ExternalFunctions.cpp revision 360784 
1//===-- ExternalFunctions.cpp - Implement External Functions --------------===//
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//  This file contains both code to deal with invoking "external" functions, but
10//  also contains code that implements "exported" external functions.
11//
12//  There are currently two mechanisms for handling external functions in the
13//  Interpreter.  The first is to implement lle_* wrapper functions that are
14//  specific to well-known library functions which manually translate the
15//  arguments from GenericValues and make the call.  If such a wrapper does
16//  not exist, and libffi is available, then the Interpreter will attempt to
17//  invoke the function using libffi, after finding its address.
18//
19//===----------------------------------------------------------------------===//
20
21#include "Interpreter.h"
22#include "llvm/ADT/APInt.h"
23#include "llvm/ADT/ArrayRef.h"
24#include "llvm/Config/config.h" // Detect libffi
25#include "llvm/ExecutionEngine/GenericValue.h"
26#include "llvm/IR/DataLayout.h"
27#include "llvm/IR/DerivedTypes.h"
28#include "llvm/IR/Function.h"
29#include "llvm/IR/Type.h"
30#include "llvm/Support/Casting.h"
31#include "llvm/Support/DynamicLibrary.h"
32#include "llvm/Support/ErrorHandling.h"
33#include "llvm/Support/ManagedStatic.h"
34#include "llvm/Support/Mutex.h"
35#include "llvm/Support/raw_ostream.h"
36#include <cassert>
37#include <cmath>
38#include <csignal>
39#include <cstdint>
40#include <cstdio>
41#include <cstring>
42#include <map>
43#include <mutex>
44#include <string>
45#include <utility>
46#include <vector>
47
48#ifdef HAVE_FFI_CALL
49#ifdef HAVE_FFI_H
50#include <ffi.h>
51#define USE_LIBFFI
52#elif HAVE_FFI_FFI_H
53#include <ffi/ffi.h>
54#define USE_LIBFFI
55#endif
56#endif
57
58using namespace llvm;
59
60static ManagedStatic<sys::Mutex> FunctionsLock;
61
62typedef GenericValue (*ExFunc)(FunctionType *, ArrayRef<GenericValue>);
63static ManagedStatic<std::map<const Function *, ExFunc> > ExportedFunctions;
64static ManagedStatic<std::map<std::string, ExFunc> > FuncNames;
65
66#ifdef USE_LIBFFI
67typedef void (*RawFunc)();
68static ManagedStatic<std::map<const Function *, RawFunc> > RawFunctions;
69#endif
70
71static Interpreter *TheInterpreter;
72
73static char getTypeID(Type *Ty) {
74  switch (Ty->getTypeID()) {
75  case Type::VoidTyID:    return 'V';
76  case Type::IntegerTyID:
77    switch (cast<IntegerType>(Ty)->getBitWidth()) {
78      case 1:  return 'o';
79      case 8:  return 'B';
80      case 16: return 'S';
81      case 32: return 'I';
82      case 64: return 'L';
83      default: return 'N';
84    }
85  case Type::FloatTyID:   return 'F';
86  case Type::DoubleTyID:  return 'D';
87  case Type::PointerTyID: return 'P';
88  case Type::FunctionTyID:return 'M';
89  case Type::StructTyID:  return 'T';
90  case Type::ArrayTyID:   return 'A';
91  default: return 'U';
92  }
93}
94
95// Try to find address of external function given a Function object.
96// Please note, that interpreter doesn't know how to assemble a
97// real call in general case (this is JIT job), that's why it assumes,
98// that all external functions has the same (and pretty "general") signature.
99// The typical example of such functions are "lle_X_" ones.
100static ExFunc lookupFunction(const Function *F) {
101  // Function not found, look it up... start by figuring out what the
102  // composite function name should be.
103  std::string ExtName = "lle_";
104  FunctionType *FT = F->getFunctionType();
105  ExtName += getTypeID(FT->getReturnType());
106  for (Type *T : FT->params())
107    ExtName += getTypeID(T);
108  ExtName += ("_" + F->getName()).str();
109
110  sys::ScopedLock Writer(*FunctionsLock);
111  ExFunc FnPtr = (*FuncNames)[ExtName];
112  if (!FnPtr)
113    FnPtr = (*FuncNames)[("lle_X_" + F->getName()).str()];
114  if (!FnPtr)  // Try calling a generic function... if it exists...
