Do you think the idea of bringing Mach IPC into the FreeBSD kernel and putting a Darwin based userland on top of it could have some merit? I find it interesting to say the least.
@nprofile1q...
Stacey Son has a PoC for Mach IPC on FreeBSD. The problem is that Mach IPC is pretty terrible. There is an entire generation of microkernels that were built with the sole design goal of ‘don’t do Mach IPC, it was so bad anything else is better’. NeXTSTEP / OPENSTEP / OS X / macOS / {whatever name it has next year} doesn’t use Mach IPC because it’s a good idea, it uses it because it’s there, same with Mach-O file formats.
The one thing that makes Mach-O useful is that you get a load of trailer information on messages to let you identify the sender. On FreeBSD, SCM_CREDS with ‘ SOCK_SEQPACKET` gives you most of what you want for this and is easily extensible with the rest.
The thing I would like in FreeBSD is Spring-style Doors. Doors were an IPC mechanism that did a synchronous switch to another thread (usually in another process). The kernel preserves most registers (a handful, including the stack pointer and instruction pointer) are switched, which makes easy to do fast RPC, which is what you really want for building compartmentalised software. Doors also had the option to do page flipping for large messages.
Someone did have some patches to add Doors a while ago, but they copied the Solaris APIs without implementing the bits that made Doors good. And a Solaris localisation will look very different from a BSD localisation of the ideas.
Stacey Son has a PoC for Mach IPC on FreeBSD. The problem is that Mach IPC is pretty terrible. There is an entire generation of microkernels that were built with the sole design goal of ‘don’t do Mach IPC, it was so bad anything else is better’. NeXTSTEP / OPENSTEP / OS X / macOS / {whatever name it has next year} doesn’t use Mach IPC because it’s a good idea, it uses it because it’s there, same with Mach-O file formats.
The one thing that makes Mach-O useful is that you get a load of trailer information on messages to let you identify the sender. On FreeBSD, SCM_CREDS with ‘ SOCK_SEQPACKET` gives you most of what you want for this and is easily extensible with the rest.
The thing I would like in FreeBSD is Spring-style Doors. Doors were an IPC mechanism that did a synchronous switch to another thread (usually in another process). The kernel preserves most registers (a handful, including the stack pointer and instruction pointer) are switched, which makes easy to do fast RPC, which is what you really want for building compartmentalised software. Doors also had the option to do page flipping for large messages.
Someone did have some patches to add Doors a while ago, but they copied the Solaris APIs without implementing the bits that made Doors good. And a Solaris localisation will look very different from a BSD localisation of the ideas.
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