linux-kernel - Re: [PATCH v2] ARM: mm: Provide better fault message for permission fault

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Message-ID: <YzGz7QnI0EwGheqj@shell.armlinux.org.uk>
Date:   Mon, 26 Sep 2022 15:15:09 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ARM: mm: Provide better fault message for permission
 fault

On Mon, Sep 26, 2022 at 09:26:50PM +0800, Kefeng Wang wrote:
> 
> On 2022/9/26 18:13, Russell King (Oracle) wrote:
> > On Mon, Sep 19, 2022 at 06:38:45PM +0800, Kefeng Wang wrote:
> > > If there is a permission fault in __do_kernel_fault(), we only
> > > print the generic "paging request" message which don't show
> > > read, write or excute information, let's provide better fault
> > > message for them.
> > I don't like this change. With CPUs that do not have the ability to
> > relocate the vectors to 0xffff0000, the vectors live at address 0,
> > so NULL pointer dereferences can produce permission faults.
> The __do_user_fault(), do_DataAbort() and do_PrefetchAbort() shows
> the FSR when printing, we could do it in die_kernel_fault(), and
> which will be easy for us to check whether the page fault is permision
> fault,

We print the hex value already in the oops:

Internal error: Oops: (fsr hex value) [#num] ...

-- 
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