linux/mm/Kconfig.debug, branch v5.0

mm: clarify CONFIG_PAGE_POISONING and usage

2018-08-22T17:52:44Z

The Kconfig text for CONFIG_PAGE_POISONING doesn't mention that it has to be enabled explicitly. This updates the documentation for that and adds a note about CONFIG_PAGE_POISONING to the "page_poison" command line docs. While here, change description of CONFIG_PAGE_POISONING_ZERO too, as it's not "random" data, but rather the fixed debugging value that would be used when not zeroing. Additionally removes a stray "bool" in the Kconfig. Link: http://lkml.kernel.org/r/20180725223832.GA43733@beast Signed-off-by: Kees Cook Reviewed-by: Andrew Morton Cc: Jonathan Corbet Cc: Laura Abbott Cc: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kmemcheck: rip it out

2017-11-16T02:21:05Z

Fix up makefiles, remove references, and git rm kmemcheck. Link: http://lkml.kernel.org/r/20171007030159.22241-4-alexander.levin@verizon.com Signed-off-by: Sasha Levin Cc: Steven Rostedt Cc: Vegard Nossum Cc: Pekka Enberg Cc: Michal Hocko Cc: Eric W. Biederman Cc: Alexander Potapenko Cc: Tim Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: enable page poisoning early at boot

2017-05-03T22:52:10Z

On SPARSEMEM systems page poisoning is enabled after buddy is up, because of the dependency on page extension init. This causes the pages released by free_all_bootmem not to be poisoned. This either delays or misses the identification of some issues because the pages have to undergo another cycle of alloc-free-alloc for any corruption to be detected. Enable page poisoning early by getting rid of the PAGE_EXT_DEBUG_POISON flag. Since all the free pages will now be poisoned, the flag need not be verified before checking the poison during an alloc. [vinmenon@codeaurora.org: fix Kconfig] Link: http://lkml.kernel.org/r/1490878002-14423-1-git-send-email-vinmenon@codeaurora.org Link: http://lkml.kernel.org/r/1490358246-11001-1-git-send-email-vinmenon@codeaurora.org Signed-off-by: Vinayak Menon Acked-by: Laura Abbott Tested-by: Laura Abbott Cc: Joonsoo Kim Cc: Michal Hocko Cc: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: add arch-independent testcases for RODATA

2017-02-28T02:43:48Z

This patch makes arch-independent testcases for RODATA. Both x86 and x86_64 already have testcases for RODATA, But they are arch-specific because using inline assembly directly. And cacheflush.h is not a suitable location for rodata-test related things. Since they were in cacheflush.h, If someone change the state of CONFIG_DEBUG_RODATA_TEST, It cause overhead of kernel build. To solve the above issues, write arch-independent testcases and move it to shared location. [jinb.park7@gmail.com: fix config dependency] Link: http://lkml.kernel.org/r/20170209131625.GA16954@pjb1027-Latitude-E5410 Link: http://lkml.kernel.org/r/20170129105436.GA9303@pjb1027-Latitude-E5410 Signed-off-by: Jinbum Park Acked-by: Kees Cook Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Arjan van de Ven Cc: Laura Abbott Cc: Russell King Cc: Valentin Rothberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

PM / Hibernate: allow hibernation with PAGE_POISONING_ZERO

2016-09-13T00:35:27Z

PAGE_POISONING_ZERO disables zeroing new pages on alloc, they are poisoned (zeroed) as they become available. In the hibernate use case, free pages will appear in the system without being cleared, left there by the loading kernel. This patch will make sure free pages are cleared on resume when PAGE_POISONING_ZERO is enabled. We free the pages just after resume because we can't do it later: going through any device resume code might allocate some memory and invalidate the free pages bitmap. Thus we don't need to disable hibernation when PAGE_POISONING_ZERO is enabled. Signed-off-by: Anisse Astier Reviewed-by: Kees Cook Acked-by: Pavel Machek Signed-off-by: Rafael J. Wysocki

