hansendc
There are a couple more than two, even in 2021.
Memory Protection Keys come to mind, as do the NPT/EPT tables when virtualization is in play. SEV and SGX also have their own ways of preventing the kernel from writing to memory. The CPU also has range registers that protect certain special physical address ranges, like the TDX module's range. You can't write there either.
That's all that comes to mind at the moment. It's definitely a fun question!
https://josm.openstreetmap.de/browser/josm/trunk/src/org/ope...
It used to use a linear list of points, but it was VERY slow to draw, so I hacked this in to the code base a few years ago.
From https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... :
> Specifying "gather_data_sampling=force" will use the microcode mitigation when > available or disable AVX on affected systems where the microcode hasn't been > updated to include the mitigation.
Disclaimer: I work on Linux at Intel. I probably wrote or tweaked the documentation and changelogs that are confusing folks.
I'll also add a [2]:
[2] There's no way to do it in the page tables. But, if you have Protection Keys for Userspace (PKU), you can get it ... kinda. You can have a PROT_READ|PROT_EXEC mapping, assign it a pkey, then set PKEY_DISABLE_ACCESS in the PKRU register for that key. In fact, if you have a PKU CPU and you do an unadorned mmap(PROT_EXEC), the kernel will allocate you a pkey and do this under the covers FOR you. Anyone who can execute WRPKRU can easily undo this protection, but it's better than nothing.
That said, this would be great to see in OpenBSD (or any other OS).
Granted, this was a lonely little fellow. But, he knew perfectly well what he was doing and repeatedly approached boats, despite the noise. He died after colliding with a tugboat prop.
"In a statement, Intel officials wrote: ... we do not rely on obfuscation of information behind red unlock as a security measure."
(BTW, I work on Linux at Intel, I'm not posting this in any official capacity)
https://lore.kernel.org/lkml/20210205151631.43511-1-kirill.s...
BTW, MPX was clearly not the right thing. Nobody really wanted it. The world would be a better place if these address-bit-ignoring things (ARM TBI, AMD UAI, Intel LAM) had been implemented years ago instead all the effort spent on MPX.
Believe me, I know. I put a lot of blood, sweat and tears into MPX for Linux.
Disclaimer: If you didn't figure it out by now, I work on Linux at Intel.
Even better is if an open source implementation is in the kernel tree, like in tools/testing/selftests. That makes it even less likely that the kernel code gets broken.
Disclaimer: I work on Linux at Intel, although not on drivers like this Habana one.
What does Intel get out of this? I'm really hoping that Intel gets help improving the kernel from a talented bunch of kernel developers who have experience working closely with paying customers. Intel has tons of kernel developers, but few of us are very directly customer-facing.
I also hope the Linutronix folks can spend less time on "castle maintenance" and more time on kernel maintenance. https://www.phoronix.com/scan.php?page=news_item&px=PREEMPT_...
(BTW, I work on Intel at Linux).
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...
For very selfish reasons, I'm hoping that this acquisition will give the Linutronix folks even more of an opportunity to contribute to the core kernel and especially arch/x86.
Disclaimer: I work on Linux at Intel.
Don't confuse prediction and anticipation. Prediction requires that you know what's going to happen. Anticipation is getting ready for something that might happen. Anticipation is a normal part of defensive driving every day, not prediction.
Let's go back to defensive driving 101: defensive driving allows mistakes to be made. It allows bad things to occur and still recover from them safely. Bad things happen because of mistakes are made by humans in the car, humans outside of the car and also by the computer in the car. The change here is that you the computer is being given much more latitude to make mistakes. It does NOT grant the computer the ability to remove defensive margins from driving.
If you drive (regardless of FSD) with no defensive driving margins, you immediately enter "too late" territory whenever a mistake is made.
One specific place is first sentence of the FSD Beta welcome email:
"Full Self-Driving is in limited early access Beta and must be used with additional caution. It may do the wrong thing at the worst time, so you must always keep your hands on the wheel and pay extra attention to the road. Do not become complacent."
That's been my experience with it. Right now, the beta doesn't reduce my workload, it increases it. When I want to "just drive", I turn the beta off.
That said, Tesla can and should do more. They need to better frame the capabilities of the system, staring with the silly marketing names.
This isn't limited to "Tesla-tech". The same rules apply to ALL technology.
Intel's equivalent of SEV-ES and SEV-SNP is called TDX: https://www.intel.com/content/www/us/en/developer/articles/t... . While you could probably put both under the "confidential computing" umbrella, they do really different things well. As far as I know, SGX and TDX will both be around on the same hardware.
Also, just to be explicit about it: I work on Linux at Intel, including on SGX.
I've never thought once that the rear visibility was a problem on the freeway.
As for the headrest, I've never thought about it once myself.
I'm not sure to what you are referring to here.
I was one of the people who worked on the Linux PTI implementation that mitigated Meltdown. My memory is not perfect, but I honestly don't know what you're referring to.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...
There is no way to enable or disable this particular mitigation. That's probably because it's an extremely cheap mitigation.
Disclaimer: I work on Linux at Intel.
The in-kernel Spectre-v1 mitigations, like:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...
are cheap and ubiquitous. You don't have to turn them on, and they're so cheap you can't even turn them off if you wanted.
Disclaimer: I work on Linux at Intel.
The key part of this post is "In my lab, on a vulnerable Fedora" which means that the author is using an old, known-vulnerable version of Fedora on which to do their testing.
You don't have to do anything other than be running a reasonably modern version of the kernel that gets updates from -stable or from your distro.
BTW, this is a Spectre-v1-style exploit. These are EXTREMELY widespread across lots of processors with conditional branch speculation. It's (relatively) unrelated to the family of things like MDS or Spectre-v2 where microcode updates were issued.
Disclaimer: I work on Linux at Intel, occasionally on mitigation for this stuff.
Not really. There are lots of holes in the physical address map. Look at /proc/iomem. Look at all of the gunk in there at addresses lower than the amount of RAM you have. Look at the highest “System RAM” address. It will be higher than the amount of actual physical RAM that you have.
The most relevant kernel code is here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...
I am one of the original authors listed at the top of that file.
MSRs can also be added by microcode update as we saw with MSR_IA32_SPEC_CTRL, which was used to mitigate Spectre (among other things).
Disclaimer: I work on Linux at Intel, and I was one of the ones posting in that LKML thread quoted in the article.