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  : MCSection(SV_MachO, K), TypeAndAttributes(TAA), Reserved2(reserved2) {
75  assert(Segment.size() <= 16 && Section.size() <= 16 &&
76         "Segment or section string too long");
77  for (unsigned i = 0; i != 16; ++i) {
78    if (i < Segment.size())
79      SegmentName[i] = Segment[i];
80    else
81      SegmentName[i] = 0;
82
83    if (i < Section.size())
84      SectionName[i] = Section[i];
85    else
86      SectionName[i] = 0;
87  }
88}
89
90void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI,
91                                          raw_ostream &OS,
92                                          const MCExpr *Subsection) const {
93  OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
94
95  // Get the section type and attributes.
96  unsigned TAA = getTypeAndAttributes();
97  if (TAA == 0) {
98    OS << '\n';
99    return;
100  }
101
102  MachO::SectionType SectionType = getType();
103  assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE &&
104         "Invalid SectionType specified!");
105
106  if (SectionTypeDescriptors[SectionType].AssemblerName) {
107    OS << ',';
108    OS << SectionTypeDescriptors[SectionType].AssemblerName;
109  } else {
110    // If we have no name for the attribute, stop here.
111    OS << '\n';
112    return;
113  }
114
115  // If we don't have any attributes, we're done.
116  unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES;
117  if (SectionAttrs == 0) {
118    // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
119    // the attribute specifier.
120    if (Reserved2 != 0)
121      OS << ",none," << Reserved2;
122    OS << '\n';
123    return;
124  }
125
126  // Check each attribute to see if we have it.
127  char Separator = ',';
128  for (unsigned i = 0;
129       SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
130       ++i) {
131    // Check to see if we have this attribute.
132    if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
133      continue;
134
135    // Yep, clear it and print it.
136    SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
137
138    OS << Separator;
139    if (SectionAttrDescriptors[i].AssemblerName)
140      OS << SectionAttrDescriptors[i].AssemblerName;
141    else
142      OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
143    Separator = '+';
144  }
145
146  assert(SectionAttrs == 0 && "Unknown section attributes!");
147
148  // If we have a S_SYMBOL_STUBS size specified, print it.
149  if (Reserved2 != 0)
150    OS << ',' << Reserved2;
151  OS << '\n';
152}
153
154bool MCSectionMachO::UseCodeAlign() const {
155  return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
156}
157
158bool MCSectionMachO::isVirtualSection() const {
159  return (getType() == MachO::S_ZEROFILL ||
160          getType() == MachO::S_GB_ZEROFILL ||
161          getType() == MachO::S_THREAD_LOCAL_ZEROFILL);
162}
163
164/// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
165/// This is a string that can appear after a .section directive in a mach-o
166/// flavored .s file.  If successful, this fills in the specified Out
167/// parameters and returns an empty string.  When an invalid section
168/// specifier is present, this returns a string indicating the problem.
169std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
170                                                  StringRef &Segment,    // Out.
171                                                  StringRef &Section,    // Out.
172                                                  unsigned  &TAA,        // Out.
173                                                  bool      &TAAParsed,  // Out.
174                                                  unsigned  &StubSize) { // Out.
175  TAAParsed = false;
176
177  SmallVector<StringRef, 5> SplitSpec;
178  Spec.split(SplitSpec, ",");
179  // Remove leading and trailing whitespace.
180  auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef {
181    return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef();
182  };
183  Segment = GetEmptyOrTrim(0);
184  Section = GetEmptyOrTrim(1);
185  StringRef SectionType = GetEmptyOrTrim(2);
186  StringRef Attrs = GetEmptyOrTrim(3);
187  StringRef StubSizeStr = GetEmptyOrTrim(4);
188
189  // Verify that the segment is present and not too long.
190  if (Segment.empty() || Segment.size() > 16)
191    return "mach-o section specifier requires a segment whose length is "
192           "between 1 and 16 characters";
193
194  // Verify that the section is present and not too long.
195  if (Section.empty())
196    return "mach-o section specifier requires a segment and section "
197           "separated by a comma";
198
199  if (Section.size() > 16)
200    return "mach-o section specifier requires a section whose length is "
201           "between 1 and 16 characters";
202
203  // If there is no comma after the section, we're done.
204  TAA = 0;
205  StubSize = 0;
206  if (SectionType.empty())
207    return "";
208
209  // Figure out which section type it is.
210  auto TypeDescriptor = std::find_if(
211      std::begin(SectionTypeDescriptors), std::end(SectionTypeDescriptors),
212      [&](decltype(*SectionTypeDescriptors) &Descriptor) {
213        return Descriptor.AssemblerName &&
214               SectionType == Descriptor.AssemblerName;
215      });
216
217  // If we didn't find the section type, reject it.
218  if (TypeDescriptor == std::end(SectionTypeDescriptors))
219    return "mach-o section specifier uses an unknown section type";
220
221  // Remember the TypeID.
222  TAA = TypeDescriptor - std::begin(SectionTypeDescriptors);
223  TAAParsed = true;
224
225  // If we have no comma after the section type, there are no attributes.
226  if (Attrs.empty()) {
227    // S_SYMBOL_STUBS always require a symbol stub size specifier.
228    if (TAA == MachO::S_SYMBOL_STUBS)
229      return "mach-o section specifier of type 'symbol_stubs' requires a size "
230             "specifier";
231    return "";
232  }
233
234  // The attribute list is a '+' separated list of attributes.
235  SmallVector<StringRef, 1> SectionAttrs;
236  Attrs.split(SectionAttrs, "+", /*MaxSplit=*/-1, /*KeepEmpty=*/false);
237
238  for (StringRef &SectionAttr : SectionAttrs) {
239    auto AttrDescriptorI = std::find_if(
240        std::begin(SectionAttrDescriptors), std::end(SectionAttrDescriptors),
241        [&](decltype(*SectionAttrDescriptors) &Descriptor) {
242          return Descriptor.AssemblerName &&
243                 SectionAttr.trim() == Descriptor.AssemblerName;
244        });
245    if (AttrDescriptorI == std::end(SectionAttrDescriptors))
246      return "mach-o section specifier has invalid attribute";
247
248    TAA |= AttrDescriptorI->AttrFlag;
249  }
250
251  // Okay, we've parsed the section attributes, see if we have a stub size spec.
252  if (StubSizeStr.empty()) {
253    // S_SYMBOL_STUBS always require a symbol stub size specifier.
254    if (TAA == MachO::S_SYMBOL_STUBS)
255      return "mach-o section specifier of type 'symbol_stubs' requires a size "
256      "specifier";
257    return "";
258  }
259
260  // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
261  if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS)
262    return "mach-o section specifier cannot have a stub size specified because "
263           "it does not have type 'symbol_stubs'";
264
265  // Convert the stub size from a string to an integer.
266  if (StubSizeStr.getAsInteger(0, StubSize))
267    return "mach-o section specifier has a malformed stub size";
268
269  return "";
270}
271