Viewing profile — markjdb

At least FreeBSD's syscall ABI is guaranteed to be stable, one can run ancient binaries on a modern kernel. I believe the same is not true of OpenBSD and maybe NetBSD however.

The pf maintainer in FreeBSD has been doing a ton of work to bring more recent improvements over from OpenBSD, trying to bring them in sync as much as possible without breaking com…

A design that works by default isn't automatically better either though. You have to look at the details. > I guess one might be tempted to forgive a few warts in the interface lay…

The article clearly isn't talking about technical debt within the kernel implementations of epoll and kqueue, and if one wanted, it'd be easy to define fallback EVFILT_READ/WRITE f…

Well, no, it's "this interface works fine for you if you implement it." The kernel doesn't magically know whether your device file has data available to read, your device file has …

I'm not sure. Maybe it's "wait for events that aren't tied to an fd." For instance, FreeBSD (and I think other BSDs) also have EVFILT_PROC, which lets you monitor a PID (not an fd)…

I don't think the article does a good job of arguing its premise, which I think is that kqueue is a less general interface than epoll. When adding a new descriptor type, one can de…

The same is true of kqueue/kevent though... the driver just needs to decide which filters it wants to implement. There's no need to extend kqueue when adding some custom driver or …

For what it's worth, the default root shell is now /bin/sh instead of csh. I think that's true as of 14.0. /bin/sh is also a better interactive shell than it used to be, though yea…

CHERI does more than help eliminate security vulnerabilities. Consider that today we rely on the MMU to provide memory isolation between Unix processes; CHERI enables isolation wit…

CHERI does permit tricks like storing flags in the low bits of a pointer, at least to some extent. Quite a lot of low level C code (including some in the CheriBSD kernel) needs tha…

I use "ktrace -t f" once in a while for debugging and it's really handy. Output looks like 78436 cat PFLT 0x6c71f99cda8 0x2 78436 cat PRET KERN_SUCCESS 78436 cat PFLT 0x3c6efd36c28…

I'd be amazed if it isn't a configuration error of some kind.

How much data ends up being served from RAM? I had the impression that it was negligible and that the page cache was mostly used for file metadata and infrequently accessed data.

You can even send a Unix socket over itself. The kernel has to be careful to handle that correctly. :)

This is mostly true on FreeBSD as well. The real problem is that capability mode also disallows openat(AT_FDCWD) - there has to be an explicit directory descriptor.

It depends on the bug. syzkaller does an excellent job finding race conditions, but it can be difficult to generate a reliable reproducer for them. It often succeeds nonetheless. I…

That's fair. At the time, though, it wasn't clear that the author's angle was that FreeBSD doesn't have a culture of doing code reviews. We do, and I don't think one has to look ve…

There's some discussion happening now and I do expect to see some process changes coming out of this. It's tricky. The review you link does nominally follow the process of creating…

> Or is this just how it is on FreeBSD? It's not. We do a lot of code review, and it's done publicly. It's easy to look at the commit logs. I find it telling that the article doesn…

The notion there is that at some point in the past free memory was scarce, so the kernel swapped out some pages, and that swap space may still be in use long after the shortage is …

> as many of these tests show The tests appear to compare ZFS and ext4 and clang and gcc as much as FreeBSD and Linux.

"paravirtualized Solaris kernel" isn't really accurate - it's a collection of kernel interface shims. The whole thing is quite small, about 4KLOC on FreeBSD.

A driver is in ports while the author works on getting it ready to import. Just pkg install iichid.