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      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[MCSectionMachO::LAST_KNOWN_SECTION_TYPE+1] = {
     22   { "regular",                  "S_REGULAR" },                    // 0x00
     23   { 0,                          "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   { 0, /*FIXME??*/              "S_GB_ZEROFILL" },                // 0x0C
     35   { "interposing",              "S_INTERPOSING" },                // 0x0D
     36   { "16byte_literals",          "S_16BYTE_LITERALS" },            // 0x0E
     37   { 0, /*FIXME??*/              "S_DTRACE_DOF" },                 // 0x0F
     38   { 0, /*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.  The last entry has an AttrFlagEnd
     52 /// AttrFlag value.
     53 static const struct {
     54   unsigned AttrFlag;
     55   const char *AssemblerName, *EnumName;
     56 } SectionAttrDescriptors[] = {
     57 #define ENTRY(ASMNAME, ENUM) \
     58   { MCSectionMachO::ENUM, ASMNAME, #ENUM },
     59 ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
     60 ENTRY("no_toc",              S_ATTR_NO_TOC)
     61 ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
     62 ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
     63 ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
     64 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
     65 ENTRY("debug",               S_ATTR_DEBUG)
     66 ENTRY(0 /*FIXME*/,           S_ATTR_SOME_INSTRUCTIONS)
     67 ENTRY(0 /*FIXME*/,           S_ATTR_EXT_RELOC)
     68 ENTRY(0 /*FIXME*/,           S_ATTR_LOC_RELOC)
     69 #undef ENTRY
     70   { 0, "none", 0 }, // used if section has no attributes but has a stub size
     71 #define AttrFlagEnd 0xffffffff // non legal value, multiple attribute bits set
     72   { AttrFlagEnd, 0, 0 }
     73 };
     74 
     75 MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
     76                                unsigned TAA, unsigned reserved2, SectionKind K)
     77   : MCSection(SV_MachO, K), TypeAndAttributes(TAA), Reserved2(reserved2) {
     78   assert(Segment.size() <= 16 && Section.size() <= 16 &&
     79          "Segment or section string too long");
     80   for (unsigned i = 0; i != 16; ++i) {
     81     if (i < Segment.size())
     82       SegmentName[i] = Segment[i];
     83     else
     84       SegmentName[i] = 0;
     85 
     86     if (i < Section.size())
     87       SectionName[i] = Section[i];
     88     else
     89       SectionName[i] = 0;
     90   }
     91 }
     92 
     93 void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI,
     94                                           raw_ostream &OS,
     95                                           const MCExpr *Subsection) const {
     96   OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
     97 
     98   // Get the section type and attributes.
     99   unsigned TAA = getTypeAndAttributes();
    100   if (TAA == 0) {
    101     OS << '\n';
    102     return;
    103   }
    104 
    105   unsigned SectionType = TAA & MCSectionMachO::SECTION_TYPE;
    106   assert(SectionType <= MCSectionMachO::LAST_KNOWN_SECTION_TYPE &&
    107          "Invalid SectionType specified!");
    108 
    109   if (SectionTypeDescriptors[SectionType].AssemblerName) {
    110     OS << ',';
    111     OS << SectionTypeDescriptors[SectionType].AssemblerName;
    112   } else {
    113     // If we have no name for the attribute, stop here.
    114     OS << '\n';
    115     return;
    116   }
    117 
    118   // If we don't have any attributes, we're done.
    119   unsigned SectionAttrs = TAA & MCSectionMachO::SECTION_ATTRIBUTES;
    120   if (SectionAttrs == 0) {
    121     // If we have a S_SYMBOL_STUBS size specified, print it along with 'none' as
    122     // the attribute specifier.
    123     if (Reserved2 != 0)
    124       OS << ",none," << Reserved2;
    125     OS << '\n';
    126     return;
    127   }
    128 
    129   // Check each attribute to see if we have it.
    130   char Separator = ',';
    131   for (unsigned i = 0;
    132        SectionAttrs != 0 && SectionAttrDescriptors[i].AttrFlag;
    133        ++i) {
    134     // Check to see if we have this attribute.
    135     if ((SectionAttrDescriptors[i].AttrFlag & SectionAttrs) == 0)
    136       continue;
    137 
    138     // Yep, clear it and print it.
    139     SectionAttrs &= ~SectionAttrDescriptors[i].AttrFlag;
    140 
    141     OS << Separator;
    142     if (SectionAttrDescriptors[i].AssemblerName)
    143       OS << SectionAttrDescriptors[i].AssemblerName;
    144     else
    145       OS << "<<" << SectionAttrDescriptors[i].EnumName << ">>";
    146     Separator = '+';
    147   }
    148 
    149   assert(SectionAttrs == 0 && "Unknown section attributes!");
    150 
    151   // If we have a S_SYMBOL_STUBS size specified, print it.
    152   if (Reserved2 != 0)
    153     OS << ',' << Reserved2;
    154   OS << '\n';
    155 }
    156 
    157 bool MCSectionMachO::UseCodeAlign() const {
    158   return hasAttribute(MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS);
    159 }
    160 
    161 bool MCSectionMachO::isVirtualSection() const {
    162   return (getType() == MCSectionMachO::S_ZEROFILL ||
    163           getType() == MCSectionMachO::S_GB_ZEROFILL ||
    164           getType() == MCSectionMachO::S_THREAD_LOCAL_ZEROFILL);
    165 }
    166 
    167 /// StripSpaces - This removes leading and trailing spaces from the StringRef.
