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2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc 
 kernel/mm/Kconfig.debug
....@@ -1,6 +1,7 @@
1
+# SPDX-License-Identifier: GPL-2.0-only
12 config PAGE_EXTENSION
23 	bool "Extend memmap on extra space for more information on page"
3
-	---help---
4
+	help
45 	  Extend memmap on extra space for more information on page. This
56 	  could be used for debugging features that need to insert extra
67 	  field for every page. This extension enables us to save memory
....@@ -11,19 +12,25 @@
1112 	bool "Debug page memory allocations"
1213 	depends on DEBUG_KERNEL
1314 	depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
14
-	select PAGE_EXTENSION
1515 	select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
16
-	---help---
16
+	help
1717 	  Unmap pages from the kernel linear mapping after free_pages().
1818 	  Depending on runtime enablement, this results in a small or large
1919 	  slowdown, but helps to find certain types of memory corruption.
2020 
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+	  Also, the state of page tracking structures is checked more often as
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+	  pages are being allocated and freed, as unexpected state changes
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+	  often happen for same reasons as memory corruption (e.g. double free,
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+	  use-after-free). The error reports for these checks can be augmented
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+	  with stack traces of last allocation and freeing of the page, when
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+	  PAGE_OWNER is also selected and enabled on boot.
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+
2128 	  For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
2229 	  fill the pages with poison patterns after free_pages() and verify
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-	  the patterns before alloc_pages().  Additionally,
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-	  this option cannot be enabled in combination with hibernation as
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-	  that would result in incorrect warnings of memory corruption after
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-	  a resume because free pages are not saved to the suspend image.
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+	  the patterns before alloc_pages(). Additionally, this option cannot
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+	  be enabled in combination with hibernation as that would result in
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+	  incorrect warnings of memory corruption after a resume because free
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+	  pages are not saved to the suspend image.
2734 
2835 	  By default this option will have a small overhead, e.g. by not
2936 	  allowing the kernel mapping to be backed by large pages on some
....@@ -33,16 +40,47 @@
3340 
3441 config DEBUG_PAGEALLOC_ENABLE_DEFAULT
3542 	bool "Enable debug page memory allocations by default?"
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-	default n
3743 	depends on DEBUG_PAGEALLOC
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-	---help---
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+	help
3945 	  Enable debug page memory allocations by default? This value
4046 	  can be overridden by debug_pagealloc=off|on.
4147 
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+config PAGE_OWNER
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+	bool "Track page owner"
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+	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
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+	select DEBUG_FS
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+	select STACKTRACE
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+	select STACKDEPOT
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+	select PAGE_EXTENSION
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+	help
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+	  This keeps track of what call chain is the owner of a page, may
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+	  help to find bare alloc_page(s) leaks. Even if you include this
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+	  feature on your build, it is disabled in default. You should pass
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+	  "page_owner=on" to boot parameter in order to enable it. Eats
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+	  a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
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+	  for user-space helper.
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+
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+	  If unsure, say N.
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+
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+config PAGE_PINNER
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+	bool "Track page pinner"
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+	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
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+	select DEBUG_FS
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+	select STACKTRACE
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+	select STACKDEPOT
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+	select PAGE_EXTENSION
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+	help
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+	  This keeps track of what call chain is the pinner of a page, may
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+	  help to find page migration failures. Even if you include this
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+	  feature in your build, it is disabled by default. You should pass
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+	  "page_pinner=on" to boot parameter in order to enable it. Eats
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+	  a fair amount of memory if enabled.
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+
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+	  If unsure, say N.
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+
4281 config PAGE_POISONING
4382 	bool "Poison pages after freeing"
44
-	select PAGE_POISONING_NO_SANITY if HIBERNATION
45
-	---help---
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+	help
4684 	  Fill the pages with poison patterns after free_pages() and verify
4785 	  the patterns before alloc_pages. The filling of the memory helps
4886 	  reduce the risk of information leaks from freed data. This does
....@@ -52,36 +90,17 @@
5290 	  Note that "poison" here is not the same thing as the "HWPoison"
5391 	  for CONFIG_MEMORY_FAILURE. This is software poisoning only.
