Source-singularity Alternatives

source-singularity reviews and mentions

• Fork() is evil; vfork() is goodness; afork() would be better; clone() is stupid
  9 projects | news.ycombinator.com | 28 Feb 2022

  Windows doesn't have fork as you know it. It has a POSIX-ish fork-alike for compliance, but under the hood it's CreateThread[0] with some Magic.

  in Windows, you create the thread with CreateThread, then are passed back a handle to that thread. You then can query the state of the thread using GetExitCodeThread[1] or if you need to wait for the thread to finish, you call WaitForSingleObject [2] with an Infinite timeout

  Aside: WaitForSingleObject is how you track a bunch of stuff: semaphores, mutexes, processes, events, timers, etc.

  The flipside of this is that Windows processes are buckets of handles: a Process object maintains a series of handles to (threads, files, sockets, WMI meters, etc), one of which happens to be the main thread. Once the main thread exits, the system goes back and cleans up (as it can) the rest of the threads. This is why sometimes you can get zombie'd processes holding onto a stuck thread.

  This is also how it's a very cheap operation to interrogate what's going on in a process ala Process Explorer.

  If I had to describe the difference between Windows and Linux at a process model level, I have to back up to the fundamental difference between the Linux and Windows programming models: Linux is is a kernel that has to hide its inner workings for its safety and security, passing wrapped versions of structures back and forth through the kernel-userspace boundary; Windows is a kernel that considers each portion of its core separated, isolated through ACLs, and where a handle to something can be passed around without worry. The windows ABI has been so fundamentally stable over 30 years now because so much of it is built around controlling object handles (which are allowed to change under the hood) rather than manipulation of of kernel primitives through syscalls.

  Early WinNT was very restrictive and eased up a bit as development continued so that win9x software would run on it under the VDM. Since then, most windows software insecurities are the result of people making assumptions about what will or won't happen with a particular object's ACL.

  There's a great overview of windows programming over at [3]. It covers primarily Win32, but gets into the NT kernel primitives and how it works.

  A lot of work has gone into making Windows an object-oriented kernel; where Linux has been looking at C11 as a "next step" and considering if Rust makes sense as a kernel component, Windows likely has leftovers of Midori and Singularity [4] lingering in it that have gone onto be used for core functionality where it makes sense.

  [0] https://docs.microsoft.com/en-us/windows/win32/api/processth... [1] https://docs.microsoft.com/en-us/windows/win32/api/processth... [2] https://docs.microsoft.com/en-us/windows/win32/api/synchapi/... [3] https://www.tenouk.com/cnwin32tutorials.html [4] https://www.microsoft.com/en-us/research/project/singularity...

• A few thoughts on Fuchsia security
  4 projects | news.ycombinator.com | 12 Jun 2021

  Singularity has a C++ microkernel actually.

  https://github.com/lastweek/source-singularity/tree/master/b...

  Microsoft and Oracle have removed CAS and JAAS from CLR/JVM respectively as they have failed to provided the software isolated model that was expected from them.