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      1 //===-- ExternalFunctions.cpp - Implement External Functions --------------===//
      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 //  This file contains both code to deal with invoking "external" functions, but
     11 //  also contains code that implements "exported" external functions.
     12 //
     13 //  There are currently two mechanisms for handling external functions in the
     14 //  Interpreter.  The first is to implement lle_* wrapper functions that are
     15 //  specific to well-known library functions which manually translate the
     16 //  arguments from GenericValues and make the call.  If such a wrapper does
     17 //  not exist, and libffi is available, then the Interpreter will attempt to
     18 //  invoke the function using libffi, after finding its address.
     19 //
     20 //===----------------------------------------------------------------------===//
     21 
     22 #include "Interpreter.h"
     23 #include "llvm/Config/config.h"     // Detect libffi
     24 #include "llvm/IR/DataLayout.h"
     25 #include "llvm/IR/DerivedTypes.h"
     26 #include "llvm/IR/Module.h"
     27 #include "llvm/Support/DynamicLibrary.h"
     28 #include "llvm/Support/ErrorHandling.h"
     29 #include "llvm/Support/ManagedStatic.h"
     30 #include "llvm/Support/Mutex.h"
     31 #include "llvm/Support/UniqueLock.h"
     32 #include <cmath>
     33 #include <csignal>
     34 #include <cstdio>
     35 #include <cstring>
     36 #include <map>
     37 
     38 #ifdef HAVE_FFI_CALL
     39 #ifdef HAVE_FFI_H
     40 #include <ffi.h>
     41 #define USE_LIBFFI
     42 #elif HAVE_FFI_FFI_H
     43 #include <ffi/ffi.h>
     44 #define USE_LIBFFI
     45 #endif
     46 #endif
     47 
     48 using namespace llvm;
     49 
     50 static ManagedStatic<sys::Mutex> FunctionsLock;
     51 
     52 typedef GenericValue (*ExFunc)(FunctionType *, ArrayRef<GenericValue>);
     53 static ManagedStatic<std::map<const Function *, ExFunc> > ExportedFunctions;
     54 static ManagedStatic<std::map<std::string, ExFunc> > FuncNames;
     55 
     56 #ifdef USE_LIBFFI
     57 typedef void (*RawFunc)();
     58 static ManagedStatic<std::map<const Function *, RawFunc> > RawFunctions;
     59 #endif
     60 
     61 static Interpreter *TheInterpreter;
     62 
     63 static char getTypeID(Type *Ty) {
     64   switch (Ty->getTypeID()) {
     65   case Type::VoidTyID:    return 'V';
     66   case Type::IntegerTyID:
     67     switch (cast<IntegerType>(Ty)->getBitWidth()) {
     68       case 1:  return 'o';
     69       case 8:  return 'B';
     70       case 16: return 'S';
     71       case 32: return 'I';
     72       case 64: return 'L';
     73       default: return 'N';
     74     }
     75   case Type::FloatTyID:   return 'F';
     76   case Type::DoubleTyID:  return 'D';
     77   case Type::PointerTyID: return 'P';
     78   case Type::FunctionTyID:return 'M';
     79   case Type::StructTyID:  return 'T';
     80   case Type::ArrayTyID:   return 'A';
     81   default: return 'U';
     82   }
     83 }
     84 
     85 // Try to find address of external function given a Function object.
     86 // Please note, that interpreter doesn't know how to assemble a
     87 // real call in general case (this is JIT job), that's why it assumes,
     88 // that all external functions has the same (and pretty "general") signature.
     89 // The typical example of such functions are "lle_X_" ones.
     90 static ExFunc lookupFunction(const Function *F) {
     91   // Function not found, look it up... start by figuring out what the
     92   // composite function name should be.
     93   std::string ExtName = "lle_";
     94   FunctionType *FT = F->getFunctionType();
     95   for (unsigned i = 0, e = FT->getNumContainedTypes(); i != e; ++i)
     96     ExtName += getTypeID(FT->getContainedType(i));
     97   ExtName += ("_" + F->getName()).str();
     98 
     99   sys::ScopedLock Writer(*FunctionsLock);
    100   ExFunc FnPtr = (*FuncNames)[ExtName];
    101   if (!FnPtr)
    102     FnPtr = (*FuncNames)[("lle_X_" + F->getName()).str()];
    103   if (!FnPtr)  // Try calling a generic function... if it exists...
