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[MCSectionMachO::LAST_KNOWN_SECTION_TYPE+1] = {
22  { "regular",                  "S_REGULAR" },                    // 0x00
23  { 0,                          "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  { 0, /*FIXME??*/              "S_GB_ZEROFILL" },                // 0x0C
35  { "interposing",              "S_INTERPOSING" },                // 0x0D
36  { "16byte_literals",          "S_16BYTE_LITERALS" },            // 0x0E
37  { 0, /*FIXME??*/              "S_DTRACE_DOF" },                 // 0x0F
38  { 0, /*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.  The last entry has an AttrFlagEnd
52/// AttrFlag value.
53static const struct {
54  unsigned AttrFlag;
55  const char *AssemblerName, *EnumName;
56} SectionAttrDescriptors[] = {
57#define ENTRY(ASMNAME, ENUM) \
58  { MCSectionMachO::ENUM, ASMNAME, #ENUM },
59ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
60ENTRY("no_toc",              S_ATTR_NO_TOC)
61ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
62ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
63ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
64ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
65ENTRY("debug",               S_ATTR_DEBUG)
66ENTRY(0 /*FIXME*/,           S_ATTR_SOME_INSTRUCTIONS)
67ENTRY(0 /*FIXME*/,           S_ATTR_EXT_RELOC)
68ENTRY(0 /*FIXME*/,           S_ATTR_LOC_RELOC)
69#undef ENTRY
70  { 0, "none", 0 }, // used if section has no attributes but has a stub size
71#define AttrFlagEnd 0xffffffff // non legal value, multiple attribute bits set
72  { AttrFlagEnd, 0, 0 }
73};
74
75MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
76                               unsigned TAA, unsigned reserved2, SectionKind K)
77  : MCSection(SV_MachO, K), TypeAndAttributes(TAA), Reserved2(reserved2) {
78  assert(Segment.size() <= 16 && Section.size() <= 16 &&
79         "Segment or section string too long");
80  for (unsigned i = 0; i != 16; ++i) {
81    if (i < Segment.size())
82      SegmentName[i] = Segment[i];
83    else
84      SegmentName[i] = 0;
85
86    if (i < Section.size())
87      SectionName[i] = Section[i];
88    else
89      SectionName[i] = 0;
90  }
91}
92
93void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI,
94                                          raw_ostream &OS) 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  unsigned SectionType = TAA & MCSectionMachO::SECTION_TYPE;
105  assert(SectionType <= MCSectionMachO::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 & MCSectionMachO::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(MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS);
158}
159
160bool MCSectionMachO::isVirtualSection() const {
161  return (getType() == MCSectionMachO::S_ZEROFILL ||
162          getType() == MCSectionMachO::S_GB_ZEROFILL ||
163          getType() == MCSectionMachO::S_THREAD_LOCAL_ZEROFILL);
164}
165
166/// StripSpaces - This removes leading and trailing spaces from the StringRef.
167static void StripSpaces(StringRef &Str) {
168  while (!Str.empty() && isspace(Str[0]))
169    Str = Str.substr(1);
170  while (!Str.empty() && isspace(Str.back()))
171    Str = Str.substr(0, Str.size()-1);
172}
173
174/// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
175/// This is a string that can appear after a .section directive in a mach-o
176/// flavored .s file.  If successful, this fills in the specified Out
177/// parameters and returns an empty string.  When an invalid section
178/// specifier is present, this returns a string indicating the problem.
179std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
180                                                  StringRef &Segment,    // Out.
181                                                  StringRef &Section,    // Out.
182                                                  unsigned  &TAA,        // Out.
183                                                  bool      &TAAParsed,  // Out.
184                                                  unsigned  &StubSize) { // Out.
185  TAAParsed = false;
186  // Find the first comma.
187  std::pair<StringRef, StringRef> Comma = Spec.split(',');
188
189  // If there is no comma, we fail.
190  if (Comma.second.empty())
191    return "mach-o section specifier requires a segment and section "
192           "separated by a comma";
193
194  // Capture segment, remove leading and trailing whitespace.
195  Segment = Comma.first;
196  StripSpaces(Segment);
197
198  // Verify that the segment is present and not too long.
199  if (Segment.empty() || Segment.size() > 16)
200    return "mach-o section specifier requires a segment whose length is "
201           "between 1 and 16 characters";
202
203  // Split the section name off from any attributes if present.
204  Comma = Comma.second.split(',');
205
206  // Capture section, remove leading and trailing whitespace.
207  Section = Comma.first;
208  StripSpaces(Section);
209
210  // Verify that the section is present and not too long.
211  if (Section.empty() || Section.size() > 16)
212    return "mach-o section specifier requires a section whose length is "
213           "between 1 and 16 characters";
214
215  // If there is no comma after the section, we're done.
216  TAA = 0;
217  StubSize = 0;
218  if (Comma.second.empty())
219    return "";
220
221  // Otherwise, we need to parse the section type and attributes.
222  Comma = Comma.second.split(',');
223
224  // Get the section type.
225  StringRef SectionType = Comma.first;
226  StripSpaces(SectionType);
227
228  // Figure out which section type it is.
229  unsigned TypeID;
230  for (TypeID = 0; TypeID !=MCSectionMachO::LAST_KNOWN_SECTION_TYPE+1; ++TypeID)
231    if (SectionTypeDescriptors[TypeID].AssemblerName &&
232        SectionType == SectionTypeDescriptors[TypeID].AssemblerName)
233      break;
234
235  // If we didn't find the section type, reject it.
236  if (TypeID > MCSectionMachO::LAST_KNOWN_SECTION_TYPE)
237    return "mach-o section specifier uses an unknown section type";
238
239  // Remember the TypeID.
240  TAA = TypeID;
241  TAAParsed = true;
242
243  // If we have no comma after the section type, there are no attributes.
244  if (Comma.second.empty()) {
245    // S_SYMBOL_STUBS always require a symbol stub size specifier.
246    if (TAA == MCSectionMachO::S_SYMBOL_STUBS)
247      return "mach-o section specifier of type 'symbol_stubs' requires a size "
248             "specifier";
249    return "";
250  }
251
252  // Otherwise, we do have some attributes.  Split off the size specifier if
253  // present.
254  Comma = Comma.second.split(',');
255  StringRef Attrs = Comma.first;
256
257  // The attribute list is a '+' separated list of attributes.
258  std::pair<StringRef, StringRef> Plus = Attrs.split('+');
259
260  while (1) {
261    StringRef Attr = Plus.first;
262    StripSpaces(Attr);
263
264    // Look up the attribute.
265    for (unsigned i = 0; ; ++i) {
266      if (SectionAttrDescriptors[i].AttrFlag == AttrFlagEnd)
267        return "mach-o section specifier has invalid attribute";
268
269      if (SectionAttrDescriptors[i].AssemblerName &&
270          Attr == SectionAttrDescriptors[i].AssemblerName) {
271        TAA |= SectionAttrDescriptors[i].AttrFlag;
272        break;
273      }
274    }
275
276    if (Plus.second.empty()) break;
277    Plus = Plus.second.split('+');
278  };
279
280  // Okay, we've parsed the section attributes, see if we have a stub size spec.
281  if (Comma.second.empty()) {
282    // S_SYMBOL_STUBS always require a symbol stub size specifier.
283    if (TAA == MCSectionMachO::S_SYMBOL_STUBS)
284      return "mach-o section specifier of type 'symbol_stubs' requires a size "
285      "specifier";
286    return "";
287  }
288
289  // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
290  if ((TAA & MCSectionMachO::SECTION_TYPE) != MCSectionMachO::S_SYMBOL_STUBS)
291    return "mach-o section specifier cannot have a stub size specified because "
292           "it does not have type 'symbol_stubs'";
293
294  // Okay, if we do, it must be a number.
295  StringRef StubSizeStr = Comma.second;
296  StripSpaces(StubSizeStr);
297
298  // Convert the stub size from a string to an integer.
299  if (StubSizeStr.getAsInteger(0, StubSize))
300    return "mach-o section specifier has a malformed stub size";
301
302  return "";
303}
304