/* jstack systemtap tapset, for extracting hotspot java backtraces.
   Copyright (C) 2009, 2012 Red Hat Inc.

This file is part of IcedTea.

IcedTea is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

IcedTea 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 for more details.

You should have received a copy of the GNU General Public License
along with IcedTea; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
*/

/*
 Provides helper functions to log and print hotspot java based backtraces.
 jstack() provides up to 32 pure java frames from the current probe point
 (space separated). jstack_print() does the same, but logs each frame
 immediately. jstack_full() provides up to 32 "mixed" frames, including
 full method signatures plus native code frames. print_jstack_full() does
 the same, but prints eachs frame to the log immediately. To request
 more or less frames use the jstack_n(), jstack_full_n(), print_jstack_n()
 and print_jstack_full_n() variants. And to have full controll over the
 amount of information included in each frame use the jstack_call()
 function.

 Currently only works with full path in process probes below.
 When things don't seem to work look if the correct
 jre/lib/[arch]/[client|server]/libjvm.so is used
 and exists under @prefix@/.
 This version of jstack.stp has been configured to instrument the
 libjvm.so for arch @INSTALL_ARCH_DIR@ installed at:
 @ABS_CLIENT_LIBJVM_SO@
 @ABS_SERVER_LIBJVM_SO@

 Note that you need a systemtap version > 1.0.
 Otherwise you will not be able to fetch global vars, which would show as:
 semantic error: failed to retrieve location attribute for local
*/

/* Resolve multiple installed java versions conflict. */
@define _private %( %( systemtap_v >= "3.0" %? private %) %)
@define _check_match %(
  %( systemtap_v >= "3.2" %? if (strpos(pp(), "@prefix@") < 0) next %)
  %( systemtap_v < "3.2" && systemtap_v >= "3.0" %? if (pp() !~ "@prefix@") next %)
%)

@_private global CodeCache_heap;

@_private global sp_register;
@_private global fp_register;
@_private global pc_register;
@_private global ptr_size;
@_private global ptr_mask;

@_private global constantPool_size;
@_private global HeapBlock_Header_size;

@_private global vm_inited;

/* We need to collect some global symbol addresses that cannot be resolved
   in a bare function and vm_init_end seems a good place to use. */
probe hotspot.vm_init_end11
{
  /**
   * The CodeCache class contains the static CodeHeap _heap that
   * is malloced at the start of the vm run and holds all generated
   * code. If the program counter is between the low and high memory
   * marks of the CodeHeap then it is generated code. Note that the
   * interpreter CodeBlob itself is also generated at runtime.
   *
   * The code heap is made up of segments which are described in the
   * CodeHeap _segmap. Each segment is of size _segment_size, which
   * must be an exact power of 2 (_log2_segment_size). For each segment
   * the _segmap has an unsigned char which is 0xFF if the segment
   * isn't used, 0 if the segment is the start of a block and N
   * (Where in is 1 till 0xFE) to indicate the segment belongs to
   * the segment at index - N (which can be recursive if a block
   * contains more than 0xFE segments).
   */
  CodeCache_heap[pid()] = %( systemtap_v >= "1.8"
                            %? @var("_heap@codeCache.cpp")
                            %: $_heap %);

  // Should really check arch of user space (for 32bit jvm on 64bit kernel).
  %( arch == "i386" %?
     sp_register = "esp";
     fp_register = "ebp";
     pc_register = "eip";
     ptr_size = 4;
     ptr_mask = 0xFFFFFFFF;
  %: %(arch == "x86_64" %?
     sp_register = "rsp";
     fp_register = "rbp";
     pc_register = "rip";
     ptr_size = 8; // XXX - might be probing 32-on-64 jvm.
     ptr_mask = 0xFFFFFFFFFFFFFFFF;
  %: %(arch == "arm64" %?
     sp_register = "sp";
     fp_register = "fp";
     pc_register = "pc";
     ptr_size = 8; // XXX - might be probing 32-on-64 jvm.
     ptr_mask = 0xFFFFFFFFFFFFFFFF;
  %:
     sp_register = "";
     fp_register = "";
     pc_register = "";
     ptr_size = 8;
     ptr_mask = 0xFFFFFFFFFFFFFFFF;
     error("unknown architecture")
  %) %) %)

