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 /// This represents a section on linux, lots of unix variants and some bare
25 /// metal systems.
26 class MCSectionELF final : public MCSection {
27   /// This is the sh_type field of a section, drawn from the enums below.
28   unsigned Type;
29 
30   /// This is the sh_flags field of a section, drawn from the enums below.
31   unsigned Flags;
32 
33   unsigned UniqueID;
34 
35   /// The size of each entry in this section. This size only makes sense for
36   /// sections that contain fixed-sized entries. If a section does not contain
37   /// fixed-sized entries 'EntrySize' will be 0.
38   unsigned EntrySize;
39 
40   /// The section group signature symbol (if not null) and a bool indicating
41   /// whether this is a GRP_COMDAT group.
42   const PointerIntPair<const MCSymbolELF *, 1, bool> Group;
43 
44   /// Used by SHF_LINK_ORDER. If non-null, the sh_link field will be set to the
45   /// section header index of the section where LinkedToSym is defined.
46   const MCSymbol *LinkedToSym;
47 
48 private:
49   friend class MCContext;
50 
51   // The storage of Name is owned by MCContext's ELFUniquingMap.
52   MCSectionELF(StringRef Name, unsigned type, unsigned flags, SectionKind K,
53                unsigned entrySize, const MCSymbolELF *group, bool IsComdat,
54                unsigned UniqueID, MCSymbol *Begin,
55                const MCSymbolELF *LinkedToSym)
56       : MCSection(SV_ELF, Name, K, Begin), Type(type), Flags(flags),
57         UniqueID(UniqueID), EntrySize(entrySize), Group(group, IsComdat),
58         LinkedToSym(LinkedToSym) {
59     if (Group.getPointer())
60       Group.getPointer()->setIsSignature();
61   }
62 
63   // TODO Delete after we stop supporting generation of GNU-style .zdebug_*
64   // sections.
65   void setSectionName(StringRef Name) { this->Name = Name; }
66 
67 public:
68   /// Decides whether a '.section' directive should be printed before the
69   /// section name
70   bool shouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
71 
72   unsigned getType() const { return Type; }
73   unsigned getFlags() const { return Flags; }
74   unsigned getEntrySize() const { return EntrySize; }
75   void setFlags(unsigned F) { Flags = F; }
76   const MCSymbolELF *getGroup() const { return Group.getPointer(); }
77   bool isComdat() const { return Group.getInt(); }
78 
79   void printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
80                             raw_ostream &OS,
81                             const MCExpr *Subsection) const override;
82   bool useCodeAlign() const override;
83   bool isVirtualSection() const override;
84   StringRef getVirtualSectionKind() const override;
85 
86   bool isUnique() const { return UniqueID != NonUniqueID; }
87   unsigned getUniqueID() const { return UniqueID; }
88 
89   const MCSection *getLinkedToSection() const {
90     return &LinkedToSym->getSection();
91   }
92   const MCSymbol *getLinkedToSymbol() const { return LinkedToSym; }
93 
94   static bool classof(const MCSection *S) {
95     return S->getVariant() == SV_ELF;
96   }
97 };
98 
99 } // end namespace llvm
100 
101 #endif // LLVM_MC_MCSECTIONELF_H
102