Date: Sun, 31 Dec 2000 12:45:56 +0100 From: Andre Albsmeier <andre.albsmeier@mchp.siemens.de> To: Greg Lehey <grog@lemis.com> Cc: "G. Adam Stanislav" <adam@whizkidtech.net>, chat@FreeBSD.ORG Subject: Re: Removing GNU from kernel Message-ID: <20001231124556.A99615@curry.mchp.siemens.de> In-Reply-To: <20001231121623.D3496@wantadilla.lemis.com>; from grog@lemis.com on Sun, Dec 31, 2000 at 12:16:23PM %2B1030 References: <20001230122630.A247@whizkidtech.net> <20001231121623.D3496@wantadilla.lemis.com>
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On Sun, 31-Dec-2000 at 12:16:23 +1030, Greg Lehey wrote:
> On Saturday, 30 December 2000 at 12:26:30 -0600, G. Adam Stanislav wrote:
> > Several weeks ago, I mentioned how I built my own kernel for the first
> > time, and how happy I was with the result.
> >
> > Still, I noticed the string "GCC: (GNU) 2.7.2.1" appearing in my kernel
> > several hundred times. I decided to try to get rid of it. As root, I typed:
> >
> > # strip -R .comment kernel
> >
> > Sure enough, my kernel was reduced from 1,225,217 bytes to 994,864 bytes.
> > The GNU strings are gone. The kernel still boots just as before.
>
> This is puzzling for a number of reasons. First, the kernel is very
> small by modern standards, even before the stripping. I've just
> checked my last 3.x kernel, and I find:
>
> -rwxr-xr-x 1 grog lemis 9954685 Jun 8 2000 kernel.debug
> -rwxr-xr-x 1 root lemis 1778344 Dec 31 12:13 kernel
> -rwxr-xr-x 1 root lemis 1770936 Dec 31 12:13 kernel.stripped
>
> The file kernel is kernel.debug stripped normally. And yes, it has a
> few lines of the form GCC: (GNU) 2.7.2.3 in it. The third file is the
> result of stripping the comments; I saved rather over 7 kB.
> Definitely worth doing, so much in fact that we have already done it.
> Here's the some thing on a 5.x kernel; 4.x looks the same:
>
> $ strings -a kernel.debug | grep GNU
> $
What does a
strings -a kernel.debug | grep GCC
say? I get here (on 4.2):
$ strings -a kernel.debug | grep GCC | head
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
[ASM_FILE_END]GCC: (c) 2.95.2 19991024 (release)
$
And I can do:
$ strings -a kernel.debug | grep GCC | wc
381 1905 18669
$
Some thoughts:
$ rm kernel
$ make
objcopy --strip-debug kernel.debug kernel
$ ls -l kernel*
-rwxr-xr-x 1 root wheel 2218267 Dec 31 12:40 kernel
-rwxr-xr-x 1 root wheel 8499829 Dec 31 11:33 kernel.debug
$ objcopy --strip-debug -R .comment kernel.debug kernel
$ ls -l kernel*
-rwxr-xr-x 1 root wheel 2199151 Dec 31 12:41 kernel
-rwxr-xr-x 1 root wheel 8499829 Dec 31 11:33 kernel.debug
$ strings -a kernel | grep GCC
$
-Andre
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