Introduce smp_cond_acquire() which combines a control dependency and a
read barrier to form acquire semantics.
This primitive has two benefits:
- it documents control dependencies,
- its typically cheaper than using smp_load_acquire() in a loop.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
gcc 4.9 added the function attribute assume_aligned, indicating to the
caller that the returned pointer may be assumed to have a certain minimal
alignment. This is useful if, for example, the return value is passed to
memset(). Add a shorthand macro for that.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull s390 updates from Martin Schwidefsky:
"There is only one new feature in this pull for the 4.4 merge window,
most of it is small enhancements, cleanup and bug fixes:
- Add the s390 backend for the software dirty bit tracking. This
adds two new pgtable functions pte_clear_soft_dirty and
pmd_clear_soft_dirty which is why there is a hit to
arch/x86/include/asm/pgtable.h in this pull request.
- A series of cleanup patches for the AP bus, this includes the
removal of the support for two outdated crypto cards (PCICC and
PCICA).
- The irq handling / signaling on buffer full in the runtime
instrumentation code is dropped.
- Some micro optimizations: remove unnecessary memory barriers for a
couple of functions: [smb_]rmb, [smb_]wmb, atomics, bitops, and for
spin_unlock. Use the builtin bswap if available and make
test_and_set_bit_lock more cache friendly.
- Statistics and a tracepoint for the diagnose calls to the
hypervisor.
- The CPU measurement facility support to sample KVM guests is
improved.
- The vector instructions are now always enabled for user space
processes if the hardware has the vector facility. This simplifies
the FPU handling code. The fpu-internal.h header is split into fpu
internals, api and types just like x86.
- Cleanup and improvements for the common I/O layer.
- Rework udelay to solve a problem with kprobe. udelay has busy loop
semantics but still uses an idle processor state for the wait"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (66 commits)
s390: remove runtime instrumentation interrupts
s390/cio: de-duplicate subchannel validation
s390/css: unneeded initialization in for_each_subchannel
s390/Kconfig: use builtin bswap
s390/dasd: fix disconnected device with valid path mask
s390/dasd: fix invalid PAV assignment after suspend/resume
s390/dasd: fix double free in dasd_eckd_read_conf
s390/kernel: fix ptrace peek/poke for floating point registers
s390/cio: move ccw_device_stlck functions
s390/cio: move ccw_device_call_handler
s390/topology: reduce per_cpu() invocations
s390/nmi: reduce size of percpu variable
s390/nmi: fix terminology
s390/nmi: remove casts
s390/nmi: remove pointless error strings
s390: don't store registers on disabled wait anymore
s390: get rid of __set_psw_mask()
s390/fpu: split fpu-internal.h into fpu internals, api, and type headers
s390/dasd: fix list_del corruption after lcu changes
s390/spinlock: remove unneeded serializations at unlock
...
This seems to be a mis-reading of how alpha memory ordering works, and
is not backed up by the alpha architecture manual. The helper functions
don't do anything special on any other architectures, and the arguments
that support them being safe on other architectures also argue that they
are safe on alpha.
Basically, the "control dependency" is between a previous read and a
subsequent write that is dependent on the value read. Even if the
subsequent write is actually done speculatively, there is no way that
such a speculative write could be made visible to other cpu's until it
has been committed, which requires validating the speculation.
Note that most weakely ordered architectures (very much including alpha)
do not guarantee any ordering relationship between two loads that depend
on each other on a control dependency:
read A
if (val == 1)
read B
because the conditional may be predicted, and the "read B" may be
speculatively moved up to before reading the value A. So we require the
user to insert a smp_rmb() between the two accesses to be correct:
read A;
if (A == 1)
smp_rmb()
read B
Alpha is further special in that it can break that ordering even if the
*address* of B depends on the read of A, because the cacheline that is
read later may be stale unless you have a memory barrier in between the
pointer read and the read of the value behind a pointer:
read ptr
read offset(ptr)
whereas all other weakly ordered architectures guarantee that the data
dependency (as opposed to just a control dependency) will order the two
accesses. As a result, alpha needs a "smp_read_barrier_depends()" in
between those two reads for them to be ordered.
The coontrol dependency that "READ_ONCE_CTRL()" and "atomic_read_ctrl()"
had was a control dependency to a subsequent *write*, however, and
nobody can finalize such a subsequent write without having actually done
the read. And were you to write such a value to a "stale" cacheline
(the way the unordered reads came to be), that would seem to lose the
write entirely.
So the things that make alpha able to re-order reads even more
aggressively than other weak architectures do not seem to be relevant
for a subsequent write. Alpha memory ordering may be strange, but
there's no real indication that it is *that* strange.
Also, the alpha architecture reference manual very explicitly talks
about the definition of "Dependence Constraints" in section 5.6.1.7,
where a preceding read dominates a subsequent write.
Such a dependence constraint admittedly does not impose a BEFORE (alpha
architecture term for globally visible ordering), but it does guarantee
that there can be no "causal loop". I don't see how you could avoid
such a loop if another cpu could see the stored value and then impact
the value of the first read. Put another way: the read and the write
could not be seen as being out of order wrt other cpus.
So I do not see how these "x_ctrl()" functions can currently be necessary.
I may have to eat my words at some point, but in the absense of clear
proof that alpha actually needs this, or indeed even an explanation of
how alpha could _possibly_ need it, I do not believe these functions are
called for.