    104     FnPtr = (ExFunc)(intptr_t)sys::DynamicLibrary::SearchForAddressOfSymbol(
    105         ("lle_X_" + F->getName()).str());
    106   if (FnPtr)
    107     ExportedFunctions->insert(std::make_pair(F, FnPtr));  // Cache for later
    108   return FnPtr;
    109 }
    110 
    111 #ifdef USE_LIBFFI
    112 static ffi_type *ffiTypeFor(Type *Ty) {
    113   switch (Ty->getTypeID()) {
    114     case Type::VoidTyID: return &ffi_type_void;
    115     case Type::IntegerTyID:
    116       switch (cast<IntegerType>(Ty)->getBitWidth()) {
    117         case 8:  return &ffi_type_sint8;
    118         case 16: return &ffi_type_sint16;
    119         case 32: return &ffi_type_sint32;
    120         case 64: return &ffi_type_sint64;
    121       }
    122     case Type::FloatTyID:   return &ffi_type_float;
    123     case Type::DoubleTyID:  return &ffi_type_double;
    124     case Type::PointerTyID: return &ffi_type_pointer;
    125     default: break;
    126   }
    127   // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
    128   report_fatal_error("Type could not be mapped for use with libffi.");
    129   return NULL;
    130 }
    131 
    132 static void *ffiValueFor(Type *Ty, const GenericValue &AV,
    133                          void *ArgDataPtr) {
    134   switch (Ty->getTypeID()) {
    135     case Type::IntegerTyID:
    136       switch (cast<IntegerType>(Ty)->getBitWidth()) {
    137         case 8: {
    138           int8_t *I8Ptr = (int8_t *) ArgDataPtr;
    139           *I8Ptr = (int8_t) AV.IntVal.getZExtValue();
    140           return ArgDataPtr;
    141         }
    142         case 16: {
    143           int16_t *I16Ptr = (int16_t *) ArgDataPtr;
    144           *I16Ptr = (int16_t) AV.IntVal.getZExtValue();
    145           return ArgDataPtr;
    146         }
    147         case 32: {
    148           int32_t *I32Ptr = (int32_t *) ArgDataPtr;
    149           *I32Ptr = (int32_t) AV.IntVal.getZExtValue();
    150           return ArgDataPtr;
    151         }
    152         case 64: {
    153           int64_t *I64Ptr = (int64_t *) ArgDataPtr;
    154           *I64Ptr = (int64_t) AV.IntVal.getZExtValue();
    155           return ArgDataPtr;
    156         }
    157       }
    158     case Type::FloatTyID: {
    159       float *FloatPtr = (float *) ArgDataPtr;
    160       *FloatPtr = AV.FloatVal;
    161       return ArgDataPtr;
    162     }
    163     case Type::DoubleTyID: {
    164       double *DoublePtr = (double *) ArgDataPtr;
    165       *DoublePtr = AV.DoubleVal;
    166       return ArgDataPtr;
    167     }
    168     case Type::PointerTyID: {
    169       void **PtrPtr = (void **) ArgDataPtr;
    170       *PtrPtr = GVTOP(AV);
    171       return ArgDataPtr;
    172     }
    173     default: break;
    174   }
    175   // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
    176   report_fatal_error("Type value could not be mapped for use with libffi.");
    177   return NULL;
    178 }
    179 
    180 static bool ffiInvoke(RawFunc Fn, Function *F, ArrayRef<GenericValue> ArgVals,
    181                       const DataLayout &TD, GenericValue &Result) {
    182   ffi_cif cif;
    183   FunctionType *FTy = F->getFunctionType();
    184   const unsigned NumArgs = F->arg_size();
    185 
    186   // TODO: We don't have type information about the remaining arguments, because
    187   // this information is never passed into ExecutionEngine::runFunction().
