s390: workaround invalid gcc-11 out of bounds read warning
authorHeiko Carstens <hca@linux.ibm.com>
Tue, 17 Jan 2023 18:00:59 +0000 (19:00 +0100)
committerHeiko Carstens <hca@linux.ibm.com>
Tue, 17 Jan 2023 18:00:59 +0000 (19:00 +0100)
commit41e1992665a2701fa025a8b76970c43b4148446f
treee104e90d36c50f476f98594a840f26576276dc5c
parent1ecf7bd9c267ab85aff3c4a17fe56bc9754a13be
s390: workaround invalid gcc-11 out of bounds read warning

GCC 11.1.0 and 11.2.0 generate a wrong warning when compiling the
kernel e.g. with allmodconfig:

arch/s390/kernel/setup.c: In function ‘setup_lowcore_dat_on’:
./include/linux/fortify-string.h:57:33: error: ‘__builtin_memcpy’ reading 128 bytes from a region of size 0 [-Werror=stringop-overread]
...
arch/s390/kernel/setup.c:526:9: note: in expansion of macro ‘memcpy’
  526 |         memcpy(abs_lc->cregs_save_area, S390_lowcore.cregs_save_area,
      |         ^~~~~~

This could be addressed by using absolute_pointer() with the
S390_lowcore macro, but this is not a good idea since this generates
worse code for performance critical paths.

Therefore simply use a for loop to copy the array in question and get
rid of the warning.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
arch/s390/kernel/setup.c