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From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Jungseung Lee <js07.lee@gmail.com>
Subject: Re: [PATCH v2 7/7] ARM: mm: Fix PXN process with LPAE feature
Date: Wed, 2 Jun 2021 16:58:43 +0100	[thread overview]
Message-ID: <20210602155843.GN30436@shell.armlinux.org.uk> (raw)
In-Reply-To: <62f08378-85e7-2a07-3fd0-b287047ce1b5@huawei.com>

On Wed, Jun 02, 2021 at 11:13:14PM +0800, Kefeng Wang wrote:
>   IFSR format when using the Short-descriptor translation table format
> 
>     Domain fault      01001            First level   01011     Second level
> 
>     Permission fault 01101            First level   01111     Second level
> 
>   IFSR format when using the Long-descriptor translation table format
> 
>    0011LL Permission fault. LL bits indicate levelb.
> 
> After check the ARM spec, I think for the permission fault,  we should panic
> with or without LPAE, will change to

As I explained in one of the previous patches, the page tables that get
used for mapping kernel space are the _tasks_ own page tables. Any new
kernel mappings are lazily copied to the task page tables - such as
when a module is loaded.

The first time we touch a page, we could end up with a page translation
fault. This will call do_page_fault(), and so with your proposal,
loading a module will potentially cause a kernel panic in this case,
probably leading to systems that panic early during userspace boot.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

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  reply	other threads:[~2021-06-02 16:01 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-02  7:02 [PATCH v2 0/7] ARM: mm: cleanup page fault and fix pxn process issue Kefeng Wang
2021-06-02  7:02 ` [PATCH v2 1/7] ARM: mm: Rafactor the __do_page_fault() Kefeng Wang
2021-06-02 10:29   ` Russell King (Oracle)
2021-06-02  7:02 ` [PATCH v2 2/7] ARM: mm: Kill task_struct argument for __do_page_fault() Kefeng Wang
2021-06-02 10:31   ` Russell King (Oracle)
2021-06-02  7:02 ` [PATCH v2 3/7] ARM: mm: Cleanup access_error() Kefeng Wang
2021-06-02 10:39   ` Russell King (Oracle)
2021-06-02  7:02 ` [PATCH v2 4/7] ARM: mm: print out correct page table entries Kefeng Wang
2021-06-02 10:44   ` Russell King (Oracle)
2021-06-02 11:24     ` Kefeng Wang
2021-06-02  7:02 ` [PATCH v2 5/7] ARM: mm: Print physical address of page table base in show_pte() Kefeng Wang
2021-06-02 10:47   ` Russell King (Oracle)
2021-06-02 11:25     ` Kefeng Wang
2021-06-02  7:02 ` [PATCH v2 6/7] ARM: mm: Provide die_kernel_fault() helper Kefeng Wang
2021-06-02 10:49   ` Russell King (Oracle)
2021-06-02  7:02 ` [PATCH v2 7/7] ARM: mm: Fix PXN process with LPAE feature Kefeng Wang
2021-06-02 10:52   ` Russell King (Oracle)
2021-06-02 15:13     ` Kefeng Wang
2021-06-02 15:58       ` Russell King (Oracle) [this message]
2021-06-03  9:38         ` Kefeng Wang
2021-06-07  8:32           ` Kefeng Wang

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