Subject: Re: [PATCH v5 10/10] powerpc/signal64: Use __get_user() to copy sigset_t

From: "Christopher M. Riedl" <[email-masked]>
Date: Thu, 04 Feb 2021 22:40:08 -0600

On Wed Feb 3, 2021 at 12:43 PM CST, Christopher M. Riedl wrote:
> Usually sigset_t is exactly 8B which is a "trivial" size and does not
> warrant using __copy_from_user(). Use __get_user() directly in
> anticipation of future work to remove the trivial size optimizations
> from __copy_from_user(). Calling __get_user() also results in a small
> boost to signal handling throughput here.
>
> Signed-off-by: Christopher M. Riedl <[email-masked]>

This patch triggered sparse warnings about 'different address spaces'.
This minor fixup cleans that up:

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 42fdc4a7ff72..1dfda6403e14 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -97,7 +97,7 @@ static void prepare_setup_sigcontext(struct task_struct *tsk, int ctx_has_vsx_re
 #endif /* CONFIG_VSX */
 }

-static inline int get_user_sigset(sigset_t *dst, const sigset_t *src)
+static inline int get_user_sigset(sigset_t *dst, const sigset_t __user *src)
 {
	if (sizeof(sigset_t) <= 8)
		return __get_user(dst->sig[0], &src->sig[0]);