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 } 282