ReferenceType_Out_Objc_Message
)
173 cStream
<< "Objc message: " << ReferenceName
;
174 else if(ReferenceType
==
175 LLVMDisassembler_ReferenceType_Out_Objc_Message_Ref
)
176 cStream
<< "Objc message ref: " << ReferenceName
;
177 else if(ReferenceType
==
178 LLVMDisassembler_ReferenceType_Out_Objc_Selector_Ref
)
179 cStream
<< "Objc selector ref: " << ReferenceName
;
180 else if(ReferenceType
==
181 LLVMDisassembler_ReferenceType_Out_Objc_Class_Ref
)
182 cStream
<< "Objc class ref: " << ReferenceName
;
187 MCSymbolizer
*createMCSymbolizer(StringRef TT
, LLVMOpInfoCallback GetOpInfo
,
188 LLVMSymbolLookupCallback SymbolLookUp
,
191 MCRelocationInfo
*RelInfo
) {
192 assert(Ctx
&& "No MCContext given for symbolic disassembly");
194 return new MCExternalSymbolizer(*Ctx
,
195 std::unique_ptr
<MCRelocationInfo
>(RelInfo
),
196 GetOpInfo
, SymbolLookUp
, DisInfo
);