config PAGE_EXTENSION bool "Extend memmap on extra space for more information on page" ---help--- Extend memmap on extra space for more information on page. This could be used for debugging features that need to insert extra field for every page. This extension enables us to save memory by not allocating this extra memory according to boottime configuration. config DEBUG_PAGEALLOC bool "Debug page memory allocations" depends on DEBUG_KERNEL depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC depends on !KMEMCHECK select PAGE_EXTENSION select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC ---help--- Unmap pages from the kernel linear mapping after free_pages(). Depending on runtime enablement, this results in a small or large slowdown, but helps to find certain types of memory corruption. For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC, fill the pages with poison patterns after free_pages() and verify the patterns before alloc_pages(). Additionally, this option cannot be enabled in combination with hibernation as that would result in incorrect warnings of memory corruption after a resume because free pages are not saved to the suspend image. By default this option will have a small overhead, e.g. by not allowing the kernel mapping to be backed by large pages on some architectures. Even bigger overhead comes when the debugging is enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc command line parameter. config DEBUG_PAGEALLOC_ENABLE_DEFAULT bool "Enable debug page memory allocations by default?" default n depends on DEBUG_PAGEALLOC ---help--- Enable debug page memory allocations by default? This value can be overridden by debug_pagealloc=off|on. config PAGE_POISONING bool "Poison pages after freeing" select PAGE_EXTENSION select PAGE_POISONING_NO_SANITY if HIBERNATION ---help--- Fill the pages with poison patterns after free_pages() and verify the patterns before alloc_pages. The filling of the memory helps reduce the risk of information leaks from freed data. This does have a potential performance impact. Note that "poison" here is not the same thing as the "HWPoison" for CONFIG_MEMORY_FAILURE. This is software poisoning only. If unsure, say N config PAGE_POISONING_NO_SANITY depends on PAGE_POISONING bool "Only poison, don't sanity check" ---help--- Skip the sanity checking on alloc, only fill the pages with poison on free. This reduces some of the overhead of the poisoning feature. If you are only interested in sanitization, say Y. Otherwise say N. config PAGE_POISONING_ZERO bool "Use zero for poisoning instead of random data" depends on PAGE_POISONING ---help--- Instead of using the existing poison value, fill the pages with zeros. This makes it harder to detect when errors are occurring due to sanitization but the zeroing at free means that it is no longer necessary to write zeros when GFP_ZERO is used on allocation. If unsure, say N bool config DEBUG_PAGE_REF bool "Enable tracepoint to track down page reference manipulation" depends on DEBUG_KERNEL depends on TRACEPOINTS ---help--- This is a feature to add tracepoint for tracking down page reference manipulation. This tracking is useful to diagnose functional failure due to migration failures caused by page reference mismatches. Be careful when enabling this feature because it adds about 30 KB to the kernel code. However the runtime performance overhead is virtually nil until the tracepoints are actually enabled. h>Lines