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SubjectRe: [RFC PATCH 13/21] x86/asm/crypto: Fix frame pointer usage in aesni-intel_asm.S
On Fri, Jul 17, 2015 at 01:39:09PM -0700, Andy Lutomirski wrote:
> On Fri, Jul 17, 2015 at 1:37 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > On Fri, Jul 17, 2015 at 12:44:42PM -0700, Andy Lutomirski wrote:
> >> On Fri, Jul 17, 2015 at 12:43 PM, Ingo Molnar <mingo@kernel.org> wrote:
> >> >
> >> > * Josh Poimboeuf <jpoimboe@redhat.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?
> >
> > Perhaps the macro name should describe what the epilogue does, since
> > frame pointers aren't required for _all_ functions, only those which
> > don't have call instructions.
> >
> > What do you think about ENTRY_FRAME and ENDPROC_FRAME_RETURN? The
> > ending macro is kind of long, but at least it a) matches the existing
> > ENTRY/ENDPROC convention for asm functions; b) gives a clue that frame
> > pointers are involved; and c) lets you know that the return is there.
> >
>
> This really is about frame pointers, right? How about
> ENTRY_FRAMEPTR_xyz where xyz can be prologue, epilogue, return,
> whatever?

Wouldn't the "ENTRY" in ENTRY_FRAMEPTR_RETURN be confusing at the end of
a function?

--
Josh


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