1 //===- lib/MC/MCSectionELF.cpp - ELF Code Section Representation ----------===//
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 #include "llvm/MC/MCSectionELF.h"
10 #include "llvm/ADT/Triple.h"
11 #include "llvm/BinaryFormat/ELF.h"
12 #include "llvm/MC/MCAsmInfo.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/Support/ErrorHandling.h"
15 #include "llvm/Support/raw_ostream.h"
16 #include <cassert>
17 
18 using namespace llvm;
19 
20 // Decides whether a '.section' directive
21 // should be printed before the section name.
22 bool MCSectionELF::ShouldOmitSectionDirective(StringRef Name,
23                                               const MCAsmInfo &MAI) const {
24   if (isUnique())
25     return false;
26 
27   return MAI.shouldOmitSectionDirective(Name);
28 }
29 
30 static void printName(raw_ostream &OS, StringRef Name) {
31   if (Name.find_first_not_of("0123456789_."
32                              "abcdefghijklmnopqrstuvwxyz"
33                              "ABCDEFGHIJKLMNOPQRSTUVWXYZ") == Name.npos) {
34     OS << Name;
35     return;
36   }
37   OS << '"';
38   for (const char *B = Name.begin(), *E = Name.end(); B < E; ++B) {
39     if (*B == '"') // Unquoted "
40       OS << "\\\"";
41     else if (*B != '\\') // Neither " or backslash
42       OS << *B;
43     else if (B + 1 == E) // Trailing backslash
44       OS << "\\\\";
45     else {
46       OS << B[0] << B[1]; // Quoted character
47       ++B;
48     }
49   }
50   OS << '"';
51 }
52 
53 void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
54                                         raw_ostream &OS,
55                                         const MCExpr *Subsection) const {
56   if (ShouldOmitSectionDirective(SectionName, MAI)) {
57     OS << '\t' << getSectionName();
58     if (Subsection) {
59       OS << '\t';
60       Subsection->print(OS, &MAI);
61     }
62     OS << '\n';
63     return;
64   }
65 
66   OS << "\t.section\t";
67   printName(OS, getSectionName());
68 
69   // Handle the weird solaris syntax if desired.
70   if (MAI.usesSunStyleELFSectionSwitchSyntax() &&
71       !(Flags & ELF::SHF_MERGE)) {
72     if (Flags & ELF::SHF_ALLOC)
73       OS << ",#alloc";
74     if (Flags & ELF::SHF_EXECINSTR)
75       OS << ",#execinstr";
76     if (Flags & ELF::SHF_WRITE)
77       OS << ",#write";
78     if (Flags & ELF::SHF_EXCLUDE)
79       OS << ",#exclude";
80     if (Flags & ELF::SHF_TLS)
81       OS << ",#tls";
82     OS << '\n';
83     return;
84   }
85 
86   OS << ",\"";
87   if (Flags & ELF::SHF_ALLOC)
88     OS << 'a';
89   if (Flags & ELF::SHF_EXCLUDE)
90     OS << 'e';
91   if (Flags & ELF::SHF_EXECINSTR)
92     OS << 'x';
93   if (Flags & ELF::SHF_GROUP)
94     OS << 'G';
95   if (Flags & ELF::SHF_WRITE)
96     OS << 'w';
97   if (Flags & ELF::SHF_MERGE)
98     OS << 'M';
99   if (Flags & ELF::SHF_STRINGS)
100     OS << 'S';
101   if (Flags & ELF::SHF_TLS)
102     OS << 'T';
103   if (Flags & ELF::SHF_LINK_ORDER)
104     OS << 'o';
105 
106   // If there are target-specific flags, print them.
107   Triple::ArchType Arch = T.getArch();
108   if (Arch == Triple::xcore) {
109     if (Flags & ELF::XCORE_SHF_CP_SECTION)
110       OS << 'c';
111     if (Flags & ELF::XCORE_SHF_DP_SECTION)
112       OS << 'd';
113   } else if (T.isARM() || T.isThumb()) {
114     if (Flags & ELF::SHF_ARM_PURECODE)
115       OS << 'y';
116   } else if (Arch == Triple::hexagon) {
117     if (Flags & ELF::SHF_HEX_GPREL)
118       OS << 's';
119   }
120 
121   OS << '"';
122 
123   OS << ',';
124 
125   // If comment string is '@', e.g. as on ARM - use '%' instead
126   if (MAI.getCommentString()[0] == '@')
127     OS << '%';
128   else
129     OS << '@';
130 
131   if (Type == ELF::SHT_INIT_ARRAY)
132     OS << "init_array";
133   else if (Type == ELF::SHT_FINI_ARRAY)
134     OS << "fini_array";
135   else if (Type == ELF::SHT_PREINIT_ARRAY)
136     OS << "preinit_array";
137   else if (Type == ELF::SHT_NOBITS)
138     OS << "nobits";
139   else if (Type == ELF::SHT_NOTE)
140     OS << "note";
141   else if (Type == ELF::SHT_PROGBITS)
142     OS << "progbits";
143   else if (Type == ELF::SHT_X86_64_UNWIND)
144     OS << "unwind";
145   else if (Type == ELF::SHT_MIPS_DWARF)
146     // Print hex value of the flag while we do not have
147     // any standard symbolic representation of the flag.
148     OS << "0x7000001e";
149   else if (Type == ELF::SHT_LLVM_ODRTAB)
150     OS << "llvm_odrtab";
151   else if (Type == ELF::SHT_LLVM_LINKER_OPTIONS)
152     OS << "llvm_linker_options";
153   else if (Type == ELF::SHT_LLVM_CALL_GRAPH_PROFILE)
154     OS << "llvm_call_graph_profile";
155   else if (Type == ELF::SHT_LLVM_DEPENDENT_LIBRARIES)
156     OS << "llvm_dependent_libraries";
157   else if (Type == ELF::SHT_LLVM_SYMPART)
158     OS << "llvm_sympart";
159   else
160     report_fatal_error("unsupported type 0x" + Twine::utohexstr(Type) +
161                        " for section " + getSectionName());
162 
163   if (EntrySize) {
164     assert(Flags & ELF::SHF_MERGE);
165     OS << "," << EntrySize;
166   }
167 
168   if (Flags & ELF::SHF_GROUP) {
169     OS << ",";
170     printName(OS, Group->getName());
171     OS << ",comdat";
172   }
173 
174   if (Flags & ELF::SHF_LINK_ORDER) {
175     assert(AssociatedSymbol);
176     OS << ",";
177     printName(OS, AssociatedSymbol->getName());
178   }
179 
180   if (isUnique())
181     OS << ",unique," << UniqueID;
182 
183   OS << '\n';
184 
185   if (Subsection) {
186     OS << "\t.subsection\t";
187     Subsection->print(OS, &MAI);
188     OS << '\n';
189   }
190 }
191 
192 bool MCSectionELF::UseCodeAlign() const {
193   return getFlags() & ELF::SHF_EXECINSTR;
194 }
195 
196 bool MCSectionELF::isVirtualSection() const {
197   return getType() == ELF::SHT_NOBITS;
198 }
199