Commit 1791ebd1 authored Dec 14, 2020 by Michael Ellerman

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 67d53f30 ("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
44b4c445 ("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 <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201214123011.311024-1-mpe@ellerman.id.au

parent 44b4c445

arch/powerpc/include/asm/kup.h

+6 −2

Original line number	Diff line number	Diff line
		@@ -49,8 +49,6 @@ extern bool disable_kuap;

		#include <linux/pgtable.h>

		void setup_kup(void);

		#ifdef CONFIG_PPC_KUEP
		void setup_kuep(bool disabled);
		#else
		@@ -85,6 +83,12 @@ 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)
		{
		allow_user_access(NULL, from, size, KUAP_READ);

arch/powerpc/mm/init-common.c

+0 −6

Original line number	Diff line number	Diff line
		@@ -47,12 +47,6 @@ static int __init parse_nosmap(char *p)
		}
		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)); \

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