llvm/lib/MC/MCSectionMachO.cpp

   1 //===- lib/MC/MCSectionMachO.cpp - MachO Code Section Representation ------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/MC/MCSectionMachO.h"
  10 #include "llvm/MC/SectionKind.h"
  11 #include "llvm/Support/raw_ostream.h"
  12
  13 namespace llvm {
  14 class MCAsmInfo;
  15 class MCExpr;
  16 class MCSymbol;
  17 class Triple;
  18 } // namespace llvm
  19
  20 using namespace llvm;
  21
  22 /// SectionTypeDescriptors - These are strings that describe the various section
  23 /// types.  This *must* be kept in order with and stay synchronized with the
  24 /// section type list.
  25 static constexpr struct {
  26   StringLiteral AssemblerName, EnumName;
  27 } SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE + 1] = {
  28     {StringLiteral("regular"), StringLiteral("S_REGULAR")}, // 0x00
  29     {StringLiteral("zerofill"), StringLiteral("S_ZEROFILL")}, // 0x01
  30     {StringLiteral("cstring_literals"),
  31      StringLiteral("S_CSTRING_LITERALS")}, // 0x02
  32     {StringLiteral("4byte_literals"),
  33      StringLiteral("S_4BYTE_LITERALS")}, // 0x03
  34     {StringLiteral("8byte_literals"),
  35      StringLiteral("S_8BYTE_LITERALS")}, // 0x04
  36     {StringLiteral("literal_pointers"),
  37      StringLiteral("S_LITERAL_POINTERS")}, // 0x05
  38     {StringLiteral("non_lazy_symbol_pointers"),
  39      StringLiteral("S_NON_LAZY_SYMBOL_POINTERS")}, // 0x06
  40     {StringLiteral("lazy_symbol_pointers"),
  41      StringLiteral("S_LAZY_SYMBOL_POINTERS")},                        // 0x07
  42     {StringLiteral("symbol_stubs"), StringLiteral("S_SYMBOL_STUBS")}, // 0x08
  43     {StringLiteral("mod_init_funcs"),
  44      StringLiteral("S_MOD_INIT_FUNC_POINTERS")}, // 0x09
  45     {StringLiteral("mod_term_funcs"),
  46      StringLiteral("S_MOD_TERM_FUNC_POINTERS")},                     // 0x0A
  47     {StringLiteral("coalesced"), StringLiteral("S_COALESCED")},      // 0x0B
  48     {StringLiteral("") /*FIXME??*/, StringLiteral("S_GB_ZEROFILL")}, // 0x0C
  49     {StringLiteral("interposing"), StringLiteral("S_INTERPOSING")},  // 0x0D
  50     {StringLiteral("16byte_literals"),
  51      StringLiteral("S_16BYTE_LITERALS")},                           // 0x0E
  52     {StringLiteral("") /*FIXME??*/, StringLiteral("S_DTRACE_DOF")}, // 0x0F
  53     {StringLiteral("") /*FIXME??*/,
  54      StringLiteral("S_LAZY_DYLIB_SYMBOL_POINTERS")}, // 0x10
  55     {StringLiteral("thread_local_regular"),
  56      StringLiteral("S_THREAD_LOCAL_REGULAR")}, // 0x11
  57     {StringLiteral("thread_local_zerofill"),
  58      StringLiteral("S_THREAD_LOCAL_ZEROFILL")}, // 0x12
  59     {StringLiteral("thread_local_variables"),
  60      StringLiteral("S_THREAD_LOCAL_VARIABLES")}, // 0x13
  61     {StringLiteral("thread_local_variable_pointers"),
  62      StringLiteral("S_THREAD_LOCAL_VARIABLE_POINTERS")}, // 0x14
  63     {StringLiteral("thread_local_init_function_pointers"),
  64      StringLiteral("S_THREAD_LOCAL_INIT_FUNCTION_POINTERS")}, // 0x15
  65     {StringLiteral("") /* linker-synthesized */,
  66      StringLiteral("S_INIT_FUNC_OFFSETS")}, // 0x16
  67 };
  68
  69 /// SectionAttrDescriptors - This is an array of descriptors for section
  70 /// attributes.  Unlike the SectionTypeDescriptors, this is not directly indexed
  71 /// by attribute, instead it is searched.
