Testing has shown that the backtrace sometimes does not fit into the 4kB
temporary buffer that is used in NMI context. The warnings are gone
when I double the temporary buffer size.
This patch doubles the buffer size and makes it configurable.
Note that this problem existed even in the x86-specific implementation
that was added by the commit a9edc88093 ("x86/nmi: Perform a safe NMI
stack trace on all CPUs"). Nobody noticed it because it did not print
any warnings.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk() takes some locks and could not be used a safe way in NMI
context.
The chance of a deadlock is real especially when printing stacks from
all CPUs. This particular problem has been addressed on x86 by the
commit a9edc88093 ("x86/nmi: Perform a safe NMI stack trace on all
CPUs").
The patchset brings two big advantages. First, it makes the NMI
backtraces safe on all architectures for free. Second, it makes all NMI
messages almost safe on all architectures (the temporary buffer is
limited. We still should keep the number of messages in NMI context at
minimum).
Note that there already are several messages printed in NMI context:
WARN_ON(in_nmi()), BUG_ON(in_nmi()), anything being printed out from MCE
handlers. These are not easy to avoid.
This patch reuses most of the code and makes it generic. It is useful
for all messages and architectures that support NMI.
The alternative printk_func is set when entering and is reseted when
leaving NMI context. It queues IRQ work to copy the messages into the
main ring buffer in a safe context.
__printk_nmi_flush() copies all available messages and reset the buffer.
Then we could use a simple cmpxchg operations to get synchronized with
writers. There is also used a spinlock to get synchronized with other
flushers.
We do not longer use seq_buf because it depends on external lock. It
would be hard to make all supported operations safe for a lockless use.
It would be confusing and error prone to make only some operations safe.
The code is put into separate printk/nmi.c as suggested by Steven
Rostedt. It needs a per-CPU buffer and is compiled only on
architectures that call nmi_enter(). This is achieved by the new
HAVE_NMI Kconfig flag.
The are MN10300 and Xtensa architectures. We need to clean up NMI
handling there first. Let's do it separately.
The patch is heavily based on the draft from Peter Zijlstra, see
https://lkml.org/lkml/2015/6/10/327
[arnd@arndb.de: printk-nmi: use %zu format string for size_t]
[akpm@linux-foundation.org: min_t->min - all types are size_t here]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> [arm part]
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Provides an optional config (CONFIG_SLAB_FREELIST_RANDOM) to randomize
the SLAB freelist. The list is randomized during initialization of a
new set of pages. The order on different freelist sizes is pre-computed
at boot for performance. Each kmem_cache has its own randomized
freelist. Before pre-computed lists are available freelists are
generated dynamically. This security feature reduces the predictability
of the kernel SLAB allocator against heap overflows rendering attacks
much less stable.
For example this attack against SLUB (also applicable against SLAB)
would be affected:
https://jon.oberheide.org/blog/2010/09/10/linux-kernel-can-slub-overflow/
Also, since v4.6 the freelist was moved at the end of the SLAB. It
means a controllable heap is opened to new attacks not yet publicly
discussed. A kernel heap overflow can be transformed to multiple
use-after-free. This feature makes this type of attack harder too.
To generate entropy, we use get_random_bytes_arch because 0 bits of
entropy is available in the boot stage. In the worse case this function
will fallback to the get_random_bytes sub API. We also generate a shift
random number to shift pre-computed freelist for each new set of pages.
The config option name is not specific to the SLAB as this approach will
be extended to other allocators like SLUB.
Performance results highlighted no major changes:
Hackbench (running 90 10 times):
Before average: 0.0698
After average: 0.0663 (-5.01%)
slab_test 1 run on boot. Difference only seen on the 2048 size test
being the worse case scenario covered by freelist randomization. New
slab pages are constantly being created on the 10000 allocations.
Variance should be mainly due to getting new pages every few
allocations.
Before:
Single thread testing
=====================
1. Kmalloc: Repeatedly allocate then free test
10000 times kmalloc(8) -> 99 cycles kfree -> 112 cycles
10000 times kmalloc(16) -> 109 cycles kfree -> 140 cycles
10000 times kmalloc(32) -> 129 cycles kfree -> 137 cycles
10000 times kmalloc(64) -> 141 cycles kfree -> 141 cycles
10000 times kmalloc(128) -> 152 cycles kfree -> 148 cycles
10000 times kmalloc(256) -> 195 cycles kfree -> 167 cycles
10000 times kmalloc(512) -> 257 cycles kfree -> 199 cycles
10000 times kmalloc(1024) -> 393 cycles kfree -> 251 cycles
10000 times kmalloc(2048) -> 649 cycles kfree -> 228 cycles
10000 times kmalloc(4096) -> 806 cycles kfree -> 370 cycles
10000 times kmalloc(8192) -> 814 cycles kfree -> 411 cycles
10000 times kmalloc(16384) -> 892 cycles kfree -> 455 cycles
2. Kmalloc: alloc/free test
10000 times kmalloc(8)/kfree -> 121 cycles
10000 times kmalloc(16)/kfree -> 121 cycles
10000 times kmalloc(32)/kfree -> 121 cycles
10000 times kmalloc(64)/kfree -> 121 cycles
10000 times kmalloc(128)/kfree -> 121 cycles
10000 times kmalloc(256)/kfree -> 119 cycles
10000 times kmalloc(512)/kfree -> 119 cycles
10000 times kmalloc(1024)/kfree -> 119 cycles
10000 times kmalloc(2048)/kfree -> 119 cycles
10000 times kmalloc(4096)/kfree -> 121 cycles
10000 times kmalloc(8192)/kfree -> 119 cycles
10000 times kmalloc(16384)/kfree -> 119 cycles
After:
Single thread testing
=====================
1. Kmalloc: Repeatedly allocate then free test
10000 times kmalloc(8) -> 130 cycles kfree -> 86 cycles
10000 times kmalloc(16) -> 118 cycles kfree -> 86 cycles
10000 times kmalloc(32) -> 121 cycles kfree -> 85 cycles
10000 times kmalloc(64) -> 176 cycles kfree -> 102 cycles
10000 times kmalloc(128) -> 178 cycles kfree -> 100 cycles
10000 times kmalloc(256) -> 205 cycles kfree -> 109 cycles
10000 times kmalloc(512) -> 262 cycles kfree -> 136 cycles
10000 times kmalloc(1024) -> 342 cycles kfree -> 157 cycles
10000 times kmalloc(2048) -> 701 cycles kfree -> 238 cycles
10000 times kmalloc(4096) -> 803 cycles kfree -> 364 cycles
10000 times kmalloc(8192) -> 835 cycles kfree -> 404 cycles
10000 times kmalloc(16384) -> 896 cycles kfree -> 441 cycles
2. Kmalloc: alloc/free test
10000 times kmalloc(8)/kfree -> 121 cycles
10000 times kmalloc(16)/kfree -> 121 cycles
10000 times kmalloc(32)/kfree -> 123 cycles
10000 times kmalloc(64)/kfree -> 142 cycles
10000 times kmalloc(128)/kfree -> 121 cycles
10000 times kmalloc(256)/kfree -> 119 cycles
10000 times kmalloc(512)/kfree -> 119 cycles
10000 times kmalloc(1024)/kfree -> 119 cycles
10000 times kmalloc(2048)/kfree -> 119 cycles
10000 times kmalloc(4096)/kfree -> 119 cycles
10000 times kmalloc(8192)/kfree -> 119 cycles
10000 times kmalloc(16384)/kfree -> 119 cycles
[akpm@linux-foundation.org: propagate gfp_t into cache_random_seq_create()]
Signed-off-by: Thomas Garnier <thgarnie@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Newer Fedora and OpenSUSE didn't boot with my standard configuration.
