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Diffstat (limited to 'llvm/lib/MC/MCDisassembler/MCExternalSymbolizer.cpp')
| -rw-r--r-- | llvm/lib/MC/MCDisassembler/MCExternalSymbolizer.cpp | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/llvm/lib/MC/MCDisassembler/MCExternalSymbolizer.cpp b/llvm/lib/MC/MCDisassembler/MCExternalSymbolizer.cpp new file mode 100644 index 000000000000..7befef86303c --- /dev/null +++ b/llvm/lib/MC/MCDisassembler/MCExternalSymbolizer.cpp @@ -0,0 +1,199 @@ +//===-- MCExternalSymbolizer.cpp - External symbolizer --------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#include "llvm/MC/MCDisassembler/MCExternalSymbolizer.h" +#include "llvm/MC/MCContext.h" +#include "llvm/MC/MCExpr.h" +#include "llvm/MC/MCInst.h" +#include "llvm/Support/raw_ostream.h" +#include <cstring> + +using namespace llvm; + +namespace llvm { +class Triple; +} + +// This function tries to add a symbolic operand in place of the immediate +// Value in the MCInst. The immediate Value has had any PC adjustment made by +// the caller. If the instruction is a branch instruction then IsBranch is true, +// else false. If the getOpInfo() function was set as part of the +// setupForSymbolicDisassembly() call then that function is called to get any +// symbolic information at the Address for this instruction. If that returns +// non-zero then the symbolic information it returns is used to create an MCExpr +// and that is added as an operand to the MCInst. If getOpInfo() returns zero +// and IsBranch is true then a symbol look up for Value is done and if a symbol +// is found an MCExpr is created with that, else an MCExpr with Value is +// created. This function returns true if it adds an operand to the MCInst and +// false otherwise. +bool MCExternalSymbolizer::tryAddingSymbolicOperand(MCInst &MI, + raw_ostream &cStream, + int64_t Value, + uint64_t Address, + bool IsBranch, + uint64_t Offset, + uint64_t InstSize) { + struct LLVMOpInfo1 SymbolicOp; + std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1)); + SymbolicOp.Value = Value; + + if (!GetOpInfo || + !GetOpInfo(DisInfo, Address, Offset, InstSize, 1, &SymbolicOp)) { + // Clear SymbolicOp.Value from above and also all other fields. + std::memset(&SymbolicOp, '\0', sizeof(struct LLVMOpInfo1)); + + // At this point, GetOpInfo() did not find any relocation information about + // this operand and we are left to use the SymbolLookUp() call back to guess + // if the Value is the address of a symbol. In the case this is a branch + // that always makes sense to guess. But in the case of an immediate it is + // a bit more questionable if it is an address of a symbol or some other + // reference. So if the immediate Value comes from a width of 1 byte, + // InstSize, we will not guess it is an address of a symbol. Because in + // object files assembled starting at address 0 this usually leads to + // incorrect symbolication. + if (!SymbolLookUp || (InstSize == 1 && !IsBranch)) + return false; + + uint64_t ReferenceType; + if (IsBranch) + ReferenceType = LLVMDisassembler_ReferenceType_In_Branch; + else + ReferenceType = LLVMDisassembler_ReferenceType_InOut_None; + const char *ReferenceName; + const char *Name = SymbolLookUp(DisInfo, Value, &ReferenceType, Address, + &ReferenceName); + if (Name) { + SymbolicOp.AddSymbol.Name = Name; + SymbolicOp.AddSymbol.Present = true; + // If Name is a C++ symbol name put the human readable name in a comment. + if(ReferenceType == LLVMDisassembler_ReferenceType_DeMangled_Name) + cStream << ReferenceName; + } + // For branches always create an MCExpr so it gets printed as hex address. + else if (IsBranch) { + SymbolicOp.Value = Value; + } + if(ReferenceType == LLVMDisassembler_ReferenceType_Out_SymbolStub) + cStream << "symbol stub for: " << ReferenceName; + else if(ReferenceType == LLVMDisassembler_ReferenceType_Out_Objc_Message) + cStream << "Objc message: " << ReferenceName; + if (!Name && !IsBranch) + return false; + } + + const MCExpr *Add = nullptr; + if (SymbolicOp.AddSymbol.Present) { + if (SymbolicOp.AddSymbol.Name) { + StringRef Name(SymbolicOp.AddSymbol.Name); + MCSymbol *Sym = Ctx.getOrCreateSymbol(Name); + Add = MCSymbolRefExpr::create(Sym, Ctx); + } else { + Add = MCConstantExpr::create((int)SymbolicOp.AddSymbol.Value, Ctx); + } + } + + const MCExpr *Sub = nullptr; + if (SymbolicOp.SubtractSymbol.Present) { + if (SymbolicOp.SubtractSymbol.Name) { + StringRef Name(SymbolicOp.SubtractSymbol.Name); + MCSymbol *Sym = Ctx.getOrCreateSymbol(Name); + Sub = MCSymbolRefExpr::create(Sym, Ctx); + } else { + Sub = MCConstantExpr::create((int)SymbolicOp.SubtractSymbol.Value, Ctx); + } + } + + const MCExpr *Off = nullptr; + if (SymbolicOp.Value != 0) + Off = MCConstantExpr::create(SymbolicOp.Value, Ctx); + + const MCExpr *Expr; + if (Sub) { + const MCExpr *LHS; + if (Add) + LHS = MCBinaryExpr::createSub(Add, Sub, Ctx); + else + LHS = MCUnaryExpr::createMinus(Sub, Ctx); + if (Off) + Expr = MCBinaryExpr::createAdd(LHS, Off, Ctx); + else + Expr = LHS; + } else if (Add) { + if (Off) + Expr = MCBinaryExpr::createAdd(Add, Off, Ctx); + else + Expr = Add; + } else { + if (Off) + Expr = Off; + else + Expr = MCConstantExpr::create(0, Ctx); + } + + Expr = RelInfo->createExprForCAPIVariantKind(Expr, SymbolicOp.VariantKind); + if (!Expr) + return false; + + MI.addOperand(MCOperand::createExpr(Expr)); + return true; +} + +// This function tries to add a comment as to what is being referenced by a load +// instruction with the base register that is the Pc. These can often be values +// in a literal pool near the Address of the instruction. The Address of the +// instruction and its immediate Value are used as a possible literal pool entry. +// The SymbolLookUp call back will return the name of a symbol referenced by the +// literal pool's entry if the referenced address is that of a symbol. Or it +// will return a pointer to a literal 'C' string if the referenced address of +// the literal pool's entry is an address into a section with C string literals. +// Or if the reference is to an Objective-C data structure it will return a +// specific reference type for it and a string. +void MCExternalSymbolizer::tryAddingPcLoadReferenceComment(raw_ostream &cStream, + int64_t Value, + uint64_t Address) { + if (SymbolLookUp) { + uint64_t ReferenceType = LLVMDisassembler_ReferenceType_In_PCrel_Load; + const char *ReferenceName; + (void)SymbolLookUp(DisInfo, Value, &ReferenceType, Address, &ReferenceName); + if(ReferenceType == LLVMDisassembler_ReferenceType_Out_LitPool_SymAddr) + cStream << "literal pool symbol address: " << ReferenceName; + else if(ReferenceType == + LLVMDisassembler_ReferenceType_Out_LitPool_CstrAddr) { + cStream << "literal pool for: \""; + cStream.write_escaped(ReferenceName); + cStream << "\""; + } + else if(ReferenceType == + LLVMDisassembler_ReferenceType_Out_Objc_CFString_Ref) + cStream << "Objc cfstring ref: @\"" << ReferenceName << "\""; + else if(ReferenceType == + LLVMDisassembler_ReferenceType_Out_Objc_Message) + cStream << "Objc message: " << ReferenceName; + else if(ReferenceType == + LLVMDisassembler_ReferenceType_Out_Objc_Message_Ref) + cStream << "Objc message ref: " << ReferenceName; + else if(ReferenceType == + LLVMDisassembler_ReferenceType_Out_Objc_Selector_Ref) + cStream << "Objc selector ref: " << ReferenceName; + else if(ReferenceType == + LLVMDisassembler_ReferenceType_Out_Objc_Class_Ref) + cStream << "Objc class ref: " << ReferenceName; + } +} + +namespace llvm { +MCSymbolizer *createMCSymbolizer(const Triple &TT, LLVMOpInfoCallback GetOpInfo, + LLVMSymbolLookupCallback SymbolLookUp, + void *DisInfo, MCContext *Ctx, + std::unique_ptr<MCRelocationInfo> &&RelInfo) { + assert(Ctx && "No MCContext given for symbolic disassembly"); + + return new MCExternalSymbolizer(*Ctx, std::move(RelInfo), GetOpInfo, + SymbolLookUp, DisInfo); +} +} |