linux-kernel - Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

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Message-ID: <20250207175252.wtsfjqnm52jkevog@jpoimboe>
Date: Fri, 7 Feb 2025 09:52:52 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Puranjay Mohan <puranjay@...nel.org>
Cc: Weinan Liu <wnliu@...gle.com>, indu.bhagat@...cle.com,
	irogers@...gle.com, joe.lawrence@...hat.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-toolchains@...r.kernel.org, live-patching@...r.kernel.org,
	mark.rutland@....com, peterz@...radead.org,
	roman.gushchin@...ux.dev, rostedt@...dmis.org, will@...nel.org
Subject: Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

On Fri, Feb 07, 2025 at 12:16:29PM +0000, Puranjay Mohan wrote:
> Weinan Liu <wnliu@...gle.com> writes:
> > Thank you for reporting this issue.
> > I just found out that Josh also intentionally uses '>' instead of '>=' for the same reason
> > https://lore.kernel.org/lkml/20250122225257.h64ftfnorofe7cb4@jpoimboe/T/#m6d70a20ed9f5b3bbe5b24b24b8c5dcc603a79101
> >
> > QQ, do we need to care the stacktrace after '__noreturn' function?
> 
> Yes, I think we should, but others people could add more to this.

FYI, here's how ORC handles this:

	/*
	 * Find the orc_entry associated with the text address.
	 *
	 * For a call frame (as opposed to a signal frame), state->ip points to
	 * the instruction after the call.  That instruction's stack layout
	 * could be different from the call instruction's layout, for example
	 * if the call was to a noreturn function.  So get the ORC data for the
	 * call instruction itself.
	 */
	orc = orc_find(state->signal ? state->ip : state->ip - 1);

and state->signal is only set for exceptions/interrupts (including
preemption and page faults) and newly forked tasks which haven't run
yet.

-- 
Josh