It took me some time to figure out why, in fact I had to write a script
to try different config options systematically.
The problem is that something (systemd) in dracut depends on
CONFIG_FHANDLE, which adds open by file handle syscalls.
While it is set in defconfigs it is very easy to miss when updating
older configs because it is not default y.
Make it default y and also depend on EXPERT, as dracut use is likely
widespread.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Richard Weinberger <richard.weinberger@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cgroup updates from Tejun Heo:
"cgroup changes for v4.6-rc1. No userland visible behavior changes in
this pull request. I'll send out a separate pull request for the
addition of cgroup namespace support.
- The biggest change is the revamping of cgroup core task migration
and controller handling logic. There are quite a few places where
controllers and tasks are manipulated. Previously, many of those
places implemented custom operations for each specific use case
assuming specific starting conditions. While this worked, it makes
the code fragile and difficult to follow.
The bulk of this pull request restructures these operations so that
most related operations are performed through common helpers which
implement recursive (subtrees are always processed consistently)
and idempotent (they make cgroup hierarchy converge to the target
state rather than performing operations assuming specific starting
conditions). This makes the code a lot easier to understand,
verify and extend.
- Implicit controller support is added. This is primarily for using
perf_event on the v2 hierarchy so that perf can match cgroup v2
path without requiring the user to do anything special. The kernel
portion of perf_event changes is acked but userland changes are
still pending review.
- cgroup_no_v1= boot parameter added to ease testing cgroup v2 in
certain environments.
- There is a regression introduced during v4.4 devel cycle where
attempts to migrate zombie tasks can mess up internal object
management. This was fixed earlier this week and included in this
pull request w/ stable cc'd.
- Misc non-critical fixes and improvements"
* 'for-4.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (44 commits)
cgroup: avoid false positive gcc-6 warning
cgroup: ignore css_sets associated with dead cgroups during migration
Documentation: cgroup v2: Trivial heading correction.
cgroup: implement cgroup_subsys->implicit_on_dfl
cgroup: use css_set->mg_dst_cgrp for the migration target cgroup
cgroup: make cgroup[_taskset]_migrate() take cgroup_root instead of cgroup
cgroup: move migration destination verification out of cgroup_migrate_prepare_dst()
cgroup: fix incorrect destination cgroup in cgroup_update_dfl_csses()
cgroup: Trivial correction to reflect controller.
cgroup: remove stale item in cgroup-v1 document INDEX file.
cgroup: update css iteration in cgroup_update_dfl_csses()
cgroup: allocate 2x cgrp_cset_links when setting up a new root
cgroup: make cgroup_calc_subtree_ss_mask() take @this_ss_mask
cgroup: reimplement rebind_subsystems() using cgroup_apply_control() and friends
cgroup: use cgroup_apply_enable_control() in cgroup creation path
cgroup: combine cgroup_mutex locking and offline css draining
cgroup: factor out cgroup_{apply|finalize}_control() from cgroup_subtree_control_write()
cgroup: introduce cgroup_{save|propagate|restore}_control()
cgroup: make cgroup_drain_offline() and cgroup_apply_control_{disable|enable}() recursive
cgroup: factor out cgroup_apply_control_enable() from cgroup_subtree_control_write()
...
Pull security layer updates from James Morris:
"There are a bunch of fixes to the TPM, IMA, and Keys code, with minor
fixes scattered across the subsystem.
IMA now requires signed policy, and that policy is also now measured
and appraised"
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (67 commits)
X.509: Make algo identifiers text instead of enum
akcipher: Move the RSA DER encoding check to the crypto layer
crypto: Add hash param to pkcs1pad
sign-file: fix build with CMS support disabled
MAINTAINERS: update tpmdd urls
MODSIGN: linux/string.h should be #included to get memcpy()
certs: Fix misaligned data in extra certificate list
X.509: Handle midnight alternative notation in GeneralizedTime
X.509: Support leap seconds
Handle ISO 8601 leap seconds and encodings of midnight in mktime64()
X.509: Fix leap year handling again
PKCS#7: fix unitialized boolean 'want'
firmware: change kernel read fail to dev_dbg()
KEYS: Use the symbol value for list size, updated by scripts/insert-sys-cert
KEYS: Reserve an extra certificate symbol for inserting without recompiling
modsign: hide openssl output in silent builds
tpm_tis: fix build warning with tpm_tis_resume
ima: require signed IMA policy
ima: measure and appraise the IMA policy itself
ima: load policy using path
...
Merge first patch-bomb from Andrew Morton:
- some misc things
- ofs2 updates
- about half of MM
- checkpatch updates
- autofs4 update
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (120 commits)
autofs4: fix string.h include in auto_dev-ioctl.h
autofs4: use pr_xxx() macros directly for logging
autofs4: change log print macros to not insert newline
autofs4: make autofs log prints consistent
autofs4: fix some white space errors
autofs4: fix invalid ioctl return in autofs4_root_ioctl_unlocked()
autofs4: fix coding style line length in autofs4_wait()
autofs4: fix coding style problem in autofs4_get_set_timeout()
autofs4: coding style fixes
autofs: show pipe inode in mount options
kallsyms: add support for relative offsets in kallsyms address table
kallsyms: don't overload absolute symbol type for percpu symbols
x86: kallsyms: disable absolute percpu symbols on !SMP
checkpatch: fix another left brace warning
checkpatch: improve UNSPECIFIED_INT test for bare signed/unsigned uses
checkpatch: warn on bare unsigned or signed declarations without int
checkpatch: exclude asm volatile from complex macro check
mm: memcontrol: drop unnecessary lru locking from mem_cgroup_migrate()
mm: migrate: consolidate mem_cgroup_migrate() calls
mm/compaction: speed up pageblock_pfn_to_page() when zone is contiguous
...
Similar to how relative extables are implemented, it is possible to emit
the kallsyms table in such a way that it contains offsets relative to
some anchor point in the kernel image rather than absolute addresses.
