MCSectionMachO.cpp revision fe40f9551cab75c4576ee03e6a994fe4fb4530d9 
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"
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 const struct {
19  const char *AssemblerName, *EnumName;
20} SectionTypeDescriptors[MCSectionMachO::LAST_KNOWN_SECTION_TYPE+1] = {
21  { "regular",                  "S_REGULAR" },                    // 0x00
22  { 0,                          "S_ZEROFILL" },                   // 0x01
23  { "cstring_literals",         "S_CSTRING_LITERALS" },           // 0x02
24  { "4byte_literals",           "S_4BYTE_LITERALS" },             // 0x03
25  { "8byte_literals",           "S_8BYTE_LITERALS" },             // 0x04
26  { "literal_pointers",         "S_LITERAL_POINTERS" },           // 0x05
27  { "non_lazy_symbol_pointers", "S_NON_LAZY_SYMBOL_POINTERS" },   // 0x06
28  { "lazy_symbol_pointers",     "S_LAZY_SYMBOL_POINTERS" },       // 0x07
29  { "symbol_stubs",             "S_SYMBOL_STUBS" },               // 0x08
30  { "mod_init_funcs",           "S_MOD_INIT_FUNC_POINTERS" },     // 0x09
31  { "mod_term_funcs",           "S_MOD_TERM_FUNC_POINTERS" },     // 0x0A
32  { "coalesced",                "S_COALESCED" },                  // 0x0B
33  { 0, /*FIXME??*/              "S_GB_ZEROFILL" },                // 0x0C
34  { "interposing",              "S_INTERPOSING" },                // 0x0D
35  { "16byte_literals",          "S_16BYTE_LITERALS" },            // 0x0E
36  { 0, /*FIXME??*/              "S_DTRACE_DOF" },                 // 0x0F
37  { 0, /*FIXME??*/              "S_LAZY_DYLIB_SYMBOL_POINTERS" }, // 0x10
38  { "thread_local_regular",     "S_THREAD_LOCAL_REGULAR" },       // 0x11
39  { "thread_local_zerofill",    "S_THREAD_LOCAL_ZEROFILL" },      // 0x12
40  { "thread_local_variables",   "S_THREAD_LOCAL_VARIABLES" },     // 0x13
41  { "thread_local_variable_pointers",
42    "S_THREAD_LOCAL_VARIABLE_POINTERS" },                         // 0x14
43  { "thread_local_init_function_pointers",
44    "S_THREAD_LOCAL_INIT_FUNCTION_POINTERS"},                     // 0x15
45};
46
47
48/// SectionAttrDescriptors - This is an array of descriptors for section
49/// attributes.  Unlike the SectionTypeDescriptors, this is not directly indexed
50/// by attribute, instead it is searched.  The last entry has an AttrFlagEnd
51/// AttrFlag value.
52static const struct {
53  unsigned AttrFlag;
54  const char *AssemblerName, *EnumName;
55} SectionAttrDescriptors[] = {
56#define ENTRY(ASMNAME, ENUM) \
57  { MCSectionMachO::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(0 /*FIXME*/,           S_ATTR_SOME_INSTRUCTIONS)
66ENTRY(0 /*FIXME*/,           S_ATTR_EXT_RELOC)
67ENTRY(0 /*FIXME*/,           S_ATTR_LOC_RELOC)
68#undef ENTRY
69  { 0, "none", 0 }, // used if section has no attributes but has a stub size
70#define AttrFlagEnd 0xffffffff // non legal value, multiple attribute bits set
71  { AttrFlagEnd, 0, 0 }
72};
73
74MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
75                               unsigned TAA, unsigned reserved2, SectionKind K)
76  : MCSection(SV_MachO, K), TypeAndAttributes(TAA), 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) const {
94  OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
95
96  // Get the section type and attributes.
97  unsigned TAA = getTypeAndAttributes();
98  if (TAA == 0) {
99    OS << '\n';
100    return;
101  }
102
103  OS << ',';
104
105  unsigned SectionType = TAA & MCSectionMachO::SECTION_TYPE;
106  assert(SectionType <= MCSectionMachO::LAST_KNOWN_SECTION_TYPE &&
107         "Invalid SectionType specified!");
108
109  if (SectionTypeDescriptors[SectionType].AssemblerName)
110    OS << SectionTypeDescriptors[SectionType].AssemblerName;
111  else
112    OS << "<<" << SectionTypeDescriptors[SectionType].EnumName << ">>";
113
114  // If we don't have any attributes, we're done.
115  unsigned SectionAttrs = TAA & MCSectionMachO::SECTION_ATTRIBUTES;
116  if (SectionAttrs == 0) {
117    // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
118    // the attribute specifier.
119    if (Reserved2 != 0)
120      OS << ",none," << Reserved2;
121    OS << '\n';
122    return;
123  }
124
125  // Check each attribute to see if we have it.
126  char Separator = ',';
127  for (unsigned i = 0; SectionAttrDescriptors[i].AttrFlag; ++i) {
128    // Check to see if we have this attribute.
129    if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
130      continue;
131
132    // Yep, clear it and print it.
133    SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
134
135    OS << Separator;
136    if (SectionAttrDescriptors[i].AssemblerName)
137      OS << SectionAttrDescriptors[i].AssemblerName;
138    else
139      OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
140    Separator = '+';
141  }
142
143  assert(SectionAttrs == 0 && "Unknown section attributes!");
144
145  // If we have a S_SYMBOL_STUBS size specified, print it.
