Breaking the x86 Instruction Set
Why Hacker News recommends it
HN recommends it as a clever, entertaining and easy-to-follow talk on finding hidden x86 instructions with the Sandsifter tool.
What it is
Christopher Domas presents at Black Hat 2017 how page fault analysis and processor fuzzing can exhaustively search the x86 instruction set. The talk uncovers undocumented instructions and hardware bugs and shows limits of disassemblers.
Recommended by 9 HN commenters across 8 different months, 2017 to 2022.
What Hacker News said
Recommends AceJohnny2 · 2017-09 · on “IDA: What's new in 7.00”
> I trust its disassembler (especially for mainstream languages) more than almost any other disassembler Might I suggest Christopher Domas' Black Hat talk "Breaking the x86 ISA", along the way of which he demonstrates the limitations of all disassemblers out there, including IDA's :) Talk: [this video] Slides: [LINK] Paper: [LINK]
Recommends anfractuosity · 2018-01 · on “Ask HN: What’s your favorite talk from 2017?”
One of my favourite talks I watched was "Low Cost Non-Invasive Biomedical Imaging - An Open Electrical Impedance Tomography Project" [LINK] As it presented an interesting technique I'd never heard of before, along with an implementation. Also I thought the 'Breaking the x86 Instruction Set' talk was extremely clever - [this video]
Recommends DyslexicAtheist · 2018-01 · on “Ask HN: What’s your favorite talk from 2017?”
my favorite were: - How the reputation economy is creating data-driven conformity [LINK] - DEF CON 25 (2017) - Weaponizing Machine Learning [LINK] - BlackHat 2017: Breaking the x86 Instruction Set [this video]
Recommends nnnate · 2018-10 · on “Ask HN: What are some of the best technical talks you've heard?”
Breaking the x86 Instruction Set by Christopher Domas. [this video] I found it easy to follow and pretty entertaining.
Recommends jchw · 2019-04 · on “A Complete Formal Semantics of x86-64 User-Level Instruction Set Architecture”
There was a really good Blackhat talk a year or two ago in a sort of similar vein: they developed an approach to iterate and find undocumented opcodes. [this video] The software they developed is called Sandsifter.
Recommends tyingq · 2020-11 · on “XuanTie C906 based Allwinner RISC-V processor to power $12 Linux SBC's”
"I thought you were saying that the use of microcode would complicate verification of the hardware." I do think that microcode opens up the possibility of subtle injections to follow code/hardware paths you might not easily predict. A really good talk on reverse engineering an ISA implementation: [this video]
Recommends BlackLotus89 · 2021-03 · on “Undocumented x86 instructions in Intel CPUs that can modify microcode”
There was an interesting black hat talk about automatically finding undocumented instructions. [0] Interesting comment on twitter to the instruction of the original post[1] [0] [this video] [1] [LINK]
Recommends gbrown_ · 2021-04 · on “How many x86 instructions are there? (2016)”
How about undocumented instructions? Sandsifter[1] is an interesting project and the video from BlackHat[2] is a good watch. There's also a previous discussion of it on HN[3]. [1] [LINK] [2] [this video] [3] [LINK]