mm/page_ref: add tracepoint to track down page reference manipulation

2016-03-17T22:09:34Z

CMA allocation should be guaranteed to succeed by definition, but, unfortunately, it would be failed sometimes. It is hard to track down the problem, because it is related to page reference manipulation and we don't have any facility to analyze it. This patch adds tracepoints to track down page reference manipulation. With it, we can find exact reason of failure and can fix the problem. Following is an example of tracepoint output. (note: this example is stale version that printing flags as the number. Recent version will print it as human readable string.) <...>-9018 [004] 92.678375: page_ref_set: pfn=0x17ac9 flags=0x0 count=1 mapcount=0 mapping=(nil) mt=4 val=1 <...>-9018 [004] 92.678378: kernel_stack: => get_page_from_freelist (ffffffff81176659) => __alloc_pages_nodemask (ffffffff81176d22) => alloc_pages_vma (ffffffff811bf675) => handle_mm_fault (ffffffff8119e693) => __do_page_fault (ffffffff810631ea) => trace_do_page_fault (ffffffff81063543) => do_async_page_fault (ffffffff8105c40a) => async_page_fault (ffffffff817581d8) [snip] <...>-9018 [004] 92.678379: page_ref_mod: pfn=0x17ac9 flags=0x40048 count=2 mapcount=1 mapping=0xffff880015a78dc1 mt=4 val=1 [snip] ... ... <...>-9131 [001] 93.174468: test_pages_isolated: start_pfn=0x17800 end_pfn=0x17c00 fin_pfn=0x17ac9 ret=fail [snip] <...>-9018 [004] 93.174843: page_ref_mod_and_test: pfn=0x17ac9 flags=0x40068 count=0 mapcount=0 mapping=0xffff880015a78dc1 mt=4 val=-1 ret=1 => release_pages (ffffffff8117c9e4) => free_pages_and_swap_cache (ffffffff811b0697) => tlb_flush_mmu_free (ffffffff81199616) => tlb_finish_mmu (ffffffff8119a62c) => exit_mmap (ffffffff811a53f7) => mmput (ffffffff81073f47) => do_exit (ffffffff810794e9) => do_group_exit (ffffffff81079def) => SyS_exit_group (ffffffff81079e74) => entry_SYSCALL_64_fastpath (ffffffff817560b6) This output shows that problem comes from exit path. In exit path, to improve performance, pages are not freed immediately. They are gathered and processed by batch. During this process, migration cannot be possible and CMA allocation is failed. This problem is hard to find without this page reference tracepoint facility. Enabling this feature bloat kernel text 30 KB in my configuration. text data bss dec hex filename 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled Note that, due to header file dependency problem between mm.h and tracepoint.h, this feature has to open code the static key functions for tracepoints. Proposed by Steven Rostedt in following link. https://lkml.org/lkml/2015/12/9/699 [arnd@arndb.de: crypto/async_pq: use __free_page() instead of put_page()] [iamjoonsoo.kim@lge.com: fix build failure for xtensa] [akpm@linux-foundation.org: tweak Kconfig text, per Vlastimil] Signed-off-by: Joonsoo Kim Acked-by: Michal Nazarewicz Acked-by: Vlastimil Babka Cc: Minchan Kim Cc: Mel Gorman Cc: "Kirill A. Shutemov" Cc: Sergey Senozhatsky Acked-by: Steven Rostedt Signed-off-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_poisoning.c: allow for zero poisoning

2016-03-15T23:55:16Z

By default, page poisoning uses a poison value (0xaa) on free. If this is changed to 0, the page is not only sanitized but zeroing on alloc with __GFP_ZERO can be skipped as well. The tradeoff is that detecting corruption from the poisoning is harder to detect. This feature also cannot be used with hibernation since pages are not guaranteed to be zeroed after hibernation. Credit to Grsecurity/PaX team for inspiring this work Signed-off-by: Laura Abbott Acked-by: Rafael J. Wysocki Cc: "Kirill A. Shutemov" Cc: Vlastimil Babka Cc: Michal Hocko Cc: Kees Cook Cc: Mathias Krause Cc: Dave Hansen Cc: Jianyu Zhan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_poison.c: enable PAGE_POISONING as a separate option

2016-03-15T23:55:16Z

Page poisoning is currently set up as a feature if architectures don't have architecture debug page_alloc to allow unmapping of pages. It has uses apart from that though. Clearing of the pages on free provides an increase in security as it helps to limit the risk of information leaks. Allow page poisoning to be enabled as a separate option independent of kernel_map pages since the two features do separate work. Because of how hiberanation is implemented, the checks on alloc cannot occur if hibernation is enabled. The runtime alloc checks can also be enabled with an option when !HIBERNATION. Credit to Grsecurity/PaX team for inspiring this work Signed-off-by: Laura Abbott Cc: Rafael J. Wysocki Cc: "Kirill A. Shutemov" Cc: Vlastimil Babka Cc: Michal Hocko Cc: Kees Cook Cc: Mathias Krause Cc: Dave Hansen Cc: Jianyu Zhan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/debug_pagealloc: ask users for default setting of debug_pagealloc

2016-03-15T23:55:16Z

Since commit 031bc5743f158 ("mm/debug-pagealloc: make debug-pagealloc boottime configurable") CONFIG_DEBUG_PAGEALLOC is by default not adding any page debugging. This resulted in several unnoticed bugs, e.g. https://lkml.kernel.org/g/<569F5E29.3090107@de.ibm.com> or https://lkml.kernel.org/g/<56A20F30.4050705@de.ibm.com> as this behaviour change was not even documented in Kconfig. Let's provide a new Kconfig symbol that allows to change the default back to enabled, e.g. for debug kernels. This also makes the change obvious to kernel packagers. Let's also change the Kconfig description for CONFIG_DEBUG_PAGEALLOC, to indicate that there are two stages of overhead. Signed-off-by: Christian Borntraeger Cc: Joonsoo Kim Cc: Peter Zijlstra Cc: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/debug_pagealloc: remove obsolete Kconfig options

2015-01-08T23:10:52Z

These are obsolete since commit e30825f1869a ("mm/debug-pagealloc: prepare boottime configurable") was merged. So remove them. [pebolle@tiscali.nl: find obsolete Kconfig options] Signed-off-by: Joonsoo Kim Cc: Paul Bolle Cc: Mel Gorman Cc: Johannes Weiner Cc: Minchan Kim Cc: Dave Hansen Cc: Michal Nazarewicz Cc: Jungsoo Son Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds