Re: [PATCH v2] mm: do not export ioremap_page_range symbol for external module

[zhong jiang <zhongjiang@huawei.com>]

On 2017/1/24 21:15, Michal Hocko wrote:
> On Tue 24-01-17 21:00:24, zhong jiang wrote:
>> On 2017/1/24 18:23, Michal Hocko wrote:
>>> On Mon 23-01-17 20:07:00, zhongjiang wrote:
>>>> From: zhong jiang <zhongjiang@huawei.com>
>>>>
>>>> Recently, I've found cases in which ioremap_page_range was used
>>>> incorrectly, in external modules, leading to crashes. This can be
>>>> partly attributed to the fact that ioremap_page_range is lower-level,
>>>> with fewer protections, as compared to the other functions that an
>>>> external module would typically call. Those include:
>>>>
>>>>      ioremap_cache
>>>>      ioremap_nocache
>>>>      ioremap_prot
>>>>      ioremap_uc
>>>>      ioremap_wc
>>>>      ioremap_wt
>>>>
>>>> ...each of which wraps __ioremap_caller, which in turn provides a
>>>> safer way to achieve the mapping.
>>>>
>>>> Therefore, stop EXPORT-ing ioremap_page_range.
>>>>
>>>> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
>>>> Reviewed-by: John Hubbard <jhubbard@nvidia.com> 
>>>> Suggested-by: John Hubbard <jhubbard@nvidia.com>
>>> git grep says that there are few direct users of this API in the tree.
>>> Have you checked all of them? The export has been added by 81e88fdc432a
>>> ("ACPI, APEI, Generic Hardware Error Source POLL/IRQ/NMI notification
>>> type support").
>>   I have checked more than one times.  and John also have looked through the whole own kernel.
> OK, it seems you are right. Both PCI_TEGRA and ACPI_APEI_GHES are either
> disabled or compiled in. The same applies for drivers/pci/pci.c.
> This wasn't the case at the time when the export was introduced as
> ACPI_APEI_GHES used to be tristate until 86cd47334b00 ("ACPI, APEI,
> GHES, Prevent GHES to be built as module").
>
> You can add
> Acked-by: Michal Hocko <mhocko@suse.com>
 Thanks a lot.

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