An external fragmentation event was previously described as
When the page allocator fragments memory, it records the event using
the mm_page_alloc_extfrag event. If the fallback_order is smaller
than a pageblock order (order-9 on 64-bit x86) then it's considered
an event that will cause external fragmentation issues in the future.
The kernel reduces the probability of such events by increasing the
watermark sizes by calling set_recommended_min_free_kbytes early in the
lifetime of the system. This works reasonably well in general but if
there are enough sparsely populated pageblocks then the problem can still
occur as enough memory is free overall and kswapd stays asleep.
This patch introduces a watermark_boost_factor sysctl that allows a zone
watermark to be temporarily boosted when an external fragmentation causing
events occurs. The boosting will stall allocations that would decrease
free memory below the boosted low watermark and kswapd is woken if the
calling context allows to reclaim an amount of memory relative to the size
of the high watermark and the watermark_boost_factor until the boost is
cleared. When kswapd finishes, it wakes kcompactd at the pageblock order
to clean some of the pageblocks that may have been affected by the
fragmentation event. kswapd avoids any writeback, slab shrinkage and swap
from reclaim context during this operation to avoid excessive system
disruption in the name of fragmentation avoidance. Care is taken so that
kswapd will do normal reclaim work if the system is really low on memory.
This was evaluated using the same workloads as "mm, page_alloc: Spread
allocations across zones before introducing fragmentation".
1-socket Skylake machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 1 THP allocating thread
--------------------------------------
4.20-rc3 extfrag events < order 9: 804694
4.20-rc3+patch: 408912 (49% reduction)
4.20-rc3+patch1-4: 18421 (98% reduction)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-1 653.58 ( 0.00%) 652.71 ( 0.13%)
Amean fault-huge-1 0.00 ( 0.00%) 178.93 * -99.00%*
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-1 0.00 ( 0.00%) 5.12 ( 100.00%)
Note that external fragmentation causing events are massively reduced by
this path whether in comparison to the previous kernel or the vanilla
kernel. The fault latency for huge pages appears to be increased but that
is only because THP allocations were successful with the patch applied.
1-socket Skylake machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 291392
4.20-rc3+patch: 191187 (34% reduction)
4.20-rc3+patch1-4: 13464 (95% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Min fault-base-1 912.00 ( 0.00%) 905.00 ( 0.77%)
Min fault-huge-1 127.00 ( 0.00%) 135.00 ( -6.30%)
Amean fault-base-1 1467.55 ( 0.00%) 1481.67 ( -0.96%)
Amean fault-huge-1 1127.11 ( 0.00%) 1063.88 * 5.61%*
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-1 77.64 ( 0.00%) 83.46 ( 7.49%)
As before, massive reduction in external fragmentation events, some jitter
on latencies and an increase in THP allocation success rates.
2-socket Haswell machine
config-global-dhp__workload_thpfioscale XFS (no special madvise)
4 fio threads, 5 THP allocating threads
----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 215698
4.20-rc3+patch: 200210 (7% reduction)
4.20-rc3+patch1-4: 14263 (93% reduction)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-5 1346.45 ( 0.00%) 1306.87 ( 2.94%)
Amean fault-huge-5 3418.60 ( 0.00%) 1348.94 ( 60.54%)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-5 0.78 ( 0.00%) 7.91 ( 910.64%)
There is a 93% reduction in fragmentation causing events, there is a big
reduction in the huge page fault latency and allocation success rate is
higher.
2-socket Haswell machine
global-dhp__workload_thpfioscale-madvhugepage-xfs (MADV_HUGEPAGE)
-----------------------------------------------------------------
4.20-rc3 extfrag events < order 9: 166352
4.20-rc3+patch: 147463 (11% reduction)
4.20-rc3+patch1-4: 11095 (93% reduction)
thpfioscale Fault Latencies
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Amean fault-base-5 6217.43 ( 0.00%) 7419.67 * -19.34%*
Amean fault-huge-5 3163.33 ( 0.00%) 3263.80 ( -3.18%)
4.20.0-rc3 4.20.0-rc3
lowzone-v5r8 boost-v5r8
Percentage huge-5 95.14 ( 0.00%) 87.98 ( -7.53%)
There is a large reduction in fragmentation events with some jitter around
the latencies and success rates. As before, the high THP allocation
success rate does mean the system is under a lot of pressure. However, as
the fragmentation events are reduced, it would be expected that the
long-term allocation success rate would be higher.
Link: http://lkml.kernel.org/r/20181123114528.28802-5-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The last step before devm_memremap_pages() returns success is to allocate
a release action, devm_memremap_pages_release(), to tear the entire setup
down. However, the result from devm_add_action() is not checked.
Checking the error from devm_add_action() is not enough. The api
currently relies on the fact that the percpu_ref it is using is killed by
the time the devm_memremap_pages_release() is run. Rather than continue
this awkward situation, offload the responsibility of killing the
percpu_ref to devm_memremap_pages_release() directly. This allows
devm_memremap_pages() to do the right thing relative to init failures and
shutdown.
Without this change we could fail to register the teardown of
devm_memremap_pages(). The likelihood of hitting this failure is tiny as
small memory allocations almost always succeed. However, the impact of
the failure is large given any future reconfiguration, or disable/enable,
of an nvdimm namespace will fail forever as subsequent calls to
devm_memremap_pages() will fail to setup the pgmap_radix since there will
be stale entries for the physical address range.
An argument could be made to require that the ->kill() operation be set in
the @pgmap arg rather than passed in separately. However, it helps code
readability, tracking the lifetime of a given instance, to be able to grep
the kill routine directly at the devm_memremap_pages() call site.
Link: http://lkml.kernel.org/r/154275558526.76910.7535251937849268605.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Fixes: e8d5134833 ("memremap: change devm_memremap_pages interface...")
