Re: [PATCH] x86: push old stack address on irqstack for unwinder

From: H. Peter Anvin
Date: Fri Jan 30 2009 - 19:36:09 EST

H. Peter Anvin wrote:
Martin Hicks wrote:

KDB was using this information. Could this be pushed towards 2.6.29 please?

This re-adds the old stack pointer to the top of the irqstack to help
with unwinding. It was removed in commit d99015b1abbad743aa049b439c1e1dede6d0fa49
as part of the save_args out-of-line work.

This bothers me... why should we add even a single instruction to what is arguably the single hottest path in the kernel to support an out-of-tree debugger, especially if kgdb (which is in-tree) doesn't need it?

What does kgdb do differently (or is kgdb broken too)?

Thinking about it some more, I think this makes sense under


... since if we're not building with frame pointers, this is pretty pointless, and if we are, we're adding these all over the place anyway.

Does this work for you? Let me know and I'll get it in if so.

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