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
MCSectionMachO(StringRef Segment,StringRef Section,unsigned TAA,unsigned reserved2,SectionKind K,MCSymbol * Begin)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
PrintSwitchToSection(const MCAsmInfo & MAI,const Triple & T,raw_ostream & OS,const MCExpr * Subsection) const98 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
UseCodeAlign() const162 bool MCSectionMachO::UseCodeAlign() const {
163 return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
164 }
165
isVirtualSection() const166 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.
ParseSectionSpecifier(StringRef Spec,StringRef & Segment,StringRef & Section,unsigned & TAA,bool & TAAParsed,unsigned & StubSize)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 = std::find_if(
219 std::begin(SectionTypeDescriptors), std::end(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 = std::find_if(
247 std::begin(SectionAttrDescriptors), std::end(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