Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions

From	Jiri Slaby <jslaby@suse.cz>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions
Date	2017-05-19 11:20 +0200
Message-ID	<tIMeK-8ro-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <tyHJo-6SD-29@gated-at.bofh.it> <tAkfD-408-3@gated-at.bofh.it> <tGdEv-1eG-25@gated-at.bofh.it> <tGr4J-2RP-5@gated-at.bofh.it> <tI7bA-3B5-7@gated-at.bofh.it>
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On 05/17/2017, 03:23 PM, Jiri Slaby wrote:
>> So the initial CFI state is different between the two types of
>> "functions".  And there are a lot of other differences.  C-type
>> functions have to follow frame pointer conventions, for example.  So
>> your FUNC_START macro (and objtool) would have to somehow figure out a
>> way to make a distinction between the two.  So it would probably work
>> out better if we kept the distinction between C-type functions and other
>> code.
> 
> Ok, that makes a lot of sense.

A quick question:
Do you consider these to be C-type functions?

  ENTRY(function_hook)
        ret
  END(function_hook)

or this?

  ENTRY(native_load_gs_index)
        pushfq
        DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
        SWAPGS
        movl    %edi, %gs
        SWAPGS
        popfq
        ret
  END(native_load_gs_index)

Both are called from C, but they do not setup frame pointer etc.

thanks,
-- 
js
suse labs

Thread

Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions Jiri Slaby <jslaby@suse.cz> - 2017-05-12 10:00 +0200
  Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-13 00:20 +0200
    Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions Jiri Slaby <jslaby@suse.cz> - 2017-05-17 15:30 +0200
      Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions Jiri Slaby <jslaby@suse.cz> - 2017-05-19 11:20 +0200
        Re: [PATCH v3 04/29] x86: assembly, use ENDPROC for functions Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-19 22:00 +0200

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