On 64-bit architectures, it cuts the size of the kallsyms address table
in half, since offsets between kernel symbols can typically be expressed
in 32 bits. This saves several hundreds of kilobytes of permanent
.rodata on average. In addition, the kallsyms address table is no
longer subject to dynamic relocation when CONFIG_RELOCATABLE is in
effect, so the relocation work done after decompression now doesn't have
to do relocation updates for all these values. This saves up to 24
bytes (i.e., the size of a ELF64 RELA relocation table entry) per value,
which easily adds up to a couple of megabytes of uncompressed __init
data on ppc64 or arm64. Even if these relocation entries typically
compress well, the combined size reduction of 2.8 MB uncompressed for a
ppc64_defconfig build (of which 2.4 MB is __init data) results in a ~500
KB space saving in the compressed image.
Since it is useful for some architectures (like x86) to retain the
ability to emit absolute values as well, this patch also adds support
for capturing both absolute and relative values when
KALLSYMS_ABSOLUTE_PERCPU is in effect, by emitting absolute per-cpu
addresses as positive 32-bit values, and addresses relative to the
lowest encountered relative symbol as negative values, which are
subtracted from the runtime address of this base symbol to produce the
actual address.
Support for the above is enabled by default for all architectures except
IA-64 and Tile-GX, whose symbols are too far apart to capture in this
manner.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
scripts/kallsyms.c has a special --absolute-percpu command line option
which deals with the zero based per cpu offsets that are used when
building for SMP on x86_64. This means that the option should only be
passed in that case, so add a Kconfig symbol with the correct predicate,
and use that instead.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use list_for_each_entry() instead of list_for_each() to simplify the code.
Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cpu hotplug updates from Thomas Gleixner:
"This is the first part of the ongoing cpu hotplug rework:
- Initial implementation of the state machine
- Runs all online and prepare down callbacks on the plugged cpu and
not on some random processor
- Replaces busy loop waiting with completions
- Adds tracepoints so the states can be followed"
More detailed commentary on this work from an earlier email:
"What's wrong with the current cpu hotplug infrastructure?
- Asymmetry
The hotplug notifier mechanism is asymmetric versus the bringup and
teardown. This is mostly caused by the notifier mechanism.
- Largely undocumented dependencies
While some notifiers use explicitely defined notifier priorities,
we have quite some notifiers which use numerical priorities to
express dependencies without any documentation why.
- Control processor driven
Most of the bringup/teardown of a cpu is driven by a control
processor. While it is understandable, that preperatory steps,
like idle thread creation, memory allocation for and initialization
of essential facilities needs to be done before a cpu can boot,
there is no reason why everything else must run on a control
processor. Before this patch series, bringup looks like this:
Control CPU Booting CPU
do preparatory steps
kick cpu into life
do low level init
sync with booting cpu sync with control cpu
bring the rest up
- All or nothing approach
There is no way to do partial bringups. That's something which is
really desired because we waste e.g. at boot substantial amount of
time just busy waiting that the cpu comes to life. That's stupid
as we could very well do preparatory steps and the initial IPI for
other cpus and then go back and do the necessary low level
synchronization with the freshly booted cpu.
- Minimal debuggability
Due to the notifier based design, it's impossible to switch between
two stages of the bringup/teardown back and forth in order to test
the correctness. So in many hotplug notifiers the cancel
mechanisms are either not existant or completely untested.
- Notifier [un]registering is tedious
To [un]register notifiers we need to protect against hotplug at
every callsite. There is no mechanism that bringup/teardown
callbacks are issued on the online cpus, so every caller needs to
do it itself. That also includes error rollback.
What's the new design?
The base of the new design is a symmetric state machine, where both
the control processor and the booting/dying cpu execute a well
defined set of states. Each state is symmetric in the end, except
for some well defined exceptions, and the bringup/teardown can be
stopped and reversed at almost all states.
So the bringup of a cpu will look like this in the future:
Control CPU Booting CPU
do preparatory steps
kick cpu into life
do low level init
sync with booting cpu sync with control cpu
bring itself up
The synchronization step does not require the control cpu to wait.
That mechanism can be done asynchronously via a worker or some
other mechanism.
The teardown can be made very similar, so that the dying cpu cleans
up and brings itself down. Cleanups which need to be done after
the cpu is gone, can be scheduled asynchronously as well.
There is a long way to this, as we need to refactor the notion when a
cpu is available. Today we set the cpu online right after it comes
out of the low level bringup, which is not really correct.
The proper mechanism is to set it to available, i.e. cpu local
threads, like softirqd, hotplug thread etc. can be scheduled on that
cpu, and once it finished all booting steps, it's set to online, so
general workloads can be scheduled on it. The reverse happens on
teardown. First thing to do is to forbid scheduling of general
workloads, then teardown all the per cpu resources and finally shut it
off completely.
This patch series implements the basic infrastructure for this at the
core level. This includes the following:
- Basic state machine implementation with well defined states, so
ordering and prioritization can be expressed.
- Interfaces to [un]register state callbacks
This invokes the bringup/teardown callback on all online cpus with
the proper protection in place and [un]installs the callbacks in
the state machine array.
For callbacks which have no particular ordering requirement we have
a dynamic state space, so that drivers don't have to register an
explicit hotplug state.
If a callback fails, the code automatically does a rollback to the
previous state.
- Sysfs interface to drive the state machine to a particular step.
This is only partially functional today. Full functionality and
therefor testability will be achieved once we converted all
existing hotplug notifiers over to the new scheme.
- Run all CPU_ONLINE/DOWN_PREPARE notifiers on the booting/dying
processor:
Control CPU Booting CPU
do preparatory steps
kick cpu into life
do low level init
sync with booting cpu sync with control cpu
wait for boot
bring itself up
Signal completion to control cpu
In a previous step of this work we've done a full tree mechanical
conversion of all hotplug notifiers to the new scheme. The balance
is a net removal of about 4000 lines of code.
This is not included in this series, as we decided to take a
different approach. Instead of mechanically converting everything
over, we will do a proper overhaul of the usage sites one by one so
they nicely fit into the symmetric callback scheme.
