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/Mutex.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include <cassert>
36 #include <cmath>
37 #include <csignal>
38 #include <cstdint>
39 #include <cstdio>
40 #include <cstring>
41 #include <map>
42 #include <mutex>
43 #include <string>
44 #include <utility>
45 #include <vector>
46 
47 #ifdef HAVE_FFI_CALL
48 #ifdef HAVE_FFI_H
49 #include <ffi.h>
50 #define USE_LIBFFI
51 #elif HAVE_FFI_FFI_H
52 #include <ffi/ffi.h>
53 #define USE_LIBFFI
54 #endif
55 #endif
56 
57 using namespace llvm;
58 
59 namespace {
60 
61 typedef GenericValue (*ExFunc)(FunctionType *, ArrayRef<GenericValue>);
62 typedef void (*RawFunc)();
63 
64 struct Functions {
65   sys::Mutex Lock;
66   std::map<const Function *, ExFunc> ExportedFunctions;
67   std::map<std::string, ExFunc> FuncNames;
68 #ifdef USE_LIBFFI
69   std::map<const Function *, RawFunc> RawFunctions;
70 #endif
71 };
72 
73 Functions &getFunctions() {
74   static Functions F;
75   return F;
76 }
77 
78 } // anonymous namespace
79 
80 static Interpreter *TheInterpreter;
81 
82 static char getTypeID(Type *Ty) {
83   switch (Ty->getTypeID()) {
84   case Type::VoidTyID:    return 'V';
85   case Type::IntegerTyID:
86     switch (cast<IntegerType>(Ty)->getBitWidth()) {
87       case 1:  return 'o';
88       case 8:  return 'B';
89       case 16: return 'S';
90       case 32: return 'I';
91       case 64: return 'L';
92       default: return 'N';
93     }
94   case Type::FloatTyID:   return 'F';
95   case Type::DoubleTyID:  return 'D';
96   case Type::PointerTyID: return 'P';
97   case Type::FunctionTyID:return 'M';
98   case Type::StructTyID:  return 'T';
99   case Type::ArrayTyID:   return 'A';
100   default: return 'U';
101   }
102 }
103 
104 // Try to find address of external function given a Function object.
105 // Please note, that interpreter doesn't know how to assemble a
106 // real call in general case (this is JIT job), that's why it assumes,
107 // that all external functions has the same (and pretty "general") signature.
108 // The typical example of such functions are "lle_X_" ones.
109 static ExFunc lookupFunction(const Function *F) {
110   // Function not found, look it up... start by figuring out what the
111   // composite function name should be.
112   std::string ExtName = "lle_";
113   FunctionType *FT = F->getFunctionType();
114   ExtName += getTypeID(FT->getReturnType());
115   for (Type *T : FT->params())
116     ExtName += getTypeID(T);
117   ExtName += ("_" + F->getName()).str();
118 
119   auto &Fns = getFunctions();
120   sys::ScopedLock Writer(Fns.Lock);
121   ExFunc FnPtr = Fns.FuncNames[ExtName];
122   if (!FnPtr)
123     FnPtr = Fns.FuncNames[("lle_X_" + F->getName()).str()];
124   if (!FnPtr)  // Try calling a generic function... if it exists...
