| 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. |