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| -rw-r--r-- | mm/Kconfig.debug | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug new file mode 100644 index 000000000..864f129f1 --- /dev/null +++ b/mm/Kconfig.debug @@ -0,0 +1,172 @@ +# SPDX-License-Identifier: GPL-2.0-only +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_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" + 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_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. + +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. |