Commit 2d91ecac authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

strparser: pad sk_skb_cb to avoid straddling cachelines 



sk_skb_cb lives within skb->cb[]. skb->cb[] straddles
2 cache lines, each containing 24B of data.
The first cache line does not contain much interesting
information for users of strparser, so pad things a little.
Previously strp_msg->full_len would live in the first cache
line and strp_msg->offset in the second.

We need to reorder the 8 byte temp_reg with struct tls_msg
to prevent a 4B hole which would push the struct over 48B.

Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 67d7ebde

include/net/strparser.h

+8 −4
Original line number Diff line number Diff line
@@ -65,15 +65,19 @@ struct _strp_msg { 
struct sk_skb_cb {

#define SK_SKB_CB_PRIV_LEN 20

	unsigned char data[SK_SKB_CB_PRIV_LEN];

	/* align strp on cache line boundary within skb->cb[] */

	unsigned char pad[4];

	struct _strp_msg strp;

	/* temp_reg is a temporary register used for bpf_convert_data_end_access

	 * when dst_reg == src_reg.

	 */

	u64 temp_reg;



	/* strp users' data follows */

	struct tls_msg {

		u8 control;

		u8 decrypted;

	} tls;

	/* temp_reg is a temporary register used for bpf_convert_data_end_access

	 * when dst_reg == src_reg.

	 */

	u64 temp_reg;

};



static inline struct strp_msg *strp_msg(struct sk_buff *skb)

net/strparser/strparser.c

+3 −0
Original line number Diff line number Diff line
@@ -533,6 +533,9 @@ EXPORT_SYMBOL_GPL(strp_check_rcv); 


static int __init strp_dev_init(void)

{

	BUILD_BUG_ON(sizeof(struct sk_skb_cb) >

		     sizeof_field(struct sk_buff, cb));



	strp_wq = create_singlethread_workqueue("kstrp");

	if (unlikely(!strp_wq))

		return -ENOMEM;