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Date:      Sat, 21 Aug 1999 10:14:39 +0100 (BST)
From:      Doug Rabson <dfr@nlsystems.com>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        current@FreeBSD.ORG, alpha@FreeBSD.ORG
Subject:   Re: cc -O broken in -current for Alpha KLDs
Message-ID:  <Pine.BSF.4.10.9908211014050.72739-100000@salmon.nlsystems.com>
In-Reply-To: <14269.25728.498019.956479@grasshopper.cs.duke.edu>

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On Fri, 20 Aug 1999, Andrew Gallatin wrote:

> 
> Doug Rabson writes:
>  > On Thu, 19 Aug 1999, Andrew Gallatin wrote:
>  > 
>  > > 
>  > > I do most of my development on alphas & I just turned some local code
>  > > into a loadable kernel module.  It works fine when compiled into the
>  > > kernel statically, but fails miserably when loaded into an alpha
>  > > kernel as a module.  This alpha is running -current from monday or
>  > > so. 
>  > > 
>  > > After a day or so of debugging, I decided to run
>  > > it on an x86 -- it ran just fine.  I've narrowed the problem down to
>  > > one involving optimization and have extracted a simple, reproducable
>  > > test case.
>  > > 
>  > > When the test module is loaded without optimization (CFLAGS += -g
>  > > -O0), it prints the following (which is correct):
>  > 
>  > It looks like we aren't handling the relocations correctly. When I get a
>  > chance, I will try to look at it. If you want to have another look, the
>  > code at fault is probably in alpha/alpha/elf_machdep.c and you can get a
>  > list of relocations in the module with 'objdump --dynamic-reloc foo.ko'.
> 
> Thanks for the pointer, it was right on the money.  It turns out that
> at the default optimization level, the objdump output looks like this:
> 
> <...>
> 0000000000010ea8 RELATIVE          *ABS*
> 0000000000010e80 GLOB_DAT          Xmit_completes+0x0000000000000028
> 0000000000010e88 GLOB_DAT          Xmit_completes+0x0000000000000008
> 0000000000010e90 GLOB_DAT          Xmit_completes+0x0000000000000010
> 0000000000010e98 GLOB_DAT          Xmit_completes+0x0000000000000018
> 0000000000010ea0 GLOB_DAT          Xmit_completes
> 0000000000010e70 JMP_SLOT          printf
> <...>
> 
> I've just committed a patch to alpha/alpha/elf_machdep.c which takes
> into account the addends for objects of type R_ALPHA_GLOB_DAT.  This
> fixes my problem.  Should it be MFC'ed?

I think it can be MFC'ed right away. There are no dependancies on the rest
of the system and its a serious problem.

--
Doug Rabson				Mail:  dfr@nlsystems.com
Nonlinear Systems Ltd.			Phone: +44 181 442 9037




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