mmarchini

V8 Heap Snapshot Schema

Key	Description
snapshot	Metadata from the snapshot. See snapshot
nodes	List of heap nodes. See nodes
edges	List of heap edges between nodes. See edges
trace_function_infos	???
trace_tree	???

mmarchini

# Uncomment deb-src lines on /etc/apt/sources.list
sudo apt-get update

# Or replace ~/glibc with preferred path to store libc source
mkdir -p ~/glibc
cd ~/glibc

sudo apt-get install -y dpkg-dev
sudo apt-get build-deps libc6
apt-get source libc6

mmarchini

// Node v10.15.3
uprobe:/home/mmarchini/.nvm/versions/node/v10.15.3/bin/node:_ZN2v88internal17Builtin_JsonParseEiPPNS0_6ObjectEPNS0_7IsolateE
{
  // Load constants
  $kPointerSize = (uint32)(1 << (*uaddr("v8dbg_PointerSizeLog2")));
  $stringLengthOffset = (uint32)*uaddr("v8dbg_class_String__length__SMI");
  $kTag = (uint32)*uaddr("v8dbg_HeapObjectTag");
  $kTagMask = (uint32)*uaddr("v8dbg_SmiTagMask");
  $kShiftSize = (uint32)*uaddr("v8dbg_SmiShiftSize");

mmarchini

$ make LDFLAGS=-static NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 NO_JVMTI=1
  BUILD:   Doing 'make -j8' parallel build
  HOSTCC   fixdep.o
  HOSTLD   fixdep-in.o
  LINK     fixdep

Auto-detecting system features:
...                         dwarf: [ on  ]
...            dwarf_getlocations: [ on  ]
...                         glibc: [ on  ]

mmarchini

(lldb) target create "/home/mmarchini/.nvm/versions/node/v12.3.0/bin/node" --core "core.frame-scenario.1"
Core file '/home/mmarchini/workspace/nodejs/llnode/core.frame-scenario.1' (x86_64) was loaded.
(lldb) plugin load '/home/mmarchini/workspace/nodejs/llnode/llnode.so'
(lldb) settings set prompt '(llnode) '
(llnode) command script import diagnose_unwind
bind: Invalid command `enable-meta-key'.
The "diagnose-unwind" command has been installed, type "help diagnose-unwind" for detailed help.
(llnode) diagnose-unwind
LLDB version lldb version 6.0.1
Unwind diagnostics for thread 1

mmarchini

#!/usr/bin/env python3

from subprocess import run, PIPE

completed_process = run(["docker-machine.exe", "env", "--shell", "bash"], stdout=PIPE)

docker_env = completed_process.stdout.decode("ascii")

for line in docker_env.split("\n"):
    if "DOCKER_CERT_PATH" in line:

mmarchini

Goals

When a promise is rejected with no catch handler attached, it should:

• Aborting with error code for unhandled rejection to generate core-dump
• Get stack trace from the point where the error was thrown
• Inspecting arguments, closures and variables

Current State

mmarchini

#include <v8.h>
#include <v8-postmortem.h>
#include <napi.h>
#include <lldb/API/SBDebugger.h>
#include <lldb/API/SBTarget.h>
#include <lldb/API/SBProcess.h>

#include <iostream>

using lldb::addr_t;

mmarchini

'use strict';

const http = require('http');
const port = 3000;

class Visit {
  constructor(visit_id, headers) {
    this.visit_id = visit_id;
    this.headers = headers;
  }

mmarchini

#!/usr/bin/env zsh

local LAMBDA="%(?,%{$fg_bold[green]%}λ,%{$fg_bold[red]%}λ)"

function get_pwd(){
  git_root=$PWD
  while [[ $git_root != / && ! -e $git_root/.git ]]; do
    git_root=$git_root:h
  done
  if [[ $git_root = / ]]; then