Re: [patch] system_process_attributes for OpenBSD

[Omar Polo <op@omarpolo.com>]

Timo Myyrä <timo.myyra@bittivirhe.fi> writes:

> Omar Polo <op@omarpolo.com> [2021-01-01, 23:29 +0100]:
>
>[snip]
>
> Hi Omar,
>
> Are you sure you need kvm? I'm under impression its frowned upon to
> access that from userland.

Thanks for sharing!  I haven't followed closely the development of
OpenBSD, but at least on -CURRENT trying to get a struct kinfo_proc for
a specific pid via sysctl results in errors (both from sysctl(8) and
sysctl(3)):

    $ sysctl kern.proc
    sysctl: use ps to view kern.proc information
    $ sysctl kern.proc 75056  # a valid pid
    sysctl: use ps to view kern.proc information
    sysctl: top level name 75056 in 75056 is invalid

    $ cat <<EOF > pid.c
    #include <sys/types.h>
    #include <sys/sysctl.h>
    #include <err.h>
    #include <stdlib.h>

    int
    main(void)
    {
            pid_t pid = 75056; /* valid pid */
            int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PID, pid };
            struct kinfo_proc proc;
            size_t len = sizeof(proc);

            if (sysctl(mib, 4, &proc, &len, NULL, 0) != 0 || len == 0)
                    err(1, "sysctl");
            return 0;
    }
    EOF
    $ cc pid.c -o pid && ./pid
    pid: sysctl: Invalid argument
    $ ps 75056
    75056 ??  S        0:38.85 emacs --daemon (emacs-27.1)

This plus the fact that both top and ps in base uses kvm were the
rationale for my choice.

Regarding list_system_processes, I still have to check the differences,
but the current version on master is fundamentally equivalent to yours
(modulo a bunch of #ifdefs for freebsd and macos), so I guess it was
merged at some point?  Here on emacs-27.1 (list-system-processes)
returns nil, but on emacs compiled from master it works correctly.