linux-kernel - Re: [PATCH v2 02/10] x86: assembly, FUNC_START for fn, DATA

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Date:   Wed, 22 Mar 2017 08:46:16 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     Pavel Machek <pavel@....cz>, Josh Poimboeuf <jpoimboe@...hat.com>,
        mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 02/10] x86: assembly, FUNC_START for fn, DATA_START
 for data


* Jiri Slaby <jslaby@...e.cz> wrote:

> On 03/22/2017, 08:25 AM, Ingo Molnar wrote:
> > 
> > * Pavel Machek <pavel@....cz> wrote:
> > 
> >> Hi!
> >>
> >>> -ENTRY(saved_rbp)	.quad	0
> >>> -ENTRY(saved_rsi)	.quad	0
> >>> -ENTRY(saved_rdi)	.quad	0
> >>> -ENTRY(saved_rbx)	.quad	0
> >>> +SYM_DATA_START(saved_rbp)		.quad	0
> >>> +SYM_DATA_START(saved_rsi)		.quad	0
> >>> +SYM_DATA_START(saved_rdi)		.quad	0
> >>> +SYM_DATA_START(saved_rbx)		.quad	0
> >>
> >> Does it make sense to call it SYM_DATA_*START* when there's no
> >> corresponding end?
> > 
> > That looks like a bug - I think we should strive for them to always be in pairs.
> > 
> > Jiri, Josh, could objtool help here perhaps, to detect 'non-terminated' 
> > SYM_*_START() uses? This could be done by emitting debug data into a special 
> > section and then analyzing that section for unpaired entries. The section can be 
> > discarded in the final link, it won't show up in the kernel image.
> 
> It should be easier than that. No introduction of other info needed --
> every global symbol without a ".type" or ".size" (i.e. SYM_*_END) should
> be a bug now.

I'm all for that!

Can we detect double ends as well - i.e. do a build check of the full syntax of 
these symbol definition primitives?

Thanks,

	Ingo