200 lines
8.3 KiB
C++
200 lines
8.3 KiB
C++
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//===-- MCExternalSymbolizer.cpp - External symbolizer --------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCDisassembler/MCExternalSymbolizer.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cstring>
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using namespace llvm;
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namespace llvm {
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class Triple;
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}
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// This function tries to add a symbolic operand in place of the immediate
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// Value in the MCInst. The immediate Value has had any PC adjustment made by
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// the caller. If the instruction is a branch instruction then IsBranch is true,
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// else false. If the getOpInfo() function was set as part of the
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// setupForSymbolicDisassembly() call then that function is called to get any
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// symbolic information at the Address for this instruction. If that returns
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// non-zero then the symbolic information it returns is used to create an MCExpr
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// and that is added as an operand to the MCInst. If getOpInfo() returns zero
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// and IsBranch is true then a symbol look up for Value is done and if a symbol
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// is found an MCExpr is created with that, else an MCExpr with Value is
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// created. This function returns true if it adds an operand to the MCInst and
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// false otherwise.
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bool MCExternalSymbolizer::tryAddingSymbolicOperand(MCInst &MI,
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raw_ostream &cStream,
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int64_t Value,
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uint64_t Address,
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bool IsBranch,
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uint64_t Offset,
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uint64_t InstSize) {
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struct LLVMOpInfo1 SymbolicOp;
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std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1));
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SymbolicOp.Value = Value;
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if (!GetOpInfo ||
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!GetOpInfo(DisInfo, Address, Offset, InstSize, 1, &SymbolicOp)) {
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// Clear SymbolicOp.Value from above and also all other fields.
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std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1));
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// At this point, GetOpInfo() did not find any relocation information about
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// this operand and we are left to use the SymbolLookUp() call back to guess
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// if the Value is the address of a symbol. In the case this is a branch
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// that always makes sense to guess. But in the case of an immediate it is
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// a bit more questionable if it is an address of a symbol or some other
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// reference. So if the immediate Value comes from a width of 1 byte,
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// InstSize, we will not guess it is an address of a symbol. Because in
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// object files assembled starting at address 0 this usually leads to
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// incorrect symbolication.
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if (!SymbolLookUp || (InstSize == 1 && !IsBranch))
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return false;
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uint64_t ReferenceType;
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if (IsBranch)
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ReferenceType = LLVMDisassembler_ReferenceType_In_Branch;
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else
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ReferenceType = LLVMDisassembler_ReferenceType_InOut_None;
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const char *ReferenceName;
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const char *Name = SymbolLookUp(DisInfo, Value, &ReferenceType, Address,
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&ReferenceName);
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if (Name) {
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SymbolicOp.AddSymbol.Name = Name;
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SymbolicOp.AddSymbol.Present = true;
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// If Name is a C++ symbol name put the human readable name in a comment.
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if(ReferenceType == LLVMDisassembler_ReferenceType_DeMangled_Name)
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cStream << ReferenceName;
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}
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// For branches always create an MCExpr so it gets printed as hex address.
