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