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