Reviewed-by: "Jérôme Glisse" <jglisse@redhat.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since a2468cc9bf ("swap: choose swap device according to numa node"),
avail_lists field of swap_info_struct is changed to an array with
MAX_NUMNODES elements. This made swap_info_struct size increased to 40KiB
and needs an order-4 page to hold it.
This is not optimal in that:
1 Most systems have way less than MAX_NUMNODES(1024) nodes so it
is a waste of memory;
2 It could cause swapon failure if the swap device is swapped on
after system has been running for a while, due to no order-4
page is available as pointed out by Vasily Averin.
Solve the above two issues by using nr_node_ids(which is the actual
possible node number the running system has) for avail_lists instead of
MAX_NUMNODES.
nr_node_ids is unknown at compile time so can't be directly used when
declaring this array. What I did here is to declare avail_lists as zero
element array and allocate space for it when allocating space for
swap_info_struct. The reason why keep using array but not pointer is
plist_for_each_entry needs the field to be part of the struct, so pointer
will not work.
This patch is on top of Vasily Averin's fix commit. I think the use of
kvzalloc for swap_info_struct is still needed in case nr_node_ids is
really big on some systems.
Link: http://lkml.kernel.org/r/20181115083847.GA11129@intel.com
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Currently used jhash are slow enough and replace it allow as
to make KSM", v8.
Apeed (in kernel):
ksm: crc32c hash() 12081 MB/s
ksm: xxh64 hash() 8770 MB/s
ksm: xxh32 hash() 4529 MB/s
ksm: jhash2 hash() 1569 MB/s
Sioh Lee's testing (copy from other mail):
Test platform: openstack cloud platform (NEWTON version)
Experiment node: openstack based cloud compute node (CPU: xeon E5-2620 v3, memory 64gb)
VM: (2 VCPU, RAM 4GB, DISK 20GB) * 4
Linux kernel: 4.14 (latest version)
KSM setup - sleep_millisecs: 200ms, pages_to_scan: 200
Experiment process:
Firstly, we turn off KSM and launch 4 VMs. Then we turn on the KSM and
measure the checksum computation time until full_scans become two.
The experimental results (the experimental value is the average of the measured values)
crc32c_intel: 1084.10ns
crc32c (no hardware acceleration): 7012.51ns
xxhash32: 2227.75ns
xxhash64: 1413.16ns
jhash2: 5128.30ns
In summary, the result shows that crc32c_intel has advantages over all of
the hash function used in the experiment. (decreased by 84.54% compared
to crc32c, 78.86% compared to jhash2, 51.33% xxhash32, 23.28% compared to
xxhash64) the results are similar to those of Timofey.
But, use only xxhash for now, because for using crc32c, cryptoapi must be
initialized first - that require some tricky solution to work good in all
situations.
So:
- First patch implement compile time pickup of fastest implementation of
xxhash for target platform.
- The second patch replaces jhash2 with xxhash
This patch (of 2):
xxh32() - fast on both 32/64-bit platforms
xxh64() - fast only on 64-bit platform
Create xxhash() which will pick up the fastest version at compile time.
Link: http://lkml.kernel.org/r/20181023182554.23464-2-nefelim4ag@gmail.com
Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: leesioh <solee@os.korea.ac.kr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Heiko has complained that his log is swamped by warnings from
has_unmovable_pages
[ 20.536664] page dumped because: has_unmovable_pages
[ 20.536792] page:000003d081ff4080 count:1 mapcount:0 mapping:000000008ff88600 index:0x0 compound_mapcount: 0
[ 20.536794] flags: 0x3fffe0000010200(slab|head)
[ 20.536795] raw: 03fffe0000010200 0000000000000100 0000000000000200 000000008ff88600
[ 20.536796] raw: 0000000000000000 0020004100000000 ffffffff00000001 0000000000000000
[ 20.536797] page dumped because: has_unmovable_pages
[ 20.536814] page:000003d0823b0000 count:1 mapcount:0 mapping:0000000000000000 index:0x0
[ 20.536815] flags: 0x7fffe0000000000()
[ 20.536817] raw: 07fffe0000000000 0000000000000100 0000000000000200 0000000000000000
[ 20.536818] raw: 0000000000000000 0000000000000000 ffffffff00000001 0000000000000000
which are not triggered by the memory hotplug but rather CMA allocator.
The original idea behind dumping the page state for all call paths was
that these messages will be helpful debugging failures. From the above it
seems that this is not the case for the CMA path because we are lacking
much more context. E.g the second reported page might be a CMA allocated
page. It is still interesting to see a slab page in the CMA area but it
is hard to tell whether this is bug from the above output alone.
Address this issue by dumping the page state only on request. Both
start_isolate_page_range and has_unmovable_pages already have an argument
to ignore hwpoison pages so make this argument more generic and turn it
into flags and allow callers to combine non-default modes into a mask.
While we are at it, has_unmovable_pages call from
is_pageblock_removable_nolock (sysfs removable file) is questionable to
report the failure so drop it from there as well.
Link: http://lkml.kernel.org/r/20181218092802.31429-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This happened while running in qemu-system-aarch64, the AMBA PL011 UART
driver when enabling CONFIG_DEBUG_TEST_DRIVER_REMOVE.
arch_initcall(pl011_init) came before subsys_initcall(default_bdi_init),
devtmpfs' handle_remove() crashes because the reference count is a NULL
pointer only because wb->bdi hasn't been initialized yet.
Rework so that wb_put have an extra check if wb->bdi before decrement
wb->refcnt and also add a WARN_ON_ONCE to get a warning if it happens
again in other drivers.
