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
MCSectionMachO(StringRef Segment,StringRef Section,unsigned TAA,unsigned reserved2,SectionKind K,MCSymbol * Begin)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
PrintSwitchToSection(const MCAsmInfo & MAI,raw_ostream & OS,const MCExpr * Subsection) const92 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
UseCodeAlign() const156 bool MCSectionMachO::UseCodeAlign() const {
157 return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
158 }
159
isVirtualSection() const160 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.
ParseSectionSpecifier(StringRef Spec,StringRef & Segment,StringRef & Section,unsigned & TAA,bool & TAAParsed,unsigned & StubSize)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