I decided to do that after I looked at the ugliness of some of the
converted sites and figured out that their hotplug mechanism is
completely buggered anyway. So there is no point to do a
mechanical conversion first as we need to go through the usage
sites one by one again in order to achieve a full symmetric and
testable behaviour"
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
cpu/hotplug: Document states better
cpu/hotplug: Fix smpboot thread ordering
cpu/hotplug: Remove redundant state check
cpu/hotplug: Plug death reporting race
rcu: Make CPU_DYING_IDLE an explicit call
cpu/hotplug: Make wait for dead cpu completion based
cpu/hotplug: Let upcoming cpu bring itself fully up
arch/hotplug: Call into idle with a proper state
cpu/hotplug: Move online calls to hotplugged cpu
cpu/hotplug: Create hotplug threads
cpu/hotplug: Split out the state walk into functions
cpu/hotplug: Unpark smpboot threads from the state machine
cpu/hotplug: Move scheduler cpu_online notifier to hotplug core
cpu/hotplug: Implement setup/removal interface
cpu/hotplug: Make target state writeable
cpu/hotplug: Add sysfs state interface
cpu/hotplug: Hand in target state to _cpu_up/down
cpu/hotplug: Convert the hotplugged cpu work to a state machine
cpu/hotplug: Convert to a state machine for the control processor
cpu/hotplug: Add tracepoints
...
Pull read-only kernel memory updates from Ingo Molnar:
"This tree adds two (security related) enhancements to the kernel's
handling of read-only kernel memory:
- extend read-only kernel memory to a new class of formerly writable
kernel data: 'post-init read-only memory' via the __ro_after_init
attribute, and mark the ARM and x86 vDSO as such read-only memory.
This kind of attribute can be used for data that requires a once
per bootup initialization sequence, but is otherwise never modified
after that point.
This feature was based on the work by PaX Team and Brad Spengler.
(by Kees Cook, the ARM vDSO bits by David Brown.)
- make CONFIG_DEBUG_RODATA always enabled on x86 and remove the
Kconfig option. This simplifies the kernel and also signals that
read-only memory is the default model and a first-class citizen.
(Kees Cook)"
* 'mm-readonly-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
ARM/vdso: Mark the vDSO code read-only after init
x86/vdso: Mark the vDSO code read-only after init
lkdtm: Verify that '__ro_after_init' works correctly
arch: Introduce post-init read-only memory
x86/mm: Always enable CONFIG_DEBUG_RODATA and remove the Kconfig option
mm/init: Add 'rodata=off' boot cmdline parameter to disable read-only kernel mappings
asm-generic: Consolidate mark_rodata_ro()
Trivial correction in menuconfig help to reflect PIDs as
controller instead of subsystem to align to rest of the text
and documentation.
Signed-off-by: Parav Pandit <pandit.parav@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Move the RSA EMSA-PKCS1-v1_5 encoding from the asymmetric-key public_key
subtype to the rsa crypto module's pkcs1pad template. This means that the
public_key subtype no longer has any dependencies on public key type.
To make this work, the following changes have been made:
(1) The rsa pkcs1pad template is now used for RSA keys. This strips off the
padding and returns just the message hash.
(2) In a previous patch, the pkcs1pad template gained an optional second
parameter that, if given, specifies the hash used. We now give this,
and pkcs1pad checks the encoded message E(M) for the EMSA-PKCS1-v1_5
encoding and verifies that the correct digest OID is present.
(3) The crypto driver in crypto/asymmetric_keys/rsa.c is now reduced to
something that doesn't care about what the encryption actually does
and and has been merged into public_key.c.
(4) CONFIG_PUBLIC_KEY_ALGO_RSA is gone. Module signing must set
CONFIG_CRYPTO_RSA=y instead.
Thoughts:
(*) Should the encoding style (eg. raw, EMSA-PKCS1-v1_5) also be passed to
the padding template? Should there be multiple padding templates
registered that share most of the code?
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Handle the smpboot threads in the state machine.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.295777684@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Move the split out steps into a callback array and let the cpu_up/down
code iterate through the array functions. For now most of the
callbacks are asymmetric to resemble the current hotplug maze.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.671816690@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
It may be useful to debug writes to the readonly sections of memory,
so provide a cmdline "rodata=off" to allow for this. This can be
expanded in the future to support "log" and "write" modes, but that
will need to be architecture-specific.
This also makes KDB software breakpoints more usable, as read-only
mappings can now be disabled on any kernel.
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Brown <david.brown@linaro.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch <linux-arch@vger.kernel.org>
Link: http://lkml.kernel.org/r/1455748879-21872-3-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Lockdep is initialized at compile time now. Get rid of lockdep_init().
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Krinkin <krinkin.m.u@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: mm-commits@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
What CONFIG_INET and CONFIG_LEGACY_KMEM guard inside the memory
controller code is insignificant, having these conditionals is not
worth the complication and fragility that comes with them.
[akpm@linux-foundation.org: rework mem_cgroup_css_free() statement ordering]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Let the user know that CONFIG_MEMCG_KMEM does not apply to the cgroup2
interface. This also makes legacy-only code sections stand out better.
[arnd@arndb.de: mm: memcontrol: only manage socket pressure for CONFIG_INET]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make initrd_load() return bool due to this particular function only using
either one or zero as its return value.
No functional change.
Signed-off-by: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make obsolete_checksetup() return bool due to this particular function
only using either one or zero as its return value.
No functional change.
Signed-off-by: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull audit updates from Paul Moore:
"Seven audit patches for 4.5, all very minor despite the diffstat.
The diffstat churn for linux/audit.h can be attributed to needing to
reshuffle the linux/audit.h header to fix the seccomp auditing issue
(see the commit description for details).
Besides the seccomp/audit fix, most of the fixes are around trying to
improve the connection with the audit daemon and a Kconfig
simplification. Nothing crazy, and everything passes our little
audit-testsuite"
* 'upstream' of git://git.infradead.org/users/pcmoore/audit:
audit: always enable syscall auditing when supported and audit is enabled
audit: force seccomp event logging to honor the audit_enabled flag
audit: Delete unnecessary checks before two function calls
audit: wake up threads if queue switched from limited to unlimited
audit: include auditd's threads in audit_log_start() wait exception
audit: remove audit_backlog_wait_overflow
audit: don't needlessly reset valid wait time
Merge second patch-bomb from Andrew Morton:
- more MM stuff:
- Kirill's page-flags rework
- Kirill's now-allegedly-fixed THP rework
- MADV_FREE implementation
- DAX feature work (msync/fsync). This isn't quite complete but DAX
is new and it's good enough and the guys have a handle on what
needs to be done - I expect this to be wrapped in the next week or
two.
- some vsprintf maintenance work
- various other misc bits
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (145 commits)
printk: change recursion_bug type to bool
lib/vsprintf: factor out %pN[F] handler as netdev_bits()
lib/vsprintf: refactor duplicate code to special_hex_number()
printk-formats.txt: remove unimplemented %pT
printk: help pr_debug and pr_devel to optimize out arguments
lib/test_printf.c: test dentry printing
lib/test_printf.c: add test for large bitmaps
lib/test_printf.c: account for kvasprintf tests
lib/test_printf.c: add a few number() tests
lib/test_printf.c: test precision quirks
lib/test_printf.c: check for out-of-bound writes
lib/test_printf.c: don't BUG
lib/kasprintf.c: add sanity check to kvasprintf
lib/vsprintf.c: warn about too large precisions and field widths
lib/vsprintf.c: help gcc make number() smaller
lib/vsprintf.c: expand field_width to 24 bits
lib/vsprintf.c: eliminate potential race in string()
lib/vsprintf.c: move string() below widen_string()
lib/vsprintf.c: pull out padding code from dentry_name()
printk: do cond_resched() between lines while outputting to consoles
...
fixes and various document tweaks.
