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/MCAsmInfo.h"
12 #include "llvm/MC/MCContext.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/MC/MCSymbol.h"
15 #include "llvm/Support/ELF.h"
16 #include "llvm/Support/raw_ostream.h"
17 
18 using namespace llvm;
19 
20 MCSectionELF::~MCSectionELF() {} // anchor.
21 
22 // Decides whether a '.section' directive
23 // should be printed before the section name.
24 bool MCSectionELF::ShouldOmitSectionDirective(StringRef Name,
25                                               const MCAsmInfo &MAI) const {
26 
27   if (isUnique())
28     return false;
29 
30   // FIXME: Does .section .bss/.data/.text work everywhere??
31   if (Name == ".text" || Name == ".data" ||
32       (Name == ".bss" && !MAI.usesELFSectionDirectiveForBSS()))
33     return true;
34 
35   return false;
36 }
37 
38 static void printName(raw_ostream &OS, StringRef Name) {
39   if (Name.find_first_not_of("0123456789_."
40                              "abcdefghijklmnopqrstuvwxyz"
41                              "ABCDEFGHIJKLMNOPQRSTUVWXYZ") == Name.npos) {
42     OS << Name;
43     return;
44   }
45   OS << '"';
46   for (const char *B = Name.begin(), *E = Name.end(); B < E; ++B) {
47     if (*B == '"') // Unquoted "
48       OS << "\\\"";
49     else if (*B != '\\') // Neither " or backslash
50       OS << *B;
51     else if (B + 1 == E) // Trailing backslash
52       OS << "\\\\";
53     else {
54       OS << B[0] << B[1]; // Quoted character
55       ++B;
56     }
57   }
58   OS << '"';
59 }
60 
61 void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
62                                         raw_ostream &OS,
63                                         const MCExpr *Subsection) const {
64 
65   if (ShouldOmitSectionDirective(SectionName, MAI)) {
66     OS << '\t' << getSectionName();
67     if (Subsection) {
68       OS << '\t';
69       Subsection->print(OS, &MAI);
70     }
71     OS << '\n';
72     return;
73   }
74 
75   OS << "\t.section\t";
76   printName(OS, getSectionName());
77 
78   // Handle the weird solaris syntax if desired.
79   if (MAI.usesSunStyleELFSectionSwitchSyntax() &&
80       !(Flags & ELF::SHF_MERGE)) {
81     if (Flags & ELF::SHF_ALLOC)
82       OS << ",#alloc";
83     if (Flags & ELF::SHF_EXECINSTR)
84       OS << ",#execinstr";
85     if (Flags & ELF::SHF_WRITE)
86       OS << ",#write";
87     if (Flags & ELF::SHF_EXCLUDE)
88       OS << ",#exclude";
89     if (Flags & ELF::SHF_TLS)
90       OS << ",#tls";
91     OS << '\n';
92     return;
93   }
94 
95   OS << ",\"";
96   if (Flags & ELF::SHF_ALLOC)
97     OS << 'a';
98   if (Flags & ELF::SHF_EXCLUDE)
99     OS << 'e';
100   if (Flags & ELF::SHF_EXECINSTR)
101     OS << 'x';
102   if (Flags & ELF::SHF_GROUP)
103     OS << 'G';
104   if (Flags & ELF::SHF_WRITE)
105     OS << 'w';
106   if (Flags & ELF::SHF_MERGE)
107     OS << 'M';
108   if (Flags & ELF::SHF_STRINGS)
109     OS << 'S';
110   if (Flags & ELF::SHF_TLS)
111     OS << 'T';
112 
113   // If there are target-specific flags, print them.
114   if (Flags & ELF::XCORE_SHF_CP_SECTION)
115     OS << 'c';
116   if (Flags & ELF::XCORE_SHF_DP_SECTION)
117     OS << 'd';
118 
119   OS << '"';
120 
121   OS << ',';
122 
123   // If comment string is '@', e.g. as on ARM - use '%' instead
124   if (MAI.getCommentString()[0] == '@')
125     OS << '%';
126   else
127     OS << '@';
128 
129   if (Type == ELF::SHT_INIT_ARRAY)
130     OS << "init_array";
131   else if (Type == ELF::SHT_FINI_ARRAY)
132     OS << "fini_array";
133   else if (Type == ELF::SHT_PREINIT_ARRAY)
134     OS << "preinit_array";
135   else if (Type == ELF::SHT_NOBITS)
136     OS << "nobits";
137   else if (Type == ELF::SHT_NOTE)
138     OS << "note";
139   else if (Type == ELF::SHT_PROGBITS)
140     OS << "progbits";
141 
142   if (EntrySize) {
143     assert(Flags & ELF::SHF_MERGE);
144     OS << "," << EntrySize;
145   }
146 
147   if (Flags & ELF::SHF_GROUP) {
148     OS << ",";
149     printName(OS, Group->getName());
150     OS << ",comdat";
151   }
152 
153   if (isUnique())
154     OS << ",unique," << UniqueID;
155 
156   OS << '\n';
157 
158   if (Subsection) {
159     OS << "\t.subsection\t";
160     Subsection->print(OS, &MAI);
161     OS << '\n';
162   }
163 }
164 
165 bool MCSectionELF::UseCodeAlign() const {
166   return getFlags() & ELF::SHF_EXECINSTR;
167 }
168 
169 bool MCSectionELF::isVirtualSection() const {
170   return getType() == ELF::SHT_NOBITS;
171 }
172