1 //===- lib/MC/MCSectionELF.cpp - ELF Code Section Representation ----------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "llvm/MC/MCSectionELF.h"
11 #include "llvm/MC/MCContext.h"
12 #include "llvm/Support/raw_ostream.h"
13 #include "llvm/MC/MCAsmInfo.h"
14 
15 using namespace llvm;
16 
17 MCSectionELF *MCSectionELF::
18 Create(const StringRef &Section, unsigned Type, unsigned Flags,
19        SectionKind K, bool isExplicit, MCContext &Ctx) {
20   return new (Ctx) MCSectionELF(Section, Type, Flags, K, isExplicit);
21 }
22 
23 // ShouldOmitSectionDirective - Decides whether a '.section' directive
24 // should be printed before the section name
25 bool MCSectionELF::ShouldOmitSectionDirective(const char *Name,
26                                         const MCAsmInfo &MAI) const {
27 
28   // FIXME: Does .section .bss/.data/.text work everywhere??
29   if (strcmp(Name, ".text") == 0 ||
30       strcmp(Name, ".data") == 0 ||
31       (strcmp(Name, ".bss") == 0 &&
32        !MAI.usesELFSectionDirectiveForBSS()))
33     return true;
34 
35   return false;
36 }
37 
38 // ShouldPrintSectionType - Only prints the section type if supported
39 bool MCSectionELF::ShouldPrintSectionType(unsigned Ty) const {
40 
41   if (IsExplicit && !(Ty == SHT_NOBITS || Ty == SHT_PROGBITS))
42     return false;
43 
44   return true;
45 }
46 
47 void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
48                                         raw_ostream &OS) const {
49 
50   if (ShouldOmitSectionDirective(SectionName.c_str(), MAI)) {
51     OS << '\t' << getSectionName() << '\n';
52     return;
53   }
54 
55   OS << "\t.section\t" << getSectionName();
56 
57   // Handle the weird solaris syntax if desired.
58   if (MAI.usesSunStyleELFSectionSwitchSyntax() &&
59       !(Flags & MCSectionELF::SHF_MERGE)) {
60     if (Flags & MCSectionELF::SHF_ALLOC)
61       OS << ",#alloc";
62     if (Flags & MCSectionELF::SHF_EXECINSTR)
63       OS << ",#execinstr";
64     if (Flags & MCSectionELF::SHF_WRITE)
65       OS << ",#write";
66     if (Flags & MCSectionELF::SHF_TLS)
67       OS << ",#tls";
68   } else {
69     OS << ",\"";
70     if (Flags & MCSectionELF::SHF_ALLOC)
71       OS << 'a';
72     if (Flags & MCSectionELF::SHF_EXECINSTR)
73       OS << 'x';
74     if (Flags & MCSectionELF::SHF_WRITE)
75       OS << 'w';
76     if (Flags & MCSectionELF::SHF_MERGE)
77       OS << 'M';
78     if (Flags & MCSectionELF::SHF_STRINGS)
79       OS << 'S';
80     if (Flags & MCSectionELF::SHF_TLS)
81       OS << 'T';
82 
83     // If there are target-specific flags, print them.
84     if (Flags & ~MCSectionELF::TARGET_INDEP_SHF)
85       PrintTargetSpecificSectionFlags(MAI, OS);
86 
87     OS << '"';
88 
89     if (ShouldPrintSectionType(Type)) {
90       OS << ',';
91 
92       // If comment string is '@', e.g. as on ARM - use '%' instead
93       if (MAI.getCommentString()[0] == '@')
94         OS << '%';
95       else
96         OS << '@';
97 
98       if (Type == MCSectionELF::SHT_INIT_ARRAY)
99         OS << "init_array";
100       else if (Type == MCSectionELF::SHT_FINI_ARRAY)
101         OS << "fini_array";
102       else if (Type == MCSectionELF::SHT_PREINIT_ARRAY)
103         OS << "preinit_array";
104       else if (Type == MCSectionELF::SHT_NOBITS)
105         OS << "nobits";
106       else if (Type == MCSectionELF::SHT_PROGBITS)
107         OS << "progbits";
108 
109       if (getKind().isMergeable1ByteCString()) {
110         OS << ",1";
111       } else if (getKind().isMergeable2ByteCString()) {
112         OS << ",2";
113       } else if (getKind().isMergeable4ByteCString() ||
114                  getKind().isMergeableConst4()) {
115         OS << ",4";
116       } else if (getKind().isMergeableConst8()) {
117         OS << ",8";
118       } else if (getKind().isMergeableConst16()) {
119         OS << ",16";
120       }
121     }
122   }
123 
124   OS << '\n';
125 }
126 
127 // HasCommonSymbols - True if this section holds common symbols, this is
128 // indicated on the ELF object file by a symbol with SHN_COMMON section
129 // header index.
130 bool MCSectionELF::HasCommonSymbols() const {
131 
132   if (strncmp(SectionName.c_str(), ".gnu.linkonce.", 14) == 0)
133     return true;
134 
135   return false;
136 }
137 
138 
139