One patch reaches out of the documentation subtree to fix a comment in
init/do_mounts_rd.c. There didn't seem to be anybody more appropriate to
take that one, so I accepted it.
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Merge tag 'docs-4.5' of git://git.lwn.net/linux
Pull documentation updates from Jon Corbet:
"A relatively boring cycle in the docs tree. There's a few kernel-doc
fixes and various document tweaks.
One patch reaches out of the documentation subtree to fix a comment in
init/do_mounts_rd.c. There didn't seem to be anybody more appropriate
to take that one, so I accepted it"
* tag 'docs-4.5' of git://git.lwn.net/linux: (29 commits)
thermal: add description for integral_cutoff unit
Documentation: update libhugetlbfs site url
Documentation: Explain pci=conf1,conf2 more verbosely
DMA-API: fix confusing sentence in Documentation/DMA-API.txt
Documentation: translations: update linux cross reference link
Documentation: fix typo in CodingStyle
init, Documentation: Remove ramdisk_blocksize mentions
Documentation-getdelays: Apply a recommendation from "checkpatch.pl" in main()
Documentation: HOWTO: update versions from 3.x to 4.x
Documentation: remove outdated references from translations
Doc: treewide: Fix grammar "a" to "an"
Documentation: cpu-hotplug: Fix sysfs mount instructions
can-doc: Add hint about getting timestamps
Fix CFQ I/O scheduler parameter name in documentation
Documentation: arm: remove dead links from Marvell Berlin docs
Documentation: HOWTO: update code cross reference link
Doc: Docbook/iio: Fix typo in iio.tmpl
DocBook: make index.html generation less verbose by default
DocBook: Cleanup: remove an unused $(call) line
DocBook: Add a help message for DOCBOOKS env var
...
uselib hasn't been used since libc5; glibc does not use it. Deprecate
uselib a bit more, by making the default y only if libc5 was widely used
on the plaform.
This makes arm64 kernel built with defconfig slightly smaller
bloat-o-meter:
add/remove: 0/3 grow/shrink: 0/2 up/down: 0/-1390 (-1390)
function old new delta
kernel_config_data 18164 18162 -2
uselib_flags 20 - -20
padzero 216 192 -24
sys_uselib 380 - -380
load_elf_library 964 - -964
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To the best of our knowledge, everyone who enables audit at compile
time also enables syscall auditing; this patch simplifies the Kconfig
menus by removing the option to disable syscall auditing when audit
is selected and the target arch supports it.
Signed-off-by: Paul Moore <pmoore@redhat.com>
Pull cgroup updates from Tejun Heo:
- cgroup v2 interface is now official. It's no longer hidden behind a
devel flag and can be mounted using the new cgroup2 fs type.
Unfortunately, cpu v2 interface hasn't made it yet due to the
discussion around in-process hierarchical resource distribution and
only memory and io controllers can be used on the v2 interface at the
moment.
- The existing documentation which has always been a bit of mess is
relocated under Documentation/cgroup-v1/. Documentation/cgroup-v2.txt
is added as the authoritative documentation for the v2 interface.
- Some features are added through for-4.5-ancestor-test branch to
enable netfilter xt_cgroup match to use cgroup v2 paths. The actual
netfilter changes will be merged through the net tree which pulled in
the said branch.
- Various cleanups
* 'for-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: rename cgroup documentations
cgroup: fix a typo.
cgroup: Remove resource_counter.txt in Documentation/cgroup-legacy/00-INDEX.
cgroup: demote subsystem init messages to KERN_DEBUG
cgroup: Fix uninitialized variable warning
cgroup: put controller Kconfig options in meaningful order
cgroup: clean up the kernel configuration menu nomenclature
cgroup_pids: fix a typo.
Subject: cgroup: Fix incomplete dd command in blkio documentation
cgroup: kill cgrp_ss_priv[CGROUP_CANFORK_COUNT] and friends
cpuset: Replace all instances of time_t with time64_t
cgroup: replace unified-hierarchy.txt with a proper cgroup v2 documentation
cgroup: rename Documentation/cgroups/ to Documentation/cgroup-legacy/
cgroup: replace __DEVEL__sane_behavior with cgroup2 fs type
Pull RCU changes from Paul E. McKenney:
- Adding transitivity uniformly to rcu_node structure ->lock
acquisitions. (This is implemented by the first two commits
on top of v4.4-rc2 due to the pervasive nature of this change.)
- Documentation updates, including RCU requirements.
- Expedited grace-period changes.
- Miscellaneous fixes.
- Linked-list fixes, courtesy of KTSAN.
- Torture-test updates.
- Late-breaking fix to sysrq-generated crash.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The brd driver has never supported the ramdisk_blocksize kernel
parameter that was in the rd driver it replaced, so remove
mention of this parameter from comments and Documentation.
Commit 9db5579be4 ("rewrite rd") replaced rd with brd, keeping
a brd_blocksize variable in struct brd_device but never using it.
Commit a2cba2913c ("brd: get rid of unused members from struct
brd_device") removed the unused variable.
Commit f5abc8e758 ("Documentation/blockdev/ramdisk.txt: updates")
removed mentions of ramdisk_blocksize from that file.
Signed-off-by: Robert Elliott <elliott@hpe.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
To make it easier to quickly find what's needed list the basic
resource controllers of cgroup2 first - io, memory, cpu - while
pushing the more exotic and/or legacy controllers to the bottom.
tj: Removed spurious "&& CGROUPS" from CGROUP_PERF as suggested by Li.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The config options for the different cgroup controllers use various
terms: resource controller, cgroup subsystem, etc. Simplify this to
"controller", which is clear enough in the cgroup context.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently the full stop_machine() routine is only enabled on SMP if
module unloading is enabled, or if the CPUs are hotpluggable. This
leads to configurations where stop_machine() is broken as it will then
only run the callback on the local CPU with irqs disabled, and not stop
the other CPUs or run the callback on them.
For example, this breaks MTRR setup on x86 in certain configs since
ea8596bb2d ("kprobes/x86: Remove unused text_poke_smp() and
text_poke_smp_batch() functions") as the MTRR is only established on the
boot CPU.
This patch removes the Kconfig option for STOP_MACHINE and uses the SMP
and HOTPLUG_CPU config options to compile the correct stop_machine() for
the architecture, removing the false dependency on MODULE_UNLOAD in the
process.
