svn commit: r359053 - head/sys/kern

[Ian Lepore]

On Tue, 2020-03-17 at 22:27 +0000, Conrad Meyer wrote:
> Author: cem
> Date: Tue Mar 17 22:27:16 2020
> New Revision: 359053
> URL: https://svnweb.freebsd.org/changeset/base/359053
> 
> Log:
>   Implement sysctl kern.boot_id
>   
>   Boot IDs are random, opaque 128-bit identifiers that distinguish distinct
>   system boots.  A new ID is generated each time the system boots.  Unlike
>   kern.boottime, the value is not modified by NTP adjustments.  It remains fixed
>   until the machine is restarted.
>   
>   PR:		244867
>   Reported by:	Ricardo Fraile <rfraile AT rfraile.eu>
>   MFC after:	I do not intend to, but feel free
> 
> Modified:
>   head/sys/kern/kern_mib.c
> 
> Modified: head/sys/kern/kern_mib.c
> ==============================================================================
> --- head/sys/kern/kern_mib.c	Tue Mar 17 21:29:03 2020	(r359052)
> +++ head/sys/kern/kern_mib.c	Tue Mar 17 22:27:16 2020	(r359053)
> @@ -448,6 +448,32 @@ SYSCTL_PROC(_kern, KERN_HOSTID, hostid,
>      CTLTYPE_ULONG | CTLFLAG_RW | CTLFLAG_PRISON | CTLFLAG_MPSAFE | CTLFLAG_CAPRD,
>      NULL, 0, sysctl_hostid, "LU", "Host ID");
>  
> +static struct mtx bootid_lk;
> +MTX_SYSINIT(bootid_lock, &bootid_lk, "bootid generator lock", MTX_DEF);
> +
> +static int
> +sysctl_bootid(SYSCTL_HANDLER_ARGS)
> +{
> +	static uint8_t boot_id[16];
> +	static bool initialized = false;
> +
> +	mtx_lock(&bootid_lk);
> +	if (!initialized) {
> +		if (!is_random_seeded()) {
> +			mtx_unlock(&bootid_lk);
> +			return (ENXIO);
> +		}
> +		arc4random_buf(boot_id, sizeof(boot_id));
> +		initialized = true;
> +	}
> +	mtx_unlock(&bootid_lk);
> +
> +	return (SYSCTL_OUT(req, boot_id, sizeof(boot_id)));
> +}
> +SYSCTL_PROC(_kern, OID_AUTO, boot_id,
> +    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_MPSAFE | CTLFLAG_CAPRD,
> +    NULL, 0, sysctl_bootid, "", "Random boot ID");
> +
>  /*
>   * The osrelease string is copied from the global (osrelease in vers.c) into
>   * prison0 by a sysinit and is inherited by child jails if not changed at jail

This seems a bit complex.  Why run a sysinit to init a mutex so that
you can safely do a lazy init of boot_id?  Seems like it would be much
easier to just use a sysinit at SI_SUB_LAST to init boot_id before
sysctl can reference it.

-- Ian