    188   if (ArgVals.size() > NumArgs && F->isVarArg()) {
    189     report_fatal_error("Calling external var arg function '" + F->getName()
    190                       + "' is not supported by the Interpreter.");
    191   }
    192 
    193   unsigned ArgBytes = 0;
    194 
    195   std::vector<ffi_type*> args(NumArgs);
    196   for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
    197        A != E; ++A) {
    198     const unsigned ArgNo = A->getArgNo();
    199     Type *ArgTy = FTy->getParamType(ArgNo);
    200     args[ArgNo] = ffiTypeFor(ArgTy);
    201     ArgBytes += TD.getTypeStoreSize(ArgTy);
    202   }
    203 
    204   SmallVector<uint8_t, 128> ArgData;
    205   ArgData.resize(ArgBytes);
    206   uint8_t *ArgDataPtr = ArgData.data();
    207   SmallVector<void*, 16> values(NumArgs);
    208   for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
    209        A != E; ++A) {
    210     const unsigned ArgNo = A->getArgNo();
    211     Type *ArgTy = FTy->getParamType(ArgNo);
    212     values[ArgNo] = ffiValueFor(ArgTy, ArgVals[ArgNo], ArgDataPtr);
    213     ArgDataPtr += TD.getTypeStoreSize(ArgTy);
    214   }
    215 
    216   Type *RetTy = FTy->getReturnType();
    217   ffi_type *rtype = ffiTypeFor(RetTy);
    218 
    219   if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, &args[0]) == FFI_OK) {
    220     SmallVector<uint8_t, 128> ret;
    221     if (RetTy->getTypeID() != Type::VoidTyID)
    222       ret.resize(TD.getTypeStoreSize(RetTy));
    223     ffi_call(&cif, Fn, ret.data(), values.data());
    224     switch (RetTy->getTypeID()) {
    225       case Type::IntegerTyID:
    226         switch (cast<IntegerType>(RetTy)->getBitWidth()) {
    227           case 8:  Result.IntVal = APInt(8 , *(int8_t *) ret.data()); break;
    228           case 16: Result.IntVal = APInt(16, *(int16_t*) ret.data()); break;
    229           case 32: Result.IntVal = APInt(32, *(int32_t*) ret.data()); break;
    230           case 64: Result.IntVal = APInt(64, *(int64_t*) ret.data()); break;
    231         }
    232         break;
    233       case Type::FloatTyID:   Result.FloatVal   = *(float *) ret.data(); break;
    234       case Type::DoubleTyID:  Result.DoubleVal  = *(double*) ret.data(); break;
    235       case Type::PointerTyID: Result.PointerVal = *(void **) ret.data(); break;
    236       default: break;
    237     }
    238     return true;
    239   }
    240 
    241   return false;
    242 }
    243 #endif // USE_LIBFFI
    244 
    245 GenericValue Interpreter::callExternalFunction(Function *F,
    246                                                ArrayRef<GenericValue> ArgVals) {
    247   TheInterpreter = this;
    248 
    249   unique_lock<sys::Mutex> Guard(*FunctionsLock);
    250 
    251   // Do a lookup to see if the function is in our cache... this should just be a
    252   // deferred annotation!
    253   std::map<const Function *, ExFunc>::iterator FI = ExportedFunctions->find(F);
    254   if (ExFunc Fn = (FI == ExportedFunctions->end()) ? lookupFunction(F)
    255                                                    : FI->second) {
    256     Guard.unlock();
    257     return Fn(F->getFunctionType(), ArgVals);
    258   }
    259 
    260 #ifdef USE_LIBFFI
    261   std::map<const Function *, RawFunc>::iterator RF = RawFunctions->find(F);
    262   RawFunc RawFn;
    263   if (RF == RawFunctions->end()) {
    264     RawFn = (RawFunc)(intptr_t)
    265       sys::DynamicLibrary::SearchForAddressOfSymbol(F->getName());
    266     if (!RawFn)
    267       RawFn = (RawFunc)(intptr_t)getPointerToGlobalIfAvailable(F);
    268     if (RawFn != 0)
    269       RawFunctions->insert(std::make_pair(F, RawFn));  // Cache for later
    270   } else {
    271     RawFn = RF->second;
    272   }
    273 
    274   Guard.unlock();
    275 
    276   GenericValue Result;
    277   if (RawFn != 0 && ffiInvoke(RawFn, F, ArgVals, getDataLayout(), Result))
    278     return Result;
    279 #endif // USE_LIBFFI
    280 
    281   if (F->getName() == "__main")
    282     errs() << "Tried to execute an unknown external function: "
    283       << *F->getType() << " __main\n";
    284   else
    285     report_fatal_error("Tried to execute an unknown external function: " +
    286                        F->getName());
    287 #ifndef USE_LIBFFI
    288   errs() << "Recompiling LLVM with --enable-libffi might help.\n";
    289 #endif
    290   return GenericValue();
    291 }
    292 
    293 
    294 //===----------------------------------------------------------------------===//
    295 //  Functions "exported" to the running application...
    296 //
    297 
    298 // void atexit(Function*)
    299 static GenericValue lle_X_atexit(FunctionType *FT,
    300                                  ArrayRef<GenericValue> Args) {
    301   assert(Args.size() == 1);
    302   TheInterpreter->addAtExitHandler((Function*)GVTOP(Args[0]));
    303   GenericValue GV;
    304   GV.IntVal = 0;
    305   return GV;
    306 }
    307 
    308 // void exit(int)
    309 static GenericValue lle_X_exit(FunctionType *FT, ArrayRef<GenericValue> Args) {
    310   TheInterpreter->exitCalled(Args[0]);
    311   return GenericValue();
    312 }
    313 
    314 // void abort(void)
    315 static GenericValue lle_X_abort(FunctionType *FT, ArrayRef<GenericValue> Args) {
    316   //FIXME: should we report or raise here?
