Messages in this thread | | | Date | Fri, 30 Jan 2015 20:51:24 +0300 | From | Andrey Ryabinin <> | Subject | Re: [PATCH v10 13/17] mm: vmalloc: add flag preventing guard hole allocation |
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On 01/30/2015 02:12 AM, Andrew Morton wrote: > On Thu, 29 Jan 2015 18:11:57 +0300 Andrey Ryabinin <a.ryabinin@samsung.com> wrote: > >> For instrumenting global variables KASan will shadow memory >> backing memory for modules. So on module loading we will need >> to allocate shadow memory and map it at exact virtual address. > > I don't understand. What does "map it at exact virtual address" mean? >
I mean that if module_alloc() returned address x, than shadow memory should be mapped exactly at address kasan_mem_to_shadow(x).
>> __vmalloc_node_range() seems like the best fit for that purpose, >> except it puts a guard hole after allocated area. > > Why is the guard hole a problem? >
Because of guard hole in shadow some future allocations of shadow memory will fail. Requested address ( kasan_mem_to_shadow(x) ) will be already occupied by guard hole of previous allocation.
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