  // Pretend we have an array at address zero and take address of second
  // element and we have the size.
  constantPool_size = &@cast(0, "ConstantPool")[1];

  // Really should get from dwarf: @size("HeapBlock::Header"), @size("oopDesc")
  HeapBlock_Header_size = 2 * ptr_size;

  vm_inited[pid()] = 1;
}

probe hotspot.vm_shutdown
{
  delete(CodeCache_heap[pid()]);
  delete(vm_inited[pid()]);
}

function jstack:string()
{
  @_check_match

  // java backtraces can be a lot bigger, but we risk going over MAXACTION.
  // 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
  max_depth = 32;

  return jstack_n(max_depth);
}

function jstack_n:string(max_depth:long)
{
  @_check_match

  // Whether to log the method signatures.
  log_sig = 0;

  // Set to zero to only print pure java frames
  log_native = 0;

  // whether to print or just return the frames as space separated string
  print_frames = 0;

  return jstack_call(max_depth, log_sig, log_native, print_frames);
}

function print_jstack()
{
  @_check_match

  // java backtraces can be a lot bigger, but we risk going over MAXACTION.
  // 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
  max_depth = 32;

  return print_jstack_n(max_depth);
}

function print_jstack_n:string(max_depth:long)
{
  @_check_match

  // Whether to log the method signatures.
  log_sig = 0;

  // Set to zero to only print pure java frames
  log_native = 0;

  // whether to print or just return the frames as space separated string
  print_frames = 1;

  jstack_call(max_depth, log_sig, log_native, print_frames);
}

function jstack_full:string()
{
  @_check_match

  // java backtraces can be a lot bigger, but we risk going over MAXACTION.
  // 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
  max_depth = 32;

  return jstack_full_n(max_depth);
}

function jstack_full_n:string(max_depth:long)
{
  @_check_match

  // Whether to log the method signatures.
  log_sig = 1;

  // Set to zero to only print pure java frames
  log_native = 1;

  // whether to print or just return the frames as space separated string
  print_frames = 0;

  return jstack_call(max_depth, log_sig, log_native, print_frames);
}

function print_jstack_full()
{
  @_check_match

  // java backtraces can be a lot bigger, but we risk going over MAXACTION.
  // 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
  max_depth = 32;

  return print_jstack_full_n(max_depth);
}

function print_jstack_full_n:string(max_depth:long)
{
  @_check_match

  // Whether to log the method signatures.
  log_sig = 1;

  // Set to zero to only print pure java frames
  log_native = 1;

  // whether to print or just return the frames as space separated string
  print_frames = 1;

  jstack_call(max_depth, log_sig, log_native, print_frames);
}

function jstack_call:string(max_depth:long, log_sig:long, log_native:long,
                            print_frames:long)
{
  @_check_match

  if (! vm_inited[pid()])
    {
      frame = "<vm-not-inited>";
      if (print_frames)
        {
          log(frame);
          return "";
        }
      else
        return frame;
    }

  // Extract code bounds.
  CodeCache_low = @cast(CodeCache_heap[pid()], "CodeHeap",
                        "@ABS_SERVER_LIBJVM_SO@")->_memory->_low;
  CodeCache_high =  @cast(CodeCache_heap[pid()], "CodeHeap",
                          "@ABS_SERVER_LIBJVM_SO@")->_memory->_high;

  CodeHeap_log2_segment_size = @cast(CodeCache_heap[pid()],
                                     "CodeHeap",
                                     "@ABS_SERVER_LIBJVM_SO@")->_log2_segment_size;
  CodeCache_segmap_low = @cast(CodeCache_heap[pid()],
                               "CodeHeap",
                               "@ABS_SERVER_LIBJVM_SO@")->_segmap->_low;

  // Might want to sanity check above values.

