Commit Graph

6 Commits

Author SHA1 Message Date
Mark Rutland dc1b4df09a atomics: Fix atomic64_{read_acquire,set_release} fallbacks
Arnd reports that on 32-bit architectures, the fallbacks for
atomic64_read_acquire() and atomic64_set_release() are broken as they
use smp_load_acquire() and smp_store_release() respectively, which do
not work on types larger than the native word size.

Since those contain compiletime_assert_atomic_type(), any attempt to use
those fallbacks will result in a build-time error. e.g. with the
following added to arch/arm/kernel/setup.c:

| void test_atomic64(atomic64_t *v)
| {
|        atomic64_set_release(v, 5);
|        atomic64_read_acquire(v);
| }

The compiler will complain as follows:

| In file included from <command-line>:
| In function 'arch_atomic64_set_release',
|     inlined from 'test_atomic64' at ./include/linux/atomic/atomic-instrumented.h:669:2:
| ././include/linux/compiler_types.h:346:38: error: call to '__compiletime_assert_9' declared with attribute error: Need native word sized stores/loads for atomicity.
|   346 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|       |                                      ^
| ././include/linux/compiler_types.h:327:4: note: in definition of macro '__compiletime_assert'
|   327 |    prefix ## suffix();    \
|       |    ^~~~~~
| ././include/linux/compiler_types.h:346:2: note: in expansion of macro '_compiletime_assert'
|   346 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|       |  ^~~~~~~~~~~~~~~~~~~
| ././include/linux/compiler_types.h:349:2: note: in expansion of macro 'compiletime_assert'
|   349 |  compiletime_assert(__native_word(t),    \
|       |  ^~~~~~~~~~~~~~~~~~
| ./include/asm-generic/barrier.h:133:2: note: in expansion of macro 'compiletime_assert_atomic_type'
|   133 |  compiletime_assert_atomic_type(*p);    \
|       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| ./include/asm-generic/barrier.h:164:55: note: in expansion of macro '__smp_store_release'
|   164 | #define smp_store_release(p, v) do { kcsan_release(); __smp_store_release(p, v); } while (0)
|       |                                                       ^~~~~~~~~~~~~~~~~~~
| ./include/linux/atomic/atomic-arch-fallback.h:1270:2: note: in expansion of macro 'smp_store_release'
|  1270 |  smp_store_release(&(v)->counter, i);
|       |  ^~~~~~~~~~~~~~~~~
| make[2]: *** [scripts/Makefile.build:288: arch/arm/kernel/setup.o] Error 1
| make[1]: *** [scripts/Makefile.build:550: arch/arm/kernel] Error 2
| make: *** [Makefile:1831: arch/arm] Error 2

Fix this by only using smp_load_acquire() and smp_store_release() for
native atomic types, and otherwise falling back to the regular barriers
necessary for acquire/release semantics, as we do in the more generic
acquire and release fallbacks.

Since the fallback templates are used to generate the atomic64_*() and
atomic_*() operations, the __native_word() check is added to both. For
the atomic_*() operations, which are always 32-bit, the __native_word()
check is redundant but not harmful, as it is always true.

For the example above this works as expected on 32-bit, e.g. for arm
multi_v7_defconfig:

| <test_atomic64>:
|         push    {r4, r5}
|         dmb     ish
|         pldw    [r0]
|         mov     r2, #5
|         mov     r3, #0
|         ldrexd  r4, [r0]
|         strexd  r4, r2, [r0]
|         teq     r4, #0
|         bne     484 <test_atomic64+0x14>
|         ldrexd  r2, [r0]
|         dmb     ish
|         pop     {r4, r5}
|         bx      lr

... and also on 64-bit, e.g. for arm64 defconfig:

| <test_atomic64>:
|         bti     c
|         paciasp
|         mov     x1, #0x5
|         stlr    x1, [x0]
|         ldar    x0, [x0]
|         autiasp
|         ret

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20220207101943.439825-1-mark.rutland@arm.com
2022-02-11 12:13:56 +01:00
Mark Rutland f3e615b4db locking/atomic: remove ARCH_ATOMIC remanants
Now that gen-atomic-fallback.sh is only used to generate the arch_*
fallbacks, we don't need to also generate the non-arch_* forms, and can
removethe infrastructure this needed.

There is no change to any of the generated headers as a result of this
patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210713105253.7615-3-mark.rutland@arm.com
2021-07-16 18:46:44 +02:00
Peter Zijlstra 37f8173dd8 locking/atomics: Flip fallbacks and instrumentation
Currently instrumentation of atomic primitives is done at the architecture
level, while composites or fallbacks are provided at the generic level.

