linux-kernel - Re: [PATCH 2/2] x86/entry: Fix unwinding from kprobe on PUSH/POP instruction

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Date:   Tue, 14 Feb 2023 12:35:04 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Chen Zhongjin <chenzhongjin@...wei.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 2/2] x86/entry: Fix unwinding from kprobe on PUSH/POP
 instruction

On Mon, Feb 13, 2023 at 11:43:57PM +0900, Masami Hiramatsu wrote:

> > Fix it by annotating the #BP exception as a non-signal stack frame,
> > which tells the ORC unwinder to decrement the instruction pointer before
> > looking up the corresponding ORC entry.
> 
> Just to make it clear, this sounds like a 'hack' use of non-signal stack
> frame. If so, can we change the flag name as 'literal' or 'non-literal' etc?
> I concern that the 'signal' flag is used differently in the future.

Oooh, bike-shed :-) Let me suggest trap=1, where a trap is a fault with
a different return address, specifically the instruction after the
faulting instruction.