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

[zhong jiang <zhongjiang@huawei.com>]

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.

  Thanks
  zhongjiang
> Other than that this looks reasonably to me.
>
>> ---
>>  lib/ioremap.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/lib/ioremap.c b/lib/ioremap.c
>> index 86c8911..a3e14ce 100644
>> --- a/lib/ioremap.c
>> +++ b/lib/ioremap.c
>> @@ -144,4 +144,3 @@ int ioremap_page_range(unsigned long addr,
>>  
>>  	return err;
>>  }
>> -EXPORT_SYMBOL_GPL(ioremap_page_range);
>> -- 
>> 1.8.3.1


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