1 //===- lib/MC/MCSectionMachO.cpp - MachO Code Section Representation ------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "llvm/MC/MCSectionMachO.h" 11 #include "llvm/MC/MCContext.h" 12 #include "llvm/Support/raw_ostream.h" 13 #include <cctype> 14 using namespace llvm; 15 16 /// SectionTypeDescriptors - These are strings that describe the various section 17 /// types. This *must* be kept in order with and stay synchronized with the 18 /// section type list. 19 static const struct { 20 const char *AssemblerName, *EnumName; 21 } SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE+1] = { 22 { "regular", "S_REGULAR" }, // 0x00 23 { nullptr, "S_ZEROFILL" }, // 0x01 24 { "cstring_literals", "S_CSTRING_LITERALS" }, // 0x02 25 { "4byte_literals", "S_4BYTE_LITERALS" }, // 0x03 26 { "8byte_literals", "S_8BYTE_LITERALS" }, // 0x04 27 { "literal_pointers", "S_LITERAL_POINTERS" }, // 0x05 28 { "non_lazy_symbol_pointers", "S_NON_LAZY_SYMBOL_POINTERS" }, // 0x06 29 { "lazy_symbol_pointers", "S_LAZY_SYMBOL_POINTERS" }, // 0x07 30 { "symbol_stubs", "S_SYMBOL_STUBS" }, // 0x08 31 { "mod_init_funcs", "S_MOD_INIT_FUNC_POINTERS" }, // 0x09 32 { "mod_term_funcs", "S_MOD_TERM_FUNC_POINTERS" }, // 0x0A 33 { "coalesced", "S_COALESCED" }, // 0x0B 34 { nullptr, /*FIXME??*/ "S_GB_ZEROFILL" }, // 0x0C 35 { "interposing", "S_INTERPOSING" }, // 0x0D 36 { "16byte_literals", "S_16BYTE_LITERALS" }, // 0x0E 37 { nullptr, /*FIXME??*/ "S_DTRACE_DOF" }, // 0x0F 38 { nullptr, /*FIXME??*/ "S_LAZY_DYLIB_SYMBOL_POINTERS" }, // 0x10 39 { "thread_local_regular", "S_THREAD_LOCAL_REGULAR" }, // 0x11 40 { "thread_local_zerofill", "S_THREAD_LOCAL_ZEROFILL" }, // 0x12 41 { "thread_local_variables", "S_THREAD_LOCAL_VARIABLES" }, // 0x13 42 { "thread_local_variable_pointers", 43 "S_THREAD_LOCAL_VARIABLE_POINTERS" }, // 0x14 44 { "thread_local_init_function_pointers", 45 "S_THREAD_LOCAL_INIT_FUNCTION_POINTERS"}, // 0x15 46 }; 47 48 49 /// SectionAttrDescriptors - This is an array of descriptors for section 50 /// attributes. Unlike the SectionTypeDescriptors, this is not directly indexed 51 /// by attribute, instead it is searched. 52 static const struct { 53 unsigned AttrFlag; 54 const char *AssemblerName, *EnumName; 55 } SectionAttrDescriptors[] = { 56 #define ENTRY(ASMNAME, ENUM) \ 57 { MachO::ENUM, ASMNAME, #ENUM }, 58 ENTRY("pure_instructions", S_ATTR_PURE_INSTRUCTIONS) 59 ENTRY("no_toc", S_ATTR_NO_TOC) 60 ENTRY("strip_static_syms", S_ATTR_STRIP_STATIC_SYMS) 61 ENTRY("no_dead_strip", S_ATTR_NO_DEAD_STRIP) 62 ENTRY("live_support", S_ATTR_LIVE_SUPPORT) 63 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE) 64 ENTRY("debug", S_ATTR_DEBUG) 65 ENTRY(nullptr /*FIXME*/, S_ATTR_SOME_INSTRUCTIONS) 66 ENTRY(nullptr /*FIXME*/, S_ATTR_EXT_RELOC) 67 ENTRY(nullptr /*FIXME*/, S_ATTR_LOC_RELOC) 68 #undef ENTRY 69 { 0, "none", nullptr }, // used if section has no attributes but has a stub size 70 }; 71 72 MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section, 73 unsigned TAA, unsigned reserved2, SectionKind K, 74 MCSymbol *Begin) 75 : MCSection(SV_MachO, K, Begin), TypeAndAttributes(TAA), 76 Reserved2(reserved2) { 77 assert(Segment.size() <= 16 && Section.size() <= 16 && 78 "Segment or section string too long"); 79 for (unsigned i = 0; i != 16; ++i) { 80 if (i < Segment.size()) 81 SegmentName[i] = Segment[i]; 82 else 83 SegmentName[i] = 0; 84 85 if (i < Section.size()) 86 SectionName[i] = Section[i]; 87 else 88 SectionName[i] = 0; 89 } 90 } 91 92 void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI, 93 raw_ostream &OS, 94 const MCExpr *Subsection) const { 95 OS << "\t.section\t" << getSegmentName() << ',' << getSectionName(); 96 97 // Get the section type and attributes. 98 unsigned TAA = getTypeAndAttributes(); 99 if (TAA == 0) { 100 OS << '\n'; 101 return; 102 } 103 104 MachO::SectionType SectionType = getType(); 105 assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE && 106 "Invalid SectionType specified!"); 107 108 if (SectionTypeDescriptors[SectionType].AssemblerName) { 109 OS << ','; 110 OS << SectionTypeDescriptors[SectionType].AssemblerName; 111 } else { 112 // If we have no name for the attribute, stop here. 113 OS << '\n'; 114 return; 115 } 116 117 // If we don't have any attributes, we're done. 118 unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES; 119 if (SectionAttrs == 0) { 120 // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as 121 // the attribute specifier. 122 if (Reserved2 != 0) 123 OS << ",none," << Reserved2; 124 OS << '\n'; 125 return; 126 } 127 128 // Check each attribute to see if we have it. 129 char Separator = ','; 130 for (unsigned i = 0; 131 SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag; 132 ++i) { 133 // Check to see if we have this attribute. 