On Thu, 7 Dec 2017 16:31:23 +0300 Andrey Ryabinin <[email protected]> wrote:
> On 12/07/2017 03:49 AM, Andrew Morton wrote: > > (correcting Andrey's email address) > > > > > > From: Ding Tianhong <[email protected]> > > Subject: lib/ubsan.c: don't handle misaligned address when kernel supports > > unaligned access > > > > ubsan reports a warning like: > > > > UBSAN: Undefined behaviour in ../include/linux/etherdevice.h:386:9 > > load of misaligned address ffffffc069ba0482 for type 'long unsigned int' > > which requires 8 byte alignment > > CPU: 0 PID: 901 Comm: sshd Not tainted 4.xx+ #1 > > Hardware name: linux,dummy-virt (DT) > > Call trace: > > [<ffffffc000093600>] dump_backtrace+0x0/0x348 > > [<ffffffc000093968>] show_stack+0x20/0x30 > > [<ffffffc001651664>] dump_stack+0x144/0x1b4 > > [<ffffffc0016519b0>] ubsan_epilogue+0x18/0x74 > > [<ffffffc001651bac>] __ubsan_handle_type_mismatch+0x1a0/0x25c > > [<ffffffc00125d8a0>] dev_gro_receive+0x17d8/0x1830 > > [<ffffffc00125d928>] napi_gro_receive+0x30/0x158 > > [<ffffffc000f4f93c>] virtnet_receive+0xad4/0x1fa8 > > > > The reason is that when enabling the CONFIG_UBSAN_ALIGNMENT, ubsan will > > report the unaligned access even if the system supports it > > (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). This produces a lot of noise > > in the log and causes confusion. > > > > NACK. This doesn't make sense. If you don't want to see misaligned access > reports > you simply shouldn't enable CONFIG_UBSAN_ALIGNMENT. So should UBSAN Kconfig disable CONFIG_UBSAN_ALIGNMENT when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y?
