linux-kernel - Re: linux-next: build warnings after merge of the tip tree

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Message-ID: <20220321123905.5696c6c0@gandalf.local.home>
Date:   Mon, 21 Mar 2022 12:39:05 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        mhiramat@...nel.org, ast@...nel.org, hjl.tools@...il.com,
        rick.p.edgecombe@...el.com, rppt@...nel.org,
        linux-toolchains@...r.kernel.org, Andrew.Cooper3@...rix.com,
        ndesaulniers@...gle.com
Subject: Re: linux-next: build warnings after merge of the tip tree

On Mon, 21 Mar 2022 12:22:59 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> Or maybe another solution is:
> 
> funcA:
> 	[..]
> 	jmp funcB
> 	call __fexit__
> 	ret
> 
> And if funcA is being traced, we change jmp to a call.
> 
> 	[..]
> 	call funcB
> 	call __fexit__

We could also make __fexit__ a tail call:

> 	ret


funcA:
	[..]
	call funcB
	jmp __fexit__

We would also need a way to know that funcA has a tail call at the end. So
more help from either the compiler or objtool.

-- Steve