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 } 294