1 //===-- llvm/MC/SectionKind.h - Classification of sections ------*- C++ -*-===// 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 #ifndef LLVM_MC_SECTIONKIND_H 10 #define LLVM_MC_SECTIONKIND_H 11 12 namespace llvm { 13 14 /// SectionKind - This is a simple POD value that classifies the properties of 15 /// a section. A section is classified into the deepest possible 16 /// classification, and then the target maps them onto their sections based on 17 /// what capabilities they have. 18 /// 19 /// The comments below describe these as if they were an inheritance hierarchy 20 /// in order to explain the predicates below. 21 /// 22 class SectionKind { 23 enum Kind { 24 /// Metadata - Debug info sections or other metadata. 25 Metadata, 26 27 /// Exclude - This section will be excluded from the final executable or 28 /// shared library. Only valid for ELF / COFF targets. 29 Exclude, 30 31 /// Text - Text section, used for functions and other executable code. 32 Text, 33 34 /// ExecuteOnly, Text section that is not readable. 35 ExecuteOnly, 36 37 /// ReadOnly - Data that is never written to at program runtime by the 38 /// program or the dynamic linker. Things in the top-level readonly 39 /// SectionKind are not mergeable. 40 ReadOnly, 41 42 /// MergableCString - Any null-terminated string which allows merging. 43 /// These values are known to end in a nul value of the specified size, 44 /// not otherwise contain a nul value, and be mergable. This allows the 45 /// linker to unique the strings if it so desires. 46 47 /// Mergeable1ByteCString - 1 byte mergable, null terminated, string. 48 Mergeable1ByteCString, 49 50 /// Mergeable2ByteCString - 2 byte mergable, null terminated, string. 51 Mergeable2ByteCString, 52 53 /// Mergeable4ByteCString - 4 byte mergable, null terminated, string. 54 Mergeable4ByteCString, 55 56 /// MergeableConst - These are sections for merging fixed-length 57 /// constants together. For example, this can be used to unique 58 /// constant pool entries etc. 59 60 /// MergeableConst4 - This is a section used by 4-byte constants, 61 /// for example, floats. 62 MergeableConst4, 63 64 /// MergeableConst8 - This is a section used by 8-byte constants, 65 /// for example, doubles. 66 MergeableConst8, 67 68 /// MergeableConst16 - This is a section used by 16-byte constants, 69 /// for example, vectors. 70 MergeableConst16, 71 72 /// MergeableConst32 - This is a section used by 32-byte constants, 73 /// for example, vectors. 74 MergeableConst32, 75 76 /// Writeable - This is the base of all segments that need to be written 77 /// to during program runtime. 78 79 /// ThreadLocal - This is the base of all TLS segments. All TLS 80 /// objects must be writeable, otherwise there is no reason for them to 81 /// be thread local! 82 83 /// ThreadBSS - Zero-initialized TLS data objects. 84 ThreadBSS, 85 86 /// ThreadData - Initialized TLS data objects. 87 ThreadData, 88 89 /// ThreadBSSLocal - Zero-initialized TLS data objects with local linkage. 90 ThreadBSSLocal, 91 92 /// GlobalWriteableData - Writeable data that is global (not thread 93 /// local). 94 95 /// BSS - Zero initialized writeable data. 96 BSS, 97 98 /// BSSLocal - This is BSS (zero initialized and writable) data 99 /// which has local linkage. 100 BSSLocal, 101 102 /// BSSExtern - This is BSS data with normal external linkage. 103 BSSExtern, 104 105 /// Common - Data with common linkage. These represent tentative 106 /// definitions, which always have a zero initializer and are never 107 /// marked 'constant'. 108 Common, 109 110 /// This is writeable data that has a non-zero initializer. 111 Data, 112 113 /// ReadOnlyWithRel - These are global variables that are never 114 /// written to by the program, but that have relocations, so they 115 /// must be stuck in a writeable section so that the dynamic linker 116 /// can write to them. If it chooses to, the dynamic linker can 117 /// mark the pages these globals end up on as read-only after it is 118 /// done with its relocation phase. 