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