It's been a while since I last (and actually first) posted about Fuzzinator. Now I think that I have enough new experiences worth sharing.
More than a year ago, when I started fuzzing, I was mostly focusing on mutation-based fuzzer technologies since they were easy to build and pretty effective. Having a nice error-prone test suite (e.g. LayoutTests) was the warrant for fresh new bugs. At least for a while.
What is ASM.JS?
Lately, I came up with the idea to do some development on Aarch64. However, I couldn't get my hands on real hardware easily so I started to look for alternatives (i.e., emulators). The ARMv8 Foundation Model seemed to be the trivial solution but I've heard that QEMU is somewhat faster so I gave it a try. My goal was to set up the VM as quick as possible: reuse whatever is already "out there" and rebuild only what's utterly necessary. In the end it turned out that it's quite easy to get such a VM working ... once you know what you need.
Fuzzers are widely used tools for testing software. They can generate random test cases and use them as input against the software under fuzzing/testing. Since the tests have randomly-built content, it is not necessary to check them for correctness, but they are suitable for catching rough bugs like use-after-frees, memory corruptions, assertion failures and further crashes. There are many approaches how to generate these tests, but all of them can be categorized into three main groups: whitebox, blackbox and graybox fuzzers.
Last year I got a Nokia N9 on Qt Developer Days, it's a great mobile phone, I really like it, but I haven't published any memory measurement results about it yet. In my last post I did WebKit memory profiling on it with Valgrind, but it was all about heap usage. I think a number of persons are interested in the overall memory usage such as peak memory usage, the sizes of the used libraries, etc. During QtWebKit's life-cycle we switch from one library to another, usually because of performance considerations. In the past we do not take too much attention to memory consumption-related topics while switching between libraries, although it would be very vital to keep eye on this area as well.
In this post I would like to share with you one of my latest memory consumption measurements about the heap usage of QtWebKit.
64 bit systems allow allocating more memory, but this extra space has a trade-of: the pointers are grown to 64 bit wide which increases the total memory consumption. Ever wondered about the price of 64 bit? Well, you can find comparisons here about some popular pages on the Qt port of WebKit. Furthermore, we offer some CSS subsystem related comparisons at the end of the post.
ARM-NEON is a SIMD (Single instruction, multiple data) instruction set for the latest ARM cores. The NEON instruction set focuses on integer (8, 16 and 32 bit) and single precision floating point arithmetic. It also has some unique features like using the same register array as the Vector Floating Point (VFP) unit which allows mixing SIMD and common floating point instructions.
A long time has passed since I’ve written, but lately I did some interesting memory consumption measurements on QtWebKit’s WebKit2 implementation. First, let’s talk a little about WebKit2’s process models. There are 2 process models in WebKit (more precisely, there are 3, but for now I don’t take with thread-based solutions into account): the default is the secondary process model, and we can easily switch to shared process model as well. Balazs experienced with a third one called service model which works like a classic server-client connection.