To: Martin Mares <mj@ucw.cz>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86 Boot enhancements, pic 16 4/9
In-Reply-To: <m11ydwu5at.fsf@frodo.biederman.org> <20020405080115.GA409@ucw.cz>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: 05 Apr 2002 01:29:49 -0700
Message-ID: <m1k7rmpmyq.fsf@frodo.biederman.org>
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Martin Mares <mj@ucw.cz> writes:

> Hello!
> 
> > Instead removes the assumption the code is linked to run at 0.  The
> > binary code is already PIC, this makes the build process the same way,
> > making the build requirements more flexible. 
> 
> What are the reasons to do this change? The assumption that "linked at 0"
> assumptions looks pretty harmless and the "-start"'s everywhere are ugly.

Short answer the current assembly is broken.

Long answer.

Without the "-start"'s the gas generates a relocation record for
every one of those instructions.  The correct syntax with gas is ugly.
If you can find the gas equivalent of an assume %ds ... directive I will use
it.   

The fact that you can't treat the generated .o as a normal object
is simply a maintenance nightmare.

With this change it is possible to write a linker script that
generates a bzImage.  I won't do it as every other build of ld
is broken with respect to interesting linker scripts.   But there are
still some subsets of that idea that make sense.

Eric
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