Top all-time · #4524
Jan de Mooij
Personal blog · jandemooij.nl/blogprogrammingsystems
Jan de Mooij's personal blog at jandemooij.nl covers programming and systems. Since 2014, 17 different Hacker News readers have linked it 24 times, most often “W^X JIT-code enabled in Firefox”. The last post was in 2017, but the archive is still widely read.
Too few sampled comments (12) to say how often HN recommends it.?
Why HN links it
HN readers cite Jan de Mooij's posts on Firefox and SpiderMonkey as sources: W^X JIT code, 32-bit precision in Math.random, and SpiderMonkey performance optimizations. Comments cite them without judging them.
Summarised by Claude from a sample of 12 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- W^X JIT-code enabled in Firefox5 people · 6 mentions · first linked 2015-12-29
- Some SpiderMonkey Optimizations in Firefox Quantum3 people · 3 mentions · first linked 2017-12-06
- Math.random() and 32-bit precision3 people · 3 mentions · first linked 2015-11-27
- /blog/math-random-and-32-bit-precision/2 people · 2 mentions · first linked 2023-08-20
- Testing Math.random(): Crushing the browser2 people · 2 mentions · first linked 2015-11-30
- /blog/wx-jit-code-enabled-in-firefox/2 people · 2 mentions · first linked 2021-05-24
What Hacker News says?
> [mapping memory WX] hasn't been forbidden on any of the prior platforms that Dolphin supports Well, rarely completely forbidden, but e.g. I think OpenBSD has been W^X by default for quite some time (though IIRC with a WX allowed flag per… FS mount?). Now on FreeBSD it's not default but it's there, and if you turn it on, you have to mark WX-mapping binaries by running `elfctl -e +wxneeded`. Firefox actually became…
Comment linking /blog/wx-jit-code-enabled-in-firefox/
on “Temptation of the Apple: Dolphin on macOS M1”Submitted Some SpiderMonkey Optimizations in Firefox Quantum as a story · 212 points
HN discussionThanks for the correction; my knowledge is a bit out of date, Firefox at least (not sure about Safari) switched to W^X JIT a good while back: https://jandemooij.nl/blog/wx-jit-code-enabled-in-firefox/ . That's cool. W^X is more difficult to exploit for sure, but as other commenters point out, unfortunately still possible.
Comment linking /blog/wx-jit-code-enabled-in-firefox/
on “About Lockdown Mode”Submitted Testing Math.random(): Crushing the browser as a story · 36 points
HN discussionI highly doubt js engines would compile a string down to a linked list. But you're right they might compile it to a circular buffer or deque which can have O(1) prepends. Quick googling shows that this optimization might exist but only for firefox and only if you use "unshift": https://lannonbr.com/blog/2020-01-27-shift-optimizations https://jandemooij.nl/blog/2017/12/06/some-spidermonkey-opti... But it's very unlik…
Comment linking /blog/2017/12/06/some-spidermonkey-optimizations-in-firefox-quantum/
on “Never use a dependency that you could replace with an afternoon of programming”Submitted Math.random() and 32-bit precision as a story · 32 points
HN discussionFWIW Firefox manages to use W^X in their JIT (the experimental patch back in 2011 had a very interesting idea: one process w writing out to memory mapped RW, another process with the same mapped executable): http://jandemooij.nl/blog/2015/12/29/wx-jit-code-enabled-in-...
Comment linking /blog/2015/12/29/wx-jit-code-enabled-in-firefox/
on “W^X now mandatory in OpenBSD”Submitted Using Rust to generate Mercurial short-hash collisions as a story · 32 points
HN discussionFirefox works fine with it: http://jandemooij.nl/blog/2015/12/29/wx-jit-code-enabled-in-... After that, the performance overhead was pretty small on all benchmarks and websites I tested: Kraken and Octane are less than 1% slower with W^X enabled. On (ancient) SunSpider the overhead is bigger, because most tests finish in a few milliseconds, so any compile-time overhead is measurable. Still, it's less than 3% on Wind…
Comment linking /blog/2015/12/29/wx-jit-code-enabled-in-firefox/
on “W^X now mandatory in OpenBSD”Submitted Fast arrow functions in Firefox 31 as a story · 22 points
HN discussionNo http://jandemooij.nl/blog/2015/12/29/wx-jit-code-enabled-in-...
Comment linking /blog/2015/12/29/wx-jit-code-enabled-in-firefox/
on “W^X now mandatory in OpenBSD”Submitted W^X JIT-code enabled in Firefox as a story · 7 points
HN discussionThose lines are showing up because the old algorithm can't produce all possible values in the 0-1 range. 32 bits of internal state simply aren't enough for that. The problem is highlighted by the images in this article: http://jandemooij.nl/blog/2015/11/27/math-random-and-32-bit-...
Comment linking /blog/2015/11/27/math-random-and-32-bit-precision/
on “There's Math.random(), and then there's Math.random()”Submitted CacheIR: A New Approach to Inline Caching in Firefox as a story · 4 points
HN discussionJan also wrote about this http://jandemooij.nl/blog/2015/11/27/math-random-and-32-bit-... in the context of Spidermonkey.
Comment linking /blog/2015/11/27/math-random-and-32-bit-precision/
on “There's Math.random(), and then there's Math.random()”Submitted Using segfaults to interrupt jit code as a story · 4 points
HN discussionIn other news, the next firefox release is going to have W^X https://www.mozilla.org/en-US/firefox/46.0beta/releasenotes/ http://jandemooij.nl/blog/2015/12/29/wx-jit-code-enabled-in-...
Comment linking /blog/2015/12/29/wx-jit-code-enabled-in-firefox/
on “Firefox vs. rthreads”Submitted CacheIR: A New Approach to Inline Caching in Firefox as a story · 2 points
HN discussionMozilla people have been working on SpiderMonkey performance already: https://jandemooij.nl/blog/2017/12/06/some-spidermonkey-opti... , it's just not some wholesale replacement, so it probably never makes the top of the list for what they shout about. It also sounds like it has been a steady progression rather than a big jump, so maybe not quite as noticeable.
Comment linking /blog/2017/12/06/some-spidermonkey-optimizations-in-firefox-quantum/
on “WebAssembly Raytracer”Submitted Testing Math.random(): Crushing the browser as a story · 2 points
HN discussionAfter the linked article as well as https://jandemooij.nl/blog/math-random-and-32-bit-precision/ which follows from it, the main three browsers (Chrome[0], Firefox[1], Safari[2]) actually switched to Xorshift128+. So these days Math.random is nowhere near as horrifying as it was back then, however it's still not a system or a userland CSPRNG, for that you need `crypto.getRandomValues()` ( https://developer.mozilla.o…
Comment linking /blog/math-random-and-32-bit-precision/
on “Spotify Annoyed by People Uploading Hours of White Noise”Submitted Making `this` a real binding in SpiderMonkey as a story · 2 points
HN discussionInteresting to revisit. Have there been more changes to Math.random() since 2015 when this bug was fixed? https://jandemooij.nl/blog/math-random-and-32-bit-precision/ https://trac.webkit.org/changeset/192855/webkit This StackExchange answer provides a good writeup, especially about some added requirements for Math.random() from ES6: https://security.stackexchange.com/questions/84906/predictin... Are the 3 major brow…
Comment linking /blog/math-random-and-32-bit-precision/
on “Randomness in the Web Browser (2015)”Submitted W^X JIT-code enabled in Firefox as a story · 1 points
HN discussion
