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 }; 66 67 /// SectionAttrDescriptors - This is an array of descriptors for section 68 /// attributes. Unlike the SectionTypeDescriptors, this is not directly indexed 69 /// by attribute, instead it is searched. 70 static constexpr struct { 71 unsigned AttrFlag; 72 StringLiteral AssemblerName, EnumName; 73 } SectionAttrDescriptors[] = { 74 #define ENTRY(ASMNAME, ENUM) \ 75 { MachO::ENUM, StringLiteral(ASMNAME), StringLiteral(#ENUM) }, 76 ENTRY("pure_instructions", S_ATTR_PURE_INSTRUCTIONS) 77 ENTRY("no_toc", S_ATTR_NO_TOC) 78 ENTRY("strip_static_syms", S_ATTR_STRIP_STATIC_SYMS) 79 ENTRY("no_dead_strip", S_ATTR_NO_DEAD_STRIP) 80 ENTRY("live_support", S_ATTR_LIVE_SUPPORT) 81 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE) 82 ENTRY("debug", S_ATTR_DEBUG) 83 ENTRY("" /*FIXME*/, S_ATTR_SOME_INSTRUCTIONS) 84 ENTRY("" /*FIXME*/, S_ATTR_EXT_RELOC) 85 ENTRY("" /*FIXME*/, S_ATTR_LOC_RELOC) 86 #undef ENTRY 87 { 0, StringLiteral("none"), StringLiteral("") }, // used if section has no attributes but has a stub size 88 }; 89 90 MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section, 91 unsigned TAA, unsigned reserved2, SectionKind K, 92 MCSymbol *Begin) 93 : MCSection(SV_MachO, Section, K, Begin), TypeAndAttributes(TAA), 94 Reserved2(reserved2) { 95 assert(Segment.size() <= 16 && Section.size() <= 16 && 96 "Segment or section string too long"); 97 for (unsigned i = 0; i != 16; ++i) { 98 if (i < Segment.size()) 99 SegmentName[i] = Segment[i]; 100 else 101 SegmentName[i] = 0; 102 } 103 } 104 105 void MCSectionMachO::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T, 106 raw_ostream &OS, 107 const MCExpr *Subsection) const { 108 OS << "\t.section\t" << getSegmentName() << ',' << getName(); 109 110 // Get the section type and attributes. 111 unsigned TAA = getTypeAndAttributes(); 112 if (TAA == 0) { 113 OS << '\n'; 114 return; 115 } 116 117 MachO::SectionType SectionType = getType(); 118 assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE && 119 "Invalid SectionType specified!"); 120 121 if (!SectionTypeDescriptors[SectionType].AssemblerName.empty()) { 122 OS << ','; 123 OS << SectionTypeDescriptors[SectionType].AssemblerName; 124 } else { 125 // If we have no name for the attribute, stop here. 126 OS << '\n'; 127 return; 128 } 129 130 // If we don't have any attributes, we're done. 131 unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES; 132 if (SectionAttrs == 0) { 133 // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as 134 // the attribute specifier. 135 if (Reserved2 != 0) 136 OS << ",none," << Reserved2; 137 OS << '\n'; 138 return; 139 } 140 141 // Check each attribute to see if we have it. 142 char Separator = ','; 143 for (unsigned i = 0; 144 SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag; 145 ++i) { 146 // Check to see if we have this attribute. 147 if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0) 148 continue; 149 150 // Yep, clear it and print it. 151 SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag; 152 153 OS << Separator; 154 if (!SectionAttrDescriptors[i].AssemblerName.empty()) 155 OS << SectionAttrDescriptors[i].AssemblerName; 156 else 157 OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>"; 158 Separator = '+'; 159 } 160 161 assert(SectionAttrs == 0 && "Unknown section attributes!"); 162 163 // If we have a S_SYMBOL_STUBS size specified, print it. 164 if (Reserved2 != 0) 165 OS << ',' << Reserved2; 166 OS << '\n'; 167 } 168 169 bool MCSectionMachO::useCodeAlign() const { 170 return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS); 171 } 172 173 bool MCSectionMachO::isVirtualSection() const { 174 return (getType() == MachO::S_ZEROFILL || 175 getType() == MachO::S_GB_ZEROFILL || 176 getType() == MachO::S_THREAD_LOCAL_ZEROFILL); 177 } 178 179 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec". 