Then please enlighten me, what was the "fairly serious CPU correctness bug found by [my] employer"?
-
-
As I'm sure you know, the details of these bugs are usually NDA'd when they're found outside of vendors. There's a public errata for it, but I'm not going to describe the finding of an NDA'd bug on public twitter.
1 reply 0 retweets 1 like -
At my current (much smaller than Google) employer, we just found an issue that causes data corruption on a CPU from one of your whitelisted vendors. If you speak with people in the platforms group at any large company, you'll find people run into these with some regularity.
1 reply 0 retweets 1 like -
Do you honestly think I don't read errata? Unless it affects the subset of functionality that NaCl relies on, please explain the relevance. CPUs have bugs, CPUs interpret the specs differently, behave differently on edge cases, etc. That's the whole point of the whitelist.
1 reply 0 retweets 0 likes -
No, and I never said that. The bug we ran into causes effectively arbitrary data corruption. I admit I haven't read all of the NaCl code, but I would be pretty surprised if it's robust against arbitrary data corruption.
2 replies 0 retweets 0 likes -
I'd be curious to know how reading CPU errata is helpful. A typical errata will say something like "under certain conditions, unexpected behavior may occur" and it will then describe corruption of {cache, registers, IP, flags, etc.} What can any software do to work around that?
2 replies 0 retweets 2 likes -
In the case of the bug you linked to earlier, the full phrase is "which may occur under complex microarchitectural conditions involving jump instructions that span 64-byte boundaries (cross cache lines)", which does tell you how to avoid it.
2 replies 0 retweets 1 like -
It was an example. If you search for "complex microarchitectural conditions" you can find plenty that don't have a reasonable software workaround (other than a ucode patch), the first document I found when searching for that has multiple examples.
1 reply 0 retweets 0 likes -
Can you find one that is relevant? I wonder if I can find a relevant one in transmeta errata
2 replies 0 retweets 1 like -
As I said, I'd be happy have a discussion in another medium if you'd like to discuss what I'm saying instead of dropping nice sounding but irrelevant point scoring bon mots. If you want to decline my invitation again and respond with more sarcasm, that's fine too. Your call.
1 reply 0 retweets 0 likes
I'd be more than happy to discuss it once you've read the paper you're criticizing. I fail to see how pointing out that a relevant errata was actually prevented by a vendor whitelist is point scoring, doesn't that prove that it's useful?
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.