aio_*(2): mention ENOSYS under ERRORS

[ngie]

Summary

ENOSYS can occur if aio(4) is not loaded in the kernel. Document this
behavior so consumers on FreeBSD can better understand that this is a
possible scenario.

Clean up the manpages slightly while here:

• Sort ERRORS by errno(3).
• Use .Fx instead of FreeBSD.

PR: 190942

Test Plan

• igor/manlint pass with the changes (ignore the .Dd complaints):

% for i in aio_cancel.2 aio_error.2 aio_fsync.2 aio_mlock.2 aio_read.2 aio_return.2 aio_suspend.2 aio_waitcomplete.2 aio_write.2 ; do mandoc -Tlint  $PWD/$i; done
% for i in aio_cancel.2 aio_error.2 aio_fsync.2 aio_mlock.2 aio_read.2 aio_return.2 aio_suspend.2 aio_waitcomplete.2 aio_write.2 ; do igor $PWD/$i; done
aio_cancel.2:25:date not today, March 25, 2025:.Dd [January 19, 2000]
aio_error.2:25:date not today, March 25, 2025:.Dd [January 2, 2021]
aio_fsync.2:25:date not today, March 25, 2025:.Dd [November 15, 2023]
aio_mlock.2:25:date not today, March 25, 2025:.Dd [August 19, 2016]
aio_read.2:25:date not today, March 25, 2025:.Dd [February 1, 2024]
aio_return.2:25:date not today, March 25, 2025:.Dd [January 11, 2021]
aio_suspend.2:25:date not today, March 25, 2025:.Dd [October 23, 2017]
aio_waitcomplete.2:25:date not today, March 25, 2025:.Dd [March 21, 2016]
aio_write.2:25:date not today, March 25, 2025:.Dd [February 1, 2024]

• The rendered output looks good after the change.

[ziaee]

Thank you so much for doing this!

[imp]

Do you need to mention the SIGSYS issue? Unless you have blocked SIGSYS, any system call that returns ENOSYS will generate that signal.

[ngie]

In D49502#1128871, @imp wrote:

Do you need to mention the SIGSYS issue? Unless you have blocked SIGSYS, any system call that returns ENOSYS will generate that signal.

Good question. It looks like ENOSYS without SIGSYS is the standard in libsys:

% rg -l SIGSYS lib/libsys/*.2 | wc -l
       1
% rg -l ENOSYS lib/libsys/*.2 | wc -l
      24

[imp]

In D49502#1128876, @ngie wrote:

In D49502#1128871, @imp wrote:

Do you need to mention the SIGSYS issue? Unless you have blocked SIGSYS, any system call that returns ENOSYS will generate that signal.

Good question. It looks like ENOSYS without SIGSYS is the standard in libsys:

% rg -l SIGSYS lib/libsys/*.2 | wc -l
       1
% rg -l ENOSYS lib/libsys/*.2 | wc -l
      24

Ok looks like intro covers it

[ngie]

In D49502#1128880, @imp wrote:

In D49502#1128876, @ngie wrote:

In D49502#1128871, @imp wrote:

Do you need to mention the SIGSYS issue? Unless you have blocked SIGSYS, any system call that returns ENOSYS will generate that signal.

Good question. It looks like ENOSYS without SIGSYS is the standard in libsys:

% rg -l SIGSYS lib/libsys/*.2 | wc -l
       1
% rg -l ENOSYS lib/libsys/*.2 | wc -l
      24

Ok looks like intro covers it

👍