Link: https://lkml.org/lkml/2014/10/8/124
References: https://bugs.freedesktop.org/show_bug.cgi?id=84794
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Pranith Kumar <bobby.prani@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Iulia Manda <iulia.manda21@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Chuck Ebbert <cebbert.lkml@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit adds the invocation of rcu_end_inkernel_boot() just before
init is invoked. This allows the CONFIG_RCU_EXPEDITE_BOOT Kconfig
option to do something useful and prepares for the upcoming
rcupdate.rcu_normal_after_boot kernel parameter.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Here is an implementation of a new system call, sys_membarrier(), which
executes a memory barrier on all threads running on the system. It is
implemented by calling synchronize_sched(). It can be used to
distribute the cost of user-space memory barriers asymmetrically by
transforming pairs of memory barriers into pairs consisting of
sys_membarrier() and a compiler barrier. For synchronization primitives
that distinguish between read-side and write-side (e.g. userspace RCU
[1], rwlocks), the read-side can be accelerated significantly by moving
the bulk of the memory barrier overhead to the write-side.
The existing applications of which I am aware that would be improved by
this system call are as follows:
* Through Userspace RCU library (http://urcu.so)
- DNS server (Knot DNS) https://www.knot-dns.cz/
- Network sniffer (http://netsniff-ng.org/)
- Distributed object storage (https://sheepdog.github.io/sheepdog/)
- User-space tracing (http://lttng.org)
- Network storage system (https://www.gluster.org/)
- Virtual routers (https://events.linuxfoundation.org/sites/events/files/slides/DPDK_RCU_0MQ.pdf)
- Financial software (https://lkml.org/lkml/2015/3/23/189)
Those projects use RCU in userspace to increase read-side speed and
scalability compared to locking. Especially in the case of RCU used by
libraries, sys_membarrier can speed up the read-side by moving the bulk of
the memory barrier cost to synchronize_rcu().
* Direct users of sys_membarrier
- core dotnet garbage collector (https://github.com/dotnet/coreclr/issues/198)
Microsoft core dotnet GC developers are planning to use the mprotect()
side-effect of issuing memory barriers through IPIs as a way to implement
Windows FlushProcessWriteBuffers() on Linux. They are referring to
sys_membarrier in their github thread, specifically stating that
sys_membarrier() is what they are looking for.
To explain the benefit of this scheme, let's introduce two example threads:
Thread A (non-frequent, e.g. executing liburcu synchronize_rcu())
Thread B (frequent, e.g. executing liburcu
rcu_read_lock()/rcu_read_unlock())
In a scheme where all smp_mb() in thread A are ordering memory accesses
with respect to smp_mb() present in Thread B, we can change each
smp_mb() within Thread A into calls to sys_membarrier() and each
smp_mb() within Thread B into compiler barriers "barrier()".
Before the change, we had, for each smp_mb() pairs:
Thread A Thread B
previous mem accesses previous mem accesses
smp_mb() smp_mb()
following mem accesses following mem accesses
After the change, these pairs become:
Thread A Thread B
prev mem accesses prev mem accesses
sys_membarrier() barrier()
follow mem accesses follow mem accesses
As we can see, there are two possible scenarios: either Thread B memory
accesses do not happen concurrently with Thread A accesses (1), or they
do (2).
1) Non-concurrent Thread A vs Thread B accesses:
Thread A Thread B
prev mem accesses
sys_membarrier()
follow mem accesses
prev mem accesses
barrier()
follow mem accesses
In this case, thread B accesses will be weakly ordered. This is OK,
because at that point, thread A is not particularly interested in
ordering them with respect to its own accesses.
2) Concurrent Thread A vs Thread B accesses
Thread A Thread B
prev mem accesses prev mem accesses
sys_membarrier() barrier()
follow mem accesses follow mem accesses
In this case, thread B accesses, which are ensured to be in program
order thanks to the compiler barrier, will be "upgraded" to full
smp_mb() by synchronize_sched().
* Benchmarks
On Intel Xeon E5405 (8 cores)
(one thread is calling sys_membarrier, the other 7 threads are busy
looping)
1000 non-expedited sys_membarrier calls in 33s =3D 33 milliseconds/call.
* User-space user of this system call: Userspace RCU library
Both the signal-based and the sys_membarrier userspace RCU schemes
permit us to remove the memory barrier from the userspace RCU
rcu_read_lock() and rcu_read_unlock() primitives, thus significantly
accelerating them. These memory barriers are replaced by compiler
barriers on the read-side, and all matching memory barriers on the
write-side are turned into an invocation of a memory barrier on all
active threads in the process. By letting the kernel perform this
synchronization rather than dumbly sending a signal to every process
threads (as we currently do), we diminish the number of unnecessary wake
ups and only issue the memory barriers on active threads. Non-running
threads do not need to execute such barrier anyway, because these are
implied by the scheduler context switches.
Results in liburcu:
Operations in 10s, 6 readers, 2 writers:
memory barriers in reader: 1701557485 reads, 2202847 writes
signal-based scheme: 9830061167 reads, 6700 writes
sys_membarrier: 9952759104 reads, 425 writes
sys_membarrier (dyn. check): 7970328887 reads, 425 writes
The dynamic sys_membarrier availability check adds some overhead to
the read-side compared to the signal-based scheme, but besides that,
sys_membarrier slightly outperforms the signal-based scheme. However,
this non-expedited sys_membarrier implementation has a much slower grace
period than signal and memory barrier schemes.
Besides diminishing the number of wake-ups, one major advantage of the
membarrier system call over the signal-based scheme is that it does not
need to reserve a signal. This plays much more nicely with libraries,
and with processes injected into for tracing purposes, for which we
cannot expect that signals will be unused by the application.
An expedited version of this system call can be added later on to speed
up the grace period. Its implementation will likely depend on reading
the cpu_curr()->mm without holding each CPU's rq lock.
This patch adds the system call to x86 and to asm-generic.
[1] http://urcu.so
membarrier(2) man page:
MEMBARRIER(2) Linux Programmer's Manual MEMBARRIER(2)
NAME
membarrier - issue memory barriers on a set of threads
SYNOPSIS
#include <linux/membarrier.h>
int membarrier(int cmd, int flags);
DESCRIPTION
The cmd argument is one of the following:
MEMBARRIER_CMD_QUERY
Query the set of supported commands. It returns a bitmask of
supported commands.
MEMBARRIER_CMD_SHARED
Execute a memory barrier on all threads running on the system.
Upon return from system call, the caller thread is ensured that
all running threads have passed through a state where all memory
accesses to user-space addresses match program order between
entry to and return from the system call (non-running threads
are de facto in such a state). This covers threads from all pro=E2=80=90
cesses running on the system. This command returns 0.
The flags argument needs to be 0. For future extensions.
