On Sun, 2016-05-29 at 22:03 +1000, Anton Blanchard wrote:
> From: Anton Blanchard <an...@samba.org>
>
> In setup_sigcontext(), we set current->thread.vrsave then use it
> straight after. Since current is hidden from the compiler via inline
> assembly, it cannot optimise this and we end up with a load hit store.
Is setup_sigcontext() really a fast path we need to optimise?
Mikey
> Fix this by using a temporary.
>
> Signed-off-by: Anton Blanchard <an...@samba.org>
> ---
> arch/powerpc/kernel/signal_64.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/signal_64.c
> b/arch/powerpc/kernel/signal_64.c
> index 2552079..7e49984 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -104,6 +104,7 @@ static long setup_sigcontext(struct sigcontext __user
> *sc, struct pt_regs *regs,
> */
> #ifdef CONFIG_ALTIVEC
> elf_vrreg_t __user *v_regs = sigcontext_vmx_regs(sc);
> + unsigned long vrsave;
> #endif
> unsigned long msr = regs->msr;
> long err = 0;
> @@ -125,9 +126,13 @@ static long setup_sigcontext(struct sigcontext
> __user *sc, struct pt_regs *regs,
> /* We always copy to/from vrsave, it's 0 if we don't have or
> don't
> * use altivec.
> */
> - if (cpu_has_feature(CPU_FTR_ALTIVEC))
> - current->thread.vrsave = mfspr(SPRN_VRSAVE);
> - err |= __put_user(current->thread.vrsave, (u32 __user
> *)&v_regs[33]);
> + vrsave = 0;
> + if (cpu_has_feature(CPU_FTR_ALTIVEC)) {
> + vrsave = mfspr(SPRN_VRSAVE);
> + current->thread.vrsave = vrsave;
> + }
> +
> + err |= __put_user(vrsave, (u32 __user *)&v_regs[33]);
> #else /* CONFIG_ALTIVEC */
> err |= __put_user(0, &sc->v_regs);
> #endif /* CONFIG_ALTIVEC */
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