125     FnPtr = (ExFunc)(intptr_t)sys::DynamicLibrary::SearchForAddressOfSymbol(
126         ("lle_X_" + F->getName()).str());
127   if (FnPtr)
128     Fns.ExportedFunctions.insert(std::make_pair(F, FnPtr)); // Cache for later
129   return FnPtr;
130 }
131 
132 #ifdef USE_LIBFFI
133 static ffi_type *ffiTypeFor(Type *Ty) {
134   switch (Ty->getTypeID()) {
135     case Type::VoidTyID: return &ffi_type_void;
136     case Type::IntegerTyID:
137       switch (cast<IntegerType>(Ty)->getBitWidth()) {
138         case 8:  return &ffi_type_sint8;
139         case 16: return &ffi_type_sint16;
140         case 32: return &ffi_type_sint32;
141         case 64: return &ffi_type_sint64;
142       }
143       llvm_unreachable("Unhandled integer type bitwidth");
144     case Type::FloatTyID:   return &ffi_type_float;
145     case Type::DoubleTyID:  return &ffi_type_double;
146     case Type::PointerTyID: return &ffi_type_pointer;
147     default: break;
148   }
149   // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
150   report_fatal_error("Type could not be mapped for use with libffi.");
151   return NULL;
152 }
153 
154 static void *ffiValueFor(Type *Ty, const GenericValue &AV,
155                          void *ArgDataPtr) {
156   switch (Ty->getTypeID()) {
157     case Type::IntegerTyID:
158       switch (cast<IntegerType>(Ty)->getBitWidth()) {
159         case 8: {
160           int8_t *I8Ptr = (int8_t *) ArgDataPtr;
161           *I8Ptr = (int8_t) AV.IntVal.getZExtValue();
162           return ArgDataPtr;
163         }
164         case 16: {
165           int16_t *I16Ptr = (int16_t *) ArgDataPtr;
166           *I16Ptr = (int16_t) AV.IntVal.getZExtValue();
167           return ArgDataPtr;
168         }
169         case 32: {
170           int32_t *I32Ptr = (int32_t *) ArgDataPtr;
171           *I32Ptr = (int32_t) AV.IntVal.getZExtValue();
172           return ArgDataPtr;
173         }
174         case 64: {
175           int64_t *I64Ptr = (int64_t *) ArgDataPtr;
176           *I64Ptr = (int64_t) AV.IntVal.getZExtValue();
177           return ArgDataPtr;
178         }
179       }
180       llvm_unreachable("Unhandled integer type bitwidth");
181     case Type::FloatTyID: {
182       float *FloatPtr = (float *) ArgDataPtr;
183       *FloatPtr = AV.FloatVal;
184       return ArgDataPtr;
185     }
186     case Type::DoubleTyID: {
187       double *DoublePtr = (double *) ArgDataPtr;
188       *DoublePtr = AV.DoubleVal;
189       return ArgDataPtr;
190     }
191     case Type::PointerTyID: {
192       void **PtrPtr = (void **) ArgDataPtr;
193       *PtrPtr = GVTOP(AV);
194       return ArgDataPtr;
195     }
196     default: break;
197   }
198   // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
199   report_fatal_error("Type value could not be mapped for use with libffi.");
200   return NULL;
201 }
202 
203 static bool ffiInvoke(RawFunc Fn, Function *F, ArrayRef<GenericValue> ArgVals,
204                       const DataLayout &TD, GenericValue &Result) {
205   ffi_cif cif;
206   FunctionType *FTy = F->getFunctionType();
207   const unsigned NumArgs = F->arg_size();
208 
209   // TODO: We don't have type information about the remaining arguments, because
210   // this information is never passed into ExecutionEngine::runFunction().
211   if (ArgVals.size() > NumArgs && F->isVarArg()) {
212     report_fatal_error("Calling external var arg function '" + F->getName()
213                       + "' is not supported by the Interpreter.");
214   }
215 
216   unsigned ArgBytes = 0;
217 
218   std::vector<ffi_type*> args(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     args[ArgNo] = ffiTypeFor(ArgTy);
224     ArgBytes += TD.getTypeStoreSize(ArgTy);
225   }
226 
227   SmallVector<uint8_t, 128> ArgData;
228   ArgData.resize(ArgBytes);
229   uint8_t *ArgDataPtr = ArgData.data();
230   SmallVector<void*, 16> values(NumArgs);
231   for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
232        A != E; ++A) {
233     const unsigned ArgNo = A->getArgNo();
234     Type *ArgTy = FTy->getParamType(ArgNo);
235     values[ArgNo] = ffiValueFor(ArgTy, ArgVals[ArgNo], ArgDataPtr);
236     ArgDataPtr += TD.getTypeStoreSize(ArgTy);
237   }
238 
239   Type *RetTy = FTy->getReturnType();
240   ffi_type *rtype = ffiTypeFor(RetTy);
241 