  // Loop through all the frames. The program counter is the starting
  // point to find the CodeBlob corresponding to the current frame. In
  // most cases the frame pointer will help us detect the class/method
  // and next pc value. But we need the stack pointer to help us out
  // to "recover" the previous fp in case we hit a code blob that didn't
  // preserve it.
  frames = "";
  sp = register(sp_register);
  fp = register(fp_register);
  pc = register(pc_register);
  depth = 0;
  while (pc != 0 && depth < max_depth)
    {
      frame = "";

      // Assume things are fine unless indicated otherwise.
      trust_fp = 1;

      // Generated code? (Interpreter and stub methods are also generated)
      if (CodeCache_low <= pc && pc < CodeCache_high)
        {
          // Find the start of the code segment and code block that
          // this pc is in.
          segments = 0;
          segment = (pc - CodeCache_low) >> CodeHeap_log2_segment_size;
          tag = user_char(CodeCache_segmap_low + segment) & 0xFF;
	  while (tag > 0 && segments < 16)
            {
              segment = segment - tag;
              tag = user_char(CodeCache_segmap_low + segment) & 0xFF;
              segments++;
            }
          block = CodeCache_low + (segment << CodeHeap_log2_segment_size);

          // Some of this is "fuzzy" so catch any read error in case we
          // "guessed" wrong.
          try
            {

              // Do some sanity checking.
              used = @cast(block, "HeapBlock",
                           "@ABS_SERVER_LIBJVM_SO@")->_header->_used;
              if (used != 1)
                {
                  // Something very odd has happened.
                  frame = sprintf("<unused_code_block@0x%x>", pc);
                  blob_name = "unused";
                  trust_fp = 0;
                  frame_size = 0;
                }
              else
                {
                  // We don't like spaces in frames (makes it hard to return
                  // a space separated frame list). So make sure they are
                  // replaced by underscores when used in frames.
                  blob = block + HeapBlock_Header_size;
                  blob_name_ptr = @cast(blob, "CodeBlob",
                                        "@ABS_SERVER_LIBJVM_SO@")->_name;
                  blob_name = ((blob_name_ptr == 0) ? "<unknown-code-blob>"
                               : user_string(blob_name_ptr));
                }

              // For compiled code the methodOop is part of the code blob.
              // For the interpreter (and other code blobs) it is on the
              // stack relative to the frame pointer.
              if (blob_name == "nmethod")
                methodPtr = @cast(blob, "nmethod",
                                     "@ABS_SERVER_LIBJVM_SO@")->_method
              else 
                methodPtr = user_long(fp + (-3 * ptr_size)) & ptr_mask

              // The java class is the holder of the constants (strings)
              // that describe the method and signature. This constant pool
              // contains symbolic information that describe the properties
              // of the class. The indexes for methods and signaturates in
              // the constant pool are Symbols that contain utf8
              // strings (plus lenghts). (We could also sanity check that
              // the tag value is correct [CONSTANT_String = 8]).
              // Note that the class name uses '/' instead of '.' as
              // package name separator and that the method signature is
              // encoded as a method descriptor string. Both of which we
              // don't demangle here.
              constMethod = @cast(methodPtr, "Method",
                                          "@ABS_SERVER_LIBJVM_SO@")->_constMethod;
              constantPool = @cast(constMethod, "ConstMethod",
                                          "@ABS_SERVER_LIBJVM_SO@")->_constants;
              constantPool_base = constantPool + constantPool_size;

              klass = @cast(constantPool, "ConstantPool",
                               "@ABS_SERVER_LIBJVM_SO@")->_pool_holder;
              klassSymbol = @cast(klass, "Klass",
                                  "@ABS_SERVER_LIBJVM_SO@")->_name;
              klassName = &@cast(klassSymbol, "Symbol",
                                 "@ABS_SERVER_LIBJVM_SO@")->_body[0];
              klassLength = @cast(klassSymbol, "Symbol",
                                  "@ABS_SERVER_LIBJVM_SO@")->_length;

              methodIndex = @cast(constMethod, "ConstMethod",
                                  "@ABS_SERVER_LIBJVM_SO@")->_name_index;
              methodSymbol = user_long(constantPool_base + (methodIndex * ptr_size));
              methodName = &@cast(methodSymbol, "Symbol",
                                  "@ABS_SERVER_LIBJVM_SO@")->_body[0];
              methodLength = @cast(methodSymbol, "Symbol",
                                   "@ABS_SERVER_LIBJVM_SO@")->_length;