All memory accesses performed in program order from each targeted
thread is guaranteed to be ordered with respect to sys_membarrier(). If
we use the semantic "barrier()" to represent a compiler barrier forcing
memory accesses to be performed in program order across the barrier,
and smp_mb() to represent explicit memory barriers forcing full memory
ordering across the barrier, we have the following ordering table for
each pair of barrier(), sys_membarrier() and smp_mb():
The pair ordering is detailed as (O: ordered, X: not ordered):
barrier() smp_mb() sys_membarrier()
barrier() X X O
smp_mb() X O O
sys_membarrier() O O O
RETURN VALUE
On success, these system calls return zero. On error, -1 is returned,
and errno is set appropriately. For a given command, with flags
argument set to 0, this system call is guaranteed to always return the
same value until reboot.
ERRORS
ENOSYS System call is not implemented.
EINVAL Invalid arguments.
Linux 2015-04-15 MEMBARRIER(2)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nicholas Miell <nmiell@comcast.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Pranith Kumar <bobby.prani@gmail.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are two kexec load syscalls, kexec_load another and kexec_file_load.
kexec_file_load has been splited as kernel/kexec_file.c. In this patch I
split kexec_load syscall code to kernel/kexec.c.
And add a new kconfig option KEXEC_CORE, so we can disable kexec_load and
use kexec_file_load only, or vice verse.
The original requirement is from Ted Ts'o, he want kexec kernel signature
being checked with CONFIG_KEXEC_VERIFY_SIG enabled. But kexec-tools use
kexec_load syscall can bypass the checking.
Vivek Goyal proposed to create a common kconfig option so user can compile
in only one syscall for loading kexec kernel. KEXEC/KEXEC_FILE selects
KEXEC_CORE so that old config files still work.
Because there's general code need CONFIG_KEXEC_CORE, so I updated all the
architecture Kconfig with a new option KEXEC_CORE, and let KEXEC selects
KEXEC_CORE in arch Kconfig. Also updated general kernel code with to
kexec_load syscall.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Dave Young <dyoung@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Petr Tesarik <ptesarik@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We need to launch the usermodehelper kernel threads with the widest
affinity and this is partly why we use khelper. This workqueue has
unbound properties and thus a wide affinity inherited by all its children.
Now khelper also has special properties that we aren't much interested in:
ordered and singlethread. There is really no need about ordering as all
we do is creating kernel threads. This can be done concurrently. And
singlethread is a useless limitation as well.
The workqueue engine already proposes generic unbound workqueues that
don't share these useless properties and handle well parallel jobs.
The only worrysome specific is their affinity to the node of the current
CPU. It's fine for creating the usermodehelper kernel threads but those
inherit this affinity for longer jobs such as requesting modules.
This patch proposes to use these node affine unbound workqueues assuming
that a node is sufficient to handle several parallel usermodehelper
requests.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull security subsystem updates from James Morris:
"Highlights:
- PKCS#7 support added to support signed kexec, also utilized for
module signing. See comments in 3f1e1bea.
** NOTE: this requires linking against the OpenSSL library, which
must be installed, e.g. the openssl-devel on Fedora **
- Smack
- add IPv6 host labeling; ignore labels on kernel threads
- support smack labeling mounts which use binary mount data
- SELinux:
- add ioctl whitelisting (see
http://kernsec.org/files/lss2015/vanderstoep.pdf)
- fix mprotect PROT_EXEC regression caused by mm change
- Seccomp:
- add ptrace options for suspend/resume"
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (57 commits)
PKCS#7: Add OIDs for sha224, sha284 and sha512 hash algos and use them
Documentation/Changes: Now need OpenSSL devel packages for module signing
scripts: add extract-cert and sign-file to .gitignore
modsign: Handle signing key in source tree
modsign: Use if_changed rule for extracting cert from module signing key
Move certificate handling to its own directory
sign-file: Fix warning about BIO_reset() return value
PKCS#7: Add MODULE_LICENSE() to test module
Smack - Fix build error with bringup unconfigured
sign-file: Document dependency on OpenSSL devel libraries
PKCS#7: Appropriately restrict authenticated attributes and content type
KEYS: Add a name for PKEY_ID_PKCS7
PKCS#7: Improve and export the X.509 ASN.1 time object decoder
modsign: Use extract-cert to process CONFIG_SYSTEM_TRUSTED_KEYS
extract-cert: Cope with multiple X.509 certificates in a single file
sign-file: Generate CMS message as signature instead of PKCS#7
PKCS#7: Support CMS messages also [RFC5652]
X.509: Change recorded SKID & AKID to not include Subject or Issuer
PKCS#7: Check content type and versions
MAINTAINERS: The keyrings mailing list has moved
...
Pull vfs updates from Al Viro:
"In this one:
- d_move fixes (Eric Biederman)
- UFS fixes (me; locking is mostly sane now, a bunch of bugs in error
handling ought to be fixed)
- switch of sb_writers to percpu rwsem (Oleg Nesterov)
- superblock scalability (Josef Bacik and Dave Chinner)
- swapon(2) race fix (Hugh Dickins)"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (65 commits)
vfs: Test for and handle paths that are unreachable from their mnt_root
dcache: Reduce the scope of i_lock in d_splice_alias
dcache: Handle escaped paths in prepend_path
mm: fix potential data race in SyS_swapon
inode: don't softlockup when evicting inodes
inode: rename i_wb_list to i_io_list
sync: serialise per-superblock sync operations
inode: convert inode_sb_list_lock to per-sb
inode: add hlist_fake to avoid the inode hash lock in evict
writeback: plug writeback at a high level
change sb_writers to use percpu_rw_semaphore
shift percpu_counter_destroy() into destroy_super_work()
percpu-rwsem: kill CONFIG_PERCPU_RWSEM
percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem_acquire()
percpu-rwsem: introduce percpu_down_read_trylock()
document rwsem_release() in sb_wait_write()
fix the broken lockdep logic in __sb_start_write()
introduce __sb_writers_{acquired,release}() helpers
ufs_inode_get{frag,block}(): get rid of 'phys' argument
ufs_getfrag_block(): tidy up a bit
...
Merge patch-bomb from Andrew Morton:
- a few misc things
- Andy's "ambient capabilities"
- fs/nofity updates
- the ocfs2 queue
- kernel/watchdog.c updates and feature work.
- some of MM. Includes Andrea's userfaultfd feature.
