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Breaking the x86 Instruction Set

Black Hat · talk · Watch on YouTube

Security & hackingComputer architecture & CPUs

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.

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.

  • 9 people recommended it
  • 8 different months
  • 0 strong recommendations
  • first 2017, last 2022

What HN commenters said

  1. “he demonstrates the limitations of all disassemblers out there, including IDA's”

    Shows limitations of all disassemblers including IDA's.

    AceJohnny2, 2017-09 · Recommendation · in “IDA: What's new in 7.00”

  2. “I thought the 'Breaking the x86 Instruction Set' talk was extremely clever”

    Extremely clever talk on undocumented x86 instructions.

    anfractuosity, 2018-01 · Recommendation · in “Ask HN: What’s your favorite talk from 2017?”

  3. “BlackHat 2017: Breaking the x86 Instruction Set”

    Listed among favorite talks of 2017.

    DyslexicAtheist, 2018-01 · Recommendation · in “Ask HN: What’s your favorite talk from 2017?”

  4. “I found it easy to follow and pretty entertaining.”

    Easy to follow and entertaining talk by Christopher Domas.

    nnnate, 2018-10 · Recommendation · in “Ask HN: What are some of the best technical talks you've heard?”

  5. “There was a really good Blackhat talk a year or two ago”

    Talk on finding undocumented opcodes via Sandsifter.

    jchw, 2019-04 · Recommendation · in “A Complete Formal Semantics of x86-64 User-Level Instruction Set Architecture”

  6. “A really good talk on reverse engineering an ISA implementation”

    Good talk on reverse engineering an ISA implementation.

    tyingq, 2020-11 · Recommendation · in “XuanTie C906 based Allwinner RISC-V processor to power $12 Linux SBC's”

  7. “There was an interesting black hat talk about automatically finding undocumented instructions.”

    Interesting talk on automatically finding undocumented instructions.

    BlackLotus89, 2021-03 · Recommendation · in “Undocumented x86 instructions in Intel CPUs that can modify microcode”

  8. “the video from BlackHat[2] is a good watch”

    Good watch on finding undocumented x86 instructions.

    gbrown_, 2021-04 · Recommendation · in “How many x86 instructions are there? (2016)”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: x86, fuzzing, sandsifter, disassemblers, cpu security, reverse engineering

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