              if (log_sig)
                {
                  sigIndex = @cast(constMethod, "ConstMethod",
                                   "@ABS_SERVER_LIBJVM_SO@")->_signature_index;
                  sigSymbol = user_long(constantPool_base
                                         + (sigIndex * ptr_size));
                  sigName = &@cast(sigSymbol, "Symbol",
                                   "@ABS_SERVER_LIBJVM_SO@")->_body[0];
                  sigLength = @cast(sigSymbol, "Symbol",
                                    "@ABS_SERVER_LIBJVM_SO@")->_length;
                  sig = user_string_n(sigName, sigLength);
                }
              else
                sig = "";

              code_name = (log_native
                           ? sprintf("<%s@0x%x>",
                                     str_replace(blob_name, " ", "_"), pc)
                           : "");

              frame = sprintf("%s.%s%s%s",
                              user_string_n(klassName, klassLength),
                              user_string_n(methodName, methodLength),
                              sig, code_name);

              // We cannot trust the frame pointer of compiled methods.
              // The server (c2) jit compiler uses the fp register.
              // We do know the method frame size on the stack. But
              // this seems to be useful only as a hint of the minimum
              // stack being used.
              if (blob_name == "nmethod")
                {
                  trust_fp = 0;
                  frame_size = @cast(blob, "CodeBlob",
                                     "@ABS_SERVER_LIBJVM_SO@")->_frame_size;
                }

            }
          catch
            {
              // Some assumption above totally failed and we got an address
              // read error. Give up and mark frame pointer as suspect.
              frame = sprintf("<unknown_frame@0x%x>", pc);
              trust_fp = 0;
            }
        }
      else
        {
          // "Normal" hotspot code. Just print what usymname() gets us.
          // All such code is compiled with -fno-omit-frame-pointer so
          // we can use that to get at the next frame.
          // Theoretically there could be libraries or jni code not
          // compiled with -fno-omit-frame-pointer, then we should really
          // use the dwarf unwinder or some stack crawling heuristics.
          if (log_native)
            frame = usymname(pc);
        }

        // Get next frame by assuming frame pointers are being used.
        // (which is not always true for c2 (server) compiled nmethods).
        old_fp = fp;
        old_sp = sp

        sp = fp;
        fp = user_long(sp);
        pc = user_long(fp + ptr_size);

        // Do we need to double check? We do not want to do this
        // unless necessary. We have to assume most code is "sane"
        // and has fp setup correctly because we do not have good
        // heuristics that cover all cases (native code, interpreted
        // code, client code, codeblob stubs). So we only check and try
        // to adapt for nmethods. Scanning the stack for plausible
        // looking fp and pc values might make us skip a frame.
        if (!trust_fp)
          {
            max_stack_scan = 96; // Arbitrary limit

            // Note that first while iteration actually checks that
            // the fp and pc from trusting the old fp might be correct
            // (it often is if the nmethod come from the client compiler).
            // The only validly looking pc values that we know of are in
            // the CodeCache (so, we might be skipping native frames).
            // The nmethod has a frame_size which gives a hint as to
            // how much stack we have to skip at least.
            i = 1;
            while (i < max_stack_scan
                   && (CodeCache_low > pc
                       || pc >= CodeCache_high
                       || fp <= old_fp))
              {
                sp = old_sp + ((frame_size + i) * ptr_size);
                fp = user_long(sp);
                pc = user_long(fp + ptr_size);
                i++;
              }
            if (i == max_stack_scan)
              {
                if (! print_frames)
                  frames = frames . " <stack_lost>"
                else
                  log("<stack_lost>")
                pc = 0;
              }
          }

      if (frame != "")
        {
          if (! print_frames)
            {
              space = (depth != 0) ? " " : "";
              frames = frames . space . frame;
            }
          else
            log (frame);
          depth++;
        }
    }

  if (depth == max_depth)
    {
      frame = "<stack_truncated>";
      if (! print_frames)
        frames = frames . " " . frame
      else
        log (frame);
    }

  return frames;
}