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net: remove one stac/clac pair from move_addr_to_user()

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Convert the get_user() and __put_user() code to the
fast masked_user_access_begin()/unsafe_{get|put}_user()
variant.

This patch increases the performance of an UDP recvfrom()
receiver (netserver) on 120 bytes messages by 7 %
on an AMD EPYC 7B12 64-Core Processor platform.

Presence of audit_sockaddr() makes difficult
to avoid the stac/clac pair in the copy_to_user() call,
this is left for a future patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250925230929.3727873-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-09-25 23:09:29 +00:00 committed by Jakub Kicinski
parent 2b235765e9
commit 1fb0e47161
1 changed files with 24 additions and 11 deletions
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35
net/socket.c
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@ -276,28 +276,41 @@ int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr_storage *k
static int move_addr_to_user(struct sockaddr_storage *kaddr, int klen, static int move_addr_to_user(struct sockaddr_storage *kaddr, int klen,
void __user *uaddr, int __user *ulen) void __user *uaddr, int __user *ulen)
{ {
int err;
int len; int len;
BUG_ON(klen > sizeof(struct sockaddr_storage)); BUG_ON(klen > sizeof(struct sockaddr_storage));
err = get_user(len, ulen);
if (err) if (can_do_masked_user_access())
return err; ulen = masked_user_access_begin(ulen);
else if (!user_access_begin(ulen, 4))
return -EFAULT;
unsafe_get_user(len, ulen, efault_end);
if (len > klen) if (len > klen)
len = klen; len = klen;
if (len < 0) /*
return -EINVAL; * "fromlen shall refer to the value before truncation.."
* 1003.1g
*/
if (len >= 0)
unsafe_put_user(klen, ulen, efault_end);
user_access_end();
if (len) { if (len) {
if (len < 0)
return -EINVAL;
if (audit_sockaddr(klen, kaddr)) if (audit_sockaddr(klen, kaddr))
return -ENOMEM; return -ENOMEM;
if (copy_to_user(uaddr, kaddr, len)) if (copy_to_user(uaddr, kaddr, len))
return -EFAULT; return -EFAULT;
} }
/* return 0;
* "fromlen shall refer to the value before truncation.."
* 1003.1g efault_end:
*/ user_access_end();
return __put_user(klen, ulen); return -EFAULT;
} }
static struct kmem_cache *sock_inode_cachep __ro_after_init; static struct kmem_cache *sock_inode_cachep __ro_after_init;