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 constexpr struct {
  20   StringLiteral AssemblerName, EnumName;
  21 } SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE + 1] = {
  22     {StringLiteral("regular"), StringLiteral("S_REGULAR")}, // 0x00
  23     {StringLiteral(""), StringLiteral("S_ZEROFILL")},       // 0x01
  24     {StringLiteral("cstring_literals"),
  25      StringLiteral("S_CSTRING_LITERALS")}, // 0x02
  26     {StringLiteral("4byte_literals"),
  27      StringLiteral("S_4BYTE_LITERALS")}, // 0x03
  28     {StringLiteral("8byte_literals"),
  29      StringLiteral("S_8BYTE_LITERALS")}, // 0x04
  30     {StringLiteral("literal_pointers"),
  31      StringLiteral("S_LITERAL_POINTERS")}, // 0x05
  32     {StringLiteral("non_lazy_symbol_pointers"),
  33      StringLiteral("S_NON_LAZY_SYMBOL_POINTERS")}, // 0x06
  34     {StringLiteral("lazy_symbol_pointers"),
  35      StringLiteral("S_LAZY_SYMBOL_POINTERS")},                        // 0x07
  36     {StringLiteral("symbol_stubs"), StringLiteral("S_SYMBOL_STUBS")}, // 0x08
  37     {StringLiteral("mod_init_funcs"),
  38      StringLiteral("S_MOD_INIT_FUNC_POINTERS")}, // 0x09
  39     {StringLiteral("mod_term_funcs"),
  40      StringLiteral("S_MOD_TERM_FUNC_POINTERS")},                     // 0x0A
  41     {StringLiteral("coalesced"), StringLiteral("S_COALESCED")},      // 0x0B
  42     {StringLiteral("") /*FIXME??*/, StringLiteral("S_GB_ZEROFILL")}, // 0x0C
  43     {StringLiteral("interposing"), StringLiteral("S_INTERPOSING")},  // 0x0D
  44     {StringLiteral("16byte_literals"),
  45      StringLiteral("S_16BYTE_LITERALS")},                           // 0x0E
  46     {StringLiteral("") /*FIXME??*/, StringLiteral("S_DTRACE_DOF")}, // 0x0F
  47     {StringLiteral("") /*FIXME??*/,
  48      StringLiteral("S_LAZY_DYLIB_SYMBOL_POINTERS")}, // 0x10
  49     {StringLiteral("thread_local_regular"),
  50      StringLiteral("S_THREAD_LOCAL_REGULAR")}, // 0x11
  51     {StringLiteral("thread_local_zerofill"),
  52      StringLiteral("S_THREAD_LOCAL_ZEROFILL")}, // 0x12
  53     {StringLiteral("thread_local_variables"),
  54      StringLiteral("S_THREAD_LOCAL_VARIABLES")}, // 0x13
  55     {StringLiteral("thread_local_variable_pointers"),
  56      StringLiteral("S_THREAD_LOCAL_VARIABLE_POINTERS")}, // 0x14
  57     {StringLiteral("thread_local_init_function_pointers"),
  58      StringLiteral("S_THREAD_LOCAL_INIT_FUNCTION_POINTERS")}, // 0x15
  59 };
  60
  61 /// SectionAttrDescriptors - This is an array of descriptors for section
  62 /// attributes.  Unlike the SectionTypeDescriptors, this is not directly indexed
  63 /// by attribute, instead it is searched.
