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_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. config DEBUG_RODATA_TEST    bool "Testcase for the marking rodata read-only"    depends on STRICT_KERNEL_RWX    ---help---      This option enables a testcase for the setting rodata read-only.