[v3] x86/eal: gcc 10 ignore stringop-overflow warnings

stringop-overflow warns when it sees a possible overflow
in a string operation.

In the rte_memcpy functions different branches are taken
depending on the size. stringop-overflow is raised for the
branches in the function where it sees the static size of the
src could be overflowed.

However, in reality a correct size argument and in some cases
dynamic allocation would ensure that this does not happen.

For example, in the case below for key, the correct path will be
chosen in rte_memcpy_generic at runtime based on the size argument
but as some paths in the function could lead to a cast to 32 bytes
a warning is raised.

In function ‘_mm256_storeu_si256’,
inlined from ‘rte_memcpy_generic’
at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:315:2,
inlined from ‘iavf_configure_rss_key’
at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:869:10:

/usr/lib/gcc/x86_64-redhat-linux/10/include/avxintrin.h:928:8:
warning: writing 32 bytes into a region of size 1 [-Wstringop-overflow=]
  928 |   *__P = __A;
      |   ~~~~~^~~~~
In file included
from ../drivers/net/iavf/../../common/iavf/iavf_prototype.h:10,
from ../drivers/net/iavf/iavf.h:9,
from ../drivers/net/iavf/iavf_vchnl.c:22:

../drivers/net/iavf/iavf_vchnl.c:
In function ‘iavf_configure_rss_key’:

../drivers/net/iavf/../../common/iavf/virtchnl.h:508:5:
note: at offset 0 to object ‘key’ with size 1 declared here
  508 |  u8 key[1];         /* RSS hash key, packed bytes */
      |     ^~~

Ignore the stringop-overflow warnings for rte_memcpy.h functions.

Bugzilla ID: 394
Bugzilla ID: 421

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>

---
v3: Add push/pop to not leak the ignore warning
v2: Change from a global disable to just disabling for x86/rte_memcpy.h
---
 lib/librte_eal/x86/include/rte_memcpy.h | 9 +++++++++
 1 file changed, 9 insertions(+)
  

On Fri, Apr 17, 2020 at 5:44 PM Kevin Traynor <ktraynor@redhat.com> wrote:
>
> stringop-overflow warns when it sees a possible overflow
> in a string operation.
>
> In the rte_memcpy functions different branches are taken
> depending on the size. stringop-overflow is raised for the
> branches in the function where it sees the static size of the
> src could be overflowed.
>
> However, in reality a correct size argument and in some cases
> dynamic allocation would ensure that this does not happen.
>
> For example, in the case below for key, the correct path will be
> chosen in rte_memcpy_generic at runtime based on the size argument
> but as some paths in the function could lead to a cast to 32 bytes
> a warning is raised.
>
> In function ‘_mm256_storeu_si256’,
> inlined from ‘rte_memcpy_generic’
> at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:315:2,
> inlined from ‘iavf_configure_rss_key’
> at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:869:10:
>
> /usr/lib/gcc/x86_64-redhat-linux/10/include/avxintrin.h:928:8:
> warning: writing 32 bytes into a region of size 1 [-Wstringop-overflow=]
>   928 |   *__P = __A;
>       |   ~~~~~^~~~~
> In file included
> from ../drivers/net/iavf/../../common/iavf/iavf_prototype.h:10,
> from ../drivers/net/iavf/iavf.h:9,
> from ../drivers/net/iavf/iavf_vchnl.c:22:
>
> ../drivers/net/iavf/iavf_vchnl.c:
> In function ‘iavf_configure_rss_key’:
>
> ../drivers/net/iavf/../../common/iavf/virtchnl.h:508:5:
> note: at offset 0 to object ‘key’ with size 1 declared here
>   508 |  u8 key[1];         /* RSS hash key, packed bytes */
>       |     ^~~
>
> Ignore the stringop-overflow warnings for rte_memcpy.h functions.
>
> Bugzilla ID: 394
> Bugzilla ID: 421
>

Cc: stable@dpdk.org

> Signed-off-by: Kevin Traynor <ktraynor@redhat.com>

Acked-by: Bruce Richardson <bruce.richardson@@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>


Applied, thanks.