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