242   if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, args.data()) ==
243       FFI_OK) {
244     SmallVector<uint8_t, 128> ret;
245     if (RetTy->getTypeID() != Type::VoidTyID)
246       ret.resize(TD.getTypeStoreSize(RetTy));
247     ffi_call(&cif, Fn, ret.data(), values.data());
248     switch (RetTy->getTypeID()) {
249       case Type::IntegerTyID:
250         switch (cast<IntegerType>(RetTy)->getBitWidth()) {
251           case 8:  Result.IntVal = APInt(8 , *(int8_t *) ret.data()); break;
252           case 16: Result.IntVal = APInt(16, *(int16_t*) ret.data()); break;
253           case 32: Result.IntVal = APInt(32, *(int32_t*) ret.data()); break;
254           case 64: Result.IntVal = APInt(64, *(int64_t*) ret.data()); break;
255         }
256         break;
257       case Type::FloatTyID:   Result.FloatVal   = *(float *) ret.data(); break;
258       case Type::DoubleTyID:  Result.DoubleVal  = *(double*) ret.data(); break;
259       case Type::PointerTyID: Result.PointerVal = *(void **) ret.data(); break;
260       default: break;
261     }
262     return true;
263   }
264 
265   return false;
266 }
267 #endif // USE_LIBFFI
268 
269 GenericValue Interpreter::callExternalFunction(Function *F,
270                                                ArrayRef<GenericValue> ArgVals) {
271   TheInterpreter = this;
272 
273   auto &Fns = getFunctions();
274   std::unique_lock<sys::Mutex> Guard(Fns.Lock);
275 
276   // Do a lookup to see if the function is in our cache... this should just be a
277   // deferred annotation!
278   std::map<const Function *, ExFunc>::iterator FI =
279       Fns.ExportedFunctions.find(F);
280   if (ExFunc Fn = (FI == Fns.ExportedFunctions.end()) ? lookupFunction(F)
281                                                       : FI->second) {
282     Guard.unlock();
283     return Fn(F->getFunctionType(), ArgVals);
284   }
285 
286 #ifdef USE_LIBFFI
287   std::map<const Function *, RawFunc>::iterator RF = Fns.RawFunctions.find(F);
288   RawFunc RawFn;
289   if (RF == Fns.RawFunctions.end()) {
290     RawFn = (RawFunc)(intptr_t)
291       sys::DynamicLibrary::SearchForAddressOfSymbol(std::string(F->getName()));
292     if (!RawFn)
293       RawFn = (RawFunc)(intptr_t)getPointerToGlobalIfAvailable(F);
294     if (RawFn != 0)
295       Fns.RawFunctions.insert(std::make_pair(F, RawFn)); // Cache for later
296   } else {
297     RawFn = RF->second;
298   }
299 
300   Guard.unlock();
301 
302   GenericValue Result;
303   if (RawFn != 0 && ffiInvoke(RawFn, F, ArgVals, getDataLayout(), Result))
304     return Result;
305 #endif // USE_LIBFFI
306 
307   if (F->getName() == "__main")
308     errs() << "Tried to execute an unknown external function: "
309       << *F->getType() << " __main\n";
310   else
311     report_fatal_error("Tried to execute an unknown external function: " +
312                        F->getName());
313 #ifndef USE_LIBFFI
314   errs() << "Recompiling LLVM with --enable-libffi might help.\n";
315 #endif
316   return GenericValue();
317 }
318 
319 //===----------------------------------------------------------------------===//
320 //  Functions "exported" to the running application...
321 //
322 
323 // void atexit(Function*)
324 static GenericValue lle_X_atexit(FunctionType *FT,
325                                  ArrayRef<GenericValue> Args) {
326   assert(Args.size() == 1);
327   TheInterpreter->addAtExitHandler((Function*)GVTOP(Args[0]));
328   GenericValue GV;
329   GV.IntVal = 0;
330   return GV;
331 }
332 
333 // void exit(int)
334 static GenericValue lle_X_exit(FunctionType *FT, ArrayRef<GenericValue> Args) {
335   TheInterpreter->exitCalled(Args[0]);
336   return GenericValue();
337 }
338 
339 // void abort(void)
340 static GenericValue lle_X_abort(FunctionType *FT, ArrayRef<GenericValue> Args) {
341   //FIXME: should we report or raise here?
342   //report_fatal_error("Interpreted program raised SIGABRT");
343   raise (SIGABRT);
344   return GenericValue();
345 }
346 
347 // Silence warnings about sprintf. (See also
348 // https://github.com/llvm/llvm-project/issues/58086)
349 #if defined(__clang__)
350 #pragma clang diagnostic push
351 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
352 #endif
353 // int sprintf(char *, const char *, ...) - a very rough implementation to make
354 // output useful.