And if it turns out that alpha really _does_ need a barrier for this
case, that barrier still should not be "smp_read_barrier_depends()".
We'd have to make up some new speciality barrier just for alpha, along
with the documentation for why it really is necessary.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul E McKenney <paulmck@us.ibm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some code may perform racy by design memory reads. This could be
harmless, yet such code may produce KASAN warnings.
To hide such accesses from KASAN this patch introduces
READ_ONCE_NOCHECK() macro. KASAN will not check the memory
accessed by READ_ONCE_NOCHECK(). The KernelThreadSanitizer
(KTSAN) is going to ignore it as well.
This patch creates __read_once_size_nocheck() a clone of
__read_once_size(). The only difference between them is
'no_sanitized_address' attribute appended to '*_nocheck'
function. This attribute tells the compiler that instrumentation
of memory accesses should not be applied to that function. We
declare it as static '__maybe_unsed' because GCC is not capable
to inline such function:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
With KASAN=n READ_ONCE_NOCHECK() is just a clone of READ_ONCE().
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Link: http://lkml.kernel.org/r/1445243838-17763-2-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
sparse does not understand the s390 specific hotpatch attribute and
floods the log with messages like
include/uapi/linux/swab.h:92:8: error: attribute 'hotpatch': unknown attribute
Let's just dont use it, if __CHECKER__ is defined.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
The kernel build bot showed a new warning triggered by commit:
76695af20c ("locking, arch: use WRITE_ONCE()/READ_ONCE() in smp_store_release()/smp_load_acquire()")
because Sparse does not like WRITE_ONCE() accessing elements
from the (sparse) RCU address space:
fs/afs/inode.c:448:9: sparse: incorrect type in initializer (different address spaces)
fs/afs/inode.c:448:9: expected struct afs_permits *__val
fs/afs/inode.c:448:9: got void [noderef] <asn:4>*<noident>
Solution is to force cast away the sparse attributes for the initializer
of the union in WRITE_ONCE().
(And as this now gets too long, also split the macro into multiple lines.)
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1438674948-38310-2-git-send-email-borntraeger@de.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull libnvdimm fixes from Dan Williams:
"1) Fixes for a handful of smatch reports (Thanks Dan C.!) and minor
bug fixes (patches 1-6)
2) Correctness fixes to the BLK-mode nvdimm driver (patches 7-10).
Granted these are slightly large for a -rc update. They have been
out for review in one form or another since the end of May and were
deferred from the merge window while we settled on the "PMEM API"
for the PMEM-mode nvdimm driver (ie memremap_pmem, memcpy_to_pmem,
and wmb_pmem).
Now that those apis are merged we implement them in the BLK driver
to guarantee that mmio aperture moves stay ordered with respect to
incoming read/write requests, and that writes are flushed through
those mmio-windows and platform-buffers to be persistent on media.
These pass the sub-system unit tests with the updates to
tools/testing/nvdimm, and have received a successful build-report from
the kbuild robot (468 configs).
With acks from Rafael for the touches to drivers/acpi/"
* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm:
nfit: add support for NVDIMM "latch" flag
nfit: update block I/O path to use PMEM API
tools/testing/nvdimm: add mock acpi_nfit_flush_address entries to nfit_test
tools/testing/nvdimm: fix return code for unimplemented commands
tools/testing/nvdimm: mock ioremap_wt
pmem: add maintainer for include/linux/pmem.h
nfit: fix smatch "use after null check" report
nvdimm: Fix return value of nvdimm_bus_init() if class_create() fails
libnvdimm: smatch cleanups in __nd_ioctl
sparse: fix misplaced __pmem definition
Main excitement here is Peter Zijlstra's lockless rbtree optimization to
speed module address lookup. He found some abusers of the module lock
doing that too.
A little bit of parameter work here too; including Dan Streetman's breaking
up the big param mutex so writing a parameter can load another module (yeah,
really). Unfortunately that broke the usual suspects, !CONFIG_MODULES and
!CONFIG_SYSFS, so those fixes were appended too.
Cheers,
Rusty.
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Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
Pull module updates from Rusty Russell:
"Main excitement here is Peter Zijlstra's lockless rbtree optimization
to speed module address lookup. He found some abusers of the module
lock doing that too.
A little bit of parameter work here too; including Dan Streetman's
breaking up the big param mutex so writing a parameter can load
another module (yeah, really). Unfortunately that broke the usual
suspects, !CONFIG_MODULES and !CONFIG_SYSFS, so those fixes were
appended too"
* tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (26 commits)
modules: only use mod->param_lock if CONFIG_MODULES
param: fix module param locks when !CONFIG_SYSFS.
rcu: merge fix for Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()
module: add per-module param_lock
module: make perm const
params: suppress unused variable error, warn once just in case code changes.
modules: clarify CONFIG_MODULE_COMPRESS help, suggest 'N'.
kernel/module.c: avoid ifdefs for sig_enforce declaration
kernel/workqueue.c: remove ifdefs over wq_power_efficient
kernel/params.c: export param_ops_bool_enable_only
kernel/params.c: generalize bool_enable_only
kernel/module.c: use generic module param operaters for sig_enforce
kernel/params: constify struct kernel_param_ops uses
sysfs: tightened sysfs permission checks
module: Rework module_addr_{min,max}
module: Use __module_address() for module_address_lookup()
module: Make the mod_tree stuff conditional on PERF_EVENTS || TRACING
module: Optimize __module_address() using a latched RB-tree
rbtree: Implement generic latch_tree
seqlock: Introduce raw_read_seqcount_latch()
...
