[PATCH] jump_label: align jump_entry table to at least 4-bytes

Michael Ellerman
2017-03-01T06:34:51Z

Jason Baron <jbaron@akamai.com> 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.

cheers