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
18using namespace llvm;
19
20// Decides whether a '.section' directive
21// should be printed before the section name.
22bool MCSectionELF::ShouldOmitSectionDirective(StringRef Name,
23                                              const MCAsmInfo &MAI) const {
24  if (isUnique())
25    return false;
26
27  return MAI.shouldOmitSectionDirective(Name);
28}
29
30static 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
53void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
54                                        raw_ostream &OS,
55                                        const MCExpr *Subsection) const {
56  if (ShouldOmitSectionDirective(getName(), MAI)) {
57    OS << '\t' << getName();
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, getName());
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 " + getName());
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(LinkedToSym);
176    OS << ",";
177    printName(OS, LinkedToSym->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
192bool MCSectionELF::UseCodeAlign() const {
193  return getFlags() & ELF::SHF_EXECINSTR;
194}
195
196bool MCSectionELF::isVirtualSection() const {
197  return getType() == ELF::SHT_NOBITS;
198}
199
200StringRef MCSectionELF::getVirtualSectionKind() const { return "SHT_NOBITS"; }
201