Move the definition of __pmem outside of CONFIG_SPARSE_RCU_POINTER to fix:
drivers/nvdimm/pmem.c:198:17: sparse: too many arguments for function __builtin_expect
drivers/nvdimm/pmem.c:36:33: sparse: expected ; at end of declaration
drivers/nvdimm/pmem.c:48:21: sparse: void declaration
...due to __pmem failing to be defined in some configurations when
CONFIG_SPARSE_RCU_POINTER=y.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
4 drivers / enabling modules:
NFIT:
Instantiates an "nvdimm bus" with the core and registers memory devices
(NVDIMMs) enumerated by the ACPI 6.0 NFIT (NVDIMM Firmware Interface
table). After registering NVDIMMs the NFIT driver then registers
"region" devices. A libnvdimm-region defines an access mode and the
boundaries of persistent memory media. A region may span multiple
NVDIMMs that are interleaved by the hardware memory controller. In
turn, a libnvdimm-region can be carved into a "namespace" device and
bound to the PMEM or BLK driver which will attach a Linux block device
(disk) interface to the memory.
PMEM:
Initially merged in v4.1 this driver for contiguous spans of persistent
memory address ranges is re-worked to drive PMEM-namespaces emitted by
the libnvdimm-core. In this update the PMEM driver, on x86, gains the
ability to assert that writes to persistent memory have been flushed all
the way through the caches and buffers in the platform to persistent
media. See memcpy_to_pmem() and wmb_pmem().
BLK:
This new driver enables access to persistent memory media through "Block
Data Windows" as defined by the NFIT. The primary difference of this
driver to PMEM is that only a small window of persistent memory is
mapped into system address space at any given point in time. Per-NVDIMM
windows are reprogrammed at run time, per-I/O, to access different
portions of the media. BLK-mode, by definition, does not support DAX.
BTT:
This is a library, optionally consumed by either PMEM or BLK, that
converts a byte-accessible namespace into a disk with atomic sector
update semantics (prevents sector tearing on crash or power loss). The
sinister aspect of sector tearing is that most applications do not know
they have a atomic sector dependency. At least today's disk's rarely
ever tear sectors and if they do one almost certainly gets a CRC error
on access. NVDIMMs will always tear and always silently. Until an
application is audited to be robust in the presence of sector-tearing
the usage of BTT is recommended.
Thanks to: Ross Zwisler, Jeff Moyer, Vishal Verma, Christoph Hellwig,
Ingo Molnar, Neil Brown, Boaz Harrosh, Robert Elliott, Matthew Wilcox,
Andy Rudoff, Linda Knippers, Toshi Kani, Nicholas Moulin, Rafael
Wysocki, and Bob Moore.
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Merge tag 'libnvdimm-for-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm
Pull libnvdimm subsystem from Dan Williams:
"The libnvdimm sub-system introduces, in addition to the
libnvdimm-core, 4 drivers / enabling modules:
NFIT:
Instantiates an "nvdimm bus" with the core and registers memory
devices (NVDIMMs) enumerated by the ACPI 6.0 NFIT (NVDIMM Firmware
Interface table).
After registering NVDIMMs the NFIT driver then registers "region"
devices. A libnvdimm-region defines an access mode and the
boundaries of persistent memory media. A region may span multiple
NVDIMMs that are interleaved by the hardware memory controller. In
turn, a libnvdimm-region can be carved into a "namespace" device and
bound to the PMEM or BLK driver which will attach a Linux block
device (disk) interface to the memory.
PMEM:
Initially merged in v4.1 this driver for contiguous spans of
persistent memory address ranges is re-worked to drive
PMEM-namespaces emitted by the libnvdimm-core.
In this update the PMEM driver, on x86, gains the ability to assert
that writes to persistent memory have been flushed all the way
through the caches and buffers in the platform to persistent media.
See memcpy_to_pmem() and wmb_pmem().
BLK:
This new driver enables access to persistent memory media through
"Block Data Windows" as defined by the NFIT. The primary difference
of this driver to PMEM is that only a small window of persistent
memory is mapped into system address space at any given point in
time.
Per-NVDIMM windows are reprogrammed at run time, per-I/O, to access
different portions of the media. BLK-mode, by definition, does not
support DAX.
BTT:
This is a library, optionally consumed by either PMEM or BLK, that
converts a byte-accessible namespace into a disk with atomic sector
update semantics (prevents sector tearing on crash or power loss).
The sinister aspect of sector tearing is that most applications do
not know they have a atomic sector dependency. At least today's
disk's rarely ever tear sectors and if they do one almost certainly
gets a CRC error on access. NVDIMMs will always tear and always
silently. Until an application is audited to be robust in the
presence of sector-tearing the usage of BTT is recommended.
