/*

 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "utilities/globalDefinitions.hpp"

#include "symbolengine.hpp"

#include "utilities/debug.hpp"

#include "utilities/ostream.hpp"

#include "windbghelp.hpp"

#include <windows.h>

#include <imagehlp.h>

#include <psapi.h>

// This code may be invoked normally but also as part of error reporting

// In the latter case, we may run under tight memory constraints (native oom)

// or in a stack overflow situation or the C heap may be corrupted. We may

// run very early before VM initialization or very late when C exit handlers

// run. In all these cases, callstacks would still be nice, so lets be robust.

//

// We need a number of buffers - for the pdb search path, module handle

// lists, for demangled symbols, etc.

//

// These buffers, while typically small, may need to be large for corner

// cases (e.g. templatized C++ symbols, or many DLLs loaded). Where do we

// allocate them?

//

// We may be in error handling for a stack overflow, so lets not put them on

// the stack.

//

// Dynamically allocating them may fail if we are handling a native OOM. It

// is also a bit dangerous, as the C heap may be corrupted already.

//

// That leaves pre-allocating them globally, which is safe and should always

// work (if we synchronize access) but incurs an undesirable footprint for

// non-error cases.

//

// We follow a two-way strategy: Allocate the buffers on the C heap in a

// reasonable large size. Failing that, fall back to static preallocated

// buffers. The size of the latter is large enough to handle common scenarios

// but small enough not to drive up the footprint too much (several kb).

//

// We keep these buffers around once allocated, for subsequent requests. This

// means that by running the initialization early at a safe time - before

// any error happens - buffers can be pre-allocated. This increases the chance

// of useful callstacks in error scenarios in exchange for a some cycles spent

// at startup. This behavior can be controlled with -XX:+InitializeDbgHelpEarly

// and is off by default.

///////

// A simple buffer which attempts to allocate an optimal size but will

// fall back to a static minimally sized array on allocation error.

template <class T, int MINIMAL_CAPACITY, int OPTIMAL_CAPACITY>

class SimpleBufferWithFallback {

  T _fallback_buffer[MINIMAL_CAPACITY];

  T* _p;

  int _capacity;

  // A sentinel at the end of the buffer to catch overflows.

  void imprint_sentinel() {

    assert(_p && _capacity > 0, "Buffer must be allocated");

    _p[_capacity - 1] = (T)'X';

    _capacity --;

  }

public:

  SimpleBufferWithFallback<T, MINIMAL_CAPACITY, OPTIMAL_CAPACITY> ()

    : _p(NULL), _capacity(0)

  {}

  // Note: no destructor because these buffers should, once

  // allocated, live until process end.

  // ~SimpleBufferWithFallback()

  // Note: We use raw ::malloc/::free here instead of os::malloc()/os::free

  // to prevent circularities or secondary crashes during error reporting.

  virtual void initialize () {

    assert(_p == NULL && _capacity == 0, "Only call once.");

    const size_t bytes = OPTIMAL_CAPACITY * sizeof(T);

    T* q = (T*) ::malloc(bytes);

    if (q != NULL) {

      _p = q;

      _capacity = OPTIMAL_CAPACITY;

    } else {

      _p = _fallback_buffer;

      _capacity = (int)(sizeof(_fallback_buffer) / sizeof(T));

    }

    _p[0] = '\0';

    imprint_sentinel();

  }

  // We need a way to reset the buffer to fallback size for one special

  // case, where two buffers need to be of identical capacity.

  void reset_to_fallback_capacity() {

    if (_p != _fallback_buffer) {

      ::free(_p);

    }

    _p = _fallback_buffer;

    _capacity = (int)(sizeof(_fallback_buffer) / sizeof(T));

    _p[0] = '\0';

    imprint_sentinel();

  }

  T* ptr()                { return _p; }

  const T* ptr() const    { return _p; }

  int capacity() const    { return _capacity; }

#ifdef ASSERT

  void check() const {

    assert(_p[_capacity] == (T)'X', "sentinel lost");

  }

#else

  void check() const {}

#endif

};

////

// ModuleHandleArray: a list holding module handles. Needs to be large enough

// to hold one handle per loaded DLL.

