linux-kernel - Re: [PATCH] ARC: Change ld.as instruction to regular ld.

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Message-ID: <57ce386e-d8f1-90f0-fb7c-c1f7b4589fa9@synopsys.com>
Date:   Thu, 25 Aug 2016 10:40:17 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "liavr@...lanox.com" <liavr@...lanox.com>
CC:     Cupertino Miranda <Cupertino.Miranda@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "eladkan@...lanox.com" <eladkan@...lanox.com>,
        "noamca@...lanox.com" <noamca@...lanox.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH] ARC: Change ld.as instruction to regular ld.

On 08/25/2016 05:05 AM, Alexey Brodkin wrote:
> Hi Liav,
>
> On Wed, 2016-08-17 at 09:23 +0300, Liav Rehana wrote:
>> From: Liav Rehana <liavr@...lanox.com>
>>
>> User mode callee regs are explicitly collected before signal delivery
>> or breakpoint trap. r25 is special for kernel as it serves as task
>> pointer, so user mode value is clobbered very early. It is saved in
>> pt_regs where generally only scratch (caller saved) res are saved.
>> The code to access the corresponding pt_regs location had a subtle bug
>> as it was using load/store with scaling of offset, whereas the offset
>> was already byte wise correct. So fix this by replacing LD.AS with a
>> standard LD
>>
>> Signed-off-by: Liav Rehana <liavr@...lanox.com>
> That nice patch really fixes quite annoying issue when r25 got
> printed improperly in gdb!
>
> So
>
> Tested-by: Alexey Brodkin <abrodkin@...opsys.com>


Indeed this becomes even more important given that r25 is Thread pointer regs in
ARC ABI !
This patch is already merged upstream by Linus.

Thx,
-Vineet