Link: http://lkml.kernel.org/r/20181030113545.30999-2-anders.roxell@linaro.org
Fixes: 52ebea749a ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Multiple people have reported the following sparse warning:
./include/linux/slab.h:332:43: warning: dubious: x & !y
The minimal fix would be to change the logical & to boolean &&, which
emits the same code, but Andrew has suggested that the branch-avoiding
tricks are maybe not worthwile. David Laight provided a nice comparison
of disassembly of multiple variants, which shows that the current version
produces a 4 deep dependency chain, and fixing the sparse warning by
changing logical and to multiplication emits an IMUL, making it even more
expensive.
The code as rewritten by this patch yielded the best disassembly, with a
single predictable branch for the most common case, and a ternary operator
for the rest, which gcc seems to compile without a branch or cmov by
itself.
The result should be more readable, without a sparse warning and probably
also faster for the common case.
Link: http://lkml.kernel.org/r/80340595-d7c5-97b9-4f6c-23fa893a91e9@suse.cz
Fixes: 1291523f2c ("mm, slab/slub: introduce kmalloc-reclaimable caches")
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Bart Van Assche <bvanassche@acm.org>
Reported-by: Darryl T. Agostinelli <dagostinelli@gmail.com>
Reported-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tag-based KASAN doesn't check memory accesses through pointers tagged with
0xff. When page_address is used to get pointer to memory that corresponds
to some page, the tag of the resulting pointer gets set to 0xff, even
though the allocated memory might have been tagged differently.
For slab pages it's impossible to recover the correct tag to return from
page_address, since the page might contain multiple slab objects tagged
with different values, and we can't know in advance which one of them is
going to get accessed. For non slab pages however, we can recover the tag
in page_address, since the whole page was marked with the same tag.
This patch adds tagging to non slab memory allocated with pagealloc. To
set the tag of the pointer returned from page_address, the tag gets stored
to page->flags when the memory gets allocated.
Link: http://lkml.kernel.org/r/d758ddcef46a5abc9970182b9137e2fbee202a2c.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
While with SLUB we can actually preassign tags for caches with contructors
and store them in pointers in the freelist, SLAB doesn't allow that since
the freelist is stored as an array of indexes, so there are no pointers to
store the tags.
Instead we compute the tag twice, once when a slab is created before
calling the constructor and then again each time when an object is
allocated with kmalloc. Tag is computed simply by taking the lowest byte
of the index that corresponds to the object. However in kasan_kmalloc we
only have access to the objects pointer, so we need a way to find out
which index this object corresponds to.
This patch moves obj_to_index from slab.c to include/linux/slab_def.h to
be reused by KASAN.
Link: http://lkml.kernel.org/r/c02cd9e574cfd93858e43ac94b05e38f891fef64.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
that exists now);
2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.
The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
another hardware tag-based KASAN mode, that will rely on hardware memory
tagging support in arm64.
With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
instrument kernel files with -fsantize=kernel-hwaddress (except the ones
for which KASAN_SANITIZE := n is set).
Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.
This commit also adds empty placeholder (for now) implementation of
tag-based KASAN specific hooks inserted by the compiler and adjusts
common hooks implementation.
While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option
is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will
enable once all the infrastracture code has been added.
Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "kasan: add software tag-based mode for arm64", v13.
This patchset adds a new software tag-based mode to KASAN [1]. (Initially
this mode was called KHWASAN, but it got renamed, see the naming rationale
at the end of this section).
The plan is to implement HWASan [2] for the kernel with the incentive,
that it's going to have comparable to KASAN performance, but in the same
time consume much less memory, trading that off for somewhat imprecise bug
detection and being supported only for arm64.
The underlying ideas of the approach used by software tag-based KASAN are:
1. By using the Top Byte Ignore (TBI) arm64 CPU feature, we can store
pointer tags in the top byte of each kernel pointer.
2. Using shadow memory, we can store memory tags for each chunk of kernel
memory.
3. On each memory allocation, we can generate a random tag, embed it into
the returned pointer and set the memory tags that correspond to this
chunk of memory to the same value.
4. By using compiler instrumentation, before each memory access we can add
a check that the pointer tag matches the tag of the memory that is being
accessed.
5. On a tag mismatch we report an error.
With this patchset the existing KASAN mode gets renamed to generic KASAN,
with the word "generic" meaning that the implementation can be supported
by any architecture as it is purely software.
The new mode this patchset adds is called software tag-based KASAN. The
word "tag-based" refers to the fact that this mode uses tags embedded into
the top byte of kernel pointers and the TBI arm64 CPU feature that allows
to dereference such pointers. The word "software" here means that shadow
memory manipulation and tag checking on pointer dereference is done in
software. As it is the only tag-based implementation right now, "software
tag-based" KASAN is sometimes referred to as simply "tag-based" in this
patchset.
A potential expansion of this mode is a hardware tag-based mode, which
would use hardware memory tagging support (announced by Arm [3]) instead
of compiler instrumentation and manual shadow memory manipulation.
Same as generic KASAN, software tag-based KASAN is strictly a debugging
feature.
[1] https://www.kernel.org/doc/html/latest/dev-tools/kasan.html
[2] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
[3] https://community.arm.com/processors/b/blog/posts/arm-a-profile-architecture-2018-developments-armv85a
====== Rationale
On mobile devices generic KASAN's memory usage is significant problem.
One of the main reasons to have tag-based KASAN is to be able to perform a
similar set of checks as the generic one does, but with lower memory
requirements.
Comment from Vishwath Mohan <vishwath@google.com>:
I don't have data on-hand, but anecdotally both ASAN and KASAN have proven
problematic to enable for environments that don't tolerate the increased
memory pressure well. This includes
(a) Low-memory form factors - Wear, TV, Things, lower-tier phones like Go,
(c) Connected components like Pixel's visual core [1].
