linux-kernel - Re: [PATCH] sparc64: Swap registers for fault code and address in mna trap

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Message-ID: <CAGRGNgVYA0-hsw+mMwjAxOm-NRTDr9x+XfB2F2YUQEBf+6mAzw@mail.gmail.com>
Date:	Fri, 17 Jun 2016 10:47:56 +1000
From:	Julian Calaby <julian.calaby@...il.com>
To:	神田 尚 <hikanda@...b.co.jp>
Cc:	"sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sparc64: Swap registers for fault code and address in mna trap

Hi Hisashi,

On Fri, Jun 17, 2016 at 10:05 AM, 神田　尚 <hikanda@...b.co.jp> wrote:
> From: "Hisashi Kanda" <hikanda at zlab dot co dot jp>

Could you please put your real email address here?

> I found a logical bug in SPARC code.
> So, I send this patch. Please check it.

Leave this part out, we only need the explanation of the potential
bug, if you're not sure, put any notes like this below the "---".

> This bug may occur in the following.
>
> user_rtt_fill_64bit          <= If mna trap occurred, call do_mna
> +-> do_mna                   <= Mistake storing registers for fault code and address
>     +-> winfix_mna
>         +-> user_rtt_fill_fixup  <= Put fault address into thread_info->flag's TI_FAULT_CODE
>             +-> do_sparc64_fault() <= If fault address has FAULT_CODE_ITLB and FAULT_CODE_DTLB bits, call BUG()
>                 +-> BUG()
>
> If mna trap occured in user_rtt_fill_64bit, then do_mna is called.
> So, fault address is loaded into %g4, and fault code is loaded into %g5 in do_mna.
> But, %g4 is stored into thread_info->flag's TI_FAULT_CODE, and
> %g5 is stored into thread_info->flag's TI_FAULT_ADDR in user_rtt_fill_fixup.
> This is a mistake. If fault address has FAULT_CODE_ITLB and
> FAULT_CODE_DTLB bits, BUG() may occur in do_sparc64_fault().
>
> The patch for this bug is the following.
> Kernel version is Linux 4.7-rc3.

You should put the kernel version this applies to below the "---".

> Signed-off-by: Hisashi Kanda <hikanda@...b.co.jp>
>
> ---

i.e. here.

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/