Thanks to: Ross Zwisler, Jeff Moyer, Vishal Verma, Christoph Hellwig,
Ingo Molnar, Neil Brown, Boaz Harrosh, Robert Elliott, Matthew Wilcox,
Andy Rudoff, Linda Knippers, Toshi Kani, Nicholas Moulin, Rafael
Wysocki, and Bob Moore"
* tag 'libnvdimm-for-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm: (33 commits)
arch, x86: pmem api for ensuring durability of persistent memory updates
libnvdimm: Add sysfs numa_node to NVDIMM devices
libnvdimm: Set numa_node to NVDIMM devices
acpi: Add acpi_map_pxm_to_online_node()
libnvdimm, nfit: handle unarmed dimms, mark namespaces read-only
pmem: flag pmem block devices as non-rotational
libnvdimm: enable iostat
pmem: make_request cleanups
libnvdimm, pmem: fix up max_hw_sectors
libnvdimm, blk: add support for blk integrity
libnvdimm, btt: add support for blk integrity
fs/block_dev.c: skip rw_page if bdev has integrity
libnvdimm: Non-Volatile Devices
tools/testing/nvdimm: libnvdimm unit test infrastructure
libnvdimm, nfit, nd_blk: driver for BLK-mode access persistent memory
nd_btt: atomic sector updates
libnvdimm: infrastructure for btt devices
libnvdimm: write blk label set
libnvdimm: write pmem label set
libnvdimm: blk labels and namespace instantiation
...
Based on an original patch by Ross Zwisler [1].
Writes to persistent memory have the potential to be posted to cpu
cache, cpu write buffers, and platform write buffers (memory controller)
before being committed to persistent media. Provide apis,
memcpy_to_pmem(), wmb_pmem(), and memremap_pmem(), to write data to
pmem and assert that it is durable in PMEM (a persistent linear address
range). A '__pmem' attribute is added so sparse can track proper usage
of pointers to pmem.
This continues the status quo of pmem being x86 only for 4.2, but
reworks to ioremap, and wider implementation of memremap() will enable
other archs in 4.3.
[1]: https://lists.01.org/pipermail/linux-nvdimm/2015-May/000932.html
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
[djbw: various reworks]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This mirrors the change introduced by 7d0ae8086b of same title
in Linus' tree; it's not obvious as a merge resolution since we moved
the function.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Pull locking updates from Ingo Molnar:
"The main changes are:
- 'qspinlock' support, enabled on x86: queued spinlocks - these are
now the spinlock variant used by x86 as they outperform ticket
spinlocks in every category. (Waiman Long)
- 'pvqspinlock' support on x86: paravirtualized variant of queued
spinlocks. (Waiman Long, Peter Zijlstra)
- 'qrwlock' support, enabled on x86: queued rwlocks. Similar to
queued spinlocks, they are now the variant used by x86:
CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y
CONFIG_QUEUED_SPINLOCKS=y
CONFIG_ARCH_USE_QUEUED_RWLOCKS=y
CONFIG_QUEUED_RWLOCKS=y
- various lockdep fixlets
- various locking primitives cleanups, further WRITE_ONCE()
propagation"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
locking/lockdep: Remove hard coded array size dependency
locking/qrwlock: Don't contend with readers when setting _QW_WAITING
lockdep: Do not break user-visible string
locking/arch: Rename set_mb() to smp_store_mb()
locking/arch: Add WRITE_ONCE() to set_mb()
rtmutex: Warn if trylock is called from hard/softirq context
arch: Remove __ARCH_HAVE_CMPXCHG
locking/rtmutex: Drop usage of __HAVE_ARCH_CMPXCHG
locking/qrwlock: Rename QUEUE_RWLOCK to QUEUED_RWLOCKS
locking/pvqspinlock: Rename QUEUED_SPINLOCK to QUEUED_SPINLOCKS
locking/pvqspinlock: Replace xchg() by the more descriptive set_mb()
locking/pvqspinlock, x86: Enable PV qspinlock for Xen
locking/pvqspinlock, x86: Enable PV qspinlock for KVM
locking/pvqspinlock, x86: Implement the paravirt qspinlock call patching
locking/pvqspinlock: Implement simple paravirt support for the qspinlock
locking/qspinlock: Revert to test-and-set on hypervisors
locking/qspinlock: Use a simple write to grab the lock
locking/qspinlock: Optimize for smaller NR_CPUS
locking/qspinlock: Extract out code snippets for the next patch
locking/qspinlock: Add pending bit
...
I want to use lockless_dereference() from seqlock.h, which would mean
including rcupdate.h from it, however rcupdate.h already includes
seqlock.h.
Avoid this by moving lockless_dereference() into compiler.h. This is
somewhat tricky since it uses smp_read_barrier_depends() which isn't
available there, but its a CPP macro so we can get away with it.
The alternative would be moving it into asm/barrier.h, but that would
be updating each arch (I can do if people feel that is more
appropriate).
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
The current formulation of control dependencies fails on DEC Alpha,
which does not respect dependencies of any kind unless an explicit
memory barrier is provided. This means that the current fomulation of
control dependencies fails on Alpha. This commit therefore creates a
READ_ONCE_CTRL() that has the same overhead on non-Alpha systems, but
causes Alpha to produce the needed ordering. This commit also applies
READ_ONCE_CTRL() to the one known use of control dependencies.
Use of READ_ONCE_CTRL() also has the beneficial effect of adding a bit
of self-documentation to control dependencies.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Since we assume set_mb() to result in a single store followed by a
full memory barrier, employ WRITE_ONCE().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Looks like commit :
43239cbe79 ("kernel: Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)")
left behind a reference to ASSIGN_ONCE(). Update this to WRITE_ONCE().
Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: borntraeger@de.ibm.com
Cc: dave@stgolabs.net
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/20150430115721.22278.94082.stgit@preeti.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In commit 0b053c9518 ("lib: memzero_explicit: use barrier instead
of OPTIMIZER_HIDE_VAR"), we made memzero_explicit() more robust in
case LTO would decide to inline memzero_explicit() and eventually
find out it could be elimiated as dead store.
While using barrier() works well for the case of gcc, recent efforts
from LLVMLinux people suggest to use llvm as an alternative to gcc,
and there, Stephan found in a simple stand-alone user space example
that llvm could nevertheless optimize and thus elimitate the memset().
A similar issue has been observed in the referenced llvm bug report,
which is regarded as not-a-bug.
Based on some experiments, icc is a bit special on its own, while it
doesn't seem to eliminate the memset(), it could do so with an own
implementation, and then result in similar findings as with llvm.
The fix in this patch now works for all three compilers (also tested
with more aggressive optimization levels). Arguably, in the current
kernel tree it's more of a theoretical issue, but imho, it's better
to be pedantic about it.
It's clearly visible with gcc/llvm though, with the below code: if we
would have used barrier() only here, llvm would have omitted clearing,
not so with barrier_data() variant:
static inline void memzero_explicit(void *s, size_t count)
{
memset(s, 0, count);
barrier_data(s);
}
int main(void)
{
char buff[20];
memzero_explicit(buff, sizeof(buff));
return 0;
}
$ gcc -O2 test.c
$ gdb a.out
(gdb) disassemble main
Dump of assembler code for function main:
0x0000000000400400 <+0>: lea -0x28(%rsp),%rax
0x0000000000400405 <+5>: movq $0x0,-0x28(%rsp)
0x000000000040040e <+14>: movq $0x0,-0x20(%rsp)
0x0000000000400417 <+23>: movl $0x0,-0x18(%rsp)
0x000000000040041f <+31>: xor %eax,%eax
0x0000000000400421 <+33>: retq
End of assembler dump.
$ clang -O2 test.c
$ gdb a.out
(gdb) disassemble main
Dump of assembler code for function main:
0x00000000004004f0 <+0>: xorps %xmm0,%xmm0
0x00000000004004f3 <+3>: movaps %xmm0,-0x18(%rsp)
0x00000000004004f8 <+8>: movl $0x0,-0x8(%rsp)
0x0000000000400500 <+16>: lea -0x18(%rsp),%rax
0x0000000000400505 <+21>: xor %eax,%eax
0x0000000000400507 <+23>: retq
End of assembler dump.
As gcc, clang, but also icc defines __GNUC__, it's sufficient to define
this in compiler-gcc.h only to be picked up. For a fallback or otherwise
unsupported compiler, we define it as a barrier. Similarly, for ecc which
does not support gcc inline asm.
Reference: https://llvm.org/bugs/show_bug.cgi?id=15495
Reported-by: Stephan Mueller <smueller@chronox.de>
Tested-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Stephan Mueller <smueller@chronox.de>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: mancha security <mancha1@zoho.com>
Cc: Mark Charlebois <charlebm@gmail.com>
Cc: Behan Webster <behanw@converseincode.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The fact that volatile allows for atomic load/stores is a special case
not a requirement for {READ,WRITE}_ONCE(). Their primary purpose is to
force the compiler to emit load/stores _once_.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The use of READ_ONCE() causes lots of warnings witht he pending paravirt
spinlock fixes, because those ends up having passing a member to a
'const' structure to READ_ONCE().
There should certainly be nothing wrong with using READ_ONCE() with a
const source, but the helper function __read_once_size() would cause
warnings because it would drop the 'const' qualifier, but also because
the destination would be marked 'const' too due to the use of 'typeof'.
Use a union of types in READ_ONCE() to avoid this issue.
Also make sure to use parenthesis around the macro arguments to avoid
possible operator precedence issues.
Tested-by: Ingo Molnar <mingo@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This series tightens the rules for ACCESS_ONCE to only work
on scalar types. It also contains the necessary fixups as
indicated by build bots of linux-next.
Now everything is in place to prevent new non-scalar users
of ACCESS_ONCE and we can continue to convert code to
READ_ONCE/WRITE_ONCE.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux
Pull ACCESS_ONCE() rule tightening from Christian Borntraeger:
"Tighten rules for ACCESS_ONCE
This series tightens the rules for ACCESS_ONCE to only work on scalar
types. It also contains the necessary fixups as indicated by build
bots of linux-next. Now everything is in place to prevent new
non-scalar users of ACCESS_ONCE and we can continue to convert code to
READ_ONCE/WRITE_ONCE"
* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux:
kernel: Fix sparse warning for ACCESS_ONCE
next: sh: Fix compile error
kernel: tighten rules for ACCESS ONCE
mm/gup: Replace ACCESS_ONCE with READ_ONCE
x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE
x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE
ppc/hugetlbfs: Replace ACCESS_ONCE with READ_ONCE
ppc/kvm: Replace ACCESS_ONCE with READ_ONCE
Pull s390 updates from Martin Schwidefsky:
- The remaining patches for the z13 machine support: kernel build
option for z13, the cache synonym avoidance, SMT support,
compare-and-delay for spinloops and the CES5S crypto adapater.
- The ftrace support for function tracing with the gcc hotpatch option.
This touches common code Makefiles, Steven is ok with the changes.
- The hypfs file system gets an extension to access diagnose 0x0c data
in user space for performance analysis for Linux running under z/VM.
