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, Begin), TypeAndAttributes(TAA),
  96       Reserved2(reserved2) {
  97   assert(Segment.size() <= 16 && Section.size() <= 16 &&
  98          "Segment or section string too long");
  99   for (unsigned i = 0; i != 16; ++i) {
 100     if (i < Segment.size())
 101       SegmentName[i] = Segment[i];
 102     else
 103       SegmentName[i] = 0;
 104   }
 105 }
 106
 107 void MCSectionMachO::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
 108                                           raw_ostream &OS,
 109                                           const MCExpr *Subsection) const {
 110   OS << "\t.section\t" << getSegmentName() << ',' << getName();
 111
 112   // Get the section type and attributes.
 113   unsigned TAA = getTypeAndAttributes();
 114   if (TAA == 0) {
 115     OS << '\n';
 116     return;
 117   }
 118
 119   MachO::SectionType SectionType = getType();
 120   assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE &&
 121          "Invalid SectionType specified!");
 122
 123   if (!SectionTypeDescriptors[SectionType].AssemblerName.empty()) {
 124     OS << ',';
 125     OS << SectionTypeDescriptors[SectionType].AssemblerName;
 126   } else {
 127     // If we have no name for the attribute, stop here.
 128     OS << '\n';
 129     return;
 130   }
 131
 132   // If we don't have any attributes, we're done.
 133   unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES;
 134   if (SectionAttrs == 0) {
 135     // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
 136     // the attribute specifier.
 137     if (Reserved2 != 0)
 138       OS << ",none," << Reserved2;
 139     OS << '\n';
 140     return;
 141   }
 142
 143   // Check each attribute to see if we have it.
 144   char Separator = ',';
 145   for (unsigned i = 0;
 146        SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
 147        ++i) {
 148     // Check to see if we have this attribute.
 149     if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
 150       continue;
 151
 152     // Yep, clear it and print it.
 153     SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
 154
 155     OS << Separator;
 156     if (!SectionAttrDescriptors[i].AssemblerName.empty())
 157       OS << SectionAttrDescriptors[i].AssemblerName;
 158     else
 159       OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
 160     Separator = '+';
 161   }
 162
 163   assert(SectionAttrs == 0 && "Unknown section attributes!");
 164
 165   // If we have a S_SYMBOL_STUBS size specified, print it.
 166   if (Reserved2 != 0)
 167     OS << ',' << Reserved2;
 168   OS << '\n';
 169 }
 170
 171 bool MCSectionMachO::useCodeAlign() const {
 172   return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
 173 }
 174
 175 bool MCSectionMachO::isVirtualSection() const {
 176   return (getType() == MachO::S_ZEROFILL ||
 177           getType() == MachO::S_GB_ZEROFILL ||
 178           getType() == MachO::S_THREAD_LOCAL_ZEROFILL);
 179 }
 180
 181 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
 182 /// This is a string that can appear after a .section directive in a mach-o
 183 /// flavored .s file.  If successful, this fills in the specified Out
 184 /// parameters and returns an empty string.  When an invalid section
 185 /// specifier is present, this returns a string indicating the problem.
 186 Error MCSectionMachO::ParseSectionSpecifier(StringRef Spec,       // In.
 187                                             StringRef &Segment,   // Out.
 188                                             StringRef &Section,   // Out.
 189                                             unsigned &TAA,        // Out.
 190                                             bool &TAAParsed,      // Out.
 191                                             unsigned &StubSize) { // Out.
 192   TAAParsed = false;
 193
 194   SmallVector<StringRef, 5> SplitSpec;
 195   Spec.split(SplitSpec, ',');
 196   // Remove leading and trailing whitespace.
 197   auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef {
 198     return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef();
 199   };
 200   Segment = GetEmptyOrTrim(0);
 201   Section = GetEmptyOrTrim(1);
 202   StringRef SectionType = GetEmptyOrTrim(2);
 203   StringRef Attrs = GetEmptyOrTrim(3);
 204   StringRef StubSizeStr = GetEmptyOrTrim(4);
 205
 206   // Verify that the section is present.
 207   if (Section.empty())
 208     return createStringError(inconvertibleErrorCode(),
 209                              "mach-o section specifier requires a segment "
 210                              "and section separated by a comma");
 211
 212   // Verify that the section is not too long.
 213   if (Section.size() > 16)
 214     return createStringError(inconvertibleErrorCode(),
 215                              "mach-o section specifier requires a section "
 216                              "whose length is between 1 and 16 characters");
 217
 218   // If there is no comma after the section, we're done.
 219   TAA = 0;
 220   StubSize = 0;
 221   if (SectionType.empty())
 222     return Error::success();
 223
 224   // Figure out which section type it is.
 225   auto TypeDescriptor =
 226       llvm::find_if(SectionTypeDescriptors,
 227                     [&](decltype(*SectionTypeDescriptors) &Descriptor) {
 228                       return SectionType == Descriptor.AssemblerName;
 229                     });
 230
 231   // If we didn't find the section type, reject it.
 232   if (TypeDescriptor == std::end(SectionTypeDescriptors))
 233     return createStringError(inconvertibleErrorCode(),
 234                              "mach-o section specifier uses an unknown "
 235                              "section type");
 236
 237   // Remember the TypeID.
 238   TAA = TypeDescriptor - std::begin(SectionTypeDescriptors);
 239   TAAParsed = true;
 240
 241   // If we have no comma after the section type, there are no attributes.
 242   if (Attrs.empty()) {
 243     // S_SYMBOL_STUBS always require a symbol stub size specifier.
 244     if (TAA == MachO::S_SYMBOL_STUBS)
 245       return createStringError(inconvertibleErrorCode(),
 246                                "mach-o section specifier of type "
 247                                "'symbol_stubs' requires a size specifier");
 248     return Error::success();
 249   }
 250
 251   // The attribute list is a '+' separated list of attributes.
 252   SmallVector<StringRef, 1> SectionAttrs;
 253   Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
 254
 255   for (StringRef &SectionAttr : SectionAttrs) {
 256     auto AttrDescriptorI =
 257         llvm::find_if(SectionAttrDescriptors,
 258                       [&](decltype(*SectionAttrDescriptors) &Descriptor) {
 259                         return SectionAttr.trim() == Descriptor.AssemblerName;
 260                       });
 261     if (AttrDescriptorI == std::end(SectionAttrDescriptors))
 262       return createStringError(inconvertibleErrorCode(),
 263                                "mach-o section specifier has invalid "
 264                                "attribute");
 265
 266     TAA |= AttrDescriptorI->AttrFlag;
 267   }
 268
 269   // Okay, we've parsed the section attributes, see if we have a stub size spec.
 270   if (StubSizeStr.empty()) {
 271     // S_SYMBOL_STUBS always require a symbol stub size specifier.
 272     if (TAA == MachO::S_SYMBOL_STUBS)
 273       return createStringError(inconvertibleErrorCode(),
 274                                "mach-o section specifier of type "
 275                                "'symbol_stubs' requires a size specifier");
 276     return Error::success();
 277   }
 278
 279   // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
 280   if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS)
 281     return createStringError(inconvertibleErrorCode(),
 282                              "mach-o section specifier cannot have a stub "
 283                              "size specified because it does not have type "
 284                              "'symbol_stubs'");
 285
 286   // Convert the stub size from a string to an integer.
 287   if (StubSizeStr.getAsInteger(0, StubSize))
 288     return createStringError(inconvertibleErrorCode(),
 289                              "mach-o section specifier has a malformed "
 290                              "stub size");
 291
 292   return Error::success();
 293 }