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

[Michal Hocko <mhocko@kernel.org>]

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>
-- 
Michal Hocko
SUSE Labs

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