path: root/libjava/stacktrace.cc

// stacktrace.cc - Functions for unwinding & inspecting the call stack.

/* Copyright (C) 2005  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

#include <config.h>

#include <jvm.h>
#include <gcj/cni.h>
#include <java-interp.h>
#include <java-stack.h>

#ifdef HAVE_DLFCN_H
#include <dlfcn.h>
#endif

#include <stdio.h>

#include <java/lang/Class.h>
#include <java/lang/Long.h>
#include <java/util/ArrayList.h>
#include <java/util/IdentityHashMap.h>
#include <gnu/java/lang/MainThread.h>
#include <gnu/gcj/runtime/NameFinder.h>

#include <sysdep/backtrace.h>

using namespace java::lang;
using namespace java::lang::reflect;
using namespace java::util;
using namespace gnu::gcj::runtime;

// Maps ncode values to their containing native class.
// NOTE: Currently this Map contradicts class GC for native classes. This map
// (and the "new class stack") will need to use WeakReferences in order to 
// enable native class GC.
static java::util::IdentityHashMap *ncodeMap;

// Check the "class stack" for any classes initialized since we were last 
// called, and add them to ncodeMap.
void 
_Jv_StackTrace::UpdateNCodeMap ()
{
  // The Map should be large enough so that a typical Java app doesn't cause 
  // it to rehash, without using too much memory. ~5000 entries should be 
  // enough.
  if (ncodeMap == NULL)
    ncodeMap = new java::util::IdentityHashMap (5087);
  
  jclass klass;
  while ((klass = _Jv_PopClass ()))
    {
      //printf ("got %s\n", klass->name->data);
#ifdef INTERPRETER
      JvAssert (! _Jv_IsInterpretedClass (klass));
#endif
      for (int i=0; i < klass->method_count; i++)
        {
	  _Jv_Method *method = &klass->methods[i];
	  // Add non-abstract methods to ncodeMap.
	  if (method->ncode)
	    {
	      //printf("map->put 0x%x / %s.%s\n", method->ncode, klass->name->data,
	      //  method->name->data);
	      ncodeMap->put ((java::lang::Object *) method->ncode, klass);
	    }
	}
    }
}

// Given a native frame, return the class which this code belongs 
// to. Returns NULL if this IP is not associated with a native Java class.
// If NCODE is supplied, it will be set with the ip for the entry point of the 
// enclosing method.
jclass
_Jv_StackTrace::ClassForFrame (_Jv_StackFrame *frame)
{
  JvAssert (frame->type == frame_native);
  jclass klass = NULL;
  // use _Unwind_FindEnclosingFunction to find start of method
  //void *entryPoint = _Unwind_FindEnclosingFunction (ip);

  // look it up in ncodeMap
  if (frame->start_ip)
    klass = (jclass) ncodeMap->get ((jobject) frame->start_ip);

  return klass;
}

_Unwind_Reason_Code
_Jv_StackTrace::UnwindTraceFn (struct _Unwind_Context *context, void *state_ptr)
{
  _Jv_UnwindState *state = (_Jv_UnwindState *) state_ptr;
  jint pos = state->pos;

  // Check if the trace buffer needs to be extended.
  if (pos == state->length)
    {
      int newLength = state->length *= 2;
      void *newFrames = _Jv_AllocBytes (newLength * sizeof(_Jv_StackFrame));
      memcpy (newFrames, state->frames, state->length * sizeof(_Jv_StackFrame));      
      state->frames = (_Jv_StackFrame *) newFrames;
      state->length = newLength;
    }
  
  _Unwind_Ptr func_addr = _Unwind_GetRegionStart (context);
  
  // If we see the interpreter's main function, "pop" an entry off the 
  // interpreter stack and use that instead, so that the trace goes through 
  // the java code and not the interpreter itself. This assumes a 1:1 
  // correspondance between call frames in the interpreted stack and occurances
  // of _Jv_InterpMethod::run() on the native stack.
#ifdef INTERPRETER
  if (func_addr == (_Unwind_Ptr) &_Jv_InterpMethod::run)
    {
      state->frames[pos].type = frame_interpreter;
      state->frames[pos].interp.meth = state->interp_frame->self;
      state->frames[pos].interp.pc = state->interp_frame->pc;
      state->interp_frame = state->interp_frame->next;
    }
  else
#endif
    {
      state->frames[pos].type = frame_native;
      state->frames[pos].ip = (void *) _Unwind_GetIP (context);
      state->frames[pos].start_ip = (void *) func_addr;
    }

