Re: kgdb support in vanilla 2.6.2
From: Andi Kleen
Date: Thu Feb 12 2004 - 02:08:39 EST
On Wed, 11 Feb 2004 17:34:13 -0800
George Anzinger <george@xxxxxxxxxx> wrote:
> > The latest binutils should support .cfi_* for i386 too. I don't see much sense
> > in making the code more ugly just for staying backwards compatible with older versions for the
> > debug case (without CONFIG_DEBUG_INFO it should be compatible though).
> > You need a fairly new gdb too anyways for it.
> Well, yes, the CVS version I mentioned in my patch is needed as I found a bug in
> the expression analizer. I am NOT trying to say compatable with old tools. I
> AM trying to do something the CURRENT tools make hard to impossible.
> The problem with the gas CFI support is that it does not provide a way to define
> CFI expressions which are needed to determine if the CFI address should be zero
> (i.e. the return is to user space) or the current adjusted stack address.
Michal, can you comment?
> I suppose the open ended .cfi_ thing could be used but it requires that you
> compute your own sleb128 and uleb128 values. It is also not clear how you tell
> this thing if you want a word or a half word as the dwarf2 spec requires. More
> info on this would be very "nice". I really would like to do this with out the
> dwarf2 macros, but, please understand, one of the main reasons for the effort
> was to tie off the bottom of the stack and that seems to require an expression
> capability for the asm code in entry.S.
The one issue that required expression support on x86-64 (switching between the
interrupt stack and the process stack) was handled by a dummy base register
with a single ifdef. This turned out to be relatively clean.
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