    317   //report_fatal_error("Interpreted program raised SIGABRT");
    318   raise (SIGABRT);
    319   return GenericValue();
    320 }
    321 
    322 // int sprintf(char *, const char *, ...) - a very rough implementation to make
    323 // output useful.
    324 static GenericValue lle_X_sprintf(FunctionType *FT,
    325                                   ArrayRef<GenericValue> Args) {
    326   char *OutputBuffer = (char *)GVTOP(Args[0]);
    327   const char *FmtStr = (const char *)GVTOP(Args[1]);
    328   unsigned ArgNo = 2;
    329 
    330   // printf should return # chars printed.  This is completely incorrect, but
    331   // close enough for now.
    332   GenericValue GV;
    333   GV.IntVal = APInt(32, strlen(FmtStr));
    334   while (1) {
    335     switch (*FmtStr) {
    336     case 0: return GV;             // Null terminator...
    337     default:                       // Normal nonspecial character
    338       sprintf(OutputBuffer++, "%c", *FmtStr++);
    339       break;
    340     case '\\': {                   // Handle escape codes
    341       sprintf(OutputBuffer, "%c%c", *FmtStr, *(FmtStr+1));
    342       FmtStr += 2; OutputBuffer += 2;
    343       break;
    344     }
    345     case '%': {                    // Handle format specifiers
    346       char FmtBuf[100] = "", Buffer[1000] = "";
    347       char *FB = FmtBuf;
    348       *FB++ = *FmtStr++;
    349       char Last = *FB++ = *FmtStr++;
    350       unsigned HowLong = 0;
    351       while (Last != 'c' && Last != 'd' && Last != 'i' && Last != 'u' &&
    352              Last != 'o' && Last != 'x' && Last != 'X' && Last != 'e' &&
    353              Last != 'E' && Last != 'g' && Last != 'G' && Last != 'f' &&
    354              Last != 'p' && Last != 's' && Last != '%') {
    355         if (Last == 'l' || Last == 'L') HowLong++;  // Keep track of l's
    356         Last = *FB++ = *FmtStr++;
    357       }
    358       *FB = 0;
    359 
    360       switch (Last) {
    361       case '%':
    362         memcpy(Buffer, "%", 2); break;
    363       case 'c':
    364         sprintf(Buffer, FmtBuf, uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
    365         break;
    366       case 'd': case 'i':
    367       case 'u': case 'o':
    368       case 'x': case 'X':
    369         if (HowLong >= 1) {
    370           if (HowLong == 1 &&
    371               TheInterpreter->getDataLayout().getPointerSizeInBits() == 64 &&
    372               sizeof(long) < sizeof(int64_t)) {
    373             // Make sure we use %lld with a 64 bit argument because we might be
    374             // compiling LLI on a 32 bit compiler.
    375             unsigned Size = strlen(FmtBuf);
    376             FmtBuf[Size] = FmtBuf[Size-1];
    377             FmtBuf[Size+1] = 0;
    378             FmtBuf[Size-1] = 'l';
    379           }
    380           sprintf(Buffer, FmtBuf, Args[ArgNo++].IntVal.getZExtValue());
    381         } else
    382           sprintf(Buffer, FmtBuf,uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
    383         break;
    384       case 'e': case 'E': case 'g': case 'G': case 'f':
    385         sprintf(Buffer, FmtBuf, Args[ArgNo++].DoubleVal); break;
    386       case 'p':
    387         sprintf(Buffer, FmtBuf, (void*)GVTOP(Args[ArgNo++])); break;
    388       case 's':
    389         sprintf(Buffer, FmtBuf, (char*)GVTOP(Args[ArgNo++])); break;
    390       default:
    391         errs() << "<unknown printf code '" << *FmtStr << "'!>";
    392         ArgNo++; break;
    393       }
    394       size_t Len = strlen(Buffer);
    395       memcpy(OutputBuffer, Buffer, Len + 1);
    396       OutputBuffer += Len;
    397       }
    398       break;
    399     }
    400   }
    401   return GV;
    402 }
    403 
    404 // int printf(const char *, ...) - a very rough implementation to make output
    405 // useful.
