105 lines
4.3 KiB
C++
105 lines
4.3 KiB
C++
//===----------------------------------------------------------------------===//
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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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///
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/// \file
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/// This file declares `DWARFCFIAnalysis` class.
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/// `DWARFCFIAnalysis` is a minimal implementation of a DWARF CFI checker
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/// described in this link:
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/// https://discourse.llvm.org/t/rfc-dwarf-cfi-validation/86936
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///
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/// The goal of the checker is to validate DWARF CFI directives using the
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/// prologue directives and the machine instructions. The main proposed
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/// algorithm validates the directives by comparing the CFI state in each
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/// instruction with the state achieved by abstract execution of the instruction
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/// on the CFI state. However, the current version implemented here is a simple
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/// conditional check based on the registers modified by each instruction.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_DWARFCFICHECKER_DWARFCFIANALYSIS_H
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#define LLVM_DWARFCFICHECKER_DWARFCFIANALYSIS_H
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#include "DWARFCFIState.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/DebugInfo/DWARF/LowLevel/DWARFUnwindTable.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCDwarf.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/MC/MCInstrInfo.h"
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#include "llvm/MC/MCRegisterInfo.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSubtargetInfo.h"
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#include "llvm/MC/TargetRegistry.h"
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#include "llvm/Support/Compiler.h"
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namespace llvm {
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/// `DWARFCFIAnalysis` validates the DWARF Call Frame Information one machine
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/// instruction at a time. This class maintains an internal CFI state
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/// initialized with the prologue directives and updated with each instruction's
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/// associated directives. In each update, it checks if the machine
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/// instruction changes the CFI state in a way that matches the changes
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/// from the CFI directives. This checking may results in errors and warnings.
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///
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/// In current stage, the analysis is only aware of what registers the
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/// instruction modifies. If the modification is happening to a sub-register,
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/// the analysis considers the super-register is modified.
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///
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/// In each update, for each register (or CFA), the following cases can happen:
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/// 1. The unwinding rule is not changed:
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/// a. The registers involved in this rule are not modified: the analysis
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/// proceeds without emitting error or warning.
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/// b. The registers involved in this rule are modified: it emits an error.
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/// 2. The unwinding rule is changed:
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/// a. The rule is structurally modified (i.e., the location is changed): It
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/// emits a warning.
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/// b. The rule is structurally the same, but the register set is changed: it
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/// emits a warning.
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/// c. The rule is structurally the same, using the same set of registers, but
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/// the offset is changed:
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/// i. If the registers included in the rule are modified as well: It
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/// emits a warning.
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/// ii. If the registers included in the rule are not modified: It emits an
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/// error.
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///
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/// The analysis only checks the CFA unwinding rule when the rule is a register
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/// plus some offset. Therefore, for CFA, only cases 1, 2.b, and 2.c are
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/// checked, and in all other case(s), a warning is emitted.
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class DWARFCFIAnalysis {
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public:
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LLVM_ABI DWARFCFIAnalysis(MCContext *Context, MCInstrInfo const &MCII,
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bool IsEH, ArrayRef<MCCFIInstruction> Prologue);
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LLVM_ABI void update(const MCInst &Inst,
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ArrayRef<MCCFIInstruction> Directives);
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private:
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void checkRegDiff(const MCInst &Inst, DWARFRegNum Reg,
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const dwarf::UnwindRow &PrevRow,
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const dwarf::UnwindRow &NextRow,
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const SmallSet<DWARFRegNum, 4> &Writes);
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void checkCFADiff(const MCInst &Inst, const dwarf::UnwindRow &PrevRow,
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const dwarf::UnwindRow &NextRow,
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const SmallSet<DWARFRegNum, 4> &Writes);
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private:
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DWARFCFIState State;
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MCContext *Context;
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MCInstrInfo const &MCII;
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MCRegisterInfo const *MCRI;
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bool IsEH;
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};
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} // namespace llvm
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#endif
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