linux-kernel - Re: [PATCH] oid_registry: allow arbitrary size OIDs

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Message-ID: <799a5022a9d427f6fb47005f7f3259bd14932e88.camel@HansenPartnership.com>
Date: Tue, 25 Nov 2025 17:12:30 -0500
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: David Howells <dhowells@...hat.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>, Andrew Morton
 <akpm@...ux-foundation.org>, Blaise Boscaccy <bboscaccy@...ux.microsoft.com>
Subject: Re: [PATCH] oid_registry: allow arbitrary size OIDs

On Tue, 2025-11-25 at 20:33 +0000, David Howells wrote:
> James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> 
> > This isn't usually a problem
> > except that it prevents us from representing the 2.25. prefix OIDs
> > which are the OID representation of UUIDs and have a 128 bit number
> > following the prefix.
> 
> Ewww.

Yes, well, not responsible for standards bodies ...

> 
> > Rather than import not often used perl arithmetic modules,
> 
> Do they not work?  Or are they just not commonly installed?

 A bit of both: Math::Int128 looked like it might solve my problem but
SUSE doesn't build it.  Math::BigInt is built but has a really horrible
API.  bc is actually an improvement: it's just really converting
decimal to binary at arbitrary size then we just do string operations
on long strings of binary numbers ... it's easier than actual maths ...

> 
> > +	# Base128 encode the number
> > +	my $j;
> > +	my $b;
> > +	for ($j = 0; $j < $tmp; $j++) {
> 
> I would do:
> 
> 	for (my $j = 0; $j < $tmp; $j++) {

OK.

> > +	    $b = oct("0b".substr($c, $j * 7, 7));
> 
> I would probably do "my $b = ..." here.

I can't do that: $b is used outside the scope.

> > +
> > +	    push @octets, $b | 0x80;
> >  	}
> > -	push @octets, $c & 0x7f;
> > +	$b = oct("0b".substr($c, $j * 7, 7));
> > +	push @octets, $b;
> 
> and just combine these two lines:
> 
> 	push @octets, oct("0b".substr($c, $j * 7, 7));

Will do (it was actually that way until I added a debugging printk.

Regards,

James


> 
> Using "oct("0b"...)" looks weird, but I guess it should work.
> 
> David
>