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To: Mike Smith <mike@smith.net.au>
cc: Doug Rabson <dfr@nlsystems.com>, cvs-committers@FreeBSD.org,
        cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/kern link_aout.c 
In-reply-to: Your message of "Sat, 10 Oct 1998 11:28:32 MST."
             <199810101828.LAA09490@dingo.cdrom.com> 
Date: Sun, 11 Oct 1998 07:47:23 +0800
From: Peter Wemm <peter@netplex.com.au>
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Mike Smith wrote:
> > 
> > The comment about not creating an a.out kernel module is an artifact of 
> > the initialization sequence.  The boot loader creates a record for the 
> > kernel, and *both* link_elf.c and link_aout.c are run.  They both see 
> > _DYNAMIC and will quite happily create a linker pseudo-file entry called 
> > "kernel".  It's kinda neat seeing two kernels loaded at once, but I didn't 
> > want to think what would happen if the a.out module tried to interpret the 
> > elf _DYNAMIC pointer as an a.out object.
> 
> If they were simply to check the *type* of the module (which they 
> really ought to in order to avoid looking for a symbol table in eg. a 
> splash screen image), then there'd be no problem with this.

This particular bit of code is intended to work even when used from the 
standard bootblocks.  It's got to build a kernel object even if there is 
no MODINFO_* type information available, otherwise the kld syscalls cannot 
work properly.

Making the decision about which link_* module is going to make a "kernel" 
object at compile time is OK.  We don't mix a.out and elf when building a 
kernel.

Cheers,
-Peter