James,
Can you merge this patch for 4.6?
On Tue, Apr 19, 2016 at 08:56:00AM -0500, Josh Poimboeuf wrote:
> objtool reports [1] the following warning:
>
> drivers/scsi/qla2xxx/qla_attr.o: warning: objtool: qla2x00_get_host_fabric_name() falls through to next function qla2x00_get_starget_port_name()
>
> This warning is due to a gcc bug [2] which causes corrupt code:
>
> 0000000000002f53 <qla2x00_get_host_fabric_name>:
> 2f53: 55 push %rbp
> 2f54: 48 89 e5 mov %rsp,%rbp
>
> 0000000000002f57 <qla2x00_get_fc_host_stats>:
> 2f57: 55 push %rbp
> 2f58: b9 e8 00 00 00 mov $0xe8,%ecx
> 2f5d: 48 89 e5 mov %rsp,%rbp
> ...
>
> Note that qla2x00_get_host_fabric_name() is inexplicably truncated after
> setting up the frame pointer. It falls through to the next function,
> which is very bad.
>
> It occurs with the combination of the following two recent commits:
>
> bc27fb68aaad ("include/uapi/linux/byteorder, swab: force inlining of some byteswap operations")
> ef3fb2422ffe ("scsi: fc: use get/put_unaligned64 for wwn access")
>
> The call chain which appears to trigger the problem is:
>
> qla2x00_get_host_fabric_name()
> wwn_to_u64()
> get_unaligned_be64()
> be64_to_cpup()
> __be64_to_cpup()
>
> The bug requires very specific conditions to trigger. According to Martin
> Jambor (from the gcc bugzilla):
>
> "This bug can occur when an inlineable function containing a call to
> __builtin_constant_p, which checks a parameter or a value it
> references and a (possibly indirect) caller of the function actually
> passes a constant, but stores it using a type of a different size."
>
> There's no reliable way to avoid (or even detect) the bug. Until it
> gets fixed in released versions of gcc, the least intrusive workaround
> for this particular issue is to force the wwn conversion functions to be
> inlined.
>
> [1] https://lists.01.org/pipermail/kbuild-all/2016-April/019579.html
> [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
>
> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
> include/scsi/scsi_transport_fc.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/scsi/scsi_transport_fc.h b/include/scsi/scsi_transport_fc.h
> index bf66ea6..1919cd4 100644
> --- a/include/scsi/scsi_transport_fc.h
> +++ b/include/scsi/scsi_transport_fc.h
> @@ -796,12 +796,12 @@ fc_remote_port_chkready(struct fc_rport *rport)
> return result;
> }
>
> -static inline u64 wwn_to_u64(u8 *wwn)
> +static __always_inline u64 wwn_to_u64(u8 *wwn)
> {
> return get_unaligned_be64(wwn);
> }
>
> -static inline void u64_to_wwn(u64 inm, u8 *wwn)
> +static __always_inline void u64_to_wwn(u64 inm, u8 *wwn)
> {
> put_unaligned_be64(inm, wwn);
> }
> --
> 2.4.11
>
--
Josh
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