  //printf ("unwind ip: %p\n", _Unwind_GetIP (context));

  _Unwind_Reason_Code result = _URC_NO_REASON;
  if (state->trace_function != NULL)
    result = (state->trace_function) (state);
  state->pos++;
  return result;
}

// Return a raw stack trace from the current point of execution. The raw 
// trace will include all functions that have unwind info.
_Jv_StackTrace *
_Jv_StackTrace::GetStackTrace(void)
{
  int trace_size = 100;
  _Jv_StackFrame frames[trace_size];
  _Jv_UnwindState state (trace_size);
  state.frames = (_Jv_StackFrame *) &frames;

#ifdef SJLJ_EXCEPTIONS
  // The Unwind interface doesn't work with the SJLJ exception model.
  // Fall back to a platform-specific unwinder.
  fallback_backtrace (&state);
#else /* SJLJ_EXCEPTIONS */  
  _Unwind_Backtrace (UnwindTraceFn, &state);
#endif /* SJLJ_EXCEPTIONS */
  
  // Copy the trace and return it.
  int traceSize = sizeof (_Jv_StackTrace) + 
    (sizeof (_Jv_StackFrame) * state.pos);
  _Jv_StackTrace *trace = (_Jv_StackTrace *) _Jv_AllocBytes (traceSize);
  trace->length = state.pos;
  memcpy (trace->frames, state.frames, sizeof (_Jv_StackFrame) * state.pos);  
  return trace;
}

void
_Jv_StackTrace::getLineNumberForFrame(_Jv_StackFrame *frame, NameFinder *finder, 
		 jstring *sourceFileName, jint *lineNum)
{
#ifdef INTERPRETER
  if (frame->type == frame_interpreter)
    {
      _Jv_InterpMethod *interp_meth = frame->interp.meth;
      _Jv_InterpClass *interp_class = 
	 (_Jv_InterpClass *) interp_meth->defining_class->aux_info;
      *sourceFileName = interp_class->source_file_name;
      *lineNum = interp_meth->get_source_line(frame->interp.pc);
      return;
    }
#endif
  // Use dladdr() to determine in which binary the address IP resides.
#if defined (HAVE_DLFCN_H) && defined (HAVE_DLADDR)
  Dl_info info;
  jstring binaryName = NULL;
  const char *argv0 = _Jv_GetSafeArg(0);

  void *ip = frame->ip;
  _Unwind_Ptr offset = 0;

  if (dladdr (ip, &info))
    {
      if (info.dli_fname)
	binaryName = JvNewStringUTF (info.dli_fname);
      else
        return;

      // addr2line expects relative addresses for shared libraries.
      if (strcmp (info.dli_fname, argv0) == 0)
        offset = (_Unwind_Ptr) ip;
      else
        offset = (_Unwind_Ptr) ip - (_Unwind_Ptr) info.dli_fbase;

      //printf ("linenum ip: %p\n", ip);
      //printf ("%s: 0x%x\n", info.dli_fname, offset);
      //offset -= sizeof(void *);
      
      // The unwinder gives us the return address. In order to get the right
      // line number for the stack trace, roll it back a little.
      offset -= 1;

      // printf ("%s: 0x%x\n", info.dli_fname, offset);
      
      finder->lookup (binaryName, (jlong) offset);
      *sourceFileName = finder->getSourceFile();
      *lineNum = finder->getLineNum();
    }
#endif
}

// Look up class and method info for the given stack frame, setting 
// frame->klass and frame->meth if they are known.
void
_Jv_StackTrace::FillInFrameInfo (_Jv_StackFrame *frame)
{
  jclass klass = NULL;
  _Jv_Method *meth = NULL;
  
  if (frame->type == frame_native)
    {
      klass = _Jv_StackTrace::ClassForFrame (frame);

      if (klass != NULL)
	// Find method in class
	for (int j = 0; j < klass->method_count; j++)
	  {
	    if (klass->methods[j].ncode == frame->start_ip)
	      {
		meth = &klass->methods[j];
		break;
	      }
	  }
    }
#ifdef INTERPRETER
  else if (frame->type == frame_interpreter)
    {
      _Jv_InterpMethod *interp_meth = frame->interp.meth;
      klass = interp_meth->defining_class;
      meth = interp_meth->self;
    }
#endif
  else
    JvFail ("Unknown frame type");
  
  frame->klass = klass;
  frame->meth = meth;
}

// Convert raw stack frames to a Java array of StackTraceElement objects.
JArray< ::java::lang::StackTraceElement *>*
_Jv_StackTrace::GetStackTraceElements (_Jv_StackTrace *trace, 
  Throwable *throwable __attribute__((unused)))
{
  ArrayList *list = new ArrayList ();