// Note: a standard OpenJDK loads normally ~30 libraries, including system

// libraries, without third party libraries.

typedef SimpleBufferWithFallback <HMODULE, 48, 512> ModuleHandleArrayBase;

class ModuleHandleArray : public ModuleHandleArrayBase {

  int _num; // Number of handles in this array (may be < capacity).

public:

  void initialize() {

    ModuleHandleArrayBase::initialize();

    _num = 0;

  }

  int num() const { return _num; }

  void set_num(int n) {

    assert(n <= capacity(), "Too large");

    _num = n;

  }

  // Compare with another list; returns true if all handles are equal (incl.

  // sort order)

  bool equals(const ModuleHandleArray& other) const {

    if (_num != other._num) {

      return false;

    }

    if (::memcmp(ptr(), other.ptr(), _num * sizeof(HMODULE)) != 0) {

      return false;

    }

    return true;

  }

  // Copy content from other list.

  void copy_content_from(ModuleHandleArray& other) {

    assert(capacity() == other.capacity(), "Different capacities.");

    memcpy(ptr(), other.ptr(), other._num * sizeof(HMODULE));

    _num = other._num;

  }

};

////

// PathBuffer: a buffer to hold and work with a pdb search PATH - a concatenation

// of multiple directories separated by ';'.

// A single directory name can be (NTFS) as long as 32K, but in reality is

// seldom larger than the (historical) MAX_PATH of 260.

#define MINIMUM_PDB_PATH_LENGTH  MAX_PATH * 4

#define OPTIMAL_PDB_PATH_LENGTH  MAX_PATH * 64

typedef SimpleBufferWithFallback<char, MINIMUM_PDB_PATH_LENGTH, OPTIMAL_PDB_PATH_LENGTH> PathBufferBase;

class PathBuffer: public PathBufferBase {

public:

  // Search PDB path for a directory. Search is case insensitive. Returns

  // true if directory was found in the path, false otherwise.

  bool contains_directory(const char* directory) {

    if (ptr() == NULL) {

      return false;

    }

    const size_t len = strlen(directory);

    if (len == 0) {

      return false;

    }

    char* p = ptr();

    for(;;) {

      char* q = strchr(p, ';');

      if (q != NULL) {

        if (len == (q - p)) {

          if (strnicmp(p, directory, len) == 0) {

            return true;

          }

        }

        p = q + 1;

      } else {

        // tail

        return stricmp(p, directory) == 0 ? true : false;

      }

    }

    return false;

  }

  // Appends the given directory to the path. Returns false if internal

  // buffer size was not sufficient.

  bool append_directory(const char* directory) {

    const size_t len = strlen(directory);

    if (len == 0) {

      return false;

    }

    char* p = ptr();

    const size_t len_now = strlen(p);

    const size_t needs_capacity = len_now + 1 + len + 1; // xxx;yy\0

    if (needs_capacity > (size_t)capacity()) {

      return false; // OOM

    }

    if (len_now > 0) { // Not the first path element.

      p += len_now;

      *p = ';';

      p ++;

    }

    strcpy(p, directory);

    return true;

  }

};

// A simple buffer to hold one single file name. A file name can be (NTFS) as

// long as 32K, but in reality is seldom larger than MAX_PATH.

typedef SimpleBufferWithFallback<char, MAX_PATH, 8 * K> FileNameBuffer;

// A buffer to hold a C++ symbol. Usually small, but symbols may be larger for

// templates.

#define MINIMUM_SYMBOL_NAME_LEN 128

#define OPTIMAL_SYMBOL_NAME_LEN 1024

typedef SimpleBufferWithFallback<uint8_t,

        sizeof(IMAGEHLP_SYMBOL64) + MINIMUM_SYMBOL_NAME_LEN,

        sizeof(IMAGEHLP_SYMBOL64) + OPTIMAL_SYMBOL_NAME_LEN> SymbolBuffer;

static struct {

  // Two buffers to hold lists of loaded modules. handles across invocations of

  // SymbolEngine::recalc_search_path().

  ModuleHandleArray loaded_modules;

  ModuleHandleArray last_loaded_modules;

  // Buffer to retrieve and assemble the pdb search path.

  PathBuffer search_path;

  // Buffer to retrieve directory names for loaded modules.

