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

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Message-ID: <CALCETrUy_CX1qe5iBEXWveXtk1EA=Di22L0ZtuHKnTLyxW+x3g@mail.gmail.com>
Date:   Sat, 20 May 2017 14:58:00 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     "H.J. Lu" <hjl.tools@...il.com>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "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 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?