115    FnPtr = (ExFunc)(intptr_t)sys::DynamicLibrary::SearchForAddressOfSymbol(
116        ("lle_X_" + F->getName()).str());
117  if (FnPtr)
118    ExportedFunctions->insert(std::make_pair(F, FnPtr));  // Cache for later
119  return FnPtr;
120}
121
122#ifdef USE_LIBFFI
123static ffi_type *ffiTypeFor(Type *Ty) {
124  switch (Ty->getTypeID()) {
125    case Type::VoidTyID: return &ffi_type_void;
126    case Type::IntegerTyID:
127      switch (cast<IntegerType>(Ty)->getBitWidth()) {
128        case 8:  return &ffi_type_sint8;
129        case 16: return &ffi_type_sint16;
130        case 32: return &ffi_type_sint32;
131        case 64: return &ffi_type_sint64;
132      }
133    case Type::FloatTyID:   return &ffi_type_float;
134    case Type::DoubleTyID:  return &ffi_type_double;
135    case Type::PointerTyID: return &ffi_type_pointer;
136    default: break;
137  }
138  // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
139  report_fatal_error("Type could not be mapped for use with libffi.");
140  return NULL;
141}
142
143static void *ffiValueFor(Type *Ty, const GenericValue &AV,
144                         void *ArgDataPtr) {
145  switch (Ty->getTypeID()) {
146    case Type::IntegerTyID:
147      switch (cast<IntegerType>(Ty)->getBitWidth()) {
148        case 8: {
149          int8_t *I8Ptr = (int8_t *) ArgDataPtr;
150          *I8Ptr = (int8_t) AV.IntVal.getZExtValue();
151          return ArgDataPtr;
152        }
153        case 16: {
154          int16_t *I16Ptr = (int16_t *) ArgDataPtr;
155          *I16Ptr = (int16_t) AV.IntVal.getZExtValue();
156          return ArgDataPtr;
157        }
158        case 32: {
159          int32_t *I32Ptr = (int32_t *) ArgDataPtr;
160          *I32Ptr = (int32_t) AV.IntVal.getZExtValue();
161          return ArgDataPtr;
162        }
163        case 64: {
164          int64_t *I64Ptr = (int64_t *) ArgDataPtr;
165          *I64Ptr = (int64_t) AV.IntVal.getZExtValue();
166          return ArgDataPtr;
167        }
168      }
169    case Type::FloatTyID: {
170      float *FloatPtr = (float *) ArgDataPtr;
171      *FloatPtr = AV.FloatVal;
172      return ArgDataPtr;
173    }
174    case Type::DoubleTyID: {
175      double *DoublePtr = (double *) ArgDataPtr;
176      *DoublePtr = AV.DoubleVal;
177      return ArgDataPtr;
178    }
179    case Type::PointerTyID: {
180      void **PtrPtr = (void **) ArgDataPtr;
181      *PtrPtr = GVTOP(AV);
182      return ArgDataPtr;
183    }
184    default: break;
185  }
186  // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
187  report_fatal_error("Type value could not be mapped for use with libffi.");
188  return NULL;
189}
190
191static bool ffiInvoke(RawFunc Fn, Function *F, ArrayRef<GenericValue> ArgVals,
192                      const DataLayout &TD, GenericValue &Result) {
193  ffi_cif cif;
194  FunctionType *FTy = F->getFunctionType();
195  const unsigned NumArgs = F->arg_size();
196
197  // TODO: We don't have type information about the remaining arguments, because
198  // this information is never passed into ExecutionEngine::runFunction().
