net/i40e: fix gcc 11 build warning on POWER architecture

-----Original Message-----
From: dev <[email protected]> On Behalf Of David Christensen
Sent: Friday, October 15, 2021 3:05 AM
To: [email protected]; Xing, Beilei <[email protected]>
Cc: [email protected]; David Christensen <[email protected]>
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 <[email protected]>

---
 drivers/net/i40e/i40e_flow.c | 4 ++++
 1 file changed, 4 insertions(+)

drivers/net/i40e/i40e_flow.c index renamed from drivers/net/i40e/i40e_flow.c +0 -0

e41a84f1d7..17ab7ad9b9 100644

drivers/net/i40e/i40e_flow.c +2 -1

@@ -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

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 <[email protected]>
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: [email protected]