    406 static GenericValue lle_X_printf(FunctionType *FT,
    407                                  ArrayRef<GenericValue> Args) {
    408   char Buffer[10000];
    409   std::vector<GenericValue> NewArgs;
    410   NewArgs.push_back(PTOGV((void*)&Buffer[0]));
    411   NewArgs.insert(NewArgs.end(), Args.begin(), Args.end());
    412   GenericValue GV = lle_X_sprintf(FT, NewArgs);
    413   outs() << Buffer;
    414   return GV;
    415 }
    416 
    417 // int sscanf(const char *format, ...);
    418 static GenericValue lle_X_sscanf(FunctionType *FT,
    419                                  ArrayRef<GenericValue> args) {
    420   assert(args.size() < 10 && "Only handle up to 10 args to sscanf right now!");
    421 
    422   char *Args[10];
    423   for (unsigned i = 0; i < args.size(); ++i)
    424     Args[i] = (char*)GVTOP(args[i]);
    425 
    426   GenericValue GV;
    427   GV.IntVal = APInt(32, sscanf(Args[0], Args[1], Args[2], Args[3], Args[4],
    428                     Args[5], Args[6], Args[7], Args[8], Args[9]));
    429   return GV;
    430 }
    431 
    432 // int scanf(const char *format, ...);
    433 static GenericValue lle_X_scanf(FunctionType *FT, ArrayRef<GenericValue> args) {
    434   assert(args.size() < 10 && "Only handle up to 10 args to scanf right now!");
    435 
    436   char *Args[10];
    437   for (unsigned i = 0; i < args.size(); ++i)
    438     Args[i] = (char*)GVTOP(args[i]);
    439 
    440   GenericValue GV;
    441   GV.IntVal = APInt(32, scanf( Args[0], Args[1], Args[2], Args[3], Args[4],
    442                     Args[5], Args[6], Args[7], Args[8], Args[9]));
    443   return GV;
    444 }
    445 
    446 // int fprintf(FILE *, const char *, ...) - a very rough implementation to make
    447 // output useful.
    448 static GenericValue lle_X_fprintf(FunctionType *FT,
    449                                   ArrayRef<GenericValue> Args) {
    450   assert(Args.size() >= 2);
    451   char Buffer[10000];
    452   std::vector<GenericValue> NewArgs;
    453   NewArgs.push_back(PTOGV(Buffer));
    454   NewArgs.insert(NewArgs.end(), Args.begin()+1, Args.end());
    455   GenericValue GV = lle_X_sprintf(FT, NewArgs);
    456 
    457   fputs(Buffer, (FILE *) GVTOP(Args[0]));
    458   return GV;
    459 }
    460 
    461 static GenericValue lle_X_memset(FunctionType *FT,
    462                                  ArrayRef<GenericValue> Args) {
    463   int val = (int)Args[1].IntVal.getSExtValue();
    464   size_t len = (size_t)Args[2].IntVal.getZExtValue();
    465   memset((void *)GVTOP(Args[0]), val, len);
    466   // llvm.memset.* returns void, lle_X_* returns GenericValue,
    467   // so here we return GenericValue with IntVal set to zero
    468   GenericValue GV;
    469   GV.IntVal = 0;
    470   return GV;
    471 }
    472 
    473 static GenericValue lle_X_memcpy(FunctionType *FT,
    474                                  ArrayRef<GenericValue> Args) {
    475   memcpy(GVTOP(Args[0]), GVTOP(Args[1]),
    476          (size_t)(Args[2].IntVal.getLimitedValue()));
    477 
    478   // llvm.memcpy* returns void, lle_X_* returns GenericValue,
    479   // so here we return GenericValue with IntVal set to zero
    480   GenericValue GV;
    481   GV.IntVal = 0;
    482   return GV;
    483 }
    484 
    485 void Interpreter::initializeExternalFunctions() {
    486   sys::ScopedLock Writer(*FunctionsLock);
    487   (*FuncNames)["lle_X_atexit"]       = lle_X_atexit;
    488   (*FuncNames)["lle_X_exit"]         = lle_X_exit;
    489   (*FuncNames)["lle_X_abort"]        = lle_X_abort;
    490 
    491   (*FuncNames)["lle_X_printf"]       = lle_X_printf;
    492   (*FuncNames)["lle_X_sprintf"]      = lle_X_sprintf;
    493   (*FuncNames)["lle_X_sscanf"]       = lle_X_sscanf;
    494   (*FuncNames)["lle_X_scanf"]        = lle_X_scanf;
    495   (*FuncNames)["lle_X_fprintf"]      = lle_X_fprintf;
    496   (*FuncNames)["lle_X_memset"]       = lle_X_memset;
    497   (*FuncNames)["lle_X_memcpy"]       = lle_X_memcpy;
    498 }
    499