  FileNameBuffer dir_name;

  // Buffer to retrieve decoded symbol information (in SymbolEngine::decode)

  SymbolBuffer decode_buffer;

  void initialize() {

    search_path.initialize();

    dir_name.initialize();

    decode_buffer.initialize();

    loaded_modules.initialize();

    last_loaded_modules.initialize();

    // Note: both module lists must have the same capacity. If one allocation

    // did fail, let them both fall back to the fallback size.

    if (loaded_modules.capacity() != last_loaded_modules.capacity()) {

      loaded_modules.reset_to_fallback_capacity();

      last_loaded_modules.reset_to_fallback_capacity();

    }

    assert(search_path.capacity() > 0 && dir_name.capacity() > 0 &&

            decode_buffer.capacity() > 0 && loaded_modules.capacity() > 0 &&

            last_loaded_modules.capacity() > 0, "Init error.");

  }

} g_buffers;

// Scan the loaded modules.

//

// For each loaded module, add the directory it is located in to the pdb search

// path, but avoid duplicates. Prior search path content is preserved.

//

// If p_search_path_was_updated is not NULL, points to a bool which, upon

// successful return from the function, contains true if the search path

// was updated, false if no update was needed because no new DLLs were

// loaded or unloaded.

//

// Returns true for success, false for error.

static bool recalc_search_path_locked(bool* p_search_path_was_updated) {

  if (p_search_path_was_updated) {

    *p_search_path_was_updated = false;

  }

  HANDLE hProcess = ::GetCurrentProcess();

  BOOL success = false;

  // 1) Retrieve current set search path.

  //    (PDB search path is a global setting and someone might have modified

  //     it, so take care not to remove directories, just to add our own).

  if (!WindowsDbgHelp::symGetSearchPath(hProcess, g_buffers.search_path.ptr(),

                                       (int)g_buffers.search_path.capacity())) {

    return false;

  }

  DEBUG_ONLY(g_buffers.search_path.check();)

  // 2) Retrieve list of modules handles of all currently loaded modules.

  DWORD bytes_needed = 0;

  const DWORD buffer_capacity_bytes = (DWORD)g_buffers.loaded_modules.capacity() * sizeof(HMODULE);

  success = ::EnumProcessModules(hProcess, g_buffers.loaded_modules.ptr(),

                                 buffer_capacity_bytes, &bytes_needed);

  DEBUG_ONLY(g_buffers.loaded_modules.check();)

  // Note: EnumProcessModules is sloppily defined in terms of whether a

  // too-small output buffer counts as error. Will it truncate but still

  // return TRUE? Nobody knows and the manpage is not telling. So we count

  // truncation it as error, disregarding the return value.

  if (!success || bytes_needed > buffer_capacity_bytes) {

    return false;

  } else {

    const int num_modules = bytes_needed / sizeof(HMODULE);

    g_buffers.loaded_modules.set_num(num_modules);

  }

  // Compare the list of module handles with the last list. If the lists are

  // identical, no additional dlls were loaded and we can stop.

  if (g_buffers.loaded_modules.equals(g_buffers.last_loaded_modules)) {

    return true;

  } else {

    // Remember the new set of module handles and continue.

    g_buffers.last_loaded_modules.copy_content_from(g_buffers.loaded_modules);

  }

  // 3) For each loaded module: retrieve directory from which it was loaded.

  //    Add directory to search path (but avoid duplicates).

  bool did_modify_searchpath = false;

  for (int i = 0; i < (int)g_buffers.loaded_modules.num(); i ++) {

    const HMODULE hMod = g_buffers.loaded_modules.ptr()[i];

    char* const filebuffer = g_buffers.dir_name.ptr();

    const int file_buffer_capacity = g_buffers.dir_name.capacity();

    const int len_returned = (int)::GetModuleFileName(hMod, filebuffer, (DWORD)file_buffer_capacity);

    DEBUG_ONLY(g_buffers.dir_name.check();)

    if (len_returned == 0) {

      // This may happen when a module gets unloaded after our call to EnumProcessModules.

      // It should be rare but may sporadically happen. Just ignore and continue with the

      // next module.

      continue;

    } else if (len_returned == file_buffer_capacity) {

      // Truncation. Just skip this module and continue with the next module.

      continue;

    }

    // Cut file name part off.

    char* last_slash = ::strrchr(filebuffer, '\\');

    if (last_slash == NULL) {

      last_slash = ::strrchr(filebuffer, '/');

    }

    if (last_slash) {

      *last_slash = '\0';

    }

    // If this is already part of the search path, ignore it, otherwise

    // append to search path.

    if (!g_buffers.search_path.contains_directory(filebuffer)) {

      if (!g_buffers.search_path.append_directory(filebuffer)) {

        return false; // oom

      }

      DEBUG_ONLY(g_buffers.search_path.check();)

      did_modify_searchpath = true;

    }

  } // for each loaded module.