These are both places I'd love to have a low(er) memory footprint option at
my disposal.
Comment from Evgenii Stepanov <eugenis@google.com>:
Looking at a live Android device under load, slab (according to
/proc/meminfo) + kernel stack take 8-10% available RAM (~350MB). KASAN's
overhead of 2x - 3x on top of it is not insignificant.
Not having this overhead enables near-production use - ex. running
KASAN/KHWASAN kernel on a personal, daily-use device to catch bugs that do
not reproduce in test configuration. These are the ones that often cost
the most engineering time to track down.
CPU overhead is bad, but generally tolerable. RAM is critical, in our
experience. Once it gets low enough, OOM-killer makes your life
miserable.
[1] https://www.blog.google/products/pixel/pixel-visual-core-image-processing-and-machine-learning-pixel-2/
====== Technical details
Software tag-based KASAN mode is implemented in a very similar way to the
generic one. This patchset essentially does the following:
1. TCR_TBI1 is set to enable Top Byte Ignore.
2. Shadow memory is used (with a different scale, 1:16, so each shadow
byte corresponds to 16 bytes of kernel memory) to store memory tags.
3. All slab objects are aligned to shadow scale, which is 16 bytes.
4. All pointers returned from the slab allocator are tagged with a random
tag and the corresponding shadow memory is poisoned with the same value.
5. Compiler instrumentation is used to insert tag checks. Either by
calling callbacks or by inlining them (CONFIG_KASAN_OUTLINE and
CONFIG_KASAN_INLINE flags are reused).
6. When a tag mismatch is detected in callback instrumentation mode
KASAN simply prints a bug report. In case of inline instrumentation,
clang inserts a brk instruction, and KASAN has it's own brk handler,
which reports the bug.
7. The memory in between slab objects is marked with a reserved tag, and
acts as a redzone.
8. When a slab object is freed it's marked with a reserved tag.
Bug detection is imprecise for two reasons:
1. We won't catch some small out-of-bounds accesses, that fall into the
same shadow cell, as the last byte of a slab object.
2. We only have 1 byte to store tags, which means we have a 1/256
probability of a tag match for an incorrect access (actually even
slightly less due to reserved tag values).
Despite that there's a particular type of bugs that tag-based KASAN can
detect compared to generic KASAN: use-after-free after the object has been
allocated by someone else.
====== Testing
Some kernel developers voiced a concern that changing the top byte of
kernel pointers may lead to subtle bugs that are difficult to discover.
To address this concern deliberate testing has been performed.
It doesn't seem feasible to do some kind of static checking to find
potential issues with pointer tagging, so a dynamic approach was taken.
All pointer comparisons/subtractions have been instrumented in an LLVM
compiler pass and a kernel module that would print a bug report whenever
two pointers with different tags are being compared/subtracted (ignoring
comparisons with NULL pointers and with pointers obtained by casting an
error code to a pointer type) has been used. Then the kernel has been
booted in QEMU and on an Odroid C2 board and syzkaller has been run.
This yielded the following results.
The two places that look interesting are:
is_vmalloc_addr in include/linux/mm.h
is_kernel_rodata in mm/util.c
Here we compare a pointer with some fixed untagged values to make sure
that the pointer lies in a particular part of the kernel address space.
Since tag-based KASAN doesn't add tags to pointers that belong to rodata
or vmalloc regions, this should work as is. To make sure debug checks to
those two functions that check that the result doesn't change whether we
operate on pointers with or without untagging has been added.
A few other cases that don't look that interesting:
Comparing pointers to achieve unique sorting order of pointee objects
(e.g. sorting locks addresses before performing a double lock):
tty_ldisc_lock_pair_timeout in drivers/tty/tty_ldisc.c
pipe_double_lock in fs/pipe.c
unix_state_double_lock in net/unix/af_unix.c
lock_two_nondirectories in fs/inode.c
mutex_lock_double in kernel/events/core.c
ep_cmp_ffd in fs/eventpoll.c
fsnotify_compare_groups fs/notify/mark.c
Nothing needs to be done here, since the tags embedded into pointers
don't change, so the sorting order would still be unique.
Checks that a pointer belongs to some particular allocation:
is_sibling_entry in lib/radix-tree.c
object_is_on_stack in include/linux/sched/task_stack.h
Nothing needs to be done here either, since two pointers can only belong
to the same allocation if they have the same tag.
Overall, since the kernel boots and works, there are no critical bugs.
As for the rest, the traditional kernel testing way (use until fails) is
the only one that looks feasible.
Another point here is that tag-based KASAN is available under a separate
config option that needs to be deliberately enabled. Even though it might
be used in a "near-production" environment to find bugs that are not found
during fuzzing or running tests, it is still a debug tool.
====== Benchmarks
The following numbers were collected on Odroid C2 board. Both generic and
tag-based KASAN were used in inline instrumentation mode.
Boot time [1]:
* ~1.7 sec for clean kernel
* ~5.0 sec for generic KASAN
* ~5.0 sec for tag-based KASAN
Network performance [2]:
* 8.33 Gbits/sec for clean kernel
* 3.17 Gbits/sec for generic KASAN
* 2.85 Gbits/sec for tag-based KASAN
Slab memory usage after boot [3]:
* ~40 kb for clean kernel
* ~105 kb (~260% overhead) for generic KASAN
* ~47 kb (~20% overhead) for tag-based KASAN
KASAN memory overhead consists of three main parts:
1. Increased slab memory usage due to redzones.
2. Shadow memory (the whole reserved once during boot).
3. Quaratine (grows gradually until some preset limit; the more the limit,
the more the chance to detect a use-after-free).
Comparing tag-based vs generic KASAN for each of these points:
1. 20% vs 260% overhead.
