1//===- lib/MC/MCSectionMachO.cpp - MachO 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/MCSectionMachO.h"
10#include "llvm/MC/MCContext.h"
11#include "llvm/Support/raw_ostream.h"
12#include <cctype>
13using namespace llvm;
14
15/// SectionTypeDescriptors - These are strings that describe the various section
16/// types.  This *must* be kept in order with and stay synchronized with the
17/// section type list.
18static constexpr struct {
19  StringLiteral AssemblerName, EnumName;
20} SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE + 1] = {
21    {StringLiteral("regular"), StringLiteral("S_REGULAR")}, // 0x00
22    {StringLiteral(""), StringLiteral("S_ZEROFILL")},       // 0x01
23    {StringLiteral("cstring_literals"),
24     StringLiteral("S_CSTRING_LITERALS")}, // 0x02
25    {StringLiteral("4byte_literals"),
26     StringLiteral("S_4BYTE_LITERALS")}, // 0x03
27    {StringLiteral("8byte_literals"),
28     StringLiteral("S_8BYTE_LITERALS")}, // 0x04
29    {StringLiteral("literal_pointers"),
30     StringLiteral("S_LITERAL_POINTERS")}, // 0x05
31    {StringLiteral("non_lazy_symbol_pointers"),
32     StringLiteral("S_NON_LAZY_SYMBOL_POINTERS")}, // 0x06
33    {StringLiteral("lazy_symbol_pointers"),
34     StringLiteral("S_LAZY_SYMBOL_POINTERS")},                        // 0x07
35    {StringLiteral("symbol_stubs"), StringLiteral("S_SYMBOL_STUBS")}, // 0x08
36    {StringLiteral("mod_init_funcs"),
37     StringLiteral("S_MOD_INIT_FUNC_POINTERS")}, // 0x09
38    {StringLiteral("mod_term_funcs"),
39     StringLiteral("S_MOD_TERM_FUNC_POINTERS")},                     // 0x0A
40    {StringLiteral("coalesced"), StringLiteral("S_COALESCED")},      // 0x0B
41    {StringLiteral("") /*FIXME??*/, StringLiteral("S_GB_ZEROFILL")}, // 0x0C
42    {StringLiteral("interposing"), StringLiteral("S_INTERPOSING")},  // 0x0D
43    {StringLiteral("16byte_literals"),
44     StringLiteral("S_16BYTE_LITERALS")},                           // 0x0E
45    {StringLiteral("") /*FIXME??*/, StringLiteral("S_DTRACE_DOF")}, // 0x0F
46    {StringLiteral("") /*FIXME??*/,
47     StringLiteral("S_LAZY_DYLIB_SYMBOL_POINTERS")}, // 0x10
48    {StringLiteral("thread_local_regular"),
49     StringLiteral("S_THREAD_LOCAL_REGULAR")}, // 0x11
50    {StringLiteral("thread_local_zerofill"),
51     StringLiteral("S_THREAD_LOCAL_ZEROFILL")}, // 0x12
52    {StringLiteral("thread_local_variables"),
53     StringLiteral("S_THREAD_LOCAL_VARIABLES")}, // 0x13
54    {StringLiteral("thread_local_variable_pointers"),
55     StringLiteral("S_THREAD_LOCAL_VARIABLE_POINTERS")}, // 0x14
56    {StringLiteral("thread_local_init_function_pointers"),
57     StringLiteral("S_THREAD_LOCAL_INIT_FUNCTION_POINTERS")}, // 0x15
58};
59
60/// SectionAttrDescriptors - This is an array of descriptors for section
61/// attributes.  Unlike the SectionTypeDescriptors, this is not directly indexed
62/// by attribute, instead it is searched.
63static constexpr struct {
64  unsigned AttrFlag;
65  StringLiteral AssemblerName, EnumName;
66} SectionAttrDescriptors[] = {
67#define ENTRY(ASMNAME, ENUM) \
68  { MachO::ENUM, StringLiteral(ASMNAME), StringLiteral(#ENUM) },
69ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
70ENTRY("no_toc",              S_ATTR_NO_TOC)
71ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
72ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
73ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
74ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
75ENTRY("debug",               S_ATTR_DEBUG)
76ENTRY("" /*FIXME*/,          S_ATTR_SOME_INSTRUCTIONS)
77ENTRY("" /*FIXME*/,          S_ATTR_EXT_RELOC)
78ENTRY("" /*FIXME*/,          S_ATTR_LOC_RELOC)
79#undef ENTRY
80  { 0, StringLiteral("none"), StringLiteral("") }, // used if section has no attributes but has a stub size
81};
82
83MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
84                               unsigned TAA, unsigned reserved2, SectionKind K,
85                               MCSymbol *Begin)
86    : MCSection(SV_MachO, K, Begin), TypeAndAttributes(TAA),
87      Reserved2(reserved2) {
88  assert(Segment.size() <= 16 && Section.size() <= 16 &&
89         "Segment or section string too long");
90  for (unsigned i = 0; i != 16; ++i) {
91    if (i < Segment.size())
92      SegmentName[i] = Segment[i];
93    else
94      SegmentName[i] = 0;
95
96    if (i < Section.size())
97      SectionName[i] = Section[i];
98    else
99      SectionName[i] = 0;
100  }
101}
102
103void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
104                                          raw_ostream &OS,
105                                          const MCExpr *Subsection) const {
106  OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
107
108  // Get the section type and attributes.
109  unsigned TAA = getTypeAndAttributes();
110  if (TAA == 0) {
111    OS << '\n';
112    return;
113  }
114
115  MachO::SectionType SectionType = getType();
116  assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE &&
117         "Invalid SectionType specified!");
118
119  if (!SectionTypeDescriptors[SectionType].AssemblerName.empty()) {
120    OS << ',';
121    OS << SectionTypeDescriptors[SectionType].AssemblerName;
122  } else {
123    // If we have no name for the attribute, stop here.