  // If we did not modify the search path, nothing further needs to be done.

  if (!did_modify_searchpath) {

    return true;

  }

  // Set the search path to its new value.

  if (!WindowsDbgHelp::symSetSearchPath(hProcess, g_buffers.search_path.ptr())) {

    return false;

  }

  if (p_search_path_was_updated) {

    *p_search_path_was_updated = true;

  }

  return true;

}

static bool demangle_locked(const char* symbol, char *buf, int buflen) {

  return WindowsDbgHelp::unDecorateSymbolName(symbol, buf, buflen, UNDNAME_COMPLETE) > 0;

}

static bool decode_locked(const void* addr, char* buf, int buflen, int* offset, bool do_demangle) {

  assert(g_buffers.decode_buffer.capacity() >= (sizeof(IMAGEHLP_SYMBOL64) + MINIMUM_SYMBOL_NAME_LEN),

         "Decode buffer too small.");

  assert(buf != NULL && buflen > 0 && offset != NULL, "invalid output buffer.");

  DWORD64 displacement;

  PIMAGEHLP_SYMBOL64 pSymbol = NULL;

  bool success = false;

  pSymbol = (PIMAGEHLP_SYMBOL64) g_buffers.decode_buffer.ptr();

  pSymbol->SizeOfStruct = sizeof(IMAGEHLP_SYMBOL64);

  pSymbol->MaxNameLength = (DWORD)(g_buffers.decode_buffer.capacity() - sizeof(IMAGEHLP_SYMBOL64) - 1);

  // It is unclear how SymGetSymFromAddr64 handles truncation. Experiments

  // show it will return TRUE but not zero terminate (which is a really bad

  // combination). Lets be super careful.

  ::memset(pSymbol->Name, 0, pSymbol->MaxNameLength); // To catch truncation.

  if (WindowsDbgHelp::symGetSymFromAddr64(::GetCurrentProcess(), (DWORD64)addr, &displacement, pSymbol)) {

    success = true;

    if (pSymbol->Name[pSymbol->MaxNameLength - 1] != '\0') {

      // Symbol was truncated. Do not attempt to demangle. Instead, zero terminate the

      // truncated string. We still return success - the truncated string may still

      // be usable for the caller.

      pSymbol->Name[pSymbol->MaxNameLength - 1] = '\0';

      do_demangle = false;

    }

    // Attempt to demangle.

    if (do_demangle && demangle_locked(pSymbol->Name, buf, buflen)) {

      // ok.

    } else {

      ::strncpy(buf, pSymbol->Name, buflen - 1);

    }

    buf[buflen - 1] = '\0';

    *offset = (int)displacement;

  }

  DEBUG_ONLY(g_buffers.decode_buffer.check();)

  return success;

}

static enum {

  state_uninitialized = 0,

  state_ready = 1,

  state_error = 2

} g_state = state_uninitialized;

static void initialize() {

  assert(g_state == state_uninitialized, "wrong sequence");

  g_state = state_error;

  // 1) Initialize buffers.

  g_buffers.initialize();

  // 1) Call SymInitialize

  HANDLE hProcess = ::GetCurrentProcess();

  WindowsDbgHelp::symSetOptions(SYMOPT_FAIL_CRITICAL_ERRORS | SYMOPT_DEFERRED_LOADS |

                        SYMOPT_EXACT_SYMBOLS | SYMOPT_LOAD_LINES);

  if (!WindowsDbgHelp::symInitialize(hProcess, NULL, TRUE)) {

    return;

  }

  // Note: we ignore any errors from this point on. The symbol engine may be

  // usable enough.

  g_state = state_ready;

  (void)recalc_search_path_locked(NULL);

}

///////////////////// External functions //////////////////////////

// All outside facing functions are synchronized. Also, we run

// initialization on first touch.

static CRITICAL_SECTION g_cs;

namespace { // Do not export.

  class SymbolEngineEntry {

   public:

    SymbolEngineEntry() {

      ::EnterCriticalSection(&g_cs);

      if (g_state == state_uninitialized) {

        initialize();

      }

    }

    ~SymbolEngineEntry() {

      ::LeaveCriticalSection(&g_cs);

    }

  };

}