Re: [PATCH 2/2] asm-generic: add an optional pfn_valid check to page_to_phys

Christophe Leroy
2024-11-05T09:56:45Z

Le 23/10/2024 à 07:36, Christoph Hellwig a écrit :
> page_to_pfn is usually implemented by pointer arithmetics on the memory
> map, which means that bogus input can lead to even more bogus output.
>
> Powerpc had a pfn_valid check on the intermediate pfn in the page_to_phys
> implementation when CONFIG_DEBUG_VIRTUAL is defined, which seems
> generally useful, so add that to the generic version.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> include/asm-generic/memory_model.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
> index a73a140cbecd..6d1fb6162ac1 100644
> --- a/include/asm-generic/memory_model.h
> +++ b/include/asm-generic/memory_model.h
> @@ -64,7 +64,17 @@ static inline int pfn_valid(unsigned long pfn)
> #define page_to_pfn __page_to_pfn
> #define pfn_to_page __pfn_to_page
>
> +#ifdef CONFIG_DEBUG_VIRTUAL
> +#define page_to_phys(page) \
> +({ \
> + unsigned long __pfn = page_to_pfn(page); \
> + \
> + WARN_ON_ONCE(!pfn_valid(__pfn)); \

On powerpc I think it was a WARN_ON().

Will a WARN_ON_ONCE() be enough ?

> + PFN_PHYS(__pfn); \
> +})
> +#else
> #define page_to_phys(page) PFN_PHYS(page_to_pfn(page))
> +#endif /* CONFIG_DEBUG_VIRTUAL */
> #define phys_to_page(phys) pfn_to_page(PHYS_PFN(phys))
>
> #endif /* __ASSEMBLY__ */