It's really bad when your unit of performance loss is "nines"...
-
-
Replying to @RichFelker @volatile_void
lol. "This spectre fix only has five nines of high unavailability."
1 reply 0 retweets 3 likes -
Replying to @sortiecat @volatile_void
With µc that adds the "flush btb" insn, a timer interrupt that's just "ibpb;iret" might not be in the "nines" level of horribleness, but I doubt ibpb is sufficient to clobber all branch prediction, just indirect.
1 reply 0 retweets 1 like -
Oh wait. If the cpu has HT, can you just steal a whole HT thread to constantly clobber BTBs?
2 replies 0 retweets 0 likes -
ugh. How about just putting *secret* data into the uncached/device memory? And not care about the non-secret?
1 reply 0 retweets 0 likes -
It doesn't scale. Requires hacks in every application that might have secrets. It's like foregoing MMU: instead of a general-purpose safety mechanism you have to manually ensure every check is right.
1 reply 0 retweets 0 likes -
If you unmap userspace memory upon kernel entry (aka Meltdown) fix and remove physmap from kernel, you shall be able to mitigate cross-app leakage. Am I right?
1 reply 0 retweets 0 likes -
No. The idea of Spectre v1 is that you trick a process to leak parts of its own memory via cache side channels. Malicious code in JIT is the obvious/easy way but far from the only one.
2 replies 0 retweets 0 likes -
Replying to @RichFelker @astarasikov and
I suspect it's even possible to make a jpeg or png whose decoding time (thus time between network requests) leaks auth tokens out of the browser.
1 reply 0 retweets 0 likes -
Ah I see, you are talking about v1 and I was thinking mostly about v2. I'll take a pause to think more about it
1 reply 0 retweets 0 likes
Yes. Spectre v2 mitigation is a solved problem except for making it less costly. Spectre v1 has no solution so far except using unaffected hardware or the above "4-5 nines" jokes.
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.