#ifdef SJLJ_EXCEPTIONS
  // We can't use the nCodeMap without unwinder support. Instead,
  // fake the method name by giving the IP in hex - better than nothing.  
  jstring hex = JvNewStringUTF ("0x");

  for (int i = 0; i < trace->length; i++)
    {
      jstring sourceFileName = NULL;
      jint lineNum = -1;
      _Jv_StackFrame *frame = &trace->frames[i];
      
      jstring className = NULL;
      jstring methodName = hex->concat (Long::toHexString ((jlong) frame->ip));

      StackTraceElement *element = new StackTraceElement (sourceFileName, 
	lineNum, className, methodName, 0);    
      list->add (element);
    }

#else /* SJLJ_EXCEPTIONS */

  //JvSynchronized (ncodeMap);
  UpdateNCodeMap ();

  NameFinder *finder = new NameFinder();
  int start_idx = 0;
  int end_idx = trace->length - 1;

  // First pass: strip superfluous frames from beginning and end of the trace.  
  for (int i = 0; i < trace->length; i++)
    {
      _Jv_StackFrame *frame = &trace->frames[i];
      FillInFrameInfo (frame);

      if (!frame->klass || !frame->meth)
        // Not a Java frame.
        continue;

      // Throw away the top of the stack till we see:
      //  - the constructor(s) of this Throwable, or
      //  - the Throwable.fillInStackTrace call.
      if (frame->klass == throwable->getClass()
          && strcmp (frame->meth->name->chars(), "<init>") == 0)
        start_idx = i + 1;

      if (frame->klass == &Throwable::class$
          && strcmp (frame->meth->name->chars(), "fillInStackTrace") == 0)
	start_idx = i + 1;

      // End the trace at the application's main() method if we see call_main.
      if (frame->klass == &gnu::java::lang::MainThread::class$
          && strcmp (frame->meth->name->chars(), "call_main") == 0)
	end_idx = i - 1;
    }
  
  // Second pass: Look up line-number info for remaining frames.
  for (int i = start_idx; i <= end_idx; i++)
    {
      _Jv_StackFrame *frame = &trace->frames[i];
      
      if (frame->klass == NULL)
        // Not a Java frame.
	continue;
      
      jstring className = frame->klass->getName ();
      jstring methodName = NULL;
      if (frame->meth)
        methodName = JvNewStringUTF (frame->meth->name->chars());
      
      jstring sourceFileName = NULL;
      jint lineNum = -1;
      
      getLineNumberForFrame(frame, finder, &sourceFileName, &lineNum);
      
      StackTraceElement *element = new StackTraceElement (sourceFileName, lineNum,
        className, methodName, 0);
      list->add (element);
    }
  
  finder->close();
#endif /* SJLJ_EXCEPTIONS */

  JArray<Object *> *array = JvNewObjectArray (list->size (), 
    &StackTraceElement::class$, NULL);

  return (JArray<StackTraceElement *>*) list->toArray (array);
}

struct CallingClassTraceData
{
  jclass checkClass;    
  jclass foundClass;
  _Jv_Method *foundMeth;
  bool seen_checkClass;
};

_Unwind_Reason_Code
_Jv_StackTrace::calling_class_trace_fn (_Jv_UnwindState *state)
{
  CallingClassTraceData *trace_data = (CallingClassTraceData *)
    state->trace_data;
  _Jv_StackFrame *frame = &state->frames[state->pos];
  FillInFrameInfo (frame);

  if (trace_data->seen_checkClass
      && frame->klass
      && frame->klass != trace_data->checkClass)
    {
      trace_data->foundClass = frame->klass;
      trace_data->foundMeth = frame->meth;
      return _URC_NORMAL_STOP;
    }
  
  if (frame->klass == trace_data->checkClass)
    trace_data->seen_checkClass = true;
    