119 ReadOnlyWithRel 120 } K : 8; 121 public: 122 isMetadata()123 bool isMetadata() const { return K == Metadata; } 124 isExclude()125 bool isExclude() const { return K == Exclude; } 126 isText()127 bool isText() const { return K == Text || K == ExecuteOnly; } 128 isExecuteOnly()129 bool isExecuteOnly() const { return K == ExecuteOnly; } 130 isReadOnly()131 bool isReadOnly() const { 132 return K == ReadOnly || isMergeableCString() || 133 isMergeableConst(); 134 } 135 isMergeableCString()136 bool isMergeableCString() const { 137 return K == Mergeable1ByteCString || K == Mergeable2ByteCString || 138 K == Mergeable4ByteCString; 139 } isMergeable1ByteCString()140 bool isMergeable1ByteCString() const { return K == Mergeable1ByteCString; } isMergeable2ByteCString()141 bool isMergeable2ByteCString() const { return K == Mergeable2ByteCString; } isMergeable4ByteCString()142 bool isMergeable4ByteCString() const { return K == Mergeable4ByteCString; } 143 isMergeableConst()144 bool isMergeableConst() const { 145 return K == MergeableConst4 || K == MergeableConst8 || 146 K == MergeableConst16 || K == MergeableConst32; 147 } isMergeableConst4()148 bool isMergeableConst4() const { return K == MergeableConst4; } isMergeableConst8()149 bool isMergeableConst8() const { return K == MergeableConst8; } isMergeableConst16()150 bool isMergeableConst16() const { return K == MergeableConst16; } isMergeableConst32()151 bool isMergeableConst32() const { return K == MergeableConst32; } 152 isWriteable()153 bool isWriteable() const { 154 return isThreadLocal() || isGlobalWriteableData(); 155 } 156 isThreadLocal()157 bool isThreadLocal() const { 158 return K == ThreadData || K == ThreadBSS || K == ThreadBSSLocal; 159 } 160 isThreadBSS()161 bool isThreadBSS() const { return K == ThreadBSS || K == ThreadBSSLocal; } isThreadData()162 bool isThreadData() const { return K == ThreadData; } isThreadBSSLocal()163 bool isThreadBSSLocal() const { return K == ThreadBSSLocal; } 164 isGlobalWriteableData()165 bool isGlobalWriteableData() const { 166 return isBSS() || isCommon() || isData() || isReadOnlyWithRel(); 167 } 168 isBSS()169 bool isBSS() const { return K == BSS || K == BSSLocal || K == BSSExtern; } isBSSLocal()170 bool isBSSLocal() const { return K == BSSLocal; } isBSSExtern()171 bool isBSSExtern() const { return K == BSSExtern; } 172 isCommon()173 bool isCommon() const { return K == Common; } 174 isData()175 bool isData() const { return K == Data; } 176 isReadOnlyWithRel()177 bool isReadOnlyWithRel() const { 178 return K == ReadOnlyWithRel; 179 } 180 private: get(Kind K)181 static SectionKind get(Kind K) { 182 SectionKind Res; 183 Res.K = K; 184 return Res; 185 } 186 public: 187 getMetadata()188 static SectionKind getMetadata() { return get(Metadata); } getExclude()189 static SectionKind getExclude() { return get(Exclude); } getText()190 static SectionKind getText() { return get(Text); } getExecuteOnly()191 static SectionKind getExecuteOnly() { return get(ExecuteOnly); } getReadOnly()192 static SectionKind getReadOnly() { return get(ReadOnly); } getMergeable1ByteCString()193 static SectionKind getMergeable1ByteCString() { 194 return get(Mergeable1ByteCString); 195 } getMergeable2ByteCString()196 static SectionKind getMergeable2ByteCString() { 197 return get(Mergeable2ByteCString); 198 } getMergeable4ByteCString()199 static SectionKind getMergeable4ByteCString() { 200 return get(Mergeable4ByteCString); 201 } getMergeableConst4()202 static SectionKind getMergeableConst4() { return get(MergeableConst4); } getMergeableConst8()203 static SectionKind getMergeableConst8() { return get(MergeableConst8); } getMergeableConst16()204 static SectionKind getMergeableConst16() { return get(MergeableConst16); } getMergeableConst32()205 static SectionKind getMergeableConst32() { return get(MergeableConst32); } getThreadBSS()206 static SectionKind getThreadBSS() { return get(ThreadBSS); } getThreadData()207 static SectionKind getThreadData() { return get(ThreadData); } getThreadBSSLocal()208 static SectionKind getThreadBSSLocal() { return get(ThreadBSSLocal); } getBSS()209 static SectionKind getBSS() { return get(BSS); } getBSSLocal()210 static SectionKind getBSSLocal() { return get(BSSLocal); } getBSSExtern()211 static SectionKind getBSSExtern() { return get(BSSExtern); } getCommon()212 static SectionKind getCommon() { return get(Common); } getData()213 static SectionKind getData() { return get(Data); } getReadOnlyWithRel()214 static SectionKind getReadOnlyWithRel() { return get(ReadOnlyWithRel); } 215 }; 216 217 } // end namespace llvm 218 219 #endif 220