Command line HSDB

When debugging remote core dumps it is easier to work with command line tools instead of GUI tools. Command line HSDB (CLHSDB) tool is alternative to SA GUI tool HSDB.

There is also JavaScript based SA command line interface called jsdb. But, CLHSDB supports Unix shell-like (or dbx/gdb-like) command line interface with support for output redirection/appending (familiar >, >>), command history and so on. Each CLHSDB command can have zero or more arguments and optionally end with output redirection (or append) to a file. Commands may be stored in a file and run using source command. help command prints usage message for all supported commands (or a specific command)

Shell/batch scripts to run command line HSDB

Annotated output of CLHSDB help command


Available commands:
  assert true | false turn on/off asserts in SA code
  attach pid | exec core  attach SA to a process or core
  buildreplayjars [all | boot | app] build jars for replay, boot.jar for bootclasses, app.jar for application classes
  class name find a Java class from debuggee and print oop
  classes print all loaded Java classes with Klass*
  detach detach SA from current target
  dis address [ length ]  disassemble (sparc/x86) specified number of instructions from given address
  dissemble address disassemble nmethod
  dumpcfg -a | id Dump the PhaseCFG for every compiler thread that has one live
  dumpclass { address | name } [ directory ] dump .class file for given Klass* or class name
  dumpcodecache dump codecache contents
  dumpheap [ file ] dump heap in hprof binary format
  dumpideal -a | id dump ideal graph like debug flag -XX:+PrintIdeal
  dumpilt -a | id dump inline tree for C2 compilation
  dumpreplaydata <address> | -a | <thread_id> [>replay.txt] dump replay data into a file
  echo [ true | false ] turn on/off command echo mode
  examine [ address/count ] | [ address,address] show contents of memory from given address
  field [ type [ name fieldtype isStatic offset address ] ] print info about a field of HotSpot type
  findpc address print info. about pointer location
  flags [ flag ] show all -XX flag name value pairs. or just show given flag
  help [ command ] print help message for all commands or just given command
  history show command history. usual !command-number syntax works.
  inspect expression inspect a given oop
  intConstant [ name [ value ] ] print out hotspot integer constant(s)
  jdis address show bytecode disassembly of a given Method*
  jhisto show Java heap histogram
  jseval script evaluate a given string as JavaScript code
  jsload file load and evaluate a JavaScript file
  jstack [-v] show Java stack trace of all Java threads. -v is verbose mode
  livenmethods show all live nmethods
  longConstant [ name [ value ] ] print out hotspot long constant(s)s
  mem address [ length ] show contents of memory -- also shows closest ELF/COFF symbol if found
  pmap show Solaris pmap-like output
  print expression print given Klass*, Method* or arbitrary address
  printas type expression print given address as given HotSpot type. eg. print JavaThread <address>
  printmdo -a | expression print method data oop
  printstatics [ type ] print static fields of given HotSpot type (or all types if none specified)
  pstack [-v] show mixed mode stack trace for all Java, non-Java threads. -v is verbose mode
  quit quit CLHSDB tool
  reattach detach and re-attach SA to current target
  revptrs  find liveness of oops
  scanoops start end [ type ] scan a Oop from given start to end address
  search [ heap | codecache | threads ] value search a value in heap or codecache or threads
  source filename load and execute CLHSDB commands from given file
  symbol name show address of a given ELF/COFF symbol
  sysprops show all Java System properties
  thread id show thread of id
  threads show all Java threads
  tokenize ...
  type [ type [ name super isOop isInteger isUnsigned size ] ] show info. on HotSpot type
  universe print gc universe
  vmstructsdump dump hotspot type library in text
  verbose true | false turn on/off verbose mode
  versioncheck [ true | false ] turn on/off debuggee VM version check
  whatis address print info about any arbitrary address
  where { -a | id } print Java stack trace of given Java thread or all Java threads (-a)

JavaScript integration

Few CLHSDB commands are already implemented in JavaScript. It is possible to extend CLHSDB command set by implementing more commands in a JavaScript file and by loading it by jsload command. jseval command may be used to evaluate arbitrary JavaScript expression from a string. Any JavaScript function may be exposed as a CLHSDB command by registering it using JavaScript registerCommand function. This function accepts command name, usage and name of the JavaScript implementation function as arguments.

Simple CLHSDB command implemented in JavaScript

File: test.js

function helloImpl(name) {
    println("hello, " + name);
}

// register the above JavaScript function as CLHSDB command
registerCommand("hello", "hello name", "helloImpl");

---------
"test.js" can be loaded in CLHSDB prompt using jsload command using

hsdb> jsload test.js

Compilation Replay

When a java process crashes in compiled method, usually a core file is saved. The replay function can reproduce the compiling process in the core. cireplay.html