1 //===- MCSectionELF.h - ELF Machine Code Sections ---------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file declares the MCSectionELF class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_MC_MCSECTIONELF_H
14 #define LLVM_MC_MCSECTIONELF_H
15 
16 #include "llvm/ADT/PointerIntPair.h"
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/MC/MCSection.h"
19 #include "llvm/MC/MCSymbolELF.h"
20 #include "llvm/MC/SectionKind.h"
21 
22 namespace llvm {
23 
24 class MCSymbol;
25 
26 /// This represents a section on linux, lots of unix variants and some bare
27 /// metal systems.
28 class MCSectionELF final : public MCSection {
29   /// This is the sh_type field of a section, drawn from the enums below.
30   unsigned Type;
31 
32   /// This is the sh_flags field of a section, drawn from the enums below.
33   unsigned Flags;
34 
35   unsigned UniqueID;
36 
37   /// The size of each entry in this section. This size only makes sense for
38   /// sections that contain fixed-sized entries. If a section does not contain
39   /// fixed-sized entries 'EntrySize' will be 0.
40   unsigned EntrySize;
41 
42   /// The section group signature symbol (if not null) and a bool indicating
43   /// whether this is a GRP_COMDAT group.
44   const PointerIntPair<const MCSymbolELF *, 1, bool> Group;
45 
46   /// Used by SHF_LINK_ORDER. If non-null, the sh_link field will be set to the
47   /// section header index of the section where LinkedToSym is defined.
48   const MCSymbol *LinkedToSym;
49 
50 private:
51   friend class MCContext;
52 
53   // The storage of Name is owned by MCContext's ELFUniquingMap.
MCSectionELF(StringRef Name,unsigned type,unsigned flags,SectionKind K,unsigned entrySize,const MCSymbolELF * group,bool IsComdat,unsigned UniqueID,MCSymbol * Begin,const MCSymbolELF * LinkedToSym)54   MCSectionELF(StringRef Name, unsigned type, unsigned flags, SectionKind K,
55                unsigned entrySize, const MCSymbolELF *group, bool IsComdat,
56                unsigned UniqueID, MCSymbol *Begin,
57                const MCSymbolELF *LinkedToSym)
58       : MCSection(SV_ELF, Name, K, Begin), Type(type), Flags(flags),
59         UniqueID(UniqueID), EntrySize(entrySize), Group(group, IsComdat),
60         LinkedToSym(LinkedToSym) {
61     if (Group.getPointer())
62       Group.getPointer()->setIsSignature();
63   }
64 
65   // TODO Delete after we stop supporting generation of GNU-style .zdebug_*
66   // sections.
setSectionName(StringRef Name)67   void setSectionName(StringRef Name) { this->Name = Name; }
68 
69 public:
70   /// Decides whether a '.section' directive should be printed before the
71   /// section name
72   bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
73 
getType()74   unsigned getType() const { return Type; }
getFlags()75   unsigned getFlags() const { return Flags; }
getEntrySize()76   unsigned getEntrySize() const { return EntrySize; }
setFlags(unsigned F)77   void setFlags(unsigned F) { Flags = F; }
getGroup()78   const MCSymbolELF *getGroup() const { return Group.getPointer(); }
isComdat()79   bool isComdat() const { return Group.getInt(); }
80 
81   void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
82                             raw_ostream &OS,
83                             const MCExpr *Subsection) const override;
84   bool UseCodeAlign() const override;
85   bool isVirtualSection() const override;
86   StringRef getVirtualSectionKind() const override;
87 
isUnique()88   bool isUnique() const { return UniqueID != NonUniqueID; }
getUniqueID()89   unsigned getUniqueID() const { return UniqueID; }
90 
getLinkedToSection()91   const MCSection *getLinkedToSection() const {
92     return &LinkedToSym->getSection();
93   }
getLinkedToSymbol()94   const MCSymbol *getLinkedToSymbol() const { return LinkedToSym; }
95 
classof(const MCSection * S)96   static bool classof(const MCSection *S) {
97     return S->getVariant() == SV_ELF;
98   }
99 };
100 
101 } // end namespace llvm
102 
103 #endif // LLVM_MC_MCSECTIONELF_H
104