  72 static constexpr struct {
  73   unsigned AttrFlag;
  74   StringLiteral AssemblerName, EnumName;
  75 } SectionAttrDescriptors[] = {
  76 #define ENTRY(ASMNAME, ENUM) \
  77   { MachO::ENUM, StringLiteral(ASMNAME), StringLiteral(#ENUM) },
  78 ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
  79 ENTRY("no_toc",              S_ATTR_NO_TOC)
  80 ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
  81 ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
  82 ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
  83 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
  84 ENTRY("debug",               S_ATTR_DEBUG)
  85 ENTRY("" /*FIXME*/,          S_ATTR_SOME_INSTRUCTIONS)
  86 ENTRY("" /*FIXME*/,          S_ATTR_EXT_RELOC)
  87 ENTRY("" /*FIXME*/,          S_ATTR_LOC_RELOC)
  88 #undef ENTRY
  89   { 0, StringLiteral("none"), StringLiteral("") }, // used if section has no attributes but has a stub size
  90 };
  91
  92 MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
  93                                unsigned TAA, unsigned reserved2, SectionKind K,
  94                                MCSymbol *Begin)
  95     : MCSection(SV_MachO, Section, K.isText(),
  96                 MachO::isVirtualSection(TAA & MachO::SECTION_TYPE), Begin),
  97       TypeAndAttributes(TAA), Reserved2(reserved2) {
  98   assert(Segment.size() <= 16 && Section.size() <= 16 &&
  99          "Segment or section string too long");
 100   for (unsigned i = 0; i != 16; ++i) {
 101     if (i < Segment.size())
 102       SegmentName[i] = Segment[i];
 103     else
 104       SegmentName[i] = 0;
 105   }
 106 }
 107
 108 void MCSectionMachO::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
 109                                           raw_ostream &OS,
 110                                           uint32_t Subsection) const {
 111   OS << "\t.section\t" << getSegmentName() << ',' << getName();
 112
 113   // Get the section type and attributes.
 114   unsigned TAA = getTypeAndAttributes();
 115   if (TAA == 0) {
 116     OS << '\n';
 117     return;
 118   }
 119
 120   MachO::SectionType SectionType = getType();
 121   assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE &&
 122          "Invalid SectionType specified!");
 123
 124   if (!SectionTypeDescriptors[SectionType].AssemblerName.empty()) {
 125     OS << ',';
 126     OS << SectionTypeDescriptors[SectionType].AssemblerName;
 127   } else {
 128     // If we have no name for the attribute, stop here.
 129     OS << '\n';
 130     return;
 131   }
 132
 133   // If we don't have any attributes, we're done.
 134   unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES;
 135   if (SectionAttrs == 0) {
 136     // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
 137     // the attribute specifier.
 138     if (Reserved2 != 0)
 139       OS << ",none," << Reserved2;
 140     OS << '\n';
 141     return;
 142   }
 143
 144   // Check each attribute to see if we have it.
 145   char Separator = ',';
 146   for (unsigned i = 0;
 147        SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
 148        ++i) {
 149     // Check to see if we have this attribute.
 150     if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
 151       continue;
 152
 153     // Yep, clear it and print it.
 154     SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
 155
 156     OS << Separator;
 157     if (!SectionAttrDescriptors[i].AssemblerName.empty())
 158       OS << SectionAttrDescriptors[i].AssemblerName;
 159     else
 160       OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
 161     Separator = '+';
 162   }
 163
 164   assert(SectionAttrs == 0 && "Unknown section attributes!");
 165
 166   // If we have a S_SYMBOL_STUBS size specified, print it.
 167   if (Reserved2 != 0)
 168     OS << ',' << Reserved2;
 169   OS << '\n';
 170 }
 171
 172 bool MCSectionMachO::useCodeAlign() const {
 173   return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
 174 }
 175
 176 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
 177 /// This is a string that can appear after a .section directive in a mach-o
 178 /// flavored .s file.  If successful, this fills in the specified Out
 179 /// parameters and returns an empty string.  When an invalid section
 180 /// specifier is present, this returns a string indicating the problem.
 181 Error MCSectionMachO::ParseSectionSpecifier(StringRef Spec,       // In.
 182                                             StringRef &Segment,   // Out.
 183                                             StringRef &Section,   // Out.
 184                                             unsigned &TAA,        // Out.
 185                                             bool &TAAParsed,      // Out.
 186                                             unsigned &StubSize) { // Out.
 187   TAAParsed = false;
 188
 189   SmallVector<StringRef, 5> SplitSpec;
 190   Spec.split(SplitSpec, ',');
 191   // Remove leading and trailing whitespace.
