netdev - [net-next 5/8] fm10k: cast page_addr to u8 * when incrementing it

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Date:   Sun,  4 Aug 2019 04:59:23 -0700
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Jacob Keller <jacob.e.keller@...el.com>, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com,
        Andrew Bowers <andrewx.bowers@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next 5/8] fm10k: cast page_addr to u8 * when incrementing it

From: Jacob Keller <jacob.e.keller@...el.com>

The page_addr variable is a void pointer. Incrementing it before calling
prefetch is technically undefined. Fix this by casting it to a u8*
pointer before incrementing it. This ensures that we increment the
pointer value in byte units, instead of relying on this undefined
behavior.

This was detected by cppcheck, and resolves the following warning
produced by that tool:

[fm10k_main.c:328]: (portability) 'page_addr' is of type 'void *'. When
using void pointers in calculations, the behaviour is undefined.

Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/fm10k/fm10k_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_main.c b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
index 9e6bddff7625..17a96a49174b 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
@@ -315,7 +315,7 @@ static struct sk_buff *fm10k_fetch_rx_buffer(struct fm10k_ring *rx_ring,
 		/* prefetch first cache line of first page */
 		prefetch(page_addr);
 #if L1_CACHE_BYTES < 128
-		prefetch(page_addr + L1_CACHE_BYTES);
+		prefetch((void *)((u8 *)page_addr + L1_CACHE_BYTES));
 #endif
 
 		/* allocate a skb to store the frags */
-- 
2.21.0