[ Hadn't noticed that userfaultfd was 'default y' when applying the
patches, so that got fixed in this merge instead. We do _not_ mark
new features that nobody uses yet 'default y' - Linus ]
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (118 commits)
mm/hugetlb.c: make vma_has_reserves() return bool
mm/madvise.c: make madvise_behaviour_valid() return bool
mm/memory.c: make tlb_next_batch() return bool
mm/dmapool.c: change is_page_busy() return from int to bool
mm: remove struct node_active_region
mremap: simplify the "overlap" check in mremap_to()
mremap: don't do uneccesary checks if new_len == old_len
mremap: don't do mm_populate(new_addr) on failure
mm: move ->mremap() from file_operations to vm_operations_struct
mremap: don't leak new_vma if f_op->mremap() fails
mm/hugetlb.c: make vma_shareable() return bool
mm: make GUP handle pfn mapping unless FOLL_GET is requested
mm: fix status code which move_pages() returns for zero page
mm: memcontrol: bring back the VM_BUG_ON() in mem_cgroup_swapout()
genalloc: add support of multiple gen_pools per device
genalloc: add name arg to gen_pool_get() and devm_gen_pool_create()
mm/memblock: WARN_ON when nid differs from overlap region
Documentation/features/vm: add feature description and arch support status for batched TLB flush after unmap
mm: defer flush of writable TLB entries
mm: send one IPI per CPU to TLB flush all entries after unmapping pages
...
An IPI is sent to flush remote TLBs when a page is unmapped that was
potentially accesssed by other CPUs. There are many circumstances where
this happens but the obvious one is kswapd reclaiming pages belonging to a
running process as kswapd and the task are likely running on separate
CPUs.
On small machines, this is not a significant problem but as machine gets
larger with more cores and more memory, the cost of these IPIs can be
high. This patch uses a simple structure that tracks CPUs that
potentially have TLB entries for pages being unmapped. When the unmapping
is complete, the full TLB is flushed on the assumption that a refill cost
is lower than flushing individual entries.
Architectures wishing to do this must give the following guarantee.
If a clean page is unmapped and not immediately flushed, the
architecture must guarantee that a write to that linear address
from a CPU with a cached TLB entry will trap a page fault.
This is essentially what the kernel already depends on but the window is
much larger with this patch applied and is worth highlighting. The
architecture should consider whether the cost of the full TLB flush is
higher than sending an IPI to flush each individual entry. An additional
architecture helper called flush_tlb_local is required. It's a trivial
wrapper with some accounting in the x86 case.
The impact of this patch depends on the workload as measuring any benefit
requires both mapped pages co-located on the LRU and memory pressure. The
case with the biggest impact is multiple processes reading mapped pages
taken from the vm-scalability test suite. The test case uses NR_CPU
readers of mapped files that consume 10*RAM.
Linear mapped reader on a 4-node machine with 64G RAM and 48 CPUs
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
Ops lru-file-mmap-read-elapsed 159.62 ( 0.00%) 120.68 ( 24.40%)
Ops lru-file-mmap-read-time_range 30.59 ( 0.00%) 2.80 ( 90.85%)
Ops lru-file-mmap-read-time_stddv 6.70 ( 0.00%) 0.64 ( 90.38%)
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
User 581.00 611.43
System 5804.93 4111.76
Elapsed 161.03 122.12
This is showing that the readers completed 24.40% faster with 29% less
system CPU time. From vmstats, it is known that the vanilla kernel was
interrupted roughly 900K times per second during the steady phase of the
test and the patched kernel was interrupts 180K times per second.
The impact is lower on a single socket machine.
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
Ops lru-file-mmap-read-elapsed 25.33 ( 0.00%) 20.38 ( 19.54%)
Ops lru-file-mmap-read-time_range 0.91 ( 0.00%) 1.44 (-58.24%)
Ops lru-file-mmap-read-time_stddv 0.28 ( 0.00%) 0.47 (-65.34%)
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
User 58.09 57.64
System 111.82 76.56
Elapsed 27.29 22.55
It's still a noticeable improvement with vmstat showing interrupts went
from roughly 500K per second to 45K per second.
The patch will have no impact on workloads with no memory pressure or have
relatively few mapped pages. It will have an unpredictable impact on the
workload running on the CPU being flushed as it'll depend on how many TLB
entries need to be refilled and how long that takes. Worst case, the TLB
will be completely cleared of active entries when the target PFNs were not
resident at all.
[sasha.levin@oracle.com: trace tlb flush after disabling preemption in try_to_unmap_flush]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This allows to select the userfaultfd during configuration to build it.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cgroup updates from Tejun Heo:
- a new PIDs controller is added. It turns out that PIDs are actually
an independent resource from kmem due to the limited PID space.
- more core preparations for the v2 interface. Once cpu side interface
is settled, it should be ready for lifting the devel mask.
for-4.3-unified-base was temporarily branched so that other trees
(block) can pull cgroup core changes that blkcg changes depend on.
- a non-critical idr_preload usage bug fix.
* 'for-4.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: pids: fix invalid get/put usage
cgroup: introduce cgroup_subsys->legacy_name
cgroup: don't print subsystems for the default hierarchy
cgroup: make cftype->private a unsigned long
cgroup: export cgrp_dfl_root
cgroup: define controller file conventions
cgroup: fix idr_preload usage
cgroup: add documentation for the PIDs controller
cgroup: implement the PIDs subsystem
cgroup: allow a cgroup subsystem to reject a fork
Move certificate handling out of the kernel/ directory and into a certs/
directory to get all the weird stuff in one place and move the generated
signing keys into this directory.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: David Woodhouse <David.Woodhouse@intel.com>
The revised sign-file program is no longer a script that wraps the openssl
program, but now rather a program that makes use of OpenSSL's crypto
library. This means that to build the sign-file program, the kernel build
process now has a dependency on the OpenSSL development packages in
addition to OpenSSL itself.
Document this in Kconfig and in module-signing.txt.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: David Woodhouse <David.Woodhouse@intel.com>
Pull RCU changes from Paul E. McKenney:
- The combination of tree geometry-initialization simplifications
and OS-jitter-reduction changes to expedited grace periods.
These two are stacked due to the large number of conflicts
that would otherwise result.
[ With one addition, a temporary commit to silence a lockdep false
positive. Additional changes to the expedited grace-period
primitives (queued for 4.4) remove the cause of this false
positive, and therefore include a revert of this temporary commit. ]
- Documentation updates.
- Torture-test updates.
- Miscellaneous fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Let the user explicitly provide a file containing trusted keys, instead of
just automatically finding files matching *.x509 in the build tree and
trusting whatever we find. This really ought to be an *explicit*
configuration, and the build rules for dealing with the files were
fairly painful too.
Fix applied from James Morris that removes an '=' from a macro definition
in kernel/Makefile as this is a feature that only exists from GNU make 3.82
onwards.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
The current rule for generating signing_key.priv and signing_key.x509 is
a classic example of a bad rule which has a tendency to break parallel
make. When invoked to create *either* target, it generates the other
target as a side-effect that make didn't predict.
So let's switch to using a single file signing_key.pem which contains
both key and certificate. That matches what we do in the case of an
external key specified by CONFIG_MODULE_SIG_KEY anyway, so it's also
slightly cleaner.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