2. 1/16th vs 1/8th of physical memory.
3. Tag-based KASAN doesn't require quarantine.
[1] Time before the ext4 driver is initialized.
[2] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`.
[3] Measured as `cat /proc/meminfo | grep Slab`.
====== Some notes
A few notes:
1. The patchset can be found here:
https://github.com/xairy/kasan-prototype/tree/khwasan
2. Building requires a recent Clang version (7.0.0 or later).
3. Stack instrumentation is not supported yet and will be added later.
This patch (of 25):
Tag-based KASAN changes the value of the top byte of pointers returned
from the kernel allocation functions (such as kmalloc). This patch
updates KASAN hooks signatures and their usage in SLAB and SLUB code to
reflect that.
Link: http://lkml.kernel.org/r/aec2b5e3973781ff8a6bb6760f8543643202c451.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Use common helpers, bitmap_zalloc() and kstrndup(), to replace open
coded versions.
* Clarify the comments around hotplug vs initial init case for the nfit
driver.
* Cleanup the libnvdimm init path.
xpo_prep_reply_hdr are not used now.
It was defined for tcp transport only, however it cannot be
called indirectly, so let's move it to its caller and
remove unused callback.
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
svc_serv-> sv_bc_xprt is netns-unsafe and cannot be used as pointer.
To prevent its misuse in future it is replaced by new boolean flag.
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
if node have NFSv41+ mounts inside several net namespaces
it can lead to use-after-free in svc_process_common()
svc_process_common()
/* Setup reply header */
rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp); <<< HERE
svc_process_common() can use incorrect rqstp->rq_xprt,
its caller function bc_svc_process() takes it from serv->sv_bc_xprt.
The problem is that serv is global structure but sv_bc_xprt
is assigned per-netnamespace.
According to Trond, the whole "let's set up rqstp->rq_xprt
for the back channel" is nothing but a giant hack in order
to work around the fact that svc_process_common() uses it
to find the xpt_ops, and perform a couple of (meaningless
for the back channel) tests of xpt_flags.
All we really need in svc_process_common() is to be able to run
rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr()
Bruce J Fields points that this xpo_prep_reply_hdr() call
is an awfully roundabout way just to do "svc_putnl(resv, 0);"
in the tcp case.
This patch does not initialiuze rqstp->rq_xprt in bc_svc_process(),
now it calls svc_process_common() with rqstp->rq_xprt = NULL.
To adjust reply header svc_process_common() just check
rqstp->rq_prot and calls svc_tcp_prep_reply_hdr() for tcp case.
To handle rqstp->rq_xprt = NULL case in functions called from
svc_process_common() patch intruduces net namespace pointer
svc_rqst->rq_bc_net and adjust SVC_NET() definition.
Some other function was also adopted to properly handle described case.
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Cc: stable@vger.kernel.org
Fixes: 23c20ecd44 ("NFS: callback up - users counting cleanup")
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Pull file locking updates from Jeff Layton:
"The main change in this set is Neil Brown's work to reduce the
thundering herd problem when a heavily-contended file lock is
released.
Previously we'd always wake up all waiters when this occurred. With
this set, we'll now we only wake up waiters that were blocked on the
range being released"
* tag 'locks-v4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
locks: Use inode_is_open_for_write
fs/locks: remove unnecessary white space.
fs/locks: merge posix_unblock_lock() and locks_delete_block()
fs/locks: create a tree of dependent requests.
fs/locks: change all *_conflict() functions to return bool.
fs/locks: always delete_block after waiting.
fs/locks: allow a lock request to block other requests.
fs/locks: use properly initialized file_lock when unlocking.
ocfs2: properly initial file_lock used for unlock.
gfs2: properly initial file_lock used for unlock.
NFS: use locks_copy_lock() to copy locks.
fs/locks: split out __locks_wake_up_blocks().
fs/locks: rename some lists and pointers.
Pull ext4 updates from Ted Ts'o:
"All cleanups and bug fixes; most notably, fix some problems discovered
in ext4's NFS support, and fix an ioctl (EXT4_IOC_GROUP_ADD) used by
old versions of e2fsprogs which we accidentally broke a while back.
Also fixed some error paths in ext4's quota and inline data support.
