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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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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 SLUB_DEBUG default y bool "Enable SLUB debugging support" if EXPERT depends on SYSFS && !SLUB_TINY select STACKDEPOT if STACKTRACE_SUPPORT help SLUB has extensive debug support features. Disabling these can result in significant savings in code size. While /sys/kernel/slab will still exist (with SYSFS enabled), it will not provide e.g. cache validation.
config SLUB_DEBUG_ON bool "SLUB debugging on by default" depends on SLUB_DEBUG select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT default n help Boot with debugging on by default. SLUB boots by default with the runtime debug capabilities switched off. Enabling this is equivalent to specifying the "slab_debug" parameter on boot. There is no support for more fine grained debug control like possible with slab_debug=xxx. SLUB debugging may be switched off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying "slab_debug=-".
config SLUB_RCU_DEBUG bool "Enable UAF detection in TYPESAFE_BY_RCU caches (for KASAN)" depends on SLUB_DEBUG # SLUB_RCU_DEBUG should build fine without KASAN, but is currently useless # without KASAN, so mark it as a dependency of KASAN for now. depends on KASAN default KASAN_GENERIC || KASAN_SW_TAGS help Make SLAB_TYPESAFE_BY_RCU caches behave approximately as if the cache was not marked as SLAB_TYPESAFE_BY_RCU and every caller used kfree_rcu() instead.
This is intended for use in combination with KASAN, to enable KASAN to detect use-after-free accesses in such caches. (KFENCE is able to do that independent of this flag.)
This might degrade performance. Unfortunately this also prevents a very specific bug pattern from triggering (insufficient checks against an object being recycled within the RCU grace period); so this option can be turned off even on KASAN builds, in case you want to test for such a bug.
If you're using this for testing bugs / fuzzing and care about catching all the bugs WAY more than performance, you might want to also turn on CONFIG_RCU_STRICT_GRACE_PERIOD.
WARNING: This is designed as a debugging feature, not a security feature. Objects are sometimes recycled without RCU delay under memory pressure.
If unsure, say N.
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/mm/page_owner_sort.c for user-space helper.
If unsure, say N.
config PAGE_TABLE_CHECK bool "Check for invalid mappings in user page tables" depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK depends on EXCLUSIVE_SYSTEM_RAM select PAGE_EXTENSION help Check that anonymous page is not being mapped twice with read write permissions. Check that anonymous and file pages are not being erroneously shared. Since the checking is performed at the time entries are added and removed to user page tables, leaking, corruption and double mapping problems are detected synchronously.
If unsure say "n".
config PAGE_TABLE_CHECK_ENFORCED bool "Enforce the page table checking by default" depends on PAGE_TABLE_CHECK help Always enable page table checking. By default the page table checking is disabled, and can be optionally enabled via page_table_check=on kernel parameter. This config enforces that page table check is always enabled.
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 ARCH_HAS_PTDUMP depends on MMU select PTDUMP 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 ARCH_HAS_PTDUMP bool
config PTDUMP bool
config PTDUMP_DEBUGFS bool "Export kernel pagetable layout to userspace via debugfs" depends on DEBUG_KERNEL depends on DEBUG_FS depends on ARCH_HAS_PTDUMP select PTDUMP 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.
config HAVE_DEBUG_KMEMLEAK bool
config DEBUG_KMEMLEAK bool "Kernel memory leak detector" depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK select DEBUG_FS select STACKTRACE if STACKTRACE_SUPPORT select KALLSYMS select CRC32 select STACKDEPOT select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF help Say Y here if you want to enable the memory leak detector. The memory allocation/freeing is traced in a way similar to the Boehm's conservative garbage collector, the difference being that the orphan objects are not freed but only shown in /sys/kernel/debug/kmemleak. Enabling this feature will introduce an overhead to memory allocations. See Documentation/dev-tools/kmemleak.rst for more details.
Enabling SLUB_DEBUG may increase the chances of finding leaks due to the slab objects poisoning.
In order to access the kmemleak file, debugfs needs to be mounted (usually at /sys/kernel/debug).
config DEBUG_KMEMLEAK_MEM_POOL_SIZE int "Kmemleak memory pool size" depends on DEBUG_KMEMLEAK range 200 1000000 default 16000 help Kmemleak must track all the memory allocations to avoid reporting false positives. Since memory may be allocated or freed before kmemleak is fully initialised, use a static pool of metadata objects to track such callbacks. After kmemleak is fully initialised, this memory pool acts as an emergency one if slab allocations fail.
config DEBUG_KMEMLEAK_DEFAULT_OFF bool "Default kmemleak to off" depends on DEBUG_KMEMLEAK help Say Y here to disable kmemleak by default. It can then be enabled on the command line via kmemleak=on.
config DEBUG_KMEMLEAK_AUTO_SCAN bool "Enable kmemleak auto scan thread on boot up" default y depends on DEBUG_KMEMLEAK help Depending on the cpu, kmemleak scan may be cpu intensive and can stall user tasks at times. This option enables/disables automatic kmemleak scan at boot up.
Say N here to disable kmemleak auto scan thread to stop automatic scanning. Disabling this option disables automatic reporting of memory leaks.
If unsure, say Y.
config DEBUG_KMEMLEAK_VERBOSE bool "Default kmemleak to verbose mode" depends on DEBUG_KMEMLEAK_AUTO_SCAN help Say Y here to have kmemleak print unreferenced object details (backtrace, hex dump, address) to dmesg when new memory leaks are detected during automatic scanning. This can also be toggled at runtime via /sys/module/kmemleak/parameters/verbose.
If unsure, say N.
config PER_VMA_LOCK_STATS bool "Statistics for per-vma locks" depends on PER_VMA_LOCK help Say Y here to enable success, retry and failure counters of page faults handled under protection of per-vma locks. When enabled, the counters are exposed in /proc/vmstat. This information is useful for kernel developers to evaluate effectiveness of per-vma locks and to identify pathological cases. Counting these events introduces a small overhead in the page fault path.
If in doubt, say N.