Re: safe_syscall design guidance

[Kyle Evans <kevans@freebsd.org>]

On Mon, Oct 28, 2019 at 7:08 PM Kyle Evans <kevans@freebsd.org> wrote:
>
> Hi,
>
> We're working on improving bsd-user in a local tree and rebasing forward
> to get our work suitable for upstreaming. I'm porting the safe_syscall stuff
> over to bsd-user, and would like to get some design guidance as it may best
> be implemented with some refactoring of linux-user.
>
> Below is an example of the refactoring my initial approach takes. I'm
> omitting !x86_64 in this e-mail because it's all along the same lines and
> only including the part relevant to linux-user. Effectively, linux-user/host
> is moved to qemu-user/host along with ^/linux-user/safe-syscall.S.
>
> Some bits specific to FreeBSD, also likely other *BSD but I've not yet
> verified, are sprinkled throughout host/*/* parts; this is the main point I
> suspect may be objectionable. FreeBSD indicates syscall error differently
> than Linux, and *context bits are also different. Other OS-specific bits
> for other arch are similar to the diff below.
>
> A full version of this can be found in my tree, currently only available on
> GitHub: https://github.com/kevans91/qemu-bsd-user/tree/safe_syscall -- this
> is applied to our version, currently based on qemu 3.1.
>
> Thoughts?
>

We've settled on duplicating the linux-user side over to bsd-user for
now to make progress, and make another attempt to solicit design
feedback later when we've rebased the rest of our work forward to
modern qemu.

Thanks,

Kyle Evans