[dpdk-dev] [PATCH] net/i40e: fix gcc 11 build warning on POWER architecture

[Zhang, Qi Z]

Hi David:

	Not sure if below patch also help to solve the issue you met on power arch,
	Looks like the error is same: "writing 1 byte into a region of size 0"
	would you help to check?

commit 1b0f3a18145468c309bb5a8cb98a8aa29af059e7
Author: Ferruh Yigit <ferruh.yigit at intel.com>
Date:   Fri Oct 29 11:37:01 2021 +0100

    net/i40e: fix build for 32-bit

    Got error with: gcc 11.2.1 "cc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1)"

    Build error:
    In function 'i40e_flow_parse_fdir_pattern',
        inlined from 'i40e_flow_parse_fdir_filter'
        at ../drivers/net/i40e/i40e_flow.c:3274:8:
    ../drivers/net/i40e/i40e_flow.c:3052:69:
        error: writing 1 byte into a region of size 0
        [-Werror=stringop-overflow=]
     3052 |                         filter->input.flow_ext.flexbytes[j] =
          |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
     3053 |                                 raw_spec->pattern[i];
          |                                 ~~~~~~~~~~~~~~~~~~~~
    In file included from ../drivers/net/i40e/i40e_flow.c:25:
      ../drivers/net/i40e/i40e_flow.c:
      In function 'i40e_flow_parse_fdir_filter':
      ../drivers/net/i40e/i40e_ethdev.h:638:17:
      note: at offset 16 into destination object 'flexbytes' of size 16
      638 |         uint8_t flexbytes[RTE_ETH_FDIR_MAX_FLEXLEN];
          |                 ^~~~~~~~~

    Fixing by adding range checks.

    Fixes: 6ced3dd72f5f ("net/i40e: support flexible payload parsing for FDIR")
    Cc: stable at dpdk.org

Thanks
Qi
	 

> -----Original Message-----
> From: dev <dev-bounces at dpdk.org> On Behalf Of David Christensen
> Sent: Friday, October 15, 2021 3:05 AM
> To: dev at dpdk.org; Xing, Beilei <beilei.xing at intel.com>
> Cc: stable at dpdk.org; David Christensen <drc at linux.vnet.ibm.com>
> Subject: [dpdk-dev] [PATCH] net/i40e: fix gcc 11 build warning on POWER
> architecture
> 
> Building DPDK with a gcc 11 based compiler such as the IBM Advanced
> Toolchain 15 (1) generates a stringop-overflow warning when using -O3
> optimization (DPDK default for production releases):
> 
> writing 1 byte into a region of size 0 [-Wstringop-overflow=]
> 
> The issue has been reported to the gcc project (2) but can be resolved by
> preventing the compiler from unrolling the loop as part of the -O3
> optimization.
> 
> (1) https://www.ibm.com/support/pages/advance-toolchain-linux-power
> (2) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102316
> 
> Bugzilla ID: 743
> 
> Signed-off-by: David Christensen <drc at linux.vnet.ibm.com>
> ---
>  drivers/net/i40e/i40e_flow.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/i40e/i40e_flow.c b/drivers/net/i40e/i40e_flow.c index
> e41a84f1d7..17ab7ad9b9 100644
> --- a/drivers/net/i40e/i40e_flow.c
> +++ b/drivers/net/i40e/i40e_flow.c
> @@ -3047,6 +3047,10 @@ i40e_flow_parse_fdir_pattern(struct rte_eth_dev
> *dev,
>  				return -rte_errno;
>  			}
> 
> +#if defined(RTE_ARCH_PPC_64) && defined(RTE_TOOLCHAIN_GCC) && \
> +(GCC_VERSION >= 110000) #pragma GCC unroll 1 #endif
>  			for (i = 0; i < raw_spec->length; i++) {
>  				j = i + next_dst_off;
>  				filter->input.flow_ext.flexbytes[j] =
> --
> 2.27.0