On 01/30/2016 03:36 AM, Mike Krinkin wrote: > Hi, > > option CONFIG_UBSAN_ALIGNMENT breaks x86-64 kernel with lockdep enabled, > i. e kernel with CONFIG_UBSAN_ALIGNMENT fails to load without even any > error message. > > The problem is that ubsan callbacks use spinlocks and might be called > before lockdep is initialized. Particularly this line in the > reserve_ebda_region function causes problem: > > lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); > > If i put lockdep_init() before reserve_ebda_region call in > x86_64_start_reservations kernel loads well. Since CONFIG_UBSAN_ALIGNMENT > isn't useful for x86 anyway it might be better to disable this option for > x86 arch? >
Alignment checks could be useful even on x86, because there are unaligned accesses in generic code. I think we can disable alignment instrumentation for arch/x86 directory only.