    168 static void StripSpaces(StringRef &Str) {
    169   while (!Str.empty() && isspace(static_cast<unsigned char>(Str[0])))
    170     Str = Str.substr(1);
    171   while (!Str.empty() && isspace(static_cast<unsigned char>(Str.back())))
    172     Str = Str.substr(0, Str.size()-1);
    173 }
    174 
    175 /// ParseSectionSpecifier - Parse the section specifier indicated by "Spec".
    176 /// This is a string that can appear after a .section directive in a mach-o
    177 /// flavored .s file.  If successful, this fills in the specified Out
    178 /// parameters and returns an empty string.  When an invalid section
    179 /// specifier is present, this returns a string indicating the problem.
    180 std::string MCSectionMachO::ParseSectionSpecifier(StringRef Spec,        // In.
    181                                                   StringRef &Segment,    // Out.
    182                                                   StringRef &Section,    // Out.
    183                                                   unsigned  &TAA,        // Out.
    184                                                   bool      &TAAParsed,  // Out.
    185                                                   unsigned  &StubSize) { // Out.
    186   TAAParsed = false;
    187   // Find the first comma.
    188   std::pair<StringRef, StringRef> Comma = Spec.split(',');
    189 
    190   // If there is no comma, we fail.
    191   if (Comma.second.empty())
    192     return "mach-o section specifier requires a segment and section "
    193            "separated by a comma";
    194 
    195   // Capture segment, remove leading and trailing whitespace.
    196   Segment = Comma.first;
    197   StripSpaces(Segment);
    198 
    199   // Verify that the segment is present and not too long.
    200   if (Segment.empty() || Segment.size() > 16)
    201     return "mach-o section specifier requires a segment whose length is "
    202            "between 1 and 16 characters";
    203 
    204   // Split the section name off from any attributes if present.
    205   Comma = Comma.second.split(',');
    206 
    207   // Capture section, remove leading and trailing whitespace.
    208   Section = Comma.first;
    209   StripSpaces(Section);
    210 
    211   // Verify that the section is present and not too long.
    212   if (Section.empty() || 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 (Comma.second.empty())
    220     return "";
    221 
    222   // Otherwise, we need to parse the section type and attributes.
    223   Comma = Comma.second.split(',');
    224 
    225   // Get the section type.
    226   StringRef SectionType = Comma.first;
    227   StripSpaces(SectionType);
    228 
    229   // Figure out which section type it is.
    230   unsigned TypeID;
    231   for (TypeID = 0; TypeID !=MCSectionMachO::LAST_KNOWN_SECTION_TYPE+1; ++TypeID)
    232     if (SectionTypeDescriptors[TypeID].AssemblerName &&
    233         SectionType == SectionTypeDescriptors[TypeID].AssemblerName)
    234       break;
    235 
    236   // If we didn't find the section type, reject it.
    237   if (TypeID > MCSectionMachO::LAST_KNOWN_SECTION_TYPE)
    238     return "mach-o section specifier uses an unknown section type";
    239 
    240   // Remember the TypeID.
    241   TAA = TypeID;
    242   TAAParsed = true;
    243 
    244   // If we have no comma after the section type, there are no attributes.
    245   if (Comma.second.empty()) {
    246     // S_SYMBOL_STUBS always require a symbol stub size specifier.
    247     if (TAA == MCSectionMachO::S_SYMBOL_STUBS)
    248       return "mach-o section specifier of type 'symbol_stubs' requires a size "
    249              "specifier";
    250     return "";
    251   }
    252 
    253   // Otherwise, we do have some attributes.  Split off the size specifier if
    254   // present.
    255   Comma = Comma.second.split(',');
    256   StringRef Attrs = Comma.first;
    257 
    258   // The attribute list is a '+' separated list of attributes.
    259   std::pair<StringRef, StringRef> Plus = Attrs.split('+');
    260 
    261   while (1) {
    262     StringRef Attr = Plus.first;
    263     StripSpaces(Attr);
    264 
    265     // Look up the attribute.
    266     for (unsigned i = 0; ; ++i) {
    267       if (SectionAttrDescriptors[i].AttrFlag == AttrFlagEnd)
    268         return "mach-o section specifier has invalid attribute";
    269 
    270       if (SectionAttrDescriptors[i].AssemblerName &&
    271           Attr == SectionAttrDescriptors[i].AssemblerName) {
    272         TAA |= SectionAttrDescriptors[i].AttrFlag;
    273         break;
    274       }
    275     }
    276 
    277     if (Plus.second.empty()) break;
    278     Plus = Plus.second.split('+');
    279   };
    280 
    281   // Okay, we've parsed the section attributes, see if we have a stub size spec.
    282   if (Comma.second.empty()) {
    283     // S_SYMBOL_STUBS always require a symbol stub size specifier.
    284     if (TAA == MCSectionMachO::S_SYMBOL_STUBS)
    285       return "mach-o section specifier of type 'symbol_stubs' requires a size "
    286       "specifier";
    287     return "";
    288   }
    289 
    290   // If we have a stub size spec, we must have a sectiontype of S_SYMBOL_STUBS.
    291   if ((TAA & MCSectionMachO::SECTION_TYPE) != MCSectionMachO::S_SYMBOL_STUBS)
    292     return "mach-o section specifier cannot have a stub size specified because "
    293            "it does not have type 'symbol_stubs'";
    294 
    295   // Okay, if we do, it must be a number.
    296   StringRef StubSizeStr = Comma.second;
    297   StripSpaces(StubSizeStr);
    298 
    299   // Convert the stub size from a string to an integer.
    300   if (StubSizeStr.getAsInteger(0, StubSize))
    301     return "mach-o section specifier has a malformed stub size";
    302 
    303   return "";
    304 }
    305