134 if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0) 135 continue; 136 137 // Yep, clear it and print it. 138 SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag; 139 140 OS << Separator; 141 if (SectionAttrDescriptors[i].AssemblerName) 142 OS << SectionAttrDescriptors[i].AssemblerName; 143 else 144 OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>"; 145 Separator = '+'; 146 } 147 148 assert(SectionAttrs == 0 && "Unknown section attributes!"); 149 150 // If we have a S_SYMBOL_STUBS size specified, print it. 151 if (Reserved2 != 0) 152 OS << ',' << Reserved2; 153 OS << '\n'; 154 } 155 156 bool MCSectionMachO::UseCodeAlign() const { 157 return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS); 158 } 159 160 bool MCSectionMachO::isVirtualSection() const { 161 return (getType() == MachO::S_ZEROFILL || 162 getType() == MachO::S_GB_ZEROFILL || 163 getType() == MachO::S_THREAD_LOCAL_ZEROFILL); 164 } 165 166 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec". 167 /// This is a string that can appear after a .section directive in a mach-o 168 /// flavored .s file. If successful, this fills in the specified Out 169 /// parameters and returns an empty string. When an invalid section 170 /// specifier is present, this returns a string indicating the problem. 171 std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec, // In. 172 StringRef &Segment, // Out. 173 StringRef &Section, // Out. 174 unsigned &TAA, // Out. 175 bool &TAAParsed, // Out. 176 unsigned &StubSize) { // Out. 177 TAAParsed = false; 178 179 SmallVector<StringRef, 5> SplitSpec; 180 Spec.split(SplitSpec, ','); 181 // Remove leading and trailing whitespace. 182 auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef { 183 return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef(); 184 }; 185 Segment = GetEmptyOrTrim(0); 186 Section = GetEmptyOrTrim(1); 187 StringRef SectionType = GetEmptyOrTrim(2); 188 StringRef Attrs = GetEmptyOrTrim(3); 189 StringRef StubSizeStr = GetEmptyOrTrim(4); 190 191 // Verify that the segment is present and not too long. 192 if (Segment.empty() || Segment.size() > 16) 193 return "mach-o section specifier requires a segment whose length is " 194 "between 1 and 16 characters"; 195 196 // Verify that the section is present and not too long. 197 if (Section.empty()) 198 return "mach-o section specifier requires a segment and section " 199 "separated by a comma"; 200 201 if (Section.size() > 16) 202 return "mach-o section specifier requires a section whose length is " 203 "between 1 and 16 characters"; 204 205 // If there is no comma after the section, we're done. 206 TAA = 0; 207 StubSize = 0; 208 if (SectionType.empty()) 209 return ""; 210 211 // Figure out which section type it is. 212 auto TypeDescriptor = std::find_if( 213 std::begin(SectionTypeDescriptors), std::end(SectionTypeDescriptors), 214 [&](decltype(*SectionTypeDescriptors) &Descriptor) { 215 return Descriptor.AssemblerName && 216 SectionType == Descriptor.AssemblerName; 217 }); 218 219 // If we didn't find the section type, reject it. 220 if (TypeDescriptor == std::end(SectionTypeDescriptors)) 221 return "mach-o section specifier uses an unknown section type"; 222 223 // Remember the TypeID. 224 TAA = TypeDescriptor - std::begin(SectionTypeDescriptors); 225 TAAParsed = true; 226 227 // If we have no comma after the section type, there are no attributes. 228 if (Attrs.empty()) { 229 // S_SYMBOL_STUBS always require a symbol stub size specifier. 230 if (TAA == MachO::S_SYMBOL_STUBS) 231 return "mach-o section specifier of type 'symbol_stubs' requires a size " 232 "specifier"; 233 return ""; 234 } 235 236 // The attribute list is a '+' separated list of attributes. 237 SmallVector<StringRef, 1> SectionAttrs; 238 Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false); 239 240 for (StringRef &SectionAttr : SectionAttrs) { 241 auto AttrDescriptorI = std::find_if( 242 std::begin(SectionAttrDescriptors), std::end(SectionAttrDescriptors), 243 [&](decltype(*SectionAttrDescriptors) &Descriptor) { 244 return Descriptor.AssemblerName && 245 SectionAttr.trim() == Descriptor.AssemblerName; 246 }); 247 if (AttrDescriptorI == std::end(SectionAttrDescriptors)) 248 return "mach-o section specifier has invalid attribute"; 249 250 TAA |= AttrDescriptorI->AttrFlag; 251 } 252 253 // Okay, we've parsed the section attributes, see if we have a stub size spec. 254 if (StubSizeStr.empty()) { 255 // S_SYMBOL_STUBS always require a symbol stub size specifier. 256 if (TAA == MachO::S_SYMBOL_STUBS) 257 return "mach-o section specifier of type 'symbol_stubs' requires a size " 258 "specifier"; 259 return ""; 260 } 261 262 // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS. 263 if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS) 264 return "mach-o section specifier cannot have a stub size specified because " 265 "it does not have type 'symbol_stubs'"; 266 267 // Convert the stub size from a string to an integer. 268 if (StubSizeStr.getAsInteger(0, StubSize)) 269 return "mach-o section specifier has a malformed stub size"; 270 271 return ""; 272 } 273