199  if (ArgVals.size() > NumArgs && F->isVarArg()) {
200    report_fatal_error("Calling external var arg function '" + F->getName()
201                      + "' is not supported by the Interpreter.");
202  }
203
204  unsigned ArgBytes = 0;
205
206  std::vector<ffi_type*> args(NumArgs);
207  for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
208       A != E; ++A) {
209    const unsigned ArgNo = A->getArgNo();
210    Type *ArgTy = FTy->getParamType(ArgNo);
211    args[ArgNo] = ffiTypeFor(ArgTy);
212    ArgBytes += TD.getTypeStoreSize(ArgTy);
213  }
214
215  SmallVector<uint8_t, 128> ArgData;
216  ArgData.resize(ArgBytes);
217  uint8_t *ArgDataPtr = ArgData.data();
218  SmallVector<void*, 16> values(NumArgs);
219  for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
220       A != E; ++A) {
221    const unsigned ArgNo = A->getArgNo();
222    Type *ArgTy = FTy->getParamType(ArgNo);
223    values[ArgNo] = ffiValueFor(ArgTy, ArgVals[ArgNo], ArgDataPtr);
224    ArgDataPtr += TD.getTypeStoreSize(ArgTy);
225  }
226
227  Type *RetTy = FTy->getReturnType();
228  ffi_type *rtype = ffiTypeFor(RetTy);
229
230  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, args.data()) ==
231      FFI_OK) {
232    SmallVector<uint8_t, 128> ret;
233    if (RetTy->getTypeID() != Type::VoidTyID)
234      ret.resize(TD.getTypeStoreSize(RetTy));
235    ffi_call(&cif, Fn, ret.data(), values.data());
236    switch (RetTy->getTypeID()) {
237      case Type::IntegerTyID:
238        switch (cast<IntegerType>(RetTy)->getBitWidth()) {
239          case 8:  Result.IntVal = APInt(8 , *(int8_t *) ret.data()); break;
240          case 16: Result.IntVal = APInt(16, *(int16_t*) ret.data()); break;
241          case 32: Result.IntVal = APInt(32, *(int32_t*) ret.data()); break;
242          case 64: Result.IntVal = APInt(64, *(int64_t*) ret.data()); break;
243        }
244        break;
245      case Type::FloatTyID:   Result.FloatVal   = *(float *) ret.data(); break;
246      case Type::DoubleTyID:  Result.DoubleVal  = *(double*) ret.data(); break;
247      case Type::PointerTyID: Result.PointerVal = *(void **) ret.data(); break;
248      default: break;
249    }
250    return true;
251  }
252
253  return false;
254}
255#endif // USE_LIBFFI
256
257GenericValue Interpreter::callExternalFunction(Function *F,
258                                               ArrayRef<GenericValue> ArgVals) {
259  TheInterpreter = this;
260
261  std::unique_lock<sys::Mutex> Guard(*FunctionsLock);
262
263  // Do a lookup to see if the function is in our cache... this should just be a
264  // deferred annotation!
265  std::map<const Function *, ExFunc>::iterator FI = ExportedFunctions->find(F);
266  if (ExFunc Fn = (FI == ExportedFunctions->end()) ? lookupFunction(F)
267                                                   : FI->second) {
268    Guard.unlock();
269    return Fn(F->getFunctionType(), ArgVals);
270  }
271
272#ifdef USE_LIBFFI
273  std::map<const Function *, RawFunc>::iterator RF = RawFunctions->find(F);
274  RawFunc RawFn;
275  if (RF == RawFunctions->end()) {
276    RawFn = (RawFunc)(intptr_t)
277      sys::DynamicLibrary::SearchForAddressOfSymbol(F->getName());
278    if (!RawFn)
279      RawFn = (RawFunc)(intptr_t)getPointerToGlobalIfAvailable(F);
280    if (RawFn != 0)
281      RawFunctions->insert(std::make_pair(F, RawFn));  // Cache for later
282  } else {
283    RawFn = RF->second;
284  }
285
286  Guard.unlock();
287
288  GenericValue Result;
289  if (RawFn != 0 && ffiInvoke(RawFn, F, ArgVals, getDataLayout(), Result))
290    return Result;
291#endif // USE_LIBFFI
292
293  if (F->getName() == "__main")
294    errs() << "Tried to execute an unknown external function: "
295      << *F->getType() << " __main\n";
296  else
297    report_fatal_error("Tried to execute an unknown external function: " +
298                       F->getName());
299#ifndef USE_LIBFFI
300  errs() << "Recompiling LLVM with --enable-libffi might help.\n";
301#endif
302  return GenericValue();
303}
304
305//===----------------------------------------------------------------------===//
306//  Functions "exported" to the running application...