- The iucv hvc console gets wildcard spport for the user id filtering.
- The cacheinfo code is converted to use the generic infrastructure.
- Cleanup and bug fixes.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (42 commits)
s390/process: free vx save area when releasing tasks
s390/hypfs: Eliminate hypfs interval
s390/hypfs: Add diagnose 0c support
s390/cacheinfo: don't use smp_processor_id() in preemptible context
s390/zcrypt: fixed domain scanning problem (again)
s390/smp: increase maximum value of NR_CPUS to 512
s390/jump label: use different nop instruction
s390/jump label: add sanity checks
s390/mm: correct missing space when reporting user process faults
s390/dasd: cleanup profiling
s390/dasd: add locking for global_profile access
s390/ftrace: hotpatch support for function tracing
ftrace: let notrace function attribute disable hotpatching if necessary
ftrace: allow architectures to specify ftrace compile options
s390: reintroduce diag 44 calls for cpu_relax()
s390/zcrypt: Add support for new crypto express (CEX5S) adapter.
s390/zcrypt: Number of supported ap domains is not retrievable.
s390/spinlock: add compare-and-delay to lock wait loops
s390/tape: remove redundant if statement
s390/hvc_iucv: add simple wildcard matches to the iucv allow filter
...
gcc supports an s390 specific function attribute called "hotpatch".
It can be used to specify the number of halfwords that shall be added before
and after a function and which shall be filled with nops for runtime patching.
s390 will use the hotpatch attribute for function tracing, therefore make
sure that the notrace function attribute either disables the mcount call
or in case of hotpatch nop generation.
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Pull RCU updates from Paul E. McKenney:
- Documentation updates.
- Miscellaneous fixes.
- Preemptible-RCU fixes, including fixing an old bug in the
interaction of RCU priority boosting and CPU hotplug.
- SRCU updates.
- RCU CPU stall-warning updates.
- RCU torture-test updates.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit 927609d622 ("kernel: tighten rules for ACCESS ONCE") results in
sparse warnings like "Using plain integer as NULL pointer" - Let's add a
type cast to the dummy assignment.
To avoid warnings lik "sparse: warning: cast to restricted __hc32" we also
use __force on that cast.
Fixes: 927609d622 ("kernel: tighten rules for ACCESS ONCE")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Now that all non-scalar users of ACCESS_ONCE have been converted
to READ_ONCE or ASSIGN once, lets tighten ACCESS_ONCE to only
work on scalar types.
This variant was proposed by Alexei Starovoitov.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Feedback has shown that WRITE_ONCE(x, val) is easier to use than
ASSIGN_ONCE(val,x).
There are no in-tree users yet, so lets change it for 3.19.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CPUs without single-byte and double-byte loads and stores place some
"interesting" requirements on concurrent code. For example (adapted
from Peter Hurley's test code), suppose we have the following structure:
struct foo {
spinlock_t lock1;
spinlock_t lock2;
char a; /* Protected by lock1. */
char b; /* Protected by lock2. */
};
struct foo *foop;
Of course, it is common (and good) practice to place data protected
by different locks in separate cache lines. However, if the locks are
rarely acquired (for example, only in rare error cases), and there are
a great many instances of the data structure, then memory footprint can
trump false-sharing concerns, so that it can be better to place them in
the same cache cache line as above.
But if the CPU does not support single-byte loads and stores, a store
to foop->a will do a non-atomic read-modify-write operation on foop->b,
which will come as a nasty surprise to someone holding foop->lock2. So we
now require CPUs to support single-byte and double-byte loads and stores.
Therefore, this commit adjusts the definition of __native_word() to allow
these sizes to be used by smp_load_acquire() and smp_store_release().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
ACCESS_ONCE does not work reliably on non-scalar types. For
example gcc 4.6 and 4.7 might remove the volatile tag for such
accesses during the SRA (scalar replacement of aggregates) step
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145)
Let's provide READ_ONCE/ASSIGN_ONCE that will do all accesses via
scalar types as suggested by Linus Torvalds. Accesses larger than
the machines word size cannot be guaranteed to be atomic. These
macros will use memcpy and emit a build warning.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Pull more perf updates from Ingo Molnar:
"A second round of perf updates:
- wide reaching kprobes sanitization and robustization, with the hope
of fixing all 'probe this function crashes the kernel' bugs, by
Masami Hiramatsu.
- uprobes updates from Oleg Nesterov: tmpfs support, corner case
fixes and robustization work.
- perf tooling updates and fixes from Jiri Olsa, Namhyung Ki, Arnaldo
et al:
* Add support to accumulate hist periods (Namhyung Kim)
* various fixes, refactorings and enhancements"
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (101 commits)
perf: Differentiate exec() and non-exec() comm events
perf: Fix perf_event_comm() vs. exec() assumption
uprobes/x86: Rename arch_uprobe->def to ->defparam, minor comment updates
perf/documentation: Add description for conditional branch filter
perf/x86: Add conditional branch filtering support
perf/tool: Add conditional branch filter 'cond' to perf record
perf: Add new conditional branch filter 'PERF_SAMPLE_BRANCH_COND'
uprobes: Teach copy_insn() to support tmpfs
uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
perf/x86: Use common PMU interrupt disabled code
perf/ARM: Use common PMU interrupt disabled code
perf: Disable sampled events if no PMU interrupt
perf: Fix use after free in perf_remove_from_context()
perf tools: Fix 'make help' message error
perf record: Fix poll return value propagation
perf tools: Move elide bool into perf_hpp_fmt struct
perf tools: Remove elide setup for SORT_MODE__MEMORY mode
perf tools: Fix "==" into "=" in ui_browser__warning assignment
perf tools: Allow overriding sysfs and proc finding with env var
perf tools: Consider header files outside perf directory in tags target
...