  return _URC_NO_REASON;
}

// Find the class immediately above the given class on the call stack. Any 
// intermediate non-Java 
// frames are ignored. If the calling class could not be determined (eg because 
// the unwinder is not supported on this platform), NULL is returned.
// This function is used to implement calling-classloader checks and reflection
// accessibility checks.
// CHECKCLASS is typically the class calling GetCallingClass. The first class
// above CHECKCLASS on the call stack will be returned.
jclass
_Jv_StackTrace::GetCallingClass (jclass checkClass)
{
  jclass result = NULL;
  GetCallerInfo (checkClass, &result, NULL);
  return result;
}

void
_Jv_StackTrace::GetCallerInfo (jclass checkClass, jclass *caller_class,
  _Jv_Method **caller_meth)
{
#ifndef SJLJ_EXCEPTIONS
  int trace_size = 20;
  _Jv_StackFrame frames[trace_size];
  _Jv_UnwindState state (trace_size);
  state.frames = (_Jv_StackFrame *) &frames;

  CallingClassTraceData trace_data;
  trace_data.checkClass = checkClass;
  trace_data.seen_checkClass = false;
  trace_data.foundClass = NULL;
  trace_data.foundMeth = NULL;

  state.trace_function = calling_class_trace_fn;
  state.trace_data = (void *) &trace_data;

  //JvSynchronized (ncodeMap);
  UpdateNCodeMap ();

  _Unwind_Backtrace (UnwindTraceFn, &state);
  
  if (caller_class)
    *caller_class = trace_data.foundClass;
  if (caller_meth)
    *caller_meth = trace_data.foundMeth;
#else
  return;
#endif
}

// Return a java array containing the Java classes on the stack above CHECKCLASS.
JArray<jclass> *
_Jv_StackTrace::GetClassContext (jclass checkClass)
{
  JArray<jclass> *result = NULL;

  int trace_size = 100;
  _Jv_StackFrame frames[trace_size];
  _Jv_UnwindState state (trace_size);
  state.frames = (_Jv_StackFrame *) &frames;

  //JvSynchronized (ncodeMap);
  UpdateNCodeMap ();

  _Unwind_Backtrace (UnwindTraceFn, &state);

  // Count the number of Java frames on the stack.
  int jframe_count = 0;
  bool seen_checkClass = false;
  int start_pos = -1;
  for (int i = 0; i < state.pos; i++)
    {
      _Jv_StackFrame *frame = &state.frames[i];
      FillInFrameInfo (frame);
      
      if (seen_checkClass)
	{
	  if (frame->klass)
	    {
	      jframe_count++;
	      if (start_pos == -1)
		start_pos = i;
	    }
	}
      else
	seen_checkClass = frame->klass == checkClass;
    }
  result = (JArray<jclass> *) _Jv_NewObjectArray (jframe_count, &Class::class$, NULL);
  int pos = 0;
  
  for (int i = start_pos; i < state.pos; i++)
    {
      _Jv_StackFrame *frame = &state.frames[i];
      if (frame->klass)
        elements(result)[pos++] = frame->klass;
    }
  return result;
}

_Unwind_Reason_Code
_Jv_StackTrace::non_system_trace_fn (_Jv_UnwindState *state)
{
  _Jv_StackFrame *frame = &state->frames[state->pos];
  FillInFrameInfo (frame);
  
  ClassLoader *classLoader = NULL;

  if (frame->klass)
    {
      classLoader = frame->klass->getClassLoaderInternal();
#ifdef INTERPRETER
      if (classLoader != NULL)
        {
          state->trace_data = (void *) classLoader;
	  return _URC_NORMAL_STOP;
	}
#endif
    }

  return _URC_NO_REASON;
}

ClassLoader *
_Jv_StackTrace::GetFirstNonSystemClassLoader ()
{
  int trace_size = 32;
  _Jv_StackFrame frames[trace_size];
  _Jv_UnwindState state (trace_size);
  state.frames = (_Jv_StackFrame *) &frames;
  state.trace_function = non_system_trace_fn;
  state.trace_data = NULL;

  //JvSynchronized (ncodeMap);
  UpdateNCodeMap ();
  
  _Unwind_Backtrace (UnwindTraceFn, &state);

  if (state.trace_data)
    return (ClassLoader *) state.trace_data;
  
  return NULL;
}