linux-kernel - Re: [PATCH 3/4] x86/jump_label: Implement arch_static

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Date:   Mon, 15 Jan 2018 18:58:46 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 3/4] x86/jump_label: Implement arch_static_assert()

On Mon, Jan 15, 2018 at 11:22:12AM -0600, Josh Poimboeuf wrote:
> On Mon, Jan 15, 2018 at 05:44:31PM +0100, Peter Zijlstra wrote:


> > +static __always_inline void arch_static_assert(void)
> > +{
> > +	asm volatile ("1:\n\t"
> > +		      ".pushsection .discard.jump_assert, \"aw\" \n\t"
> > +		      _ASM_ALIGN  "\n\t"
> > +		      _ASM_PTR "1b \n\t"
> > +		      ".popsection \n\t");
> > +}
> > +
> 
> This needs a nice comment about what exactly it asserts.

Right, I'll go write one, if you don't see anything horrendous in the
objtool code ofcourse :-)

> And also, people without objtool enabled (i.e., no ORC or livepatch)
> won't see the assertion.  Do we care about those people? :-)

Nah, we should get plenty of build coverage with the others I think.