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SubjectRe: [PATCH] Add debugging boundary check to pfn_to_page
On 06/08/11 12:18, Eric B Munson wrote:
> Bugzilla 36192 showed a problem where pages were being accessed outside of
> a node boundary. It would be helpful in diagnosing this kind of problem to
> have pfn_to_page complain when a page is accessed outside of the node boundary.
> This patch adds a new debug config option which adds a WARN_ON in pfn_to_page
> that will complain when pages are accessed outside of the node boundary.
>
> Signed-of-by: Eric B Munson <emunson@mgebm.net>
> ---
> include/asm-generic/memory_model.h | 19 +++++++++++++++----
> lib/Kconfig.debug | 10 ++++++++++
> 2 files changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
> index fb2d63f..a0f1d19 100644
> --- a/include/asm-generic/memory_model.h
> +++ b/include/asm-generic/memory_model.h
> @@ -62,11 +62,22 @@
> (unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec))); \
> })
>
> -#define __pfn_to_page(pfn) \
> -({ unsigned long __pfn = (pfn); \
> - struct mem_section *__sec = __pfn_to_section(__pfn); \
> - __section_mem_map_addr(__sec) + __pfn; \
> +#ifdef CONFIG_DEBUG_MEMORY_MODEL
> +#define __pfn_to_page(pfn) \
> +({ unsigned long __pfn = (pfn); \
> + struct mem_section *__sec = __pfn_to_section(__pfn); \
> + struct page *__page = __section_mem_map_addr(__sec) + __pfn; \
> + WARN_ON(__page->flags == 0); \
> + __page; \
> })
> +#else
> +#define __pfn_to_page(pfn) \
> +({ unsigned long __pfn = (pfn); \
> + struct mem_section *__sec = __pfn_to_section(__pfn); \
> + __section_mem_map_addr(__sec) + __pfn; \
> +})
> +#endif /* CONFIG_DEBUG_MEMORY_MODEL */
> +
> #endif /* CONFIG_FLATMEM/DISCONTIGMEM/SPARSEMEM */
>
> #define page_to_pfn __page_to_pfn
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index dd373c8..d932cbf 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -777,6 +777,16 @@ config DEBUG_MEMORY_INIT
>
> If unsure, say Y
>
> +config DEBUG_MEMORY_MODEL
> + bool "Debug memory model" if SPARSEMEM || DISCONTIGMEM
> + depends on SPARSEMEM || DISCONTIGMEM

bool <prompt> <expr>
creates the dependency, so the "depends on" line is not needed.

> + help
> + Enable this to check that page accesses are done within node
> + boundaries. The check will warn each time a page is requested
> + outside node boundaries.
> +
> + If unsure, say N
> +
> config DEBUG_LIST
> bool "Debug linked list manipulation"
> depends on DEBUG_KERNEL


--
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***


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