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else if (IsBranch) {
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SymbolicOp.Value = Value;
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}
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if(ReferenceType == LLVMDisassembler_ReferenceType_Out_SymbolStub)
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cStream << "symbol stub for: " << ReferenceName;
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else if(ReferenceType == LLVMDisassembler_ReferenceType_Out_Objc_Message)
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cStream << "Objc message: " << ReferenceName;
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if (!Name && !IsBranch)
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return false;
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}
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const MCExpr *Add = nullptr;
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if (SymbolicOp.AddSymbol.Present) {
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if (SymbolicOp.AddSymbol.Name) {
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StringRef Name(SymbolicOp.AddSymbol.Name);
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MCSymbol *Sym = Ctx.getOrCreateSymbol(Name);
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Add = MCSymbolRefExpr::create(Sym, Ctx);
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} else {
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Add = MCConstantExpr::create((int)SymbolicOp.AddSymbol.Value, Ctx);
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}
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}
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const MCExpr *Sub = nullptr;
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if (SymbolicOp.SubtractSymbol.Present) {
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if (SymbolicOp.SubtractSymbol.Name) {
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StringRef Name(SymbolicOp.SubtractSymbol.Name);
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MCSymbol *Sym = Ctx.getOrCreateSymbol(Name);
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Sub = MCSymbolRefExpr::create(Sym, Ctx);
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} else {
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Sub = MCConstantExpr::create((int)SymbolicOp.SubtractSymbol.Value, Ctx);
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}
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}
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const MCExpr *Off = nullptr;
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if (SymbolicOp.Value != 0)
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Off = MCConstantExpr::create(SymbolicOp.Value, Ctx);
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const MCExpr *Expr;
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if (Sub) {
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const MCExpr *LHS;
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if (Add)
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LHS = MCBinaryExpr::createSub(Add, Sub, Ctx);
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else
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LHS = MCUnaryExpr::createMinus(Sub, Ctx);
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if (Off)
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Expr = MCBinaryExpr::createAdd(LHS, Off, Ctx);
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else
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Expr = LHS;
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} else if (Add) {
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if (Off)
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Expr = MCBinaryExpr::createAdd(Add, Off, Ctx);
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else
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Expr = Add;
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} else {
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if (Off)
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Expr = Off;
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else
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Expr = MCConstantExpr::create(0, Ctx);
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}
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Expr = RelInfo->createExprForCAPIVariantKind(Expr, SymbolicOp.VariantKind);
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if (!Expr)
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return false;
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MI.addOperand(MCOperand::createExpr(Expr));
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return true;
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}
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// This function tries to add a comment as to what is being referenced by a load
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// instruction with the base register that is the Pc. These can often be values
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// in a literal pool near the Address of the instruction. The Address of the
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// instruction and its immediate Value are used as a possible literal pool entry.
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// The SymbolLookUp call back will return the name of a symbol referenced by the
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// literal pool's entry if the referenced address is that of a symbol. Or it
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// will return a pointer to a literal 'C' string if the referenced address of
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// the literal pool's entry is an address into a section with C string literals.
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// Or if the reference is to an Objective-C data structure it will return a
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// specific reference type for it and a string.
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void MCExternalSymbolizer::tryAddingPcLoadReferenceComment(raw_ostream &cStream,
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int64_t Value,
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uint64_t Address) {
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if (SymbolLookUp) {
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uint64_t ReferenceType = LLVMDisassembler_ReferenceType_In_PCrel_Load;
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const char *ReferenceName;
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(void)SymbolLookUp(DisInfo, Value, &ReferenceType, Address, &ReferenceName);
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if(ReferenceType == LLVMDisassembler_ReferenceType_Out_LitPool_SymAddr)
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cStream << "literal pool symbol address: " << ReferenceName;
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else if(ReferenceType ==
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LLVMDisassembler_ReferenceType_Out_LitPool_CstrAddr) {
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cStream << "literal pool for: \"";
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cStream.write_escaped(ReferenceName);
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cStream << "\"";
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}
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else if(ReferenceType ==
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LLVMDisassembler_ReferenceType_Out_Objc_CFString_Ref)
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cStream << "Objc cfstring ref: @\"" << ReferenceName << "\"";
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else if(ReferenceType ==
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LLVMDisassembler_ReferenceType_Out_Objc_Message)
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cStream << "Objc message: " << ReferenceName;
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else if(ReferenceType ==
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LLVMDisassembler_ReferenceType_Out_Objc_Message_Ref)
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cStream << "Objc message ref: " << ReferenceName;
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else if(ReferenceType ==
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LLVMDisassembler_ReferenceType_Out_Objc_Selector_Ref)
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cStream << "Objc selector ref: " << ReferenceName;
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else if(ReferenceType ==
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LLVMDisassembler_ReferenceType_Out_Objc_Class_Ref)
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cStream << "Objc class ref: " << ReferenceName;
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}
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}
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namespace llvm {
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MCSymbolizer *createMCSymbolizer(const Triple &TT, LLVMOpInfoCallback GetOpInfo,
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LLVMSymbolLookupCallback SymbolLookUp,
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void *DisInfo, MCContext *Ctx,
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std::unique_ptr<MCRelocationInfo> &&RelInfo) {
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assert(Ctx && "No MCContext given for symbolic disassembly");
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return new MCExternalSymbolizer(*Ctx, std::move(RelInfo), GetOpInfo,
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SymbolLookUp, DisInfo);
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}
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}
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