  64 static constexpr struct {
  65   unsigned AttrFlag;
  66   StringLiteral AssemblerName, EnumName;
  67 } SectionAttrDescriptors[] = {
  68 #define ENTRY(ASMNAME, ENUM) \
  69   { MachO::ENUM, StringLiteral(ASMNAME), StringLiteral(#ENUM) },
  70 ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
  71 ENTRY("no_toc",              S_ATTR_NO_TOC)
  72 ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
  73 ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
  74 ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
  75 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
  76 ENTRY("debug",               S_ATTR_DEBUG)
  77 ENTRY("" /*FIXME*/,          S_ATTR_SOME_INSTRUCTIONS)
  78 ENTRY("" /*FIXME*/,          S_ATTR_EXT_RELOC)
  79 ENTRY("" /*FIXME*/,          S_ATTR_LOC_RELOC)
  80 #undef ENTRY
  81   { 0, StringLiteral("none"), StringLiteral("") }, // used if section has no attributes but has a stub size
  82 };
  83
  84 MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
  85                                unsigned TAA, unsigned reserved2, SectionKind K,
  86                                MCSymbol *Begin)
  87     : MCSection(SV_MachO, K, Begin), TypeAndAttributes(TAA),
  88       Reserved2(reserved2) {
  89   assert(Segment.size() <= 16 && Section.size() <= 16 &&
  90          "Segment or section string too long");
  91   for (unsigned i = 0; i != 16; ++i) {
  92     if (i < Segment.size())
  93       SegmentName[i] = Segment[i];
  94     else
  95       SegmentName[i] = 0;
  96
  97     if (i < Section.size())
  98       SectionName[i] = Section[i];
  99     else
 100       SectionName[i] = 0;
 101   }
 102 }
 103
 104 void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
 105                                           raw_ostream &OS,
 106                                           const MCExpr *Subsection) const {
 107   OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
 108
 109   // Get the section type and attributes.
 110   unsigned TAA = getTypeAndAttributes();
 111   if (TAA == 0) {
 112     OS << '\n';
 113     return;
 114   }
 115
 116   MachO::SectionType SectionType = getType();
 117   assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE &&
 118          "Invalid SectionType specified!");
 119
 120   if (!SectionTypeDescriptors[SectionType].AssemblerName.empty()) {
 121     OS << ',';
 122     OS << SectionTypeDescriptors[SectionType].AssemblerName;
 123   } else {
 124     // If we have no name for the attribute, stop here.
 125     OS << '\n';
 126     return;
 127   }
 128
 129   // If we don't have any attributes, we're done.
 130   unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES;
 131   if (SectionAttrs == 0) {
 132     // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
 133     // the attribute specifier.
 134     if (Reserved2 != 0)
 135       OS << ",none," << Reserved2;
 136     OS << '\n';
 137     return;
 138   }
 139
 140   // Check each attribute to see if we have it.
 141   char Separator = ',';
 142   for (unsigned i = 0;
 143        SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
 144        ++i) {
 145     // Check to see if we have this attribute.
 146     if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
 147       continue;
 148
 149     // Yep, clear it and print it.
 150     SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
 151
 152     OS << Separator;
 153     if (!SectionAttrDescriptors[i].AssemblerName.empty())
 154       OS << SectionAttrDescriptors[i].AssemblerName;
 155     else
 156       OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
 157     Separator = '+';
 158   }
 159
 160   assert(SectionAttrs == 0 && "Unknown section attributes!");
 161
 162   // If we have a S_SYMBOL_STUBS size specified, print it.
 163   if (Reserved2 != 0)
 164     OS << ',' << Reserved2;
 165   OS << '\n';
 166 }
 167
 168 bool MCSectionMachO::UseCodeAlign() const {
 169   return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
 170 }
 171
 172 bool MCSectionMachO::isVirtualSection() const {
 173   return (getType() == MachO::S_ZEROFILL ||
 174           getType() == MachO::S_GB_ZEROFILL ||
 175           getType() == MachO::S_THREAD_LOCAL_ZEROFILL);
 176 }
 177
 178 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
 179 /// This is a string that can appear after a .section directive in a mach-o
 180 /// flavored .s file.  If successful, this fills in the specified Out
 181 /// parameters and returns an empty string.  When an invalid section
 182 /// specifier is present, this returns a string indicating the problem.
 183 std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
 184                                                   StringRef &Segment,    // Out.
 185                                                   StringRef &Section,    // Out.
 186                                                   unsigned  &TAA,        // Out.
 187                                                   bool      &TAAParsed,  // Out.
