xref: /freebsd/contrib/llvm-project/llvm/lib/MC/MCSectionMachO.cpp (revision 2f513db72b034fd5ef7f080b11be5c711c15186a)
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, 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     if (i < Section.size())
97       SectionName[i] = Section[i];
98     else
99       SectionName[i] = 0;
100   }
101 }
102 
103 void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
104                                           raw_ostream &OS,
105                                           const MCExpr *Subsection) const {
106   OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
107 
108   // Get the section type and attributes.
109   unsigned TAA = getTypeAndAttributes();
110   if (TAA == 0) {
111     OS << '\n';
112     return;
113   }
114 
115   MachO::SectionType SectionType = getType();
116   assert(SectionType <= MachO::LAST_KNOWN_SECTION_TYPE &&
117          "Invalid SectionType specified!");
118 
119   if (!SectionTypeDescriptors[SectionType].AssemblerName.empty()) {
120     OS << ',';
121     OS << SectionTypeDescriptors[SectionType].AssemblerName;
122   } else {
123     // If we have no name for the attribute, stop here.
124     OS << '\n';
125     return;
126   }
127 
128   // If we don't have any attributes, we're done.
129   unsigned SectionAttrs = TAA & MachO::SECTION_ATTRIBUTES;
130   if (SectionAttrs == 0) {
131     // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
132     // the attribute specifier.
133     if (Reserved2 != 0)
134       OS << ",none," << Reserved2;
135     OS << '\n';
136     return;
137   }
138 
139   // Check each attribute to see if we have it.
140   char Separator = ',';
141   for (unsigned i = 0;
142        SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
143        ++i) {
144     // Check to see if we have this attribute.
145     if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
146       continue;
147 
148     // Yep, clear it and print it.
149     SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
150 
151     OS << Separator;
152     if (!SectionAttrDescriptors[i].AssemblerName.empty())
153       OS << SectionAttrDescriptors[i].AssemblerName;
154     else
155       OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
156     Separator = '+';
157   }
158 
159   assert(SectionAttrs == 0 && "Unknown section attributes!");
160 
161   // If we have a S_SYMBOL_STUBS size specified, print it.
162   if (Reserved2 != 0)
163     OS << ',' << Reserved2;
164   OS << '\n';
165 }
166 
167 bool MCSectionMachO::UseCodeAlign() const {
168   return hasAttribute(MachO::S_ATTR_PURE_INSTRUCTIONS);
169 }
170 
171 bool MCSectionMachO::isVirtualSection() const {
172   return (getType() == MachO::S_ZEROFILL ||
173           getType() == MachO::S_GB_ZEROFILL ||
174           getType() == MachO::S_THREAD_LOCAL_ZEROFILL);
175 }
176 
177 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
178 /// This is a string that can appear after a .section directive in a mach-o
179 /// flavored .s file.  If successful, this fills in the specified Out
180 /// parameters and returns an empty string.  When an invalid section
181 /// specifier is present, this returns a string indicating the problem.
182 std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
183                                                   StringRef &Segment,    // Out.
184                                                   StringRef &Section,    // Out.
185                                                   unsigned  &TAA,        // Out.
186                                                   bool      &TAAParsed,  // Out.
187                                                   unsigned  &StubSize) { // Out.
188   TAAParsed = false;
189 
190   SmallVector<StringRef, 5> SplitSpec;
191   Spec.split(SplitSpec, ',');
192   // Remove leading and trailing whitespace.
193   auto GetEmptyOrTrim = [&SplitSpec](size_t Idx) -> StringRef {
194     return SplitSpec.size() > Idx ? SplitSpec[Idx].trim() : StringRef();
195   };
196   Segment = GetEmptyOrTrim(0);
197   Section = GetEmptyOrTrim(1);
198   StringRef SectionType = GetEmptyOrTrim(2);
199   StringRef Attrs = GetEmptyOrTrim(3);
200   StringRef StubSizeStr = GetEmptyOrTrim(4);
201 
202   // Verify that the segment is present and not too long.
203   if (Segment.empty() || Segment.size() > 16)
204     return "mach-o section specifier requires a segment whose length is "
205            "between 1 and 16 characters";
206 
207   // Verify that the section is present and not too long.
208   if (Section.empty())
209     return "mach-o section specifier requires a segment and section "
210            "separated by a comma";
211 
212   if (Section.size() > 16)
213     return "mach-o section specifier requires a section whose length is "
214            "between 1 and 16 characters";
215 
216   // If there is no comma after the section, we're done.
217   TAA = 0;
218   StubSize = 0;
219   if (SectionType.empty())
220     return "";
221 
222   // Figure out which section type it is.
223   auto TypeDescriptor = std::find_if(
224       std::begin(SectionTypeDescriptors), std::end(SectionTypeDescriptors),
225       [&](decltype(*SectionTypeDescriptors) &Descriptor) {
226         return SectionType == Descriptor.AssemblerName;
227       });
228 
229   // If we didn't find the section type, reject it.
230   if (TypeDescriptor == std::end(SectionTypeDescriptors))
231     return "mach-o section specifier uses an unknown section type";
232 
233   // Remember the TypeID.
234   TAA = TypeDescriptor - std::begin(SectionTypeDescriptors);
235   TAAParsed = true;
236 
237   // If we have no comma after the section type, there are no attributes.
238   if (Attrs.empty()) {
239     // S_SYMBOL_STUBS always require a symbol stub size specifier.
240     if (TAA == MachO::S_SYMBOL_STUBS)
241       return "mach-o section specifier of type 'symbol_stubs' requires a size "
242              "specifier";
243     return "";
244   }
245 
246   // The attribute list is a '+' separated list of attributes.
247   SmallVector<StringRef, 1> SectionAttrs;
248   Attrs.split(SectionAttrs, '+', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
249 
250   for (StringRef &SectionAttr : SectionAttrs) {
251     auto AttrDescriptorI = std::find_if(
252         std::begin(SectionAttrDescriptors), std::end(SectionAttrDescriptors),
253         [&](decltype(*SectionAttrDescriptors) &Descriptor) {
254           return SectionAttr.trim() == Descriptor.AssemblerName;
255         });
256     if (AttrDescriptorI == std::end(SectionAttrDescriptors))
257       return "mach-o section specifier has invalid attribute";
258 
259     TAA |= AttrDescriptorI->AttrFlag;
260   }
261 
262   // Okay, we've parsed the section attributes, see if we have a stub size spec.
263   if (StubSizeStr.empty()) {
264     // S_SYMBOL_STUBS always require a symbol stub size specifier.
265     if (TAA == MachO::S_SYMBOL_STUBS)
266       return "mach-o section specifier of type 'symbol_stubs' requires a size "
267       "specifier";
268     return "";
269   }
270 
271   // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
272   if ((TAA & MachO::SECTION_TYPE) != MachO::S_SYMBOL_STUBS)
273     return "mach-o section specifier cannot have a stub size specified because "
274            "it does not have type 'symbol_stubs'";
275 
276   // Convert the stub size from a string to an integer.
277   if (StubSizeStr.getAsInteger(0, StubSize))
278     return "mach-o section specifier has a malformed stub size";
279 
280   return "";
281 }
282