linux-kernel - Re: [PATCH] parisc: prefer _THIS_IP_ and _RET_IP

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Message-ID: <81a7e33a-0403-b6d4-fcba-c2168a608ba6@bell.net>
Date:   Fri, 3 Aug 2018 15:09:57 -0400
From:   John David Anglin <dave.anglin@...l.net>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     deller@....de, jejb@...isc-linux.org,
        Nathan Chancellor <natechancellor@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Pravin Shedge <pravin.shedge4linux@...il.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-parisc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] parisc: prefer _THIS_IP_ and _RET_IP_ statement
 expressions

On 2018-08-03 2:11 PM, Nick Desaulniers wrote:
> But the kernel uses the generic_THIS_IP_  *everywhere*, not parisc's
> custom current_text_addr().  So if this did actually break unwinding,
> you should have noticed by now.
The unwind problem was noticed.

Patches were recently applied to gcc and binutils to try and fix it.  
The gcc patch moved
branch tables to rodata so that the label at the head of the table 
wasn't in text.

https://gcc.gnu.org/ml/gcc-patches/2018-07/msg01804.html
https://sourceware.org/ml/binutils/2018-07/msg00474.html

When I saw your suggested change, I realized there was another source of 
text labels
that need linker relocations.

Dave

-- 
John David Anglin  dave.anglin@...l.net