Finally, improve tail latency in jbd2's commit code"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: check for shutdown and r/o file system in ext4_write_inode()
ext4: force inode writes when nfsd calls commit_metadata()
ext4: avoid declaring fs inconsistent due to invalid file handles
ext4: include terminating u32 in size of xattr entries when expanding inodes
ext4: compare old and new mode before setting update_mode flag
ext4: fix EXT4_IOC_GROUP_ADD ioctl
ext4: hard fail dax mount on unsupported devices
jbd2: update locking documentation for transaction_t
ext4: remove redundant condition check
jbd2: clean up indentation issue, replace spaces with tab
ext4: clean up indentation issues, remove extraneous tabs
ext4: missing unlock/put_page() in ext4_try_to_write_inline_data()
ext4: fix possible use after free in ext4_quota_enable
jbd2: avoid long hold times of j_state_lock while committing a transaction
ext4: add ext4_sb_bread() to disambiguate ENOMEM cases
Pull fsnotify updates from Jan Kara:
"Support for new FAN_OPEN_EXEC event and couple of cleanups around
fsnotify"
* tag 'fsnotify_for_v4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
fanotify: Use inode_is_open_for_write
fanotify: Make sure to check event_len when copying
fsnotify/fdinfo: include fdinfo.h for inotify_show_fdinfo()
fanotify: introduce new event mask FAN_OPEN_EXEC_PERM
fsnotify: refactor fsnotify_parent()/fsnotify() paired calls when event is on path
fanotify: introduce new event mask FAN_OPEN_EXEC
fanotify: return only user requested event types in event mask
Pull btrfs updates from David Sterba:
"New features:
- swapfile support - after a long time it's here, with some
limitations where COW design does not work well with the swap
implementation (nodatacow file, no compression, cannot be
snapshotted, not possible on multiple devices, ...), as this is the
most restricted but working setup, we'll try to improve that in the
future
- metadata uuid - an optional incompat feature to assign a new
filesystem UUID without overwriting all metadata blocks, stored
only in superblock
- more balance messages are printed to system log, initial is in the
format of the command line that would be used to start it
Fixes:
- tag pages of a snapshot to better separate pages that are involved
in the snapshot (and need to get synced) from newly dirtied pages
that could slow down or even livelock the snapshot operation
- improved check of filesystem id associated with a device during
scan to detect duplicate devices that could be mixed up during
mount
- fix device replace state transitions, eg. when it ends up
interrupted and reboot tries to restart balance too, or when
start/cancel ioctls race
- fix a crash due to a race when quotas are enabled during snapshot
creation
- GFP_NOFS/memalloc_nofs_* fixes due to GFP_KERNEL allocations in
transaction context
- fix fsync of files with multiple hard links in new directories
- fix race of send with transaction commits that create snapshots
Core changes:
- cleanups:
* further removals of now-dead fsync code
* core function for finding free extent has been split and
provides a base for further cleanups to make the logic more
understandable
* removed lot of indirect callbacks for data and metadata inodes
* simplified refcounting and locking for cloned extent buffers
* removed redundant function arguments
* defines converted to enums where appropriate
- separate reserve for delayed refs from global reserve, update logic
to do less trickery and ad-hoc heuristics, move out some related
expensive operations from transaction commit or file truncate
- dev-replace switched from custom locking scheme to semaphore
- remove first phase of balance that tried to make some space for the
relocation by calling shrink and grow, this did not work as
expected and only introduced more error states due to potential
resize failures, slightly improves the runtime as the chunks on all
devices are not needlessly enumerated
- clone and deduplication now use generic helper that adds a few more
checks that were missing from the original btrfs implementation of
the ioctls"
* tag 'for-4.21-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (125 commits)
btrfs: Fix typos in comments and strings
btrfs: improve error handling of btrfs_add_link
Btrfs: use generic_remap_file_range_prep() for cloning and deduplication
btrfs: Refactor main loop in extent_readpages
btrfs: Remove 1st shrink/grow phase from balance
Btrfs: send, fix race with transaction commits that create snapshots
Btrfs: use nofs context when initializing security xattrs to avoid deadlock
btrfs: run delayed items before dropping the snapshot
btrfs: catch cow on deleting snapshots
btrfs: extent-tree: cleanup one-shot usage of @blocksize in do_walk_down
Btrfs: scrub, move setup of nofs contexts higher in the stack
btrfs: scrub: move scrub_setup_ctx allocation out of device_list_mutex
btrfs: scrub: pass fs_info to scrub_setup_ctx
btrfs: fix truncate throttling
btrfs: don't run delayed refs in the end transaction logic
btrfs: rework btrfs_check_space_for_delayed_refs
btrfs: add new flushing states for the delayed refs rsv
btrfs: update may_commit_transaction to use the delayed refs rsv
btrfs: introduce delayed_refs_rsv
btrfs: only track ref_heads in delayed_ref_updates
...
Correct two minor kerneldoc errors:
1) missing reference to @mode in struct phy_ops
2) obsolete reference to @init_data in struct_phy_attrs,
removed in dbc98635e0
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
1) note that gianfar_phy.c was removed years ago
2) fix obvious copy and paste error in regular doc
3) change regular doc into kerneldoc for phy_modes()
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull crypto updates from Herbert Xu:
"API:
- Add 1472-byte test to tcrypt for IPsec
- Reintroduced crypto stats interface with numerous changes
- Support incremental algorithm dumps
Algorithms:
- Add xchacha12/20
- Add nhpoly1305
- Add adiantum
- Add streebog hash
- Mark cts(cbc(aes)) as FIPS allowed
Drivers:
- Improve performance of arm64/chacha20
- Improve performance of x86/chacha20
- Add NEON-accelerated nhpoly1305
- Add SSE2 accelerated nhpoly1305
- Add AVX2 accelerated nhpoly1305
- Add support for 192/256-bit keys in gcmaes AVX
- Add SG support in gcmaes AVX
- ESN for inline IPsec tx in chcr
- Add support for CryptoCell 703 in ccree
- Add support for CryptoCell 713 in ccree
- Add SM4 support in ccree
- Add SM3 support in ccree
- Add support for chacha20 in caam/qi2
- Add support for chacha20 + poly1305 in caam/jr
- Add support for chacha20 + poly1305 in caam/qi2
- Add AEAD cipher support in cavium/nitrox"
* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (130 commits)
crypto: skcipher - remove remnants of internal IV generators
crypto: cavium/nitrox - Fix build with !CONFIG_DEBUG_FS
crypto: salsa20-generic - don't unnecessarily use atomic walk
crypto: skcipher - add might_sleep() to skcipher_walk_virt()
crypto: x86/chacha - avoid sleeping under kernel_fpu_begin()
crypto: cavium/nitrox - Added AEAD cipher support
crypto: mxc-scc - fix build warnings on ARM64
crypto: api - document missing stats member
crypto: user - remove unused dump functions
crypto: chelsio - Fix wrong error counter increments
crypto: chelsio - Reset counters on cxgb4 Detach
crypto: chelsio - Handle PCI shutdown event
crypto: chelsio - cleanup:send addr as value in function argument
crypto: chelsio - Use same value for both channel in single WR
crypto: chelsio - Swap location of AAD and IV sent in WR
crypto: chelsio - remove set but not used variable 'kctx_len'
crypto: ux500 - Use proper enum in hash_set_dma_transfer
crypto: ux500 - Use proper enum in cryp_set_dma_transfer
crypto: aesni - Add scatter/gather avx stubs, and use them in C
crypto: aesni - Introduce partial block macro
..
