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kboot: For hostfs, return better errors from read, where possible.
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Authored by imp on Jan 29 2023, 3:16 PM.
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Details

Summary

Translate the Linux error return from read to a FreeBSD errno. We use a
simplified translation: 1-34 are the same between the systems, so any of
those will be returned directly. All other errno map to EINVAL. This
will suffice for some code that reads /dev/mem in producing the right
diagnostic.

A fully generalized version is much harder. Linux has a number of errno
that don't translate well and has architecture dependent
encodings. Avoid this mess with a simple macro for now. Add comment
explaining why we use the simple method we do.

Sponsored by: Netflix

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rG FreeBSD src repository
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Event Timeline

imp requested review of this revision.Jan 29 2023, 3:16 PM

rebase / refactor / redo

kevans added inline comments.
stand/kboot/host_syscall.h
211
This revision is now accepted and ready to land.Feb 2 2023, 3:58 AM
This revision now requires review to proceed.Feb 2 2023, 4:21 AM
This revision is now accepted and ready to land.Feb 2 2023, 2:55 PM

I did find myself wondering if host_to_stand_errno should assert that e <= 0 since it's a relatively common error to accidentally use positive errors when modifying linux code.

I did find myself wondering if host_to_stand_errno should assert that e <= 0 since it's a relatively common error to accidentally use positive errors when modifying linux code.

I had similar thoughts early on, but this wound up being a #define... I'll post a followup review.