1. 15 Mar, 2016 1 commit
    • Laura Abbott's avatar
      mm/page_poisoning.c: allow for zero poisoning · 1414c7f4
      Laura Abbott authored
      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: default avatarLaura Abbott <labbott@fedoraproject.org>
      Acked-by: default avatarRafael J. Wysocki <rjw@rjwysocki.net>
      Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: Michal Hocko <mhocko@suse.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Mathias Krause <minipli@googlemail.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Jianyu Zhan <nasa4836@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1414c7f4
  2. 16 Jan, 2016 1 commit
  3. 15 Jan, 2016 1 commit
    • Kirill A. Shutemov's avatar
      mm: sanitize page->mapping for tail pages · 1c290f64
      Kirill A. Shutemov authored
      We don't define meaning of page->mapping for tail pages.  Currently it's
      always NULL, which can be inconsistent with head page and potentially
      lead to problems.
      
      Let's poison the pointer to catch all illigal uses.
      
      page_rmapping(), page_mapping() and page_anon_vma() are changed to look
      on head page.
      
      The only illegal use I've caught so far is __GPF_COMP pages from sound
      subsystem, mapped with PTEs.  do_shared_fault() is changed to use
      page_rmapping() instead of direct access to fault_page->mapping.
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Reviewed-by: default avatarJérôme Glisse <jglisse@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Steve Capper <steve.capper@linaro.org>
      Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Jerome Marchand <jmarchan@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1c290f64
  4. 10 Sep, 2015 2 commits
  5. 08 Dec, 2011 1 commit
  6. 25 Jul, 2011 1 commit
  7. 11 Aug, 2010 1 commit
    • Naoya Horiguchi's avatar
      hugetlb, rmap: add reverse mapping for hugepage · 0fe6e20b
      Naoya Horiguchi authored
      This patch adds reverse mapping feature for hugepage by introducing
      mapcount for shared/private-mapped hugepage and anon_vma for
      private-mapped hugepage.
      
      While hugepage is not currently swappable, reverse mapping can be useful
      for memory error handler.
      
      Without this patch, memory error handler cannot identify processes
      using the bad hugepage nor unmap it from them. That is:
      - for shared hugepage:
        we can collect processes using a hugepage through pagecache,
        but can not unmap the hugepage because of the lack of mapcount.
      - for privately mapped hugepage:
        we can neither collect processes nor unmap the hugepage.
      This patch solves these problems.
      
      This patch include the bug fix given by commit 23be7468, so reverts it.
      
      Dependency:
        "hugetlb: move definition of is_vm_hugetlb_page() to hugepage_inline.h"
      
      ChangeLog since May 24.
      - create hugetlb_inline.h and move is_vm_hugetlb_index() in it.
      - move functions setting up anon_vma for hugepage into mm/rmap.c.
      
      ChangeLog since May 13.
      - rebased to 2.6.34
      - fix logic error (in case that private mapping and shared mapping coexist)
      - move is_vm_hugetlb_page() into include/linux/mm.h to use this function
        from linear_page_index()
      - define and use linear_hugepage_index() instead of compound_order()
      - use page_move_anon_rmap() in hugetlb_cow()
      - copy exclusive switch of __set_page_anon_rmap() into hugepage counterpart.
      - revert commit 24be7468 completely
      Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Larry Woodman <lwoodman@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      Acked-by: default avatarFengguang Wu <fengguang.wu@intel.com>
      Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
      Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
      0fe6e20b
  8. 24 Apr, 2010 1 commit
  9. 11 Jan, 2010 1 commit
  10. 22 Sep, 2009 1 commit
    • David Rientjes's avatar
      flex_array: poison free elements · 19da3dd1
      David Rientjes authored
      Newly initialized flex_array's and/or flex_array_part's are now poisoned
      with a new poison value, FLEX_ARRAY_FREE.  It's value is similar to
      POISON_FREE used in the various slab allocators, but is different to
      distinguish between flex array's poisoned kmem and slab allocator poisoned
      kmem.
      
      This will allow us to identify flex_array_part's that only contain free
      elements (and free them with an addition to the flex_array API).  This
      could also be extended in the future to identify `get' uses on elements
      that have not been `put'.
      
