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 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 SLUB_DEBUG_PANIC_ON bool "Enable to Panic on SLUB corruption detection" depends on SLUB_DEBUG help SLUB has a resiliency feature enabled which restores bytes in order for production environments to continue to operate. IN debug options this may not be desirable as it prevents from investigating the root cause which may be rooted within cache or memory. config DEBUG_PANIC_ON_OOM bool "Enable to Panic on OOM detection" help Android primarily uses an alternative mechanism to detect low memory situations and kill processes as required. The kernel oom-killer can mask problems with this feature, which may be undesireable in a debug environment. 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 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 unsure, say N config PAGE_POISONING_ENABLE_DEFAULT bool "Enable page poisoning by default?" default n depends on PAGE_POISONING help Enable page poisoning of free pages by default? This value can be overridden by page_poison=off|on. This can be used to avoid passing the kernel parameter and let page poisoning feature enabled by default. 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 debugging value" 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 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.