Re: [PATCH] powerpc: Inline setup_kup()

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 14/12/2020 à 13:30, Michael Ellerman a écrit :
> 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.
> 
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>   arch/powerpc/include/asm/kup.h | 8 ++++++--
>   arch/powerpc/mm/init-common.c  | 6 ------
>   2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
> index 5a9820c54da9..46b12c6dc728 100644
> --- a/arch/powerpc/include/asm/kup.h
> +++ b/arch/powerpc/include/asm/kup.h
> @@ -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 inline void setup_kup(void)

Should it be __always_inline ?

Christophe

> +{
> +	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);
> diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
> index afdebb95bcae..3a82f89827a5 100644
> --- a/arch/powerpc/mm/init-common.c
> +++ b/arch/powerpc/mm/init-common.c
> @@ -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));	\
>