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

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Date:   Tue, 31 Jul 2018 15:32:30 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Pirama Arumuga Nainar <pirama@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Mark Salyzyn <salyzyn@...gle.com>
Subject: Getting the instruction pointer on a per arch basis

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