Usually, BUG_ON and friends aren't even evaluated in sparse, but recently
compiletime_assert_atomic_type() was added, and that now results in a
sparse warning every time it is used.
The reason turns out to be the temporary variable, after it sparse no
longer considers the value to be a constant, and results in a warning and
an error. The error is the more annoying part of this as it suppresses
any further warnings in the same file, hiding other problems.
Unfortunately the condition cannot be simply expanded out to avoid the
temporary variable since it breaks compiletime_assert on old versions of
GCC such as GCC 4.2.4 which the latest metag compiler is based on.
Therefore #ifndef __CHECKER__ out the __compiletime_error_fallback which
uses the potentially negative size array to trigger a conditional compiler
error, so that sparse doesn't see it.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Luciano Coelho <luciano.coelho@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Introduce NOKPROBE_SYMBOL() macro which builds a kprobes
blacklist at kernel build time.
The usage of this macro is similar to EXPORT_SYMBOL(),
placed after the function definition:
NOKPROBE_SYMBOL(function);
Since this macro will inhibit inlining of static/inline
functions, this patch also introduces a nokprobe_inline macro
for static/inline functions. In this case, we must use
NOKPROBE_SYMBOL() for the inline function caller.
When CONFIG_KPROBES=y, the macro stores the given function
address in the "_kprobe_blacklist" section.
Since the data structures are not fully initialized by the
macro (because there is no "size" information), those
are re-initialized at boot time by using kallsyms.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/20140417081705.26341.96719.stgit@ltc230.yrl.intra.hitachi.co.jp
Cc: Alok Kataria <akataria@vmware.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jan-Simon Möller <dl9pf@gmx.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-sparse@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add a compiler-clang.h file to add specific macros needed for compiling the
kernel with clang.
Initially the only override required is the macro for silencing the
compiler for a purposefully uninintialized variable.
Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
A number of situations currently require the heavyweight smp_mb(),
even though there is no need to order prior stores against later
loads. Many architectures have much cheaper ways to handle these
situations, but the Linux kernel currently has no portable way
to make use of them.
This commit therefore supplies smp_load_acquire() and
smp_store_release() to remedy this situation. The new
smp_load_acquire() primitive orders the specified load against
any subsequent reads or writes, while the new smp_store_release()
primitive orders the specifed store against any prior reads or
writes. These primitives allow array-based circular FIFOs to be
implemented without an smp_mb(), and also allow a theoretical
hole in rcu_assign_pointer() to be closed at no additional
expense on most architectures.
In addition, the RCU experience transitioning from explicit
smp_read_barrier_depends() and smp_wmb() to rcu_dereference()
and rcu_assign_pointer(), respectively resulted in substantial
improvements in readability. It therefore seems likely that
replacing other explicit barriers with smp_load_acquire() and
smp_store_release() will provide similar benefits. It appears
that roughly half of the explicit barriers in core kernel code
might be so replaced.
[Changelog by PaulMck]
Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Victor Kaplansky <VICTORK@il.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/20131213150640.908486364@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Disabling compiler optimizations can be fragile, since a new
optimization could be added to -O0 or -Os that breaks the assumptions
the code is making.
Instead of disabling compiler optimizations, use a dummy inline assembly
(based on RELOC_HIDE) to block the problematic kinds of optimization,
while still allowing other optimizations to be applied to the code.
The dummy inline assembly is added after every OR, and has the
accumulator variable as its input and output. The compiler is forced to
assume that the dummy inline assembly could both depend on the
accumulator variable and change the accumulator variable, so it is
forced to compute the value correctly before the inline assembly, and
cannot assume anything about its value after the inline assembly.
This change should be enough to make crypto_memneq work correctly (with
data-independent timing) even if it is inlined at its call sites. That
can be done later in a followup patch.
Compile-tested on x86_64.
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.eti.br>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Currently, __kprobes is defined in linux/kprobes.h which
is too big to be included in small or basic headers
that want to make use of this simple attribute.
So move __kprobes definition into linux/compiler.h
in which other compiler attributes are defined.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Timo Juhani Lindfors <timo.lindfors@iki.fi>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20130404104049.21071.20908.stgit@mhiramat-M0-7522
[ Improved the attribute explanation a bit. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Introduce compiletime_assert to compiler.h, which moves the details of
how to break a build and emit an error message for a specific compiler
to the headers where these details should be. Following in the
tradition of the POSIX assert macro, compiletime_assert creates a
build-time error when the supplied condition is *false*.
Next, we add BUILD_BUG_ON_MSG to bug.h which simply wraps
compiletime_assert, inverting the logic, so that it fails when the
condition is *true*, consistent with the language "build bug on." This
macro allows you to specify the error message you want emitted when the
supplied condition is true.
Finally, we remove all other code from bug.h that mucks with these
details (BUILD_BUG & BUILD_BUG_ON), and have them all call
BUILD_BUG_ON_MSG. This not only reduces source code bloat, but also
prevents the possibility of code being changed for one macro and not for
the other (which was previously the case for BUILD_BUG and
BUILD_BUG_ON).
