linux-kernel - Re: [PATCH v3 23/39] x86/alternative: Simplify int3_selftest

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Date:   Fri, 4 Mar 2022 10:09:33 -0800
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        andrew.cooper3@...rix.com, linux-kernel@...r.kernel.org,
        ndesaulniers@...gle.com, keescook@...omium.org,
        samitolvanen@...gle.com, mark.rutland@....com,
        alyssa.milburn@...el.com, mbenes@...e.cz, rostedt@...dmis.org,
        mhiramat@...nel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH v3 23/39] x86/alternative: Simplify int3_selftest_ip

On Fri, Mar 04, 2022 at 10:02:23AM -0800, Josh Poimboeuf wrote:
> On Thu, Mar 03, 2022 at 12:23:44PM +0100, Peter Zijlstra wrote:
> > @@ -733,7 +733,7 @@ int3_exception_notify(struct notifier_bl
> >  	if (val != DIE_INT3)
> >  		return NOTIFY_DONE;
> >  
> > -	if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
> > +	if (regs->ip - INT3_INSN_SIZE != (unsigned long)&int3_selftest_ip)
> >  		return NOTIFY_DONE;
> >  
> >  	int3_emulate_call(regs, (unsigned long)&int3_magic);
> > @@ -757,14 +757,7 @@ static void __init int3_selftest(void)
> >  	 * then trigger the INT3, padded with NOPs to match a CALL instruction
> >  	 * length.
> >  	 */
> > -	asm volatile ("1: int3; nop; nop; nop; nop\n\t"
> > -		      ".pushsection .init.data,\"aw\"\n\t"
> > -		      ".align " __ASM_SEL(4, 8) "\n\t"
> > -		      ".type int3_selftest_ip, @object\n\t"
> > -		      ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
> > -		      "int3_selftest_ip:\n\t"
> > -		      __ASM_SEL(.long, .quad) " 1b\n\t"
> > -		      ".popsection\n\t"
> > +	asm volatile ("int3_selftest_ip: int3; nop; nop; nop; nop\n\t"
> >  		      : ASM_CALL_CONSTRAINT
> >  		      : __ASM_SEL_RAW(a, D) (&val)
> >  		      : "memory");
> 
> Hm, why doesn't this need ANNOTATE_NOENDBR?

Never mind, I see it's added later... though I still have the same
comment about the ANNOTATE_ENDBR coming after the label.

-- 
Josh