Messages in this thread | | | Date | Fri, 3 Mar 2017 15:28:30 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v4 1/3] x86: Introduce a new constant KERNEL_MAPPING_SIZE |
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On Fri, Mar 03, 2017 at 09:11:52PM +0800, Baoquan He wrote: > And another meaning of defining kernel iamge size and mapping size > differently is we can randomize the limited kernel image in the mapping > area. If they are the same or kernel image can be very large, the > position will be fixed or very few, kernel text KASLR will be > meaningless.
This is simply not true:
@@ -408,9 +408,9 @@ static unsigned long find_random_virt_addr(unsigned long minimum, /* * There are how many CONFIG_PHYSICAL_ALIGN-sized slots * that can hold image_size within the range of minimum to - * KERNEL_IMAGE_SIZE? + * KERNEL_MAPPING_SIZE? */ - slots = (KERNEL_IMAGE_SIZE - minimum - image_size) / + slots = (KERNEL_MAPPING_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN + 1;
*With* kaslr, KERNEL_IMAGE_SIZE = 1G and KERNEL_MAPPING_SIZE = 1G. Before your patch KERNEL_IMAGE_SIZE = 1G too with kaslr enabled.
-- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
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