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Date: Thu, 19 Oct 2023 13:07:52 +0800
From: kernel test robot <lkp@...el.com>
To: Shay Drory <shayd@...dia.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
Saeed Mahameed <saeedm@...dia.com>,
Moshe Shemesh <moshe@...dia.com>
Subject: include/linux/bitops.h:52:11: warning: array subscript 0 is outside
array bounds of 'long unsigned int[0]'
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: dd72f9c7e512da377074d47d990564959b772643
commit: b90ebfc018b087ba1e4981b298b58733236ff296 net/mlx5: Allocate command stats with xarray
date: 3 months ago
config: parisc-randconfig-r006-20230313 (https://download.01.org/0day-ci/archive/20231019/202310191307.RwgNqy0s-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231019/202310191307.RwgNqy0s-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310191307.RwgNqy0s-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from include/linux/kernel.h:22,
from arch/parisc/include/asm/bug.h:5,
from include/linux/bug.h:5,
from include/linux/thread_info.h:13,
from include/asm-generic/preempt.h:5,
from ./arch/parisc/include/generated/asm/preempt.h:1,
from include/linux/preempt.h:79,
from include/linux/spinlock.h:56,
from include/linux/wait.h:9,
from include/linux/wait_bit.h:8,
from include/linux/fs.h:6,
from include/linux/highmem.h:5,
from drivers/net/ethernet/mellanox/mlx5/core/main.c:33:
drivers/net/ethernet/mellanox/mlx5/core/main.c: In function 'mlx5_vf_get_core_dev':
>> include/linux/bitops.h:52:11: warning: array subscript 0 is outside array bounds of 'long unsigned int[0]' [-Warray-bounds=]
52 | __builtin_constant_p(*(const unsigned long *)(addr))) ? \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/bitops.h:61:41: note: in expansion of macro 'bitop'
61 | #define test_bit(nr, addr) bitop(_test_bit, nr, addr)
| ^~~~~
drivers/net/ethernet/mellanox/mlx5/core/main.c:2256:14: note: in expansion of macro 'test_bit'
2256 | if (!test_bit(MLX5_INTERFACE_STATE_UP, &mdev->intf_state)) {
| ^~~~~~~~
cc1: note: source object is likely at address zero
In file included from include/linux/bitops.h:34:
In function 'generic_test_bit',
inlined from 'mlx5_vf_get_core_dev' at drivers/net/ethernet/mellanox/mlx5/core/main.c:2256:7:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 0 is outside array bounds of 'long unsigned int[0]' [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
In function 'mlx5_vf_get_core_dev':
cc1: note: source object is likely at address zero
vim +52 include/linux/bitops.h
0e862838f29014 Alexander Lobakin 2022-06-24 35
b03fc1173c0c2b Alexander Lobakin 2022-06-24 36 /*
b03fc1173c0c2b Alexander Lobakin 2022-06-24 37 * Many architecture-specific non-atomic bitops contain inline asm code and due
b03fc1173c0c2b Alexander Lobakin 2022-06-24 38 * to that the compiler can't optimize them to compile-time expressions or
b03fc1173c0c2b Alexander Lobakin 2022-06-24 39 * constants. In contrary, generic_*() helpers are defined in pure C and
b03fc1173c0c2b Alexander Lobakin 2022-06-24 40 * compilers optimize them just well.
b03fc1173c0c2b Alexander Lobakin 2022-06-24 41 * Therefore, to make `unsigned long foo = 0; __set_bit(BAR, &foo)` effectively
b03fc1173c0c2b Alexander Lobakin 2022-06-24 42 * equal to `unsigned long foo = BIT(BAR)`, pick the generic C alternative when
b03fc1173c0c2b Alexander Lobakin 2022-06-24 43 * the arguments can be resolved at compile time. That expression itself is a
b03fc1173c0c2b Alexander Lobakin 2022-06-24 44 * constant and doesn't bring any functional changes to the rest of cases.
b03fc1173c0c2b Alexander Lobakin 2022-06-24 45 * The casts to `uintptr_t` are needed to mitigate `-Waddress` warnings when
b03fc1173c0c2b Alexander Lobakin 2022-06-24 46 * passing a bitmap from .bss or .data (-> `!!addr` is always true).
b03fc1173c0c2b Alexander Lobakin 2022-06-24 47 */
e69eb9c460f128 Alexander Lobakin 2022-06-24 48 #define bitop(op, nr, addr) \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 49 ((__builtin_constant_p(nr) && \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 50 __builtin_constant_p((uintptr_t)(addr) != (uintptr_t)NULL) && \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 51 (uintptr_t)(addr) != (uintptr_t)NULL && \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 @52 __builtin_constant_p(*(const unsigned long *)(addr))) ? \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 53 const##op(nr, addr) : op(nr, addr))
e69eb9c460f128 Alexander Lobakin 2022-06-24 54
:::::: The code at line 52 was first introduced by commit
:::::: b03fc1173c0c2bb8fad61902a862985cecdc4b1b bitops: let optimize out non-atomic bitops on compile-time constants
:::::: TO: Alexander Lobakin <alexandr.lobakin@...el.com>
:::::: CC: Yury Norov <yury.norov@...il.com>
--
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