 188                                                   unsigned  &StubSize) { // Out.
 189   TAAParsed = false;
 190
 191   SmallVector<StringRef, 5> SplitSpec;
 192   Spec.split(SplitSpec, ',');
 193   // Remove leading and trailing whitespace.
 194   auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef {
 195     return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef();
 196   };
 197   Segment = GetEmptyOrTrim(0);
 198   Section = GetEmptyOrTrim(1);
 199   StringRef SectionType = GetEmptyOrTrim(2);
 200   StringRef Attrs = GetEmptyOrTrim(3);
 201   StringRef StubSizeStr = GetEmptyOrTrim(4);
 202
 203   // Verify that the segment is present and not too long.
 204   if (Segment.empty() || Segment.size() > 16)
 205     return "mach-o section specifier requires a segment whose length is "
 206            "between 1 and 16 characters";
 207
 208   // Verify that the section is present and not too long.
 209   if (Section.empty())
 210     return "mach-o section specifier requires a segment and section "
 211            "separated by a comma";
 212
 213   if (Section.size() > 16)
 214     return "mach-o section specifier requires a section whose length is "
 215            "between 1 and 16 characters";
 216
 217   // If there is no comma after the section, we're done.
 218   TAA = 0;
 219   StubSize = 0;
 220   if (SectionType.empty())
 221     return "";
 222
 223   // Figure out which section type it is.
 224   auto TypeDescriptor = std::find_if(
 225       std::begin(SectionTypeDescriptors), std::end(SectionTypeDescriptors),
 226       [&](decltype(*SectionTypeDescriptors) &Descriptor) {
 227         return SectionType == Descriptor.AssemblerName;
 228       });
 229
 230   // If we didn't find the section type, reject it.
 231   if (TypeDescriptor == std::end(SectionTypeDescriptors))
 232     return "mach-o section specifier uses an unknown section type";
 233
 234   // Remember the TypeID.
 235   TAA = TypeDescriptor - std::begin(SectionTypeDescriptors);
 236   TAAParsed = true;
 237
 238   // If we have no comma after the section type, there are no attributes.
 239   if (Attrs.empty()) {
 240     // S_SYMBOL_STUBS always require a symbol stub size specifier.
 241     if (TAA == MachO::S_SYMBOL_STUBS)
 242       return "mach-o section specifier of type 'symbol_stubs' requires a size "
 243              "specifier";
 244     return "";
 245   }
 246
 247   // The attribute list is a '+' separated list of attributes.
 248   SmallVector<StringRef, 1> SectionAttrs;
 249   Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
 250
 251   for (StringRef &SectionAttr : SectionAttrs) {
 252     auto AttrDescriptorI = std::find_if(
 253         std::begin(SectionAttrDescriptors), std::end(SectionAttrDescriptors),
 254         [&](decltype(*SectionAttrDescriptors) &Descriptor) {
 255           return SectionAttr.trim() == Descriptor.AssemblerName;
 256         });
 257     if (AttrDescriptorI == std::end(SectionAttrDescriptors))
 258       return "mach-o section specifier has invalid attribute";
 259
 260     TAA |= AttrDescriptorI->AttrFlag;
 261   }
 262
 263   // Okay, we've parsed the section attributes, see if we have a stub size spec.
 264   if (StubSizeStr.empty()) {
 265     // S_SYMBOL_STUBS always require a symbol stub size specifier.
 266     if (TAA == MachO::S_SYMBOL_STUBS)
 267       return "mach-o section specifier of type 'symbol_stubs' requires a size "
 268       "specifier";
 269     return "";
 270   }
 271
 272   // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
 273   if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS)
 274     return "mach-o section specifier cannot have a stub size specified because "
 275            "it does not have type 'symbol_stubs'";
 276
 277   // Convert the stub size from a string to an integer.
 278   if (StubSizeStr.getAsInteger(0, StubSize))
 279     return "mach-o section specifier has a malformed stub size";
 280
 281   return "";
 282 }