lib/ubsan: default UBSAN_ALIGNMENT to not set
authorAnders Roxell <anders.roxell@linaro.org>
Fri, 8 Mar 2019 00:30:16 +0000 (16:30 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 8 Mar 2019 02:32:02 +0000 (18:32 -0800)
commit1a6a1dbeb72fce7517665b365085ea405490c2d5
treee485878f879abac0c03ab366352bfee1cfc2aa61
parent663cb6340c6e84fe29aa6d0fa63d85ea6bd6cd19
lib/ubsan: default UBSAN_ALIGNMENT to not set

When booting an allmodconfig kernel, there are a lot of false-positives.
With a message like this 'UBSAN: Undefined behaviour in...' with a call
trace that follows.

UBSAN warnings are a result of enabling noisy CONFIG_UBSAN_ALIGNMENT
which is disabled by default if HAVE_EFFICIENT_UNALIGNED_ACCESS=y.

It's noisy even if don't have efficient unaligned access, e.g.  people
often add __cacheline_aligned_in_smp in structs, but forget to align
allocations of such struct (kmalloc() give 8-byte alignment in worst
case).

Rework so that when building a allmodconfig kernel that turns everything
into '=m' or '=y' will turn off UBSAN_ALIGNMENT.

[aryabinin@virtuozzo.com: changelog addition]
Link: http://lkml.kernel.org/r/20181217150326.30933-1-anders.roxell@linaro.org
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/Kconfig.ubsan