124    OS << '\n';
125    return;
126  }
127
128  // If we don't have any attributes, we're done.
129  unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES;
130  if (SectionAttrs == 0) {
131    // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
132    // the attribute specifier.
133    if (Reserved2 != 0)
134      OS << ",none," << Reserved2;
135    OS << '\n';
136    return;
137  }
138
139  // Check each attribute to see if we have it.
140  char Separator = ',';
141  for (unsigned i = 0;
142       SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
143       ++i) {
144    // Check to see if we have this attribute.
145    if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
146      continue;
147
148    // Yep, clear it and print it.
149    SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
150
151    OS << Separator;
152    if (!SectionAttrDescriptors[i].AssemblerName.empty())
153      OS << SectionAttrDescriptors[i].AssemblerName;
154    else
155      OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
156    Separator = '+';
157  }
158
159  assert(SectionAttrs == 0 && "Unknown section attributes!");
160
161  // If we have a S_SYMBOL_STUBS size specified, print it.
162  if (Reserved2 != 0)
163    OS << ',' << Reserved2;
164  OS << '\n';
165}
166
167bool MCSectionMachO::UseCodeAlign() const {
168  return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
169}
170
171bool MCSectionMachO::isVirtualSection() const {
172  return (getType() == MachO::S_ZEROFILL ||
173          getType() == MachO::S_GB_ZEROFILL ||
174          getType() == MachO::S_THREAD_LOCAL_ZEROFILL);
175}
176
177/// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
178/// This is a string that can appear after a .section directive in a mach-o
179/// flavored .s file.  If successful, this fills in the specified Out
180/// parameters and returns an empty string.  When an invalid section
181/// specifier is present, this returns a string indicating the problem.
182std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
183                                                  StringRef &Segment,    // Out.
184                                                  StringRef &Section,    // Out.
185                                                  unsigned  &TAA,        // Out.
186                                                  bool      &TAAParsed,  // Out.
187                                                  unsigned  &StubSize) { // Out.
188  TAAParsed = false;
189
190  SmallVector<StringRef, 5> SplitSpec;
191  Spec.split(SplitSpec, ',');
192  // Remove leading and trailing whitespace.
193  auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef {
194    return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef();
195  };
196  Segment = GetEmptyOrTrim(0);
197  Section = GetEmptyOrTrim(1);
198  StringRef SectionType = GetEmptyOrTrim(2);
199  StringRef Attrs = GetEmptyOrTrim(3);
200  StringRef StubSizeStr = GetEmptyOrTrim(4);
201
202  // Verify that the segment is present and not too long.
203  if (Segment.empty() || Segment.size() > 16)
204    return "mach-o section specifier requires a segment whose length is "
205           "between 1 and 16 characters";
206
207  // Verify that the section is present and not too long.
208  if (Section.empty())
209    return "mach-o section specifier requires a segment and section "
210           "separated by a comma";
211
212  if (Section.size() > 16)
213    return "mach-o section specifier requires a section whose length is "
214           "between 1 and 16 characters";
215
216  // If there is no comma after the section, we're done.
217  TAA = 0;
218  StubSize = 0;
219  if (SectionType.empty())
220    return "";
221
222  // Figure out which section type it is.
223  auto TypeDescriptor = std::find_if(
224      std::begin(SectionTypeDescriptors), std::end(SectionTypeDescriptors),
225      [&](decltype(*SectionTypeDescriptors) &Descriptor) {
226        return SectionType == Descriptor.AssemblerName;
227      });
228
229  // If we didn't find the section type, reject it.
230  if (TypeDescriptor == std::end(SectionTypeDescriptors))
231    return "mach-o section specifier uses an unknown section type";
232
233  // Remember the TypeID.
234  TAA = TypeDescriptor - std::begin(SectionTypeDescriptors);
235  TAAParsed = true;
236
237  // If we have no comma after the section type, there are no attributes.
238  if (Attrs.empty()) {
239    // S_SYMBOL_STUBS always require a symbol stub size specifier.
240    if (TAA == MachO::S_SYMBOL_STUBS)
241      return "mach-o section specifier of type 'symbol_stubs' requires a size "
242             "specifier";
243    return "";
244  }
245
246  // The attribute list is a '+' separated list of attributes.
247  SmallVector<StringRef, 1> SectionAttrs;
248  Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
249
250  for (StringRef &SectionAttr : SectionAttrs) {
251    auto AttrDescriptorI = std::find_if(
252        std::begin(SectionAttrDescriptors), std::end(SectionAttrDescriptors),
253        [&](decltype(*SectionAttrDescriptors) &Descriptor) {
254          return SectionAttr.trim() == Descriptor.AssemblerName;
255        });
256    if (AttrDescriptorI == std::end(SectionAttrDescriptors))
257      return "mach-o section specifier has invalid attribute";
258
259    TAA |= AttrDescriptorI->AttrFlag;
260  }
261
262  // Okay, we've parsed the section attributes, see if we have a stub size spec.
263  if (StubSizeStr.empty()) {
264    // S_SYMBOL_STUBS always require a symbol stub size specifier.
265    if (TAA == MachO::S_SYMBOL_STUBS)
266      return "mach-o section specifier of type 'symbol_stubs' requires a size "
267      "specifier";
268    return "";
269  }
270
271  // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
272  if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS)
273    return "mach-o section specifier cannot have a stub size specified because "
274           "it does not have type 'symbol_stubs'";
275
276  // Convert the stub size from a string to an integer.
277  if (StubSizeStr.getAsInteger(0, StubSize))
278    return "mach-o section specifier has a malformed stub size";
279
280  return "";
281}
282