linux-kernel - Re: Getting the instruction pointer on a per arch basis

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Message-ID: <CAKwvOdn1Ri2VP9hNfKwQ3WMzL278e7-3DGusZc1cwQZbk9H6nw@mail.gmail.com>
Date:   Tue, 31 Jul 2018 16:09:06 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        ysato@...rs.sourceforge.jp, dalias@...c.org, tony.luck@...el.com,
        fenghua.yu@...el.com, msalter@...hat.com,
        jacquiot.aurelien@...il.com,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com
Cc:     Pirama Arumuga Nainar <pirama@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Mark Salyzyn <salyzyn@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-c6x-dev@...ux-c6x.org, sparclinux@...r.kernel.org
Subject: Re: Getting the instruction pointer on a per arch basis

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On Tue, Jul 31, 2018 at 3:32 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> I'm currently looking into cleaning up the code duplication between
> current_text_addr() and _THIS_IP_, virtually every implementation of
> current_text_addr() and _THIS_IP_ itself are basically:
>
> #define _THIS_IP_ ({ __label__ _l; _l: &&_l; })
>
> For a few arch's, they have inline assembly instead (for
> current_text_addr()).  Examples:
> * s390
> * sh
> * ia64
> * x86 (um and 32b)
> * c6x
> * sparc
>
> I have a patch that cuts down on the duplication, but I don't
> understand why the few arch specific implementations are necessary.  I
> could reduce the duplication further if it's ok to just use the
> statement expression.
>
> Does anyone know why this is the case?
> --
> Thanks,
> ~Nick Desaulniers