Pull networking updates from David Miller:
1) New ipset extensions for matching on destination MAC addresses, from
Stefano Brivio.
2) Add ipv4 ttl and tos, plus ipv6 flow label and hop limit offloads to
nfp driver. From Stefano Brivio.
3) Implement GRO for plain UDP sockets, from Paolo Abeni.
4) Lots of work from Michał Mirosław to eliminate the VLAN_TAG_PRESENT
bit so that we could support the entire vlan_tci value.
5) Rework the IPSEC policy lookups to better optimize more usecases,
from Florian Westphal.
6) Infrastructure changes eliminating direct manipulation of SKB lists
wherever possible, and to always use the appropriate SKB list
helpers. This work is still ongoing...
7) Lots of PHY driver and state machine improvements and
simplifications, from Heiner Kallweit.
8) Various TSO deferral refinements, from Eric Dumazet.
9) Add ntuple filter support to aquantia driver, from Dmitry Bogdanov.
10) Batch dropping of XDP packets in tuntap, from Jason Wang.
11) Lots of cleanups and improvements to the r8169 driver from Heiner
Kallweit, including support for ->xmit_more. This driver has been
getting some much needed love since he started working on it.
12) Lots of new forwarding selftests from Petr Machata.
13) Enable VXLAN learning in mlxsw driver, from Ido Schimmel.
14) Packed ring support for virtio, from Tiwei Bie.
15) Add new Aquantia AQtion USB driver, from Dmitry Bezrukov.
16) Add XDP support to dpaa2-eth driver, from Ioana Ciocoi Radulescu.
17) Implement coalescing on TCP backlog queue, from Eric Dumazet.
18) Implement carrier change in tun driver, from Nicolas Dichtel.
19) Support msg_zerocopy in UDP, from Willem de Bruijn.
20) Significantly improve garbage collection of neighbor objects when
the table has many PERMANENT entries, from David Ahern.
21) Remove egdev usage from nfp and mlx5, and remove the facility
completely from the tree as it no longer has any users. From Oz
Shlomo and others.
22) Add a NETDEV_PRE_CHANGEADDR so that drivers can veto the change and
therefore abort the operation before the commit phase (which is the
NETDEV_CHANGEADDR event). From Petr Machata.
23) Add indirect call wrappers to avoid retpoline overhead, and use them
in the GRO code paths. From Paolo Abeni.
24) Add support for netlink FDB get operations, from Roopa Prabhu.
25) Support bloom filter in mlxsw driver, from Nir Dotan.
26) Add SKB extension infrastructure. This consolidates the handling of
the auxiliary SKB data used by IPSEC and bridge netfilter, and is
designed to support the needs to MPTCP which could be integrated in
the future.
27) Lots of XDP TX optimizations in mlx5 from Tariq Toukan.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1845 commits)
net: dccp: fix kernel crash on module load
drivers/net: appletalk/cops: remove redundant if statement and mask
bnx2x: Fix NULL pointer dereference in bnx2x_del_all_vlans() on some hw
net/net_namespace: Check the return value of register_pernet_subsys()
net/netlink_compat: Fix a missing check of nla_parse_nested
ieee802154: lowpan_header_create check must check daddr
net/mlx4_core: drop useless LIST_HEAD
mlxsw: spectrum: drop useless LIST_HEAD
net/mlx5e: drop useless LIST_HEAD
iptunnel: Set tun_flags in the iptunnel_metadata_reply from src
net/mlx5e: fix semicolon.cocci warnings
staging: octeon: fix build failure with XFRM enabled
net: Revert recent Spectre-v1 patches.
can: af_can: Fix Spectre v1 vulnerability
packet: validate address length if non-zero
nfc: af_nfc: Fix Spectre v1 vulnerability
phonet: af_phonet: Fix Spectre v1 vulnerability
net: core: Fix Spectre v1 vulnerability
net: minor cleanup in skb_ext_add()
net: drop the unused helper skb_ext_get()
...
Pull modules updates from Jessica Yu:
- Some modules-related kallsyms cleanups and a kallsyms fix for ARM.
- Include keys from the secondary keyring in module signature
verification.
* tag 'modules-for-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
ARM: module: Fix function kallsyms on Thumb-2
module: Overwrite st_size instead of st_info
module: make it clearer when we're handling kallsyms symbols vs exported symbols
modsign: use all trusted keys to verify module signature
Pull audit updates from Paul Moore:
"In the finest of holiday of traditions, I have a number of gifts to
share today. While most of them are re-gifts from others, unlike the
typical re-gift, these are things you will want in and around your
tree; I promise.
This pull request is perhaps a bit larger than our typical PR, but
most of it comes from Jan's rework of audit's fanotify code; a very
welcome improvement. We ran this through our normal regression tests,
as well as some newly created stress tests and everything looks good.
Richard added a few patches, mostly cleaning up a few things and and
shortening some of the audit records that we send to userspace; a
change the userspace folks are quite happy about.
Finally YueHaibing and I kick in a few patches to simplify things a
bit and make the code less prone to errors.
