# SPDX-License-Identifier: GPL-2.0-onlyconfig 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	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. 	  Also, the state of page tracking structures is checked more often as	  pages are being allocated and freed, as unexpected state changes	  often happen for same reasons as memory corruption (e.g. double free,	  use-after-free). The error reports for these checks can be augmented	  with stack traces of last allocation and freeing of the page, when	  PAGE_OWNER is also selected and enabled on boot. 	  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?"	depends on DEBUG_PAGEALLOC	help	  Enable debug page memory allocations by default? This value	  can be overridden by debug_pagealloc=off|on. config PAGE_OWNER	bool "Track page owner"	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT	select DEBUG_FS	select STACKTRACE	select STACKDEPOT	select PAGE_EXTENSION	help	  This keeps track of what call chain is the owner of a page, may	  help to find bare alloc_page(s) leaks. Even if you include this	  feature on your build, it is disabled in default. You should pass	  "page_owner=on" to boot parameter in order to enable it. Eats	  a fair amount of memory if enabled. See tools/vm/page_owner_sort.c	  for user-space helper. 	  If unsure, say N. config PAGE_POISONING	bool "Poison pages after freeing"	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 if enabled with the	  "page_poison=1" kernel boot option. 	  Note that "poison" here is not the same thing as the "HWPoison"	  for CONFIG_MEMORY_FAILURE. This is software poisoning only. 	  If you are only interested in sanitization of freed pages without	  checking the poison pattern on alloc, you can boot the kernel with	  "init_on_free=1" instead of enabling this. 	  If unsure, say N 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. config ARCH_HAS_DEBUG_WX	bool config DEBUG_WX	bool "Warn on W+X mappings at boot"	depends on ARCH_HAS_DEBUG_WX	depends on MMU	select PTDUMP_CORE	help	  Generate a warning if any W+X mappings are found at boot. 	  This is useful for discovering cases where the kernel is leaving W+X	  mappings after applying NX, as such mappings are a security risk. 	  Look for a message in dmesg output like this: 	    <arch>/mm: Checked W+X mappings: passed, no W+X pages found. 	  or like this, if the check failed: 	    <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found. 	  Note that even if the check fails, your kernel is possibly	  still fine, as W+X mappings are not a security hole in	  themselves, what they do is that they make the exploitation	  of other unfixed kernel bugs easier. 	  There is no runtime or memory usage effect of this option	  once the kernel has booted up - it's a one time check. 	  If in doubt, say "Y". config GENERIC_PTDUMP	bool config PTDUMP_CORE	bool config PTDUMP_DEBUGFS	bool "Export kernel pagetable layout to userspace via debugfs"	depends on DEBUG_KERNEL	depends on DEBUG_FS	depends on GENERIC_PTDUMP	select PTDUMP_CORE	help	  Say Y here if you want to show the kernel pagetable layout in a	  debugfs file. This information is only useful for kernel developers	  who are working in architecture specific areas of the kernel.	  It is probably not a good idea to enable this feature in a production	  kernel. 	  If in doubt, say N.