powerpc: Inline setup_kup()

setup_kup() is used by both 64-bit and 32-bit code. However on 64-bit
it must not be __init, because it's used for CPU hotplug, whereas on
32-bit it should be __init because it calls setup_kuap/kuep() which
are __init.

We worked around that problem in the past by marking it __ref, see
commit 67d53f30e23e ("powerpc/mm: fix section mismatch for
setup_kup()").

Marking it __ref basically just omits it from section mismatch
checking, which can lead to bugs, and in fact it did, see commit
44b4c4450f8d ("powerpc/64s: Mark the kuap/kuep functions non __init")

We can avoid all these problems by just making it static inline.
Because all it does is call other functions, making it inline actually
shrinks the 32-bit vmlinux by ~76 bytes.

Make it __always_inline as pointed out by Christophe.

Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/powerpc/include/asm/kup.h

···
 
 #include <linux/pgtable.h>
 
-void setup_kup(void);
-
 #ifdef CONFIG_PPC_KUEP
 void setup_kuep(bool disabled);
 #else
···
 static inline void restore_user_access(unsigned long flags) { }
 #endif /* CONFIG_PPC_BOOK3S_64 */
 #endif /* CONFIG_PPC_KUAP */
+
+static __always_inline void setup_kup(void)
+{
+	setup_kuep(disable_kuep);
+	setup_kuap(disable_kuap);
+}
 
 static inline void allow_read_from_user(const void __user *from, unsigned long size)
 {

arch/powerpc/mm/init-common.c

···
 }
 early_param("nosmap", parse_nosmap);
 
-void __ref setup_kup(void)
-{
-	setup_kuep(disable_kuep);
-	setup_kuap(disable_kuap);
-}
-
 #define CTOR(shift) static void ctor_##shift(void *addr) \
 {							\
 	memset(addr, 0, sizeof(void *) << (shift));	\