The result is that there are no uninstrumented variants of the
fallbacks. Since there is now need of such variants to isolate text poke
from any form of instrumentation invert this ordering.

Doing this means moving the instrumentation into the generic code as
well as having (for now) two variants of the fallbacks.

Notes:

 - the various *cond_read* primitives are not proper fallbacks
   and got moved into linux/atomic.c. No arch_ variants are
   generated because the base primitives smp_cond_load*()
   are instrumented.

 - once all architectures are moved over to arch_atomic_ one of the
   fallback variants can be removed and some 2300 lines reclaimed.

 - atomic_{read,set}*() are no longer double-instrumented

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lkml.kernel.org/r/20200505134058.769149955@linutronix.de
2020-06-11 08:03:24 +02:00
Marco Elver 765dcd2099 asm-generic/atomic: Use __always_inline for fallback wrappers
Use __always_inline for atomic fallback wrappers. When building for size
(CC_OPTIMIZE_FOR_SIZE), some compilers appear to be less inclined to
inline even relatively small static inline functions that are assumed to
be inlinable such as atomic ops. This can cause problems, for example in
UACCESS regions.

While the fallback wrappers aren't pure wrappers, they are trivial
nonetheless, and the function they wrap should determine the final
inlining policy.

For x86 tinyconfig we observe:
- vmlinux baseline: 1315988
- vmlinux with patch: 1315928 (-60 bytes)

[ tglx: Cherry-picked from KCSAN ]

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2020-06-11 08:03:24 +02:00
Ingo Molnar 4d8e5cd233 locking/atomics: Fix scripts/atomic/ script permissions
Mark all these scripts executable.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: boqun.feng@gmail.com
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-11-01 12:45:46 +01:00
Mark Rutland ace9bad4df locking/atomics: Add common header generation files
To minimize repetition, to allow for future rework, and to ensure
regularity of the various atomic APIs, we'd like to automatically
generate (the bulk of) a number of headers related to atomics.

This patch adds the infrastructure to do so, leaving actual conversion
of headers to subsequent patches. This infrastructure consists of:

* atomics.tbl - a table describing the functions in the atomics API,
  with names, prototypes, and metadata describing the variants that
  exist (e.g fetch/return, acquire/release/relaxed). Note that the
  return type is dependent on the particular variant.

* atomic-tbl.sh - a library of routines useful for dealing with
  atomics.tbl (e.g. querying which variants exist, or generating
  argument/parameter lists for a given function variant).

* gen-atomic-fallback.sh - a script which generates a header of
  fallbacks, covering cases where architecture omit certain functions
  (e.g. omitting relaxed variants).

* gen-atomic-long.sh - a script which generates wrappers providing the
  atomic_long API atomic of the relevant atomic or atomic64 API,
  ensuring the APIs are consistent.

* gen-atomic-instrumented.sh - a script which generates atomic* wrappers
  atop of arch_atomic* functions, with automatically generated KASAN
  instrumentation.

* fallbacks/* - a set of fallback implementations for atomics, which
  should be used when no implementation of a given atomic is provided.
  These are used by gen-atomic-fallback.sh to generate fallbacks, and
  these are also used by other scripts to determine the set of optional
  atomics (as required to generate preprocessor guards correctly).

  Fallbacks may use the following variables:

  ${atomic}     atomic prefix: atomic/atomic64/atomic_long, which can be
		used to derive the atomic type, and to prefix functions

  ${int}        integer type: int/s64/long

  ${pfx}        variant prefix, e.g. fetch_

  ${name}       base function name, e.g. add

  ${sfx}        variant suffix, e.g. _return

  ${order}      order suffix, e.g. _relaxed

  ${atomicname} full name, e.g. atomic64_fetch_add_relaxed

  ${ret}        return type of the function, e.g. void

  ${retstmt}    a return statement (with a trailing space), unless the
                variant returns void

  ${params}     parameter list for the function declaration, e.g.
                "int i, atomic_t *v"

  ${args}       argument list for invoking the function, e.g. "i, v"

  ... for clarity, ${ret}, ${retstmt}, ${params}, and ${args} are
  open-coded for fallbacks where these do not vary, or are critical to
  understanding the logic of the fallback.

The MAINTAINERS entry for the atomic infrastructure is updated to cover
the new scripts.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Link: http://lkml.kernel.org/r/20180904104830.2975-2-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-11-01 11:00:36 +01:00