linux-kernel - Re: [Announce] Linux-tiny project revival

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <200709201818.42125.rob@landley.net>
Date:	Thu, 20 Sep 2007 18:18:41 -0500
From:	Rob Landley <rob@...dley.net>
To:	"Indan Zupancic" <indan@....nu>
Cc:	linux-tiny@...enic.com,
	"Michael Opdenacker" <michael@...e-electrons.com>,
	"CE Linux Developers List" <celinux-dev@...e.celinuxforum.org>,
	"linux kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [Announce] Linux-tiny project revival

On Thursday 20 September 2007 4:26:13 pm Indan Zupancic wrote:
> On Thu, September 20, 2007 22:38, Rob Landley wrote:
> > I've been playing with an idea for a while to improve the printk()
> > situation, but it's a more intrusive change than I've had time to bang
> > on.
> >
> > Right now, the first argument to printk() is a loglevel, but it's handled
> > via string concatenation.  I'd like to change that to be an integer, and
> > make it an actual comma-separated first argument.  (Mandatory, not
> > optional.)
> >
> > So instead of:
> >   printk(KERN_NOTICE "Fruit=%d\n", banana);
> > It would now be:
> >   printk(KERN_NOTICE, "Fruit=%d\n", banana);
> >
> > Change the header from:
> >   #define KERN_NOTICE "<5>"
> > to:
> >   #define KERN_NOTICE 5
>
> You have to jump through less hoops if you do:
>
> #define KERN_NOTICE 5,

Less change to the source, but the result is less obvious about what it's 
doing.  I'd personally rather have the churn than wind up with magic 
syntax...

> But the problem remains that there are printk's which don't have
> a KERN_* as the first argument. Those are also impossible to get
> rid off in this way, as the loglevel is unknown (and you don't want
> partially printed messages).
>
> So adding the comma is really needed and in addition all printk's
> without a loglevel should get one. Which clutters the code and may
> increase codesize.

It's ok to _explicitly_ not have a loglevel, and thus take a known default.  
The problem is printing out less than a full line, continuing it later, and 
not making obvious at compile time what the level of this chunk is.

> A quick scroll through a vmlinux binary shows that there are quite a
> lot areas consisting only of some repeated pattern. Mostly 0x00, but
> also 0x90 and ".GCC: (GNU) 4.2.1.". Getting rid of those would save
> something between 50 and 100KB.

Worse, if you feed an absolute path to O= when you build the kernel out of 
tree, then it uses absolute paths for all the __FILE__ strings and that makes 
kernel BIIIIIG.  (Did that by accident a while back.)  Too bad there's no way 
to keep the __FILE__ strings compressed at runtime and gunzip them as needed 
like busybox does with help messages... :)

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/