LLVM  12.0.0git
MCSectionMachO.cpp
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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 
10 #include "llvm/MC/MCContext.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 {
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;
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, 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 
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 
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;
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 
164 }
165 
167  return (getType() == MachO::S_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.
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(
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(
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.
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 }
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:233
S_SYMBOL_STUBS - Section with symbol stubs, byte size of stub in the Reserved2 field.
Definition: MachO.h:141
bool hasAttribute(unsigned Value) const
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:224
This class represents lattice values for constants.
Definition: AllocatorList.h:23
static constexpr struct @389 SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE+1]
SectionTypeDescriptors - These are strings that describe the various section types.
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:41
S_ATTR_STRIP_STATIC_SYMS - Ok to strip static symbols in this section in files with the MY_DYLDLINK f...
Definition: MachO.h:192
unsigned getTypeAndAttributes() const
S_ATTR_LOC_RELOC - Section has local relocation entries.
Definition: MachO.h:211
S_ATTR_SELF_MODIFYING_CODE - Used with i386 code stubs written on by dyld.
Definition: MachO.h:199
S_ATTR_EXT_RELOC - Section has external relocation entries.
Definition: MachO.h:209
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
LLVM_NODISCARD bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:156
#define ENTRY(ASMNAME, ENUM)
StringLiteral AssemblerName
StringLiteral EnumName
LLVM_NODISCARD size_t size() const
size - Get the string size.
Definition: StringRef.h:160
S_ATTR_SOME_INSTRUCTIONS - Section contains some machine instructions.
Definition: MachO.h:207
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
StringRef getSegmentName() const
std::enable_if_t< std::numeric_limits< T >::is_signed, bool > getAsInteger(unsigned Radix, T &Result) const
Parse the current string as an integer of the specified radix.
Definition: StringRef.h:511
This class is intended to be used as a base class for asm properties and features specific to the tar...
Definition: MCAsmInfo.h:56
A wrapper around a string literal that serves as a proxy for constructing global tables of StringRefs...
Definition: StringRef.h:872
static std::string ParseSectionSpecifier(StringRef Spec, StringRef &Segment, StringRef &Section, unsigned &TAA, bool &TAAParsed, unsigned &StubSize)
Parse the section specifier indicated by "Spec".
S_GB_ZEROFILL - Zero fill on demand section (that can be larger than 4 gigabytes).
Definition: MachO.h:152
S_THREAD_LOCAL_ZEROFILL - Thread local zerofill section.
Definition: MachO.h:166
StringRef getName() const
Definition: MCSection.h:115
SectionKind - This is a simple POD value that classifies the properties of a section.
Definition: SectionKind.h:22
bool UseCodeAlign() const override
Return true if a .align directive should use "optimized nops" to fill instead of 0s.
MachO::SectionType getType() const
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:45
static constexpr struct @390 SectionAttrDescriptors[]
SectionAttrDescriptors - This is an array of descriptors for section attributes.
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:883
S_ATTR_NO_DEAD_STRIP - No dead stripping.
Definition: MachO.h:194
LLVM_NODISCARD std::pair< StringRef, StringRef > split(char Separator) const
Split into two substrings around the first occurrence of a separator character.
Definition: StringRef.h:730
unsigned AttrFlag
S_ATTR_NO_TOC - Section contains coalesced symbols that are not to be in a ranlib table of contents...
Definition: MachO.h:189
S_ATTR_PURE_INSTRUCTIONS - Section contains only true machine instructions.
Definition: MachO.h:186
S_ATTR_LIVE_SUPPORT - Blocks are live if they reference live blocks.
Definition: MachO.h:196
bool isVirtualSection() const override
Check whether this section is "virtual", that is has no actual object file contents.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:46
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:57
S_ZEROFILL - Zero fill on demand section.
Definition: MachO.h:126
S_ATTR_DEBUG - A debug section.
Definition: MachO.h:201
SectionType
These are the section type and attributes fields.
Definition: MachO.h:119
auto find_if(R &&Range, UnaryPredicate P)
Provide wrappers to std::find_if which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1518
void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T, raw_ostream &OS, const MCExpr *Subsection) const override