kernel/sys.c: improve code generation
utsname() is quite expensive to calculate. Cache it in a local.
text data bss dec hex filename
before: 11136 720 16 11872 2e60 kernel/sys.o
after: 11096 720 16 11832 2e38 kernel/sys.o
Acked-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Serge E. Hallyn" <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sys.c b/kernel/sys.c
index 558b035..0bc8fa3 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1349,9 +1349,10 @@
down_write(&uts_sem);
errno = -EFAULT;
if (!copy_from_user(tmp, name, len)) {
- memcpy(utsname()->nodename, tmp, len);
- memset(utsname()->nodename + len, 0,
- sizeof(utsname()->nodename) - len);
+ struct new_utsname *u = utsname();
+
+ memcpy(u->nodename, tmp, len);
+ memset(u->nodename + len, 0, sizeof(u->nodename) - len);
errno = 0;
}
up_write(&uts_sem);
@@ -1363,15 +1364,17 @@
asmlinkage long sys_gethostname(char __user *name, int len)
{
int i, errno;
+ struct new_utsname *u;
if (len < 0)
return -EINVAL;
down_read(&uts_sem);
- i = 1 + strlen(utsname()->nodename);
+ u = utsname();
+ i = 1 + strlen(u->nodename);
if (i > len)
i = len;
errno = 0;
- if (copy_to_user(name, utsname()->nodename, i))
+ if (copy_to_user(name, u->nodename, i))
errno = -EFAULT;
up_read(&uts_sem);
return errno;
@@ -1396,9 +1399,10 @@
down_write(&uts_sem);
errno = -EFAULT;
if (!copy_from_user(tmp, name, len)) {
- memcpy(utsname()->domainname, tmp, len);
- memset(utsname()->domainname + len, 0,
- sizeof(utsname()->domainname) - len);
+ struct new_utsname *u = utsname();
+
+ memcpy(u->domainname, tmp, len);
+ memset(u->domainname + len, 0, sizeof(u->domainname) - len);
errno = 0;
}
up_write(&uts_sem);