Lastly, I want to say thanks one more time to everyone who has
contributed patches, testing, and code reviews for the audit subsystem
over the past year. The project is what it is due to your help and
contributions - thank you"
* tag 'audit-pr-20181224' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit: (22 commits)
audit: remove duplicated include from audit.c
audit: shorten PATH cap values when zero
audit: use current whenever possible
audit: minimize our use of audit_log_format()
audit: remove WATCH and TREE config options
audit: use session_info helper
audit: localize audit_log_session_info prototype
audit: Use 'mark' name for fsnotify_mark variables
audit: Replace chunk attached to mark instead of replacing mark
audit: Simplify locking around untag_chunk()
audit: Drop all unused chunk nodes during deletion
audit: Guarantee forward progress of chunk untagging
audit: Allocate fsnotify mark independently of chunk
audit: Provide helper for dropping mark's chunk reference
audit: Remove pointless check in insert_hash()
audit: Factor out chunk replacement code
audit: Make hash table insertion safe against concurrent lookups
audit: Embed key into chunk
audit: Fix possible tagging failures
audit: Fix possible spurious -ENOSPC error
...
Pull printk updates from Petr Mladek:
- Keep spinlocks busted until the end of panic()
- Fix races between calculating number of messages that would fit into
user space buffers, filling the buffers, and switching printk.time
parameter
- Some code clean up
* tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
printk: Remove print_prefix() calls with NULL buffer.
printk: fix printk_time race.
printk: Make printk_emit() local function.
panic: avoid deadlocks in re-entrant console drivers
Pull pstore updates from Kees Cook:
"Improvements and refactorings:
- Improve compression handling
- Refactor argument handling during initialization
- Avoid needless locking for saner EFI backend handling
- Add more kern-doc and improve debugging output"
* tag 'pstore-v4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
pstore/ram: Avoid NULL deref in ftrace merging failure path
pstore: Convert buf_lock to semaphore
pstore: Fix bool initialization/comparison
pstore/ram: Do not treat empty buffers as valid
pstore/ram: Simplify ramoops_get_next_prz() arguments
pstore: Map PSTORE_TYPE_* to strings
pstore: Replace open-coded << with BIT()
pstore: Improve and update some comments and status output
pstore/ram: Add kern-doc for struct persistent_ram_zone
pstore/ram: Report backend assignments with finer granularity
pstore/ram: Standardize module name in ramoops
pstore: Avoid duplicate call of persistent_ram_zap()
pstore: Remove needless lock during console writes
pstore: Do not use crash buffer for decompression
Pull powerpc updates from Michael Ellerman:
"Notable changes:
- Mitigations for Spectre v2 on some Freescale (NXP) CPUs.
- A large series adding support for pass-through of Nvidia V100 GPUs
to guests on Power9.
- Another large series to enable hardware assistance for TLB table
walk on MPC8xx CPUs.
- Some preparatory changes to our DMA code, to make way for further
cleanups from Christoph.
- Several fixes for our Transactional Memory handling discovered by
fuzzing the signal return path.
- Support for generating our system call table(s) from a text file
like other architectures.
- A fix to our page fault handler so that instead of generating a
WARN_ON_ONCE, user accesses of kernel addresses instead print a
ratelimited and appropriately scary warning.
- A cosmetic change to make our unhandled page fault messages more
similar to other arches and also more compact and informative.
- Freescale updates from Scott:
"Highlights include elimination of legacy clock bindings use from
dts files, an 83xx watchdog handler, fixes to old dts interrupt
errors, and some minor cleanup."
And many clean-ups, reworks and minor fixes etc.
Thanks to: Alexandre Belloni, Alexey Kardashevskiy, Andrew Donnellan,
Aneesh Kumar K.V, Arnd Bergmann, Benjamin Herrenschmidt, Breno Leitao,
Christian Lamparter, Christophe Leroy, Christoph Hellwig, Daniel
Axtens, Darren Stevens, David Gibson, Diana Craciun, Dmitry V. Levin,
Firoz Khan, Geert Uytterhoeven, Greg Kurz, Gustavo Romero, Hari
Bathini, Joel Stanley, Kees Cook, Madhavan Srinivasan, Mahesh
Salgaonkar, Markus Elfring, Mathieu Malaterre, Michal Suchánek, Naveen
N. Rao, Nick Desaulniers, Oliver O'Halloran, Paul Mackerras, Ram Pai,
Ravi Bangoria, Rob Herring, Russell Currey, Sabyasachi Gupta, Sam
Bobroff, Satheesh Rajendran, Scott Wood, Segher Boessenkool, Stephen
Rothwell, Tang Yuantian, Thiago Jung Bauermann, Yangtao Li, Yuantian
Tang, Yue Haibing"
* tag 'powerpc-4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (201 commits)
Revert "powerpc/fsl_pci: simplify fsl_pci_dma_set_mask"
powerpc/zImage: Also check for stdout-path
powerpc: Fix HMIs on big-endian with CONFIG_RELOCATABLE=y
macintosh: Use of_node_name_{eq, prefix} for node name comparisons
ide: Use of_node_name_eq for node name comparisons
powerpc: Use of_node_name_eq for node name comparisons
powerpc/pseries/pmem: Convert to %pOFn instead of device_node.name
powerpc/mm: Remove very old comment in hash-4k.h
powerpc/pseries: Fix node leak in update_lmb_associativity_index()
powerpc/configs/85xx: Enable CONFIG_DEBUG_KERNEL
powerpc/dts/fsl: Fix dtc-flagged interrupt errors
clk: qoriq: add more compatibles strings
powerpc/fsl: Use new clockgen binding
powerpc/83xx: handle machine check caused by watchdog timer
powerpc/fsl-rio: fix spelling mistake "reserverd" -> "reserved"
powerpc/fsl_pci: simplify fsl_pci_dma_set_mask
arch/powerpc/fsl_rmu: Use dma_zalloc_coherent
vfio_pci: Add NVIDIA GV100GL [Tesla V100 SXM2] subdriver
vfio_pci: Allow regions to add own capabilities
vfio_pci: Allow mapping extra regions
...
