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pcwalton's profile
Patrick Walton
Patrick Walton
Patrick Walton
@pcwalton

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Patrick Walton

@pcwalton

Research engineer at Mozilla

San Francisco, CA
pcwalton.github.io
Joined November 2009

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    1. comex‏ @comex 6 Dec 2016
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      aka relearning lessons of the past for the nth time. arguably. I mean, you can get big perf wins with tagged pointers - was it worth it?

      2 replies 5 retweets 4 likes
    2. comex‏ @comex 6 Dec 2016
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      I like this development because of how it could be used for software fault isolation (like NaCl).

      1 reply 1 retweet 1 like
    3. comex‏ @comex 6 Dec 2016
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      One cheap way to do SFI is to restrict processes to a 32-bit "address space" where all load/stores must be a 32bit offset to a 64b base reg.

      1 reply 1 retweet 0 likes
    4. comex‏ @comex 6 Dec 2016
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      Actually, I guess that's what NaCl does. I thought it did something else.

      1 reply 1 retweet 0 likes
    5. comex‏ @comex 6 Dec 2016
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      NaCl only cares about one sandboxed process per OS process, but imagine a kernel based on this that stuck all procs in same address space.

      1 reply 0 retweets 0 likes
    6. comex‏ @comex 6 Dec 2016
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      With 48-bit addresses, if each process uses 32 bits of address space, you can "only" have 65536 processes. Not terrible (you can swap out)…

      2 replies 0 retweets 1 like
    7. comex‏ @comex 6 Dec 2016
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      ...but a bigger address space makes things a bit easier, I think. Also improves ASLR.

      1 reply 0 retweets 0 likes
    8. comex‏ @comex 6 Dec 2016
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      Also allows giving each process a bigger address space—if you replace the mask-to-32-bit op w/ anding with a register, can be arbitrary size

      1 reply 0 retweets 0 likes
    9. comex‏ @comex 6 Dec 2016
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      Anyway, I'd love to see an OS based on SFI and some sort of typed assembly. Goal: IPC literally as cheap as a function call.

      2 replies 1 retweet 3 likes
    10. Patrick Walton‏ @pcwalton 6 Dec 2016
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      Didn’t Singularity do this?

      3 replies 0 retweets 0 likes
      Patrick Walton‏ @pcwalton 6 Dec 2016
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      Replying to @pcwalton @comex

      (Oh, also it’s hard to get IPC as cheap as a function call when you have SMP…L4 usually has struggled with that)

      11:50 AM - 6 Dec 2016
      1 reply 0 retweets 0 likes
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        2. comex‏ @comex 6 Dec 2016
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          I don't know the history with SMP, but the basic model I imagine is: you don't send messages to a thread.

          1 reply 0 retweets 0 likes
        3. comex‏ @comex 6 Dec 2016
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          Replying to @comex @pcwalton

          Instead, the process you're calling borrows the current thread from the caller process.

          1 reply 0 retweets 0 likes
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