355 static GenericValue lle_X_sprintf(FunctionType *FT,
356                                   ArrayRef<GenericValue> Args) {
357   char *OutputBuffer = (char *)GVTOP(Args[0]);
358   const char *FmtStr = (const char *)GVTOP(Args[1]);
359   unsigned ArgNo = 2;
360 
361   // printf should return # chars printed.  This is completely incorrect, but
362   // close enough for now.
363   GenericValue GV;
364   GV.IntVal = APInt(32, strlen(FmtStr));
365   while (true) {
366     switch (*FmtStr) {
367     case 0: return GV;             // Null terminator...
368     default:                       // Normal nonspecial character
369       sprintf(OutputBuffer++, "%c", *FmtStr++);
370       break;
371     case '\\': {                   // Handle escape codes
372       sprintf(OutputBuffer, "%c%c", *FmtStr, *(FmtStr+1));
373       FmtStr += 2; OutputBuffer += 2;
374       break;
375     }
376     case '%': {                    // Handle format specifiers
377       char FmtBuf[100] = "", Buffer[1000] = "";
378       char *FB = FmtBuf;
379       *FB++ = *FmtStr++;
380       char Last = *FB++ = *FmtStr++;
381       unsigned HowLong = 0;
382       while (Last != 'c' && Last != 'd' && Last != 'i' && Last != 'u' &&
383              Last != 'o' && Last != 'x' && Last != 'X' && Last != 'e' &&
384              Last != 'E' && Last != 'g' && Last != 'G' && Last != 'f' &&
385              Last != 'p' && Last != 's' && Last != '%') {
386         if (Last == 'l' || Last == 'L') HowLong++;  // Keep track of l's
387         Last = *FB++ = *FmtStr++;
388       }
389       *FB = 0;
390 
391       switch (Last) {
392       case '%':
393         memcpy(Buffer, "%", 2); break;
394       case 'c':
395         sprintf(Buffer, FmtBuf, uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
396         break;
397       case 'd': case 'i':
398       case 'u': case 'o':
399       case 'x': case 'X':
400         if (HowLong >= 1) {
401           if (HowLong == 1 &&
402               TheInterpreter->getDataLayout().getPointerSizeInBits() == 64 &&
403               sizeof(long) < sizeof(int64_t)) {
404             // Make sure we use %lld with a 64 bit argument because we might be
405             // compiling LLI on a 32 bit compiler.
406             unsigned Size = strlen(FmtBuf);
407             FmtBuf[Size] = FmtBuf[Size-1];
408             FmtBuf[Size+1] = 0;
409             FmtBuf[Size-1] = 'l';
410           }
411           sprintf(Buffer, FmtBuf, Args[ArgNo++].IntVal.getZExtValue());
412         } else
413           sprintf(Buffer, FmtBuf,uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
414         break;
415       case 'e': case 'E': case 'g': case 'G': case 'f':
416         sprintf(Buffer, FmtBuf, Args[ArgNo++].DoubleVal); break;
417       case 'p':
418         sprintf(Buffer, FmtBuf, (void*)GVTOP(Args[ArgNo++])); break;
419       case 's':
420         sprintf(Buffer, FmtBuf, (char*)GVTOP(Args[ArgNo++])); break;
421       default:
422         errs() << "<unknown printf code '" << *FmtStr << "'!>";
423         ArgNo++; break;
424       }
425       size_t Len = strlen(Buffer);
426       memcpy(OutputBuffer, Buffer, Len + 1);
427       OutputBuffer += Len;
428       }
429       break;
430     }
431   }
432   return GV;
433 }
434 #if defined(__clang__)
435 #pragma clang diagnostic pop
436 #endif
437 
438 // int printf(const char *, ...) - a very rough implementation to make output
439 // useful.
