From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/mm/Kconfig.debug | 144 ++++++++++++++++++++++++++++++++++++------------
1 files changed, 108 insertions(+), 36 deletions(-)
diff --git a/kernel/mm/Kconfig.debug b/kernel/mm/Kconfig.debug
index 9a7b8b0..0c33018 100644
--- a/kernel/mm/Kconfig.debug
+++ b/kernel/mm/Kconfig.debug
@@ -1,6 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
config PAGE_EXTENSION
bool "Extend memmap on extra space for more information on page"
- ---help---
+ 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
@@ -11,19 +12,25 @@
bool "Debug page memory allocations"
depends on DEBUG_KERNEL
depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
- select PAGE_EXTENSION
select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
- ---help---
+ 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.
+ 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
@@ -33,16 +40,47 @@
config DEBUG_PAGEALLOC_ENABLE_DEFAULT
bool "Enable debug page memory allocations by default?"
- default n
depends on DEBUG_PAGEALLOC
- ---help---
+ 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_PINNER
+ bool "Track page pinner"
+ 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 pinner of a page, may
+ help to find page migration failures. Even if you include this
+ feature in your build, it is disabled by default. You should pass
+ "page_pinner=on" to boot parameter in order to enable it. Eats
+ a fair amount of memory if enabled.
+
+ If unsure, say N.
+
config PAGE_POISONING
bool "Poison pages after freeing"
- select PAGE_POISONING_NO_SANITY if HIBERNATION
- ---help---
+ 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
@@ -52,36 +90,17 @@
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 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---
+ 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
@@ -92,5 +111,58 @@
config DEBUG_RODATA_TEST
bool "Testcase for the marking rodata read-only"
depends on STRICT_KERNEL_RWX
- ---help---
+ 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.
--
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