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From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 20 May 2017 15:20:36 -0700
Message-ID: <CAMe9rOoAuqhY_+G=8Dwrt6aJ7YXTwcHShxLEVzt6MeNYAhT9PA@mail.gmail.com>
Subject: Re: [PATCH 7/7] DWARF: add the config option
To: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jiri Slaby <jslaby@suse.cz>, Andrew Morton <akpm@linux-foundation.org>,
        live-patching@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Jiri Kosina <jikos@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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On Sat, May 20, 2017 at 2:58 PM, Andy Lutomirski <luto@kernel.org> wrote:
> On Sat, May 20, 2017 at 1:01 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Sat, May 20, 2017 at 9:20 AM, Josh Poimboeuf <jpoimboe@redhat.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.