5492 
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+	  If you are only interested in sanitization of freed pages without
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+	  checking the poison pattern on alloc, you can boot the kernel with
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+	  "init_on_free=1" instead of enabling this.
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+
5597 	  If unsure, say N
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-
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-config PAGE_POISONING_NO_SANITY
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-	depends on PAGE_POISONING
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-	bool "Only poison, don't sanity check"
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-	---help---
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-	   Skip the sanity checking on alloc, only fill the pages with
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-	   poison on free. This reduces some of the overhead of the
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-	   poisoning feature.
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-
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-	   If you are only interested in sanitization, say Y. Otherwise
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-	   say N.
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-
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-config PAGE_POISONING_ZERO
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-	bool "Use zero for poisoning instead of debugging value"
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-	depends on PAGE_POISONING
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-	---help---
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-	   Instead of using the existing poison value, fill the pages with
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-	   zeros. This makes it harder to detect when errors are occurring
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-	   due to sanitization but the zeroing at free means that it is
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-	   no longer necessary to write zeros when GFP_ZERO is used on
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-	   allocation.
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-
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-	   If unsure, say N
7998 
8099 config DEBUG_PAGE_REF
81100 	bool "Enable tracepoint to track down page reference manipulation"
82101 	depends on DEBUG_KERNEL
83102 	depends on TRACEPOINTS
84
-	---help---
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+	help
85104 	  This is a feature to add tracepoint for tracking down page reference
86105 	  manipulation. This tracking is useful to diagnose functional failure
87106 	  due to migration failures caused by page reference mismatches.  Be
....@@ -92,5 +111,58 @@
92111 config DEBUG_RODATA_TEST
93112     bool "Testcase for the marking rodata read-only"
94113     depends on STRICT_KERNEL_RWX
95
-    ---help---
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+	help
96115       This option enables a testcase for the setting rodata read-only.
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+
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+config ARCH_HAS_DEBUG_WX
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+	bool
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+
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+config DEBUG_WX
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+	bool "Warn on W+X mappings at boot"
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+	depends on ARCH_HAS_DEBUG_WX
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+	depends on MMU
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+	select PTDUMP_CORE
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+	help
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+	  Generate a warning if any W+X mappings are found at boot.
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+
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+	  This is useful for discovering cases where the kernel is leaving W+X
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+	  mappings after applying NX, as such mappings are a security risk.
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+
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+	  Look for a message in dmesg output like this:
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+
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+	    <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
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+
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+	  or like this, if the check failed:
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+
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+	    <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
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+
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+	  Note that even if the check fails, your kernel is possibly
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+	  still fine, as W+X mappings are not a security hole in
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+	  themselves, what they do is that they make the exploitation
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+	  of other unfixed kernel bugs easier.
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+
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+	  There is no runtime or memory usage effect of this option
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+	  once the kernel has booted up - it's a one time check.
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+
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+	  If in doubt, say "Y".
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+
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+config GENERIC_PTDUMP
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+	bool
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+
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+config PTDUMP_CORE
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+	bool
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+
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+config PTDUMP_DEBUGFS
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+	bool "Export kernel pagetable layout to userspace via debugfs"
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+	depends on DEBUG_KERNEL
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+	depends on DEBUG_FS
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+	depends on GENERIC_PTDUMP
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+	select PTDUMP_CORE
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+	help
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+	  Say Y here if you want to show the kernel pagetable layout in a
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+	  debugfs file. This information is only useful for kernel developers
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+	  who are working in architecture specific areas of the kernel.
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+	  It is probably not a good idea to enable this feature in a production
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+	  kernel.
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+
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+	  If in doubt, say N.