lib/MC/MCSectionMachO.cpp

   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>
  14 using 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.
  19 static 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.
  53 static const struct {
  54   unsigned AttrFlag;
  55   const char *AssemblerName, *EnumName;
  56 } SectionAttrDescriptors[] = {
  57 #define ENTRY(ASMNAME, ENUM) \
  58   { MCSectionMachO::ENUM, ASMNAME, #ENUM },
  59 ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
  60 ENTRY("no_toc",              S_ATTR_NO_TOC)
  61 ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
  62 ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
  63 ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
  64 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
  65 ENTRY("debug",               S_ATTR_DEBUG)
  66 ENTRY(0 /*FIXME*/,           S_ATTR_SOME_INSTRUCTIONS)
  67 ENTRY(0 /*FIXME*/,           S_ATTR_EXT_RELOC)
  68 ENTRY(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
  75 MCSectionMachO::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
  93 void 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
 156 bool MCSectionMachO::UseCodeAlign() const {
 157   return hasAttribute(MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS);
 158 }
 159
 160 bool 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.
 167 static 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.
 179 std::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 }