CSC/ECE 517 Fall 2014/oss M1454 rss

Implementing proper JS error reporting

This wiki page contains the implementation of JS error reporting for the Mozilla project using RUST programming language.

Introduction

Mozilla is currently working on a research project called Servo, which is a Web browser engine for a new generation of hardware: mobile devices, multi-core processors and high-performance GPUs. The goal is to create an architecture that is parallel at many levels thereby eliminating common sources of bugs and security vulnerabilities associated with incorrect memory management.

For the new browser Mozilla servo, SpiderMonkey has been used as the JavaScript search engine. SpiderMonkey basically exposes a user-specifiable callback that executes JS and throws an exception that is not caught. But, SpiderMonkey has been written in C/C++. It exposes a user-specifiable callback executing JS that throws an exception that is not caught. Initially, the library (which wraps the C-based mozjs aka SpiderMonkey) named rust-mozjs library sets this callback to a simple function that pushed the error logs on to the terminal. Thus, as a part of our OSS project, based on the requirements, we have presented a way to replace this in Servo with an ErrorEvent interface which has methods that implements the error reporting specification for web browsers.

RUST Programming Language

Servo is written in RUST programming language which is developed by Mozilla research. It is memory safe thereby ensuring a high degree of assurance in the browser’s trusted computing base. RUST also guarantees concurrency thus avoiding the problem of ‘data races’ and ensures safety and speed. Rust’s lightweight task mechanism also allows fine-grained isolation between browser components.

Servo

Mozilla has planned to deliver its new browser Servo which facilitates great features like parallel processing in the browser in order to utilize many cores present in the modern mobile devices such as smartphones and tablets in order to carry out tasks concurrently. Even the giant and famous browsers like Chrome, Internet Explorer, Firefox, Safari, have tried to implement parallel processing via different ways such as aggregating the JIT (Just in Time) compilation technique to their JS engines. But, performance and security gains need re-modelling the browser stacks of these browsers. Servo, that is being designed to be compatible with the Android OS devices, will work with the Arm-based processors.

Project Description

• The project requirements needed us to build a Servo, add a new file ErrorEvent WebIDL file along with its RUST implementation, and create the errorevent interface.
• We were required to write a errorevent.rs file, which is written in RUST programming language.
• The file on compilation generates erroreventBinding.rs file
• The project was then rebuilt and recompiled on the Servo engine.

Steps to execute our program

Step 1:

The first step includes building Servo.

./mach build

Step 2:

Once the Servo is built, the next step is to create an errorevent interface by adding a new WebIDL binding. The following are the steps to create a new WebIDL file:

• Create a new file ‘errorevent.webidl’ and add it to components/script/dom/webidls
• Create the errorevent.rs file containing a Reflector at minimum, as well as implementation of the Reflectable trait and add it at the components/script/dom location.
• Add the implementation's module to the script crate lib.rs to ensure it is compiled.
• Build servo and fix any compile errors in the implementation.

./mach build

• Check if it works using this command:

./mach run tests/html/about-mozilla.html

Design Principles

• Simple: We have tried to not complicate the code but keep it simple.
• Readable: By adding necessary and required comments, we have made our code readable to other programmers.
• Reusable: We have tried and made our code capable of being used in a completely different setting.
• Efficient: Our code gives the results in reasonable amount of time.