      If __GFP_ZERO is passed for a part's gfp mask, the poisoning is avoided.
      These elements are considered to be in-use since they have been
      initialized.
      Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
      Cc: Dave Hansen <dave@linux.vnet.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      19da3dd1
  11. 01 Apr, 2009 1 commit
  12. 30 Apr, 2008 1 commit
  13. 17 Oct, 2007 1 commit
  14. 08 May, 2007 1 commit
    • David Woodhouse's avatar
      Increase slab redzone to 64bits · b46b8f19
      David Woodhouse authored
      There are two problems with the existing redzone implementation.
      
      Firstly, it's causing misalignment of structures which contain a 64-bit
      integer, such as netfilter's 'struct ipt_entry' -- causing netfilter
      modules to fail to load because of the misalignment.  (In particular, the
      first check in
      net/ipv4/netfilter/ip_tables.c::check_entry_size_and_hooks())
      
      On ppc32 and sparc32, amongst others, __alignof__(uint64_t) == 8.
      
      With slab debugging, we use 32-bit redzones. And allocated slab objects
      aren't sufficiently aligned to hold a structure containing a uint64_t.
      
      By _just_ setting ARCH_KMALLOC_MINALIGN to __alignof__(u64) we'd disable
      redzone checks on those architectures.  By using 64-bit redzones we avoid that
      loss of debugging, and also fix the other problem while we're at it.
      
      When investigating this, I noticed that on 64-bit platforms we're using a
      32-bit value of RED_ACTIVE/RED_INACTIVE in the 64-bit memory location set
      aside for the redzone.  Which means that the four bytes immediately before
      or after the allocated object at 0x00,0x00,0x00,0x00 for LE and BE
      machines, respectively.  Which is probably not the most useful choice of
      poison value.
      
      One way to fix both of those at once is just to switch to 64-bit
      redzones in all cases.
      Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
      Acked-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
      Cc: Christoph Lameter <clameter@engr.sgi.com>
      Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b46b8f19
  15. 07 May, 2007 1 commit
    • Christoph Lameter's avatar
      SLUB core · 81819f0f
      Christoph Lameter authored
      This is a new slab allocator which was motivated by the complexity of the
      existing code in mm/slab.c. It attempts to address a variety of concerns
      with the existing implementation.
      
      A. Management of object queues
      
         A particular concern was the complex management of the numerous object
         queues in SLAB. SLUB has no such queues. Instead we dedicate a slab for
         each allocating CPU and use objects from a slab directly instead of
         queueing them up.
      
      B. Storage overhead of object queues
      
         SLAB Object queues exist per node, per CPU. The alien cache queue even
         has a queue array that contain a queue for each processor on each
         node. For very large systems the number of queues and the number of
         objects that may be caught in those queues grows exponentially. On our
         systems with 1k nodes / processors we have several gigabytes just tied up
         for storing references to objects for those queues  This does not include
         the objects that could be on those queues. One fears that the whole
         memory of the machine could one day be consumed by those queues.
      
      C. SLAB meta data overhead
      
         SLAB has overhead at the beginning of each slab. This means that data
         cannot be naturally aligned at the beginning of a slab block. SLUB keeps
         all meta data in the corresponding page_struct. Objects can be naturally
         aligned in the slab. F.e. a 128 byte object will be aligned at 128 byte
         boundaries and can fit tightly into a 4k page with no bytes left over.
         SLAB cannot do this.
      
      D. SLAB has a complex cache reaper
      
         SLUB does not need a cache reaper for UP systems. On SMP systems
         the per CPU slab may be pushed back into partial list but that
         operation is simple and does not require an iteration over a list
         of objects. SLAB expires per CPU, shared and alien object queues
         during cache reaping which may cause strange hold offs.
      
      E. SLAB has complex NUMA policy layer support
      
         SLUB pushes NUMA policy handling into the page allocator. This means that
         allocation is coarser (SLUB does interleave on a page level) but that
         situation was also present before 2.6.13. SLABs application of
         policies to individual slab objects allocated in SLAB is
         certainly a performance concern due to the frequent references to
         memory policies which may lead a sequence of objects to come from
         one node after another. SLUB will get a slab full of objects
         from one node and then will switch to the next.
      
      F. Reduction of the size of partial slab lists
      
         SLAB has per node partial lists. This means that over time a large
         number of partial slabs may accumulate on those lists. These can
         only be reused if allocator occur on specific nodes. SLUB has a global
         pool of partial slabs and will consume slabs from that pool to
         decrease fragmentation.
      
      G. Tunables
      
         SLAB has sophisticated tuning abilities for each slab cache. One can
         manipulate the queue sizes in detail. However, filling the queues still
         requires the uses of the spin lock to check out slabs. SLUB has a global
         parameter (min_slab_order) for tuning. Increasing the minimum slab
         order can decrease the locking overhead. The bigger the slab order the
         less motions of pages between per CPU and partial lists occur and the
         better SLUB will be scaling.
      