146  if (Reserved2 != 0)
147    OS << ',' << Reserved2;
148  OS << '\n';
149}
150
151bool MCSectionMachO::UseCodeAlign() const {
152  return hasAttribute(MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS);
153}
154
155/// StripSpaces - This removes leading and trailing spaces from the StringRef.
156static void StripSpaces(StringRef &Str) {
157  while (!Str.empty() && isspace(Str[0]))
158    Str = Str.substr(1);
159  while (!Str.empty() && isspace(Str.back()))
160    Str = Str.substr(0, Str.size()-1);
161}
162
163/// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
164/// This is a string that can appear after a .section directive in a mach-o
165/// flavored .s file.  If successful, this fills in the specified Out
166/// parameters and returns an empty string.  When an invalid section
167/// specifier is present, this returns a string indicating the problem.
168std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
169                                                  StringRef &Segment,    // Out.
170                                                  StringRef &Section,    // Out.
171                                                  unsigned  &TAA,        // Out.
172                                                  unsigned  &StubSize) { // Out.
173  // Find the first comma.
174  std::pair<StringRef, StringRef> Comma = Spec.split(',');
175
176  // If there is no comma, we fail.
177  if (Comma.second.empty())
178    return "mach-o section specifier requires a segment and section "
179           "separated by a comma";
180
181  // Capture segment, remove leading and trailing whitespace.
182  Segment = Comma.first;
183  StripSpaces(Segment);
184
185  // Verify that the segment is present and not too long.
186  if (Segment.empty() || Segment.size() > 16)
187    return "mach-o section specifier requires a segment whose length is "
188           "between 1 and 16 characters";
189
190  // Split the section name off from any attributes if present.
191  Comma = Comma.second.split(',');
192
193  // Capture section, remove leading and trailing whitespace.
194  Section = Comma.first;
195  StripSpaces(Section);
196
197  // Verify that the section is present and not too long.
198  if (Section.empty() || Section.size() > 16)
199    return "mach-o section specifier requires a section whose length is "
200           "between 1 and 16 characters";
201
202  // If there is no comma after the section, we're done.
203  TAA = 0;
204  StubSize = 0;
205  if (Comma.second.empty())
206    return "";
207
208  // Otherwise, we need to parse the section type and attributes.
209  Comma = Comma.second.split(',');
210
211  // Get the section type.
212  StringRef SectionType = Comma.first;
213  StripSpaces(SectionType);
214
215  // Figure out which section type it is.
216  unsigned TypeID;
217  for (TypeID = 0; TypeID !=MCSectionMachO::LAST_KNOWN_SECTION_TYPE+1; ++TypeID)
218    if (SectionTypeDescriptors[TypeID].AssemblerName &&
219        SectionType == SectionTypeDescriptors[TypeID].AssemblerName)
220      break;
221
222  // If we didn't find the section type, reject it.
223  if (TypeID > MCSectionMachO::LAST_KNOWN_SECTION_TYPE)
224    return "mach-o section specifier uses an unknown section type";
225
226  // Remember the TypeID.
227  TAA = TypeID;
228
229  // If we have no comma after the section type, there are no attributes.
230  if (Comma.second.empty()) {
231    // S_SYMBOL_STUBS always require a symbol stub size specifier.
232    if (TAA == MCSectionMachO::S_SYMBOL_STUBS)
233      return "mach-o section specifier of type 'symbol_stubs' requires a size "
234             "specifier";
235    return "";
236  }
237
238  // Otherwise, we do have some attributes.  Split off the size specifier if
239  // present.
240  Comma = Comma.second.split(',');
241  StringRef Attrs = Comma.first;
242
243  // The attribute list is a '+' separated list of attributes.
244  std::pair<StringRef, StringRef> Plus = Attrs.split('+');
245
246  while (1) {
247    StringRef Attr = Plus.first;
248    StripSpaces(Attr);
249
250    // Look up the attribute.
251    for (unsigned i = 0; ; ++i) {
252      if (SectionAttrDescriptors[i].AttrFlag == AttrFlagEnd)
253        return "mach-o section specifier has invalid attribute";
254
255      if (SectionAttrDescriptors[i].AssemblerName &&
256          Attr == SectionAttrDescriptors[i].AssemblerName) {
257        TAA |= SectionAttrDescriptors[i].AttrFlag;
258        break;
259      }
260    }
261
262    if (Plus.second.empty()) break;
263    Plus = Plus.second.split('+');
264  };
265
266  // Okay, we've parsed the section attributes, see if we have a stub size spec.
267  if (Comma.second.empty()) {
268    // S_SYMBOL_STUBS always require a symbol stub size specifier.
269    if (TAA == MCSectionMachO::S_SYMBOL_STUBS)
270      return "mach-o section specifier of type 'symbol_stubs' requires a size "
271      "specifier";
272    return "";
273  }
274
275  // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
276  if ((TAA & MCSectionMachO::SECTION_TYPE) != MCSectionMachO::S_SYMBOL_STUBS)
277    return "mach-o section specifier cannot have a stub size specified because "
278           "it does not have type 'symbol_stubs'";
279
280  // Okay, if we do, it must be a number.
281  StringRef StubSizeStr = Comma.second;
282  StripSpaces(StubSizeStr);
283
284  // Convert the stub size from a string to an integer.
285  if (StubSizeStr.getAsInteger(0, StubSize))
286    return "mach-o section specifier has a malformed stub size";
287
288  return "";
289}
290