On 03/01/2017 11:40 AM, David Daney wrote: > On 02/28/2017 10:34 PM, Michael Ellerman wrote: >> Jason Baron <jbaron@xxxxxxxxxx> writes: >> ... >>> I also checked all the other .ko files and they were properly aligned. >>> So I think this should hopefully work, and I like that its not a >>> per-arch fix. >>> >>> Sachin, sorry to bother you again, but I'm hoping you can try David's >>> latest patch to scripts/module-common.lds, just to test in your setup. >> >> It does fix the problem. >> >> I was reproducing with crc_t10dif: >> >> [ 695.890552] ------------[ cut here ]------------ >> [ 695.890709] WARNING: CPU: 15 PID: 3019 at >> ../kernel/jump_label.c:287 static_key_set_entries+0x74/0xa0 >> [ 695.890710] Modules linked in: crc_t10dif(+) crct10dif_generic >> crct10dif_common ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat >> nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 xt_addrtype >> iptable_filter ip_tables xt_conntrack x_tables nf_nat nf_conntrack >> bridge stp llc dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio >> libcrc32c kvm virtio_balloon binfmt_misc autofs4 virtio_net virtio_pci >> virtio_ring virtio >> >> Which had: >> >> [21] __jump_table PROGBITS 0000000000000000 0004e8 >> 000018 00 WA 0 0 1 >> >> >> And now has: >> >> [18] __jump_table PROGBITS 0000000000000000 0004d0 >> 000018 00 WA 0 0 8 >> >> And all other modules have an alignment of 8 on __jump_table, as >> expected. >> >> I'm inclined to merge a version of the balign patch for powerpc anyway, >> just to be on the safe side. I guess the old code was coping fine with >> the unaligned keys, but it still makes me nervous. > > > The original "balign patch" has a couple of problems: > > 1) 4-byte alignment is not sufficient for 64-bit kernels > > 2) It is redundant if the linker script patch is accepted. > > The linker script patch seems reasonable to me. Maybe its worth adding a comment that the alignment is necessary because the core jump_label makes use of the 2 lsb bits of its __jump_table pointer due to commit: 3821fd3 jump_label: Reduce the size of struct static_key Also, in the comment it says that it fixes an oops. We hit a WARN_ON() not an oops, although bad things are likely to happen when the branch is updated. Thanks, -Jason
