linux-kernel - Re: [PATCH 7/7] DWARF: add the config option

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Date:   Sat, 20 May 2017 15:20:36 -0700
From:   "H.J. Lu" <hjl.tools@...il.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        live-patching@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 7/7] DWARF: add the config option

On Sat, May 20, 2017 at 2:58 PM, Andy Lutomirski <luto@...nel.org> wrote:
> On Sat, May 20, 2017 at 1:01 PM, H.J. Lu <hjl.tools@...il.com> wrote:
>> On Sat, May 20, 2017 at 9:20 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>>
>>>>
>>>> (H.J., could we get a binutils feature that allows is to do:
>>>>
>>>> pushq %whatever
>>>> .cfi_adjust_sp -8
>>>> ...
>>>> popq %whatever
>>>> .cfi_adjust_sp 8
>>>>
>>
>> Np.  Compiler needs to generate this.
>>
>
> How would the compiler generate this when inline asm is involved?  For
> the kernel, objtool could get around the need to have these
> annotations, but not so much for user code?  Is the compiler supposed
> to parse the inline asm?  Would the compiler provide some magic % code
> to represent the current CFA base register?

Here is one example of inline asm with call frame info:

https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/x86_64/sigaction.c;h=be058bac436d1cc9794b2b03107676ed99f6b872;hb=HEAD

-- 
H.J.