Re: [PATCH 3/5] staging: rtl8188eu: use is_multicast_ether_addr in rtw_xmit.c

From: Michael Straube
Date: Thu Aug 09 2018 - 14:03:30 EST


On 8/9/18 7:51 PM, Joe Perches wrote:
On Thu, 2018-08-09 at 19:42 +0200, Michael Straube wrote:
On 8/9/18 7:13 PM, Joe Perches wrote:
On Thu, 2018-08-09 at 19:01 +0200, Michael Straube wrote:
Use is_multicast_ether_addr instead of custom IS_MCAST in
core/rtw_xmit.c.

Have you verified that all accesses are __aligned(2) ?

If so, please state that in the patch description.

diff --git a/drivers/staging/rtl8188eu/core/rtw_xmit.c b/drivers/staging/rtl8188eu/core/rtw_xmit.c

[]
@@ -460,10 +460,10 @@ static s32 update_attrib(struct adapter *padapter, struct sk_buff *pkt, struct p
if ((pattrib->ether_type == ETH_P_ARP) || (pattrib->ether_type == ETH_P_PAE) || (pattrib->dhcp_pkt == 1))
rtw_lps_ctrl_wk_cmd(padapter, LPS_CTRL_SPECIAL_PACKET, 1);
- bmcast = IS_MCAST(pattrib->ra);
+ mcast = is_multicast_ether_addr(pattrib->ra);

i.e.: is pattrib->ra __aligned(2) ?

etc...


Hi Joe,

I looked at the function comment for is_multicast_ether_addr in etherdevice.h.
There is not mentioned that __aligned(2) is required. If it is, I will check.

So, is it required although it's not mentioned for is_multicast_ether_addr?

Well, it wasn't required initially, but

commit d54385ce68cd18ab002b46f61246ad197cec92de
Author: Alexander Duyck <alexander.h.duyck@xxxxxxxxxx>
Date: Thu Apr 30 14:53:54 2015 -0700

etherdev: Process is_multicast_ether_addr at same size as other operations
This change makes it so that we process the address in
is_multicast_ether_addr at the same size as the other calls. This allows
us to avoid duplicate reads when used with other calls such as
is_zero_ether_addr or eth_addr_copy. In addition I have added a 64 bit
version of the function so in eth_type_trans we can process the destination
address as a 64 bit value throughout.
Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

changed it without adding a note in the kernel-doc.

So this is likely appropriate to avoid unaligned access traps:
---
include/linux/etherdevice.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 572e11bb8696..0f7086b4836a 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -115,6 +115,8 @@ static inline bool is_zero_ether_addr(const u8 *addr)
*
* Return true if the address is a multicast address.
* By definition the broadcast address is also a multicast address.
+ *
+ * Please note: addr must be aligned to u16.
*/
static inline bool is_multicast_ether_addr(const u8 *addr)
{


Ok, then I will check and resend the series.
Thanks again.