Since __compiletime_error_fallback is now only used in compiler.h, I'm
considering it a private macro and removing the double negation that's
now extraneous.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Prior to the introduction of __attribute__((error("msg"))) in gcc 4.3,
creating compile-time errors required a little trickery.
BUILD_BUG{,_ON} uses this attribute when available to generate
compile-time errors, but also uses the negative-sized array trick for
older compilers, resulting in two error messages in some cases. The
reason it's "some" cases is that as of gcc 4.4, the negative-sized array
will not create an error in some situations, like inline functions.
This patch replaces the negative-sized array code with the new
__compiletime_error_fallback() macro which expands to the same thing
unless the the error attribute is available, in which case it expands to
do{}while(0), resulting in exactly one compile-time error on all
versions of gcc.
Note that we are not changing the negative-sized array code for the
unoptimized version of BUILD_BUG_ON, since it has the potential to catch
problems that would be disabled in later versions of gcc were
__compiletime_error_fallback used. The reason is that that an
unoptimized build can't always remove calls to an error-attributed
function call (like we are using) that should effectively become dead
code if it were optimized. However, using a negative-sized array with a
similar value will not result in an false-positive (error). The only
caveat being that it will also fail to catch valid conditions, which we
should be expecting in an unoptimized build anyway.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__linktime_error() does the same thing as __compiletime_error() and is
only used in bug.h. Since the macro defines a function attribute that
will cause a failure at compile-time (not link-time), it makes more sense
to keep __compiletime_error(), which is also neatly mated with
__compiletime_warning().
Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
to verify the source of the module (ChromeOS) and/or use standard IMA on it
or other security hooks.
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Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
Pull module update from Rusty Russell:
"Nothing all that exciting; a new module-from-fd syscall for those who
want to verify the source of the module (ChromeOS) and/or use standard
IMA on it or other security hooks."
* tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux:
MODSIGN: Fix kbuild output when using default extra_certificates
MODSIGN: Avoid using .incbin in C source
modules: don't hand 0 to vmalloc.
module: Remove a extra null character at the top of module->strtab.
ASN.1: Use the ASN1_LONG_TAG and ASN1_INDEFINITE_LENGTH constants
ASN.1: Define indefinite length marker constant
moduleparam: use __UNIQUE_ID()
__UNIQUE_ID()
MODSIGN: Add modules_sign make target
powerpc: add finit_module syscall.
ima: support new kernel module syscall
add finit_module syscall to asm-generic
ARM: add finit_module syscall to ARM
security: introduce kernel_module_from_file hook
module: add flags arg to sys_finit_module()
module: add syscall to load module from fd
linux/compiler.h has macros to denote functions that acquire or release
locks, but not to denote functions called with a lock held that return
with the lock still held. Add a __must_hold macro to cover that case.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reported-by: Ed Cashin <ecashin@coraid.com>
Tested-by: Ed Cashin <ecashin@coraid.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Jan Beulich points out __COUNTER__ (gcc 4.3 and above), so let's use
that to create unique ids. This is better than __LINE__ which we use
today, so provide a wrapper.
Stanislaw Gruszka <sgruszka@redhat.com> reported that some module parameters
start with a digit, so we need to prepend when we for the unique id.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Jan Beulich <jbeulich@suse.com>
gcc 4.6+ has support for a externally_visible attribute that prevents the
optimizer from optimizing unused symbols away. Add a __visible macro to
use it with that compiler version or later.
This is used (at least) by the "Link Time Optimization" patchset.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We can place this in definitions that we expect the compiler to remove by
dead code elimination. If this assertion fails, we get a nice error
message at build time.
The GCC function attribute error("message") was added in version 4.3, so
we define a new macro __linktime_error(message) to expand to this for
GCC-4.3 and later. This will give us an error diagnostic from the
compiler on the line that fails. For other compilers
__linktime_error(message) expands to nothing, and we have to be content
with a link time error, but at least we will still get a build error.
BUILD_BUG() expands to the undefined function __build_bug_failed() and
will fail at link time if the compiler ever emits code for it. On GCC-4.3
and later, attribute((error())) is used so that the failure will be noted
at compile time instead.
Signed-off-by: David Daney <david.daney@cavium.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: DM <dm.n9107@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit provides definitions for the __rcu annotation defined earlier.
This annotation permits sparse to check for correct use of RCU-protected
pointers. If a pointer that is annotated with __rcu is accessed
directly (as opposed to via rcu_dereference(), rcu_assign_pointer(),
or one of their variants), sparse can be made to complain. To enable
such complaints, use the new default-disabled CONFIG_SPARSE_RCU_POINTER
kernel configuration option. Please note that these sparse complaints are
intended to be a debugging aid, -not- a code-style-enforcement mechanism.
There are special rcu_dereference_protected() and rcu_access_pointer()
accessors for use when RCU read-side protection is not required, for
example, when no other CPU has access to the data structure in question
or while the current CPU hold the update-side lock.
This patch also updates a number of docbook comments that were showing
their age.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christopher Li <sparse@chrisli.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit defines an __rcu API, but provides only vacuous definitions
for it. This breaks dependencies among most of the subsequent patches,
allowing them to reach mainline asynchronously via whatever trees are
appropriate.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Josh Triplett <josh@joshtriplett.org>