440 static GenericValue lle_X_printf(FunctionType *FT,
441                                  ArrayRef<GenericValue> Args) {
442   char Buffer[10000];
443   std::vector<GenericValue> NewArgs;
444   NewArgs.push_back(PTOGV((void*)&Buffer[0]));
445   llvm::append_range(NewArgs, Args);
446   GenericValue GV = lle_X_sprintf(FT, NewArgs);
447   outs() << Buffer;
448   return GV;
449 }
450 
451 // int sscanf(const char *format, ...);
452 static GenericValue lle_X_sscanf(FunctionType *FT,
453                                  ArrayRef<GenericValue> args) {
454   assert(args.size() < 10 && "Only handle up to 10 args to sscanf right now!");
455 
456   char *Args[10];
457   for (unsigned i = 0; i < args.size(); ++i)
458     Args[i] = (char*)GVTOP(args[i]);
459 
460   GenericValue GV;
461   GV.IntVal = APInt(32, sscanf(Args[0], Args[1], Args[2], Args[3], Args[4],
462                     Args[5], Args[6], Args[7], Args[8], Args[9]));
463   return GV;
464 }
465 
466 // int scanf(const char *format, ...);
467 static GenericValue lle_X_scanf(FunctionType *FT, ArrayRef<GenericValue> args) {
468   assert(args.size() < 10 && "Only handle up to 10 args to scanf right now!");
469 
470   char *Args[10];
471   for (unsigned i = 0; i < args.size(); ++i)
472     Args[i] = (char*)GVTOP(args[i]);
473 
474   GenericValue GV;
475   GV.IntVal = APInt(32, scanf( Args[0], Args[1], Args[2], Args[3], Args[4],
476                     Args[5], Args[6], Args[7], Args[8], Args[9]));
477   return GV;
478 }
479 
480 // int fprintf(FILE *, const char *, ...) - a very rough implementation to make
481 // output useful.
482 static GenericValue lle_X_fprintf(FunctionType *FT,
483                                   ArrayRef<GenericValue> Args) {
484   assert(Args.size() >= 2);
485   char Buffer[10000];
486   std::vector<GenericValue> NewArgs;
487   NewArgs.push_back(PTOGV(Buffer));
488   NewArgs.insert(NewArgs.end(), Args.begin()+1, Args.end());
489   GenericValue GV = lle_X_sprintf(FT, NewArgs);
490 
491   fputs(Buffer, (FILE *) GVTOP(Args[0]));
492   return GV;
493 }
494 
495 static GenericValue lle_X_memset(FunctionType *FT,
496                                  ArrayRef<GenericValue> Args) {
497   int val = (int)Args[1].IntVal.getSExtValue();
498   size_t len = (size_t)Args[2].IntVal.getZExtValue();
499   memset((void *)GVTOP(Args[0]), val, len);
500   // llvm.memset.* returns void, lle_X_* returns GenericValue,
501   // so here we return GenericValue with IntVal set to zero
502   GenericValue GV;
503   GV.IntVal = 0;
504   return GV;
505 }
506 
507 static GenericValue lle_X_memcpy(FunctionType *FT,
508                                  ArrayRef<GenericValue> Args) {
509   memcpy(GVTOP(Args[0]), GVTOP(Args[1]),
510          (size_t)(Args[2].IntVal.getLimitedValue()));
511 
512   // llvm.memcpy* returns void, lle_X_* returns GenericValue,
513   // so here we return GenericValue with IntVal set to zero
514   GenericValue GV;
515   GV.IntVal = 0;
516   return GV;
517 }
518 
519 void Interpreter::initializeExternalFunctions() {
520   auto &Fns = getFunctions();
521   sys::ScopedLock Writer(Fns.Lock);
522   Fns.FuncNames["lle_X_atexit"]       = lle_X_atexit;
523   Fns.FuncNames["lle_X_exit"]         = lle_X_exit;
524   Fns.FuncNames["lle_X_abort"]        = lle_X_abort;
525 
526   Fns.FuncNames["lle_X_printf"]       = lle_X_printf;
527   Fns.FuncNames["lle_X_sprintf"]      = lle_X_sprintf;
528   Fns.FuncNames["lle_X_sscanf"]       = lle_X_sscanf;
529   Fns.FuncNames["lle_X_scanf"]        = lle_X_scanf;
530   Fns.FuncNames["lle_X_fprintf"]      = lle_X_fprintf;
531   Fns.FuncNames["lle_X_memset"]       = lle_X_memset;
532   Fns.FuncNames["lle_X_memcpy"]       = lle_X_memcpy;
533 }
534