linux-kernel - Re: Should a x86 gdb work under an x86

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Date:	Mon, 03 Mar 2008 12:56:00 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Should a x86 gdb work under an x86_64 kernel?

"Theodore Ts'o" <tytso@....edu> writes:

> Hi,
>
> 	I've noticed that if I try to use a 32-bit x86 gdb to debug a
> 32-bit program under a 64-bit x86_64 kernel, gdb (version 6.6-debian,
> from Ubuntu Gutsy) immediately core dumps as soon as I run the test
> program under the debugger.  Is this normal/expected/known bug?

It's clearly a bug. x86-64 compat user space should be 99+% compatible
and running full 32bit user land with a 64bit kernel is supposed to work.

The main exceptions are a few programs that rely on the 3GB address space
(these can be used with linux32 --3gb), some programs which
make bogus assumptions about /proc,/sys which cannot be fixed
and a few programs which use obscure driver specific ioctls with
no compat wrapper.

-Andi
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