kcmp: Add a manual page

[markj]

Summary

Sponsored by: The FreeBSD Foundation

[emaste]

lib/libc/sys/kcmp.2

4

Standard copyright is just "The FreeBSD Foundation" (no Inc)

36

not just file descriptors though, "kernel objects" maybe?
the fd table or signal handler table aren't fds

51

is "access to" correct? or is it "reference" the same kernel object?

216

Do we want to list the known ones that are not implemented?
KCMP_IO, KCMP_SYSVSEM, KCMP_FS?

Also KCMP_FILEOBJ is FreeBSD-specific?

[markj]

Handle Ed's feedback.

[markj]

lib/libc/sys/kcmp.2

4

Oops, thanks. I copied this from sigfastblock.2 btw. In fact this "Inc" appears in quite a few FF copyright lines.

51

Yes, "reference" is more accurate.

216

I don't see much purpose in keeping a list? An interested reader can compare the two man pages.

[kib]

We should mention somewhere that the caller must have the privilege to debug both pid1 and pid2.

lib/libc/sys/kcmp.2

40

You need userspace unistd.h to get the prototype.

124

150

The order is internally defined by kernel and is stable until system reboots.

[markj]

Handle review comments from kib.

[kib]

Thank you for working on this.