180 /// This is a string that can appear after a .section directive in a mach-o 181 /// flavored .s file. If successful, this fills in the specified Out 182 /// parameters and returns an empty string. When an invalid section 183 /// specifier is present, this returns a string indicating the problem. 184 Error MCSectionMachO::ParseSectionSpecifier(StringRef Spec, // In. 185 StringRef &Segment, // Out. 186 StringRef &Section, // Out. 187 unsigned &TAA, // Out. 188 bool &TAAParsed, // Out. 189 unsigned &StubSize) { // Out. 190 TAAParsed = false; 191 192 SmallVector<StringRef, 5> SplitSpec; 193 Spec.split(SplitSpec, ','); 194 // Remove leading and trailing whitespace. 195 auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef { 196 return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef(); 197 }; 198 Segment = GetEmptyOrTrim(0); 199 Section = GetEmptyOrTrim(1); 200 StringRef SectionType = GetEmptyOrTrim(2); 201 StringRef Attrs = GetEmptyOrTrim(3); 202 StringRef StubSizeStr = GetEmptyOrTrim(4); 203 204 // Verify that the section is present. 205 if (Section.empty()) 206 return createStringError(inconvertibleErrorCode(), 207 "mach-o section specifier requires a segment " 208 "and section separated by a comma"); 209 210 // Verify that the section is not too long. 211 if (Section.size() > 16) 212 return createStringError(inconvertibleErrorCode(), 213 "mach-o section specifier requires a section " 214 "whose length is 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 Error::success(); 221 222 // Figure out which section type it is. 223 auto TypeDescriptor = 224 llvm::find_if(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 createStringError(inconvertibleErrorCode(), 232 "mach-o section specifier uses an unknown " 233 "section type"); 234 235 // Remember the TypeID. 236 TAA = TypeDescriptor - std::begin(SectionTypeDescriptors); 237 TAAParsed = true; 238 239 // If we have no comma after the section type, there are no attributes. 240 if (Attrs.empty()) { 241 // S_SYMBOL_STUBS always require a symbol stub size specifier. 242 if (TAA == MachO::S_SYMBOL_STUBS) 243 return createStringError(inconvertibleErrorCode(), 244 "mach-o section specifier of type " 245 "'symbol_stubs' requires a size specifier"); 246 return Error::success(); 247 } 248 249 // The attribute list is a '+' separated list of attributes. 250 SmallVector<StringRef, 1> SectionAttrs; 251 Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false); 252 253 for (StringRef &SectionAttr : SectionAttrs) { 254 auto AttrDescriptorI = 255 llvm::find_if(SectionAttrDescriptors, 256 [&](decltype(*SectionAttrDescriptors) &Descriptor) { 257 return SectionAttr.trim() == Descriptor.AssemblerName; 258 }); 259 if (AttrDescriptorI == std::end(SectionAttrDescriptors)) 260 return createStringError(inconvertibleErrorCode(), 261 "mach-o section specifier has invalid " 262 "attribute"); 263 264 TAA |= AttrDescriptorI->AttrFlag; 265 } 266 267 // Okay, we've parsed the section attributes, see if we have a stub size spec. 268 if (StubSizeStr.empty()) { 269 // S_SYMBOL_STUBS always require a symbol stub size specifier. 270 if (TAA == MachO::S_SYMBOL_STUBS) 271 return createStringError(inconvertibleErrorCode(), 272 "mach-o section specifier of type " 273 "'symbol_stubs' requires a size specifier"); 274 return Error::success(); 275 } 276 277 // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS. 278 if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS) 279 return createStringError(inconvertibleErrorCode(), 280 "mach-o section specifier cannot have a stub " 281 "size specified because it does not have type " 282 "'symbol_stubs'"); 283 284 // Convert the stub size from a string to an integer. 285 if (StubSizeStr.getAsInteger(0, StubSize)) 286 return createStringError(inconvertibleErrorCode(), 287 "mach-o section specifier has a malformed " 288 "stub size"); 289 290 return Error::success(); 291 } 292