307//
308
309// void atexit(Function*)
310static GenericValue lle_X_atexit(FunctionType *FT,
311                                 ArrayRef<GenericValue> Args) {
312  assert(Args.size() == 1);
313  TheInterpreter->addAtExitHandler((Function*)GVTOP(Args[0]));
314  GenericValue GV;
315  GV.IntVal = 0;
316  return GV;
317}
318
319// void exit(int)
320static GenericValue lle_X_exit(FunctionType *FT, ArrayRef<GenericValue> Args) {
321  TheInterpreter->exitCalled(Args[0]);
322  return GenericValue();
323}
324
325// void abort(void)
326static GenericValue lle_X_abort(FunctionType *FT, ArrayRef<GenericValue> Args) {
327  //FIXME: should we report or raise here?
328  //report_fatal_error("Interpreted program raised SIGABRT");
329  raise (SIGABRT);
330  return GenericValue();
331}
332
333// int sprintf(char *, const char *, ...) - a very rough implementation to make
334// output useful.
335static GenericValue lle_X_sprintf(FunctionType *FT,
336                                  ArrayRef<GenericValue> Args) {
337  char *OutputBuffer = (char *)GVTOP(Args[0]);
338  const char *FmtStr = (const char *)GVTOP(Args[1]);
339  unsigned ArgNo = 2;
340
341  // printf should return # chars printed.  This is completely incorrect, but
342  // close enough for now.
343  GenericValue GV;
344  GV.IntVal = APInt(32, strlen(FmtStr));
345  while (true) {
346    switch (*FmtStr) {
347    case 0: return GV;             // Null terminator...
348    default:                       // Normal nonspecial character
349      sprintf(OutputBuffer++, "%c", *FmtStr++);
350      break;
351    case '\\': {                   // Handle escape codes
352      sprintf(OutputBuffer, "%c%c", *FmtStr, *(FmtStr+1));
353      FmtStr += 2; OutputBuffer += 2;
354      break;
355    }
356    case '%': {                    // Handle format specifiers
357      char FmtBuf[100] = "", Buffer[1000] = "";
358      char *FB = FmtBuf;
359      *FB++ = *FmtStr++;
360      char Last = *FB++ = *FmtStr++;
361      unsigned HowLong = 0;
362      while (Last != 'c' && Last != 'd' && Last != 'i' && Last != 'u' &&
363             Last != 'o' && Last != 'x' && Last != 'X' && Last != 'e' &&
364             Last != 'E' && Last != 'g' && Last != 'G' && Last != 'f' &&
365             Last != 'p' && Last != 's' && Last != '%') {
366        if (Last == 'l' || Last == 'L') HowLong++;  // Keep track of l's
367        Last = *FB++ = *FmtStr++;
368      }
369      *FB = 0;
370
371      switch (Last) {
372      case '%':
373        memcpy(Buffer, "%", 2); break;
374      case 'c':
375        sprintf(Buffer, FmtBuf, uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
376        break;
377      case 'd': case 'i':
378      case 'u': case 'o':
379      case 'x': case 'X':
380        if (HowLong >= 1) {
381          if (HowLong == 1 &&
382              TheInterpreter->getDataLayout().getPointerSizeInBits() == 64 &&
383              sizeof(long) < sizeof(int64_t)) {
384            // Make sure we use %lld with a 64 bit argument because we might be
385            // compiling LLI on a 32 bit compiler.
386            unsigned Size = strlen(FmtBuf);
387            FmtBuf[Size] = FmtBuf[Size-1];
388            FmtBuf[Size+1] = 0;
389            FmtBuf[Size-1] = 'l';
390          }
391          sprintf(Buffer, FmtBuf, Args[ArgNo++].IntVal.getZExtValue());
392        } else
393          sprintf(Buffer, FmtBuf,uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
394        break;
395      case 'e': case 'E': case 'g': case 'G': case 'f':
396        sprintf(Buffer, FmtBuf, Args[ArgNo++].DoubleVal); break;
397      case 'p':
398        sprintf(Buffer, FmtBuf, (void*)GVTOP(Args[ArgNo++])); break;
399      case 's':
400        sprintf(Buffer, FmtBuf, (char*)GVTOP(Args[ArgNo++])); break;
401      default:
402        errs() << "<unknown printf code '" << *FmtStr << "'!>";
403        ArgNo++; break;
404      }
405      size_t Len = strlen(Buffer);
406      memcpy(OutputBuffer, Buffer, Len + 1);
407      OutputBuffer += Len;
408      }
409      break;
410    }
411  }
412  return GV;
413}
414
415// int printf(const char *, ...) - a very rough implementation to make output
416// useful.
