On 30/05/2024 6:11 pm, Yury Norov wrote:
On Wed, May 29, 2024 at 04:12:25PM +0100, Robin Murphy wrote:
Hi Alexander,
On 27/03/2024 3:23 pm, Alexander Lobakin wrote:
Now that we have generic bitmap_read() and bitmap_write(), which are
inline and try to take care of non-bound-crossing and aligned cases
to keep them optimized, collapse bitmap_{get,set}_value8() into
simple wrappers around the former ones.
bloat-o-meter shows no difference in vmlinux and -2 bytes for
gpio-pca953x.ko, which says the optimization didn't suffer due to
that change. The converted helpers have the value width embedded
and always compile-time constant and that helps a lot.
This change appears to have introduced a build failure for me on arm64
(with GCC 9.4.0 from Ubuntu 20.04.02) - reverting b44759705f7d makes
these errors go away again:
In file included from drivers/gpio/gpio-pca953x.c:12:
drivers/gpio/gpio-pca953x.c: In function ‘pca953x_probe’:
./include/linux/bitmap.h:799:17: error: array subscript [1, 1024] is outside
array bounds of ‘long unsigned int[1]’ [-Werror=array-bounds]
799 | map[index + 1] &= BITMAP_FIRST_WORD_MASK(start + nbits);
| ^~
In file included from ./include/linux/atomic.h:5,
from drivers/gpio/gpio-pca953x.c:11:
drivers/gpio/gpio-pca953x.c:1015:17: note: while referencing ‘val’
1015 | DECLARE_BITMAP(val, MAX_LINE);
| ^~~
./include/linux/types.h:11:16: note: in definition of macro ‘DECLARE_BITMAP’
11 | unsigned long name[BITS_TO_LONGS(bits)]
| ^~~~
In file included from drivers/gpio/gpio-pca953x.c:12:
./include/linux/bitmap.h:800:17: error: array subscript [1, 1024] is outside
array bounds of ‘long unsigned int[1]’ [-Werror=array-bounds]
800 | map[index + 1] |= (value >> space);
| ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
In file included from ./include/linux/atomic.h:5,
from drivers/gpio/gpio-pca953x.c:11:
drivers/gpio/gpio-pca953x.c:1015:17: note: while referencing ‘val’
1015 | DECLARE_BITMAP(val, MAX_LINE);
| ^~~
./include/linux/types.h:11:16: note: in definition of macro ‘DECLARE_BITMAP’
11 | unsigned long name[BITS_TO_LONGS(bits)]
| ^~~~
I've not dug further since I don't have any interest in the pca953x
driver - it just happened to be enabled in my config, so for now I've
turned it off. However I couldn't obviously see any other reports of
this, so here it is.
It's a compiler false-positive. The straightforward fix is to disable the
warning
For gcc9+, and it's in Andrew Morton's tree alrady. but there's some discussion
ongoing on how it should be mitigated properlu:
https://lore.kernel.org/all/0ab2702f-8245-4f02-beb7-dcc7d79d5...@app.fastmail.com/T/
Ah, great! Guess I really should have scrolled further down my lore
search results - I assumed I was looking for any other reports of a
recent regression in mainline, not ones from 6 months ago :)
Cheers,
Robin.
