Linux-libre 4.6.2-gnu

1 files changed, 66 insertions, 2 deletions

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 957d3da53..22f4cd96a 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -16,8 +16,8 @@ config DEBUG_PAGEALLOC
 	select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	---help---
 	  Unmap pages from the kernel linear mapping after free_pages().
-	  This results in a large slowdown, but helps to find certain types
-	  of memory corruption.
+	  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
@@ -26,5 +26,69 @@ config DEBUG_PAGEALLOC
 	  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.
+
+	   Enabling page poisoning with this option will disable hibernation
+
+	   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.