 192   auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef {
 193     return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef();
 194   };
 195   Segment = GetEmptyOrTrim(0);
 196   Section = GetEmptyOrTrim(1);
 197   StringRef SectionType = GetEmptyOrTrim(2);
 198   StringRef Attrs = GetEmptyOrTrim(3);
 199   StringRef StubSizeStr = GetEmptyOrTrim(4);
 200
 201   // Verify that the section is present.
 202   if (Section.empty())
 203     return createStringError(inconvertibleErrorCode(),
 204                              "mach-o section specifier requires a segment "
 205                              "and section separated by a comma");
 206
 207   // Verify that the section is not too long.
 208   if (Section.size() > 16)
 209     return createStringError(inconvertibleErrorCode(),
 210                              "mach-o section specifier requires a section "
 211                              "whose length is between 1 and 16 characters");
 212
 213   // If there is no comma after the section, we're done.
 214   TAA = 0;
 215   StubSize = 0;
 216   if (SectionType.empty())
 217     return Error::success();
 218
 219   // Figure out which section type it is.
 220   auto TypeDescriptor =
 221       llvm::find_if(SectionTypeDescriptors,
 222                     [&](decltype(*SectionTypeDescriptors) &Descriptor) {
 223                       return SectionType == Descriptor.AssemblerName;
 224                     });
 225
 226   // If we didn't find the section type, reject it.
 227   if (TypeDescriptor == std::end(SectionTypeDescriptors))
 228     return createStringError(inconvertibleErrorCode(),
 229                              "mach-o section specifier uses an unknown "
 230                              "section type");
 231
 232   // Remember the TypeID.
 233   TAA = TypeDescriptor - std::begin(SectionTypeDescriptors);
 234   TAAParsed = true;
 235
 236   // If we have no comma after the section type, there are no attributes.
 237   if (Attrs.empty()) {
 238     // S_SYMBOL_STUBS always require a symbol stub size specifier.
 239     if (TAA == MachO::S_SYMBOL_STUBS)
 240       return createStringError(inconvertibleErrorCode(),
 241                                "mach-o section specifier of type "
 242                                "'symbol_stubs' requires a size specifier");
 243     return Error::success();
 244   }
 245
 246   // The attribute list is a '+' separated list of attributes.
 247   SmallVector<StringRef, 1> SectionAttrs;
 248   Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
 249
 250   for (StringRef &SectionAttr : SectionAttrs) {
 251     auto AttrDescriptorI =
 252         llvm::find_if(SectionAttrDescriptors,
 253                       [&](decltype(*SectionAttrDescriptors) &Descriptor) {
 254                         return SectionAttr.trim() == Descriptor.AssemblerName;
 255                       });
 256     if (AttrDescriptorI == std::end(SectionAttrDescriptors))
 257       return createStringError(inconvertibleErrorCode(),
 258                                "mach-o section specifier has invalid "
 259                                "attribute");
 260
 261     TAA |= AttrDescriptorI->AttrFlag;
 262   }
 263
 264   // Okay, we've parsed the section attributes, see if we have a stub size spec.
 265   if (StubSizeStr.empty()) {
 266     // S_SYMBOL_STUBS always require a symbol stub size specifier.
 267     if (TAA == MachO::S_SYMBOL_STUBS)
 268       return createStringError(inconvertibleErrorCode(),
 269                                "mach-o section specifier of type "
 270                                "'symbol_stubs' requires a size specifier");
 271     return Error::success();
 272   }
 273
 274   // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
 275   if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS)
 276     return createStringError(inconvertibleErrorCode(),
 277                              "mach-o section specifier cannot have a stub "
 278                              "size specified because it does not have type "
 279                              "'symbol_stubs'");
 280
 281   // Convert the stub size from a string to an integer.
 282   if (StubSizeStr.getAsInteger(0, StubSize))
 283     return createStringError(inconvertibleErrorCode(),
 284                              "mach-o section specifier has a malformed "
 285                              "stub size");
 286
 287   return Error::success();
 288 }
 289
 290 void MCSectionMachO::allocAtoms() {
 291   auto *L = curFragList();
 292   if (L->Tail)
 293     Atoms.resize(L->Tail->getLayoutOrder() + 1);
 294 }
 295
 296 const MCSymbol *MCSectionMachO::getAtom(size_t I) const {
 297   return I < Atoms.size() ? Atoms[I] : nullptr;
 298 }
 299
 300 void MCSectionMachO::setAtom(size_t I, const MCSymbol *Sym) { Atoms[I] = Sym; }