linux-kernel - Re: [RFC PATCH 13/21] x86/asm/crypto: Fix frame pointer usage in aesni-intel

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Date:	Fri, 17 Jul 2015 12:44:42 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>, X86 ML <x86@...nel.org>,
	live-patching@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 13/21] x86/asm/crypto: Fix frame pointer usage in aesni-intel_asm.S

On Fri, Jul 17, 2015 at 12:43 PM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
>>  ENTRY(aesni_set_key)
>> +     FRAME
>>  #ifndef __x86_64__
>>       pushl KEYP
>>       movl 8(%esp), KEYP              # ctx
>> @@ -1905,6 +1907,7 @@ ENTRY(aesni_set_key)
>>  #ifndef __x86_64__
>>       popl KEYP
>>  #endif
>> +     ENDFRAME
>>       ret
>>  ENDPROC(aesni_set_key)
>
> So cannot we make this a bit more compact and less fragile?
>
> Instead of:
>
>         ENTRY(aesni_set_key)
>                 FRAME
>         ...
>                 ENDFRAME
>                 ret
>         ENDPROC(aesni_set_key)
>
>
> How about writing this as:
>
>         FUNCTION_ENTRY(aesni_set_key)
>         ...
>         FUNCTION_RETURN(aesni_set_key)
>
> which does the same thing in a short, symmetric construct?
>
> One potential problem with this approach would be that what 'looks' like an entry
> declaration, but it will now generate real code.
>
> OTOH if people find this intuitive enough then it's a lot harder to mess it up,
> and I think 'RETURN' makes it clear enough that there's a real instruction
> generated there.
>

How about FUNCTION_PROLOGUE and FUNCTION_EPILOGUE?

-Andy
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