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wooosh commented on TPM GPIO fail: How bad OEM firmware ruins Intel TPM security   mkukri.xyz/2024/06/01/tpm... · Posted by u/osks
izacus · 2 years ago
> Of course, that doesn't mean you're protected against attackers who have physical access to the machine; they can simply install a keylogger.

How would that attack work if someone stole my Ryzen powered laptop with full disk encryption, TPM2.0 and secure boot with firmware password enabled?

wooosh · 2 years ago
Probably not the most practical attack, but it is very possible to MITM the connection between the keyboard itself and the motherboard.
wooosh commented on Pictures of a working garbage collector   oilshell.org/blog/2023/01... · Posted by u/todsacerdoti
drmeister · 3 years ago
Get `udb` - the reversible/time-traveling debugger from Undo. I don't own any stock - I love their product. You can run your code within it, hit an error, set a watch-point, reverse-continue to where the watch-point memory was changed and then check the stack. udb will turn brain-melting, blood-freezing memory bugs into trivial problems that you can solve in a few minutes.
wooosh · 3 years ago
A similar project is rr[0], which is freely available. Like you said, I find that reversible debuggers are a huge improvement over regular debuggers because of the ability to record an execution and then effectively bisect the trace for issues.

[0]: https://rr-project.org/

wooosh commented on High speed Unicode routines using SIMD   github.com/simdutf/simdut... · Posted by u/Peter5
lifthrasiir · 4 years ago
Just in case, here "Unicode routines" refer to Unicode encoding routines, not other more complex things like normalization. They are pretty regular but their automata would be relatively simple. (By the way, SIMD-accelerated regular expression parsing is indeed a thing [1], if anyone wondered.)

[1] https://www.microsoft.com/en-us/research/wp-content/uploads/...

wooosh · 4 years ago
Intel has an implementation of this technique here as well:

https://github.com/intel/hyperscan

wooosh commented on Computing Adler32 Checksums at 41 GB/s   wooo.sh/articles/adler32.... · Posted by u/wooosh
NavinF · 4 years ago
>diminishing returns especially due to it working faster than the speed of my RAM (2667MT/s * 8 = ~21 GB/s).

That sounds kinda slow; Is there only 1 DIMM in the slots? I remember benchmarking 40GiB/s read speed on an older system that had 2 dual-rank DIMMs (4 ranks in total).

I'd expect 3200mbit/s*(64 data lines)*(2 memory channels) = ~48 GiB/s on a typical DDR4 desktop and a lot more with overclocked ram.

Great writeup either way.

wooosh · 4 years ago
Yes, this is on a single 8GB 2667MHz DIMM in a laptop.

edit: For dual channel RAM, I would suspect the throughput depends on how the kernel decides to map physical memory to virtual addresses.

u/wooosh

KarmaCake day397April 5, 2022
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