417static GenericValue lle_X_printf(FunctionType *FT,
418                                 ArrayRef<GenericValue> Args) {
419  char Buffer[10000];
420  std::vector<GenericValue> NewArgs;
421  NewArgs.push_back(PTOGV((void*)&Buffer[0]));
422  NewArgs.insert(NewArgs.end(), Args.begin(), Args.end());
423  GenericValue GV = lle_X_sprintf(FT, NewArgs);
424  outs() << Buffer;
425  return GV;
426}
427
428// int sscanf(const char *format, ...);
429static GenericValue lle_X_sscanf(FunctionType *FT,
430                                 ArrayRef<GenericValue> args) {
431  assert(args.size() < 10 && "Only handle up to 10 args to sscanf right now!");
432
433  char *Args[10];
434  for (unsigned i = 0; i < args.size(); ++i)
435    Args[i] = (char*)GVTOP(args[i]);
436
437  GenericValue GV;
438  GV.IntVal = APInt(32, sscanf(Args[0], Args[1], Args[2], Args[3], Args[4],
439                    Args[5], Args[6], Args[7], Args[8], Args[9]));
440  return GV;
441}
442
443// int scanf(const char *format, ...);
444static GenericValue lle_X_scanf(FunctionType *FT, ArrayRef<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.
459static GenericValue lle_X_fprintf(FunctionType *FT,
460                                  ArrayRef<GenericValue> Args) {
461  assert(Args.size() >= 2);
462  char Buffer[10000];
463  std::vector<GenericValue> NewArgs;
464  NewArgs.push_back(PTOGV(Buffer));
465  NewArgs.insert(NewArgs.end(), Args.begin()+1, Args.end());
466  GenericValue GV = lle_X_sprintf(FT, NewArgs);
467
468  fputs(Buffer, (FILE *) GVTOP(Args[0]));
469  return GV;
470}
471
472static GenericValue lle_X_memset(FunctionType *FT,
473                                 ArrayRef<GenericValue> Args) {
474  int val = (int)Args[1].IntVal.getSExtValue();
475  size_t len = (size_t)Args[2].IntVal.getZExtValue();
476  memset((void *)GVTOP(Args[0]), val, len);
477  // llvm.memset.* returns void, lle_X_* returns GenericValue,
478  // so here we return GenericValue with IntVal set to zero
479  GenericValue GV;
480  GV.IntVal = 0;
481  return GV;
482}
483
484static GenericValue lle_X_memcpy(FunctionType *FT,
485                                 ArrayRef<GenericValue> Args) {
486  memcpy(GVTOP(Args[0]), GVTOP(Args[1]),
487         (size_t)(Args[2].IntVal.getLimitedValue()));
488
489  // llvm.memcpy* returns void, lle_X_* returns GenericValue,
490  // so here we return GenericValue with IntVal set to zero
491  GenericValue GV;
492  GV.IntVal = 0;
493  return GV;
494}
495
496void Interpreter::initializeExternalFunctions() {
497  sys::ScopedLock Writer(*FunctionsLock);
498  (*FuncNames)["lle_X_atexit"]       = lle_X_atexit;
499  (*FuncNames)["lle_X_exit"]         = lle_X_exit;
500  (*FuncNames)["lle_X_abort"]        = lle_X_abort;
501
502  (*FuncNames)["lle_X_printf"]       = lle_X_printf;
503  (*FuncNames)["lle_X_sprintf"]      = lle_X_sprintf;
504  (*FuncNames)["lle_X_sscanf"]       = lle_X_sscanf;
505  (*FuncNames)["lle_X_scanf"]        = lle_X_scanf;
506  (*FuncNames)["lle_X_fprintf"]      = lle_X_fprintf;
507  (*FuncNames)["lle_X_memset"]       = lle_X_memset;
508  (*FuncNames)["lle_X_memcpy"]       = lle_X_memcpy;
509}
510