      G. Slab merging
      
         We often have slab caches with similar parameters. SLUB detects those
         on boot up and merges them into the corresponding general caches. This
         leads to more effective memory use. About 50% of all caches can
         be eliminated through slab merging. This will also decrease
         slab fragmentation because partial allocated slabs can be filled
         up again. Slab merging can be switched off by specifying
         slub_nomerge on boot up.
      
         Note that merging can expose heretofore unknown bugs in the kernel
         because corrupted objects may now be placed differently and corrupt
         differing neighboring objects. Enable sanity checks to find those.
      
      H. Diagnostics
      
         The current slab diagnostics are difficult to use and require a
         recompilation of the kernel. SLUB contains debugging code that
         is always available (but is kept out of the hot code paths).
         SLUB diagnostics can be enabled via the "slab_debug" option.
         Parameters can be specified to select a single or a group of
         slab caches for diagnostics. This means that the system is running
         with the usual performance and it is much more likely that
         race conditions can be reproduced.
      
      I. Resiliency
      
         If basic sanity checks are on then SLUB is capable of detecting
         common error conditions and recover as best as possible to allow the
         system to continue.
      
      J. Tracing
      
         Tracing can be enabled via the slab_debug=T,<slabcache> option
         during boot. SLUB will then protocol all actions on that slabcache
         and dump the object contents on free.
      
      K. On demand DMA cache creation.
      
         Generally DMA caches are not needed. If a kmalloc is used with
         __GFP_DMA then just create this single slabcache that is needed.
         For systems that have no ZONE_DMA requirement the support is
         completely eliminated.
      
      L. Performance increase
      
         Some benchmarks have shown speed improvements on kernbench in the
         range of 5-10%. The locking overhead of slub is based on the
         underlying base allocation size. If we can reliably allocate
         larger order pages then it is possible to increase slub
         performance much further. The anti-fragmentation patches may
         enable further performance increases.
      
      Tested on:
      i386 UP + SMP, x86_64 UP + SMP + NUMA emulation, IA64 NUMA + Simulator
      
      SLUB Boot options
      
      slub_nomerge		Disable merging of slabs
      slub_min_order=x	Require a minimum order for slab caches. This
      			increases the managed chunk size and therefore
      			reduces meta data and locking overhead.
      slub_min_objects=x	Mininum objects per slab. Default is 8.
      slub_max_order=x	Avoid generating slabs larger than order specified.
      slub_debug		Enable all diagnostics for all caches
      slub_debug=<options>	Enable selective options for all caches
      slub_debug=<o>,<cache>	Enable selective options for a certain set of
      			caches
      
      Available Debug options
      F		Double Free checking, sanity and resiliency
      R		Red zoning
      P		Object / padding poisoning
      U		Track last free / alloc
      T		Trace all allocs / frees (only use for individual slabs).
      
      To use SLUB: Apply this patch and then select SLUB as the default slab
      allocator.
      
      [hugh@veritas.com: fix an oops-causing locking error]
      [akpm@linux-foundation.org: various stupid cleanups and small fixes]
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      81819f0f
  16. 02 May, 2007 1 commit
    • Jan Beulich's avatar
      [PATCH] x86: tighten kernel image page access rights · 6fb14755
      Jan Beulich authored
      On x86-64, kernel memory freed after init can be entirely unmapped instead
      of just getting 'poisoned' by overwriting with a debug pattern.
      
      On i386 and x86-64 (under CONFIG_DEBUG_RODATA), kernel text and bug table
      can also be write-protected.
      
      Compared to the first version, this one prevents re-creating deleted
      mappings in the kernel image range on x86-64, if those got removed
      previously. This, together with the original changes, prevents temporarily
      having inconsistent mappings when cacheability attributes are being
      changed on such pages (e.g. from AGP code). While on i386 such duplicate
      mappings don't exist, the same change is done there, too, both for
      consistency and because checking pte_present() before using various other
      pte_XXX functions is a requirement anyway. At once, i386 code gets
      adjusted to use pte_huge() instead of open coding this.
      
      AK: split out cpa() changes
      Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
      Signed-off-by: default avatarAndi Kleen <ak@suse.de>
      6fb14755
  17. 03 Jul, 2006 2 commits
  18. 27 Jun, 2006 3 commits