[RESEND PATCH 5/8] ARM: signal: copy registers using __copy_to_user()

[linux@armlinux.org.uk (Russell King - ARM Linux)]

Hi Julien,

I would much prefer these to be ordered before the patches changing
__put_user() etc.  That would then allow patch 2 (which would become
the last patch) to get rid of __put_user_error() - __put_user_error()
is utterly pointless with the need to work around Spectre, and that
would reflect what was done in my series for Spectre variant 1.

In any case, removing it from signal handling, vfp and oabi compat
should mean that after your existing series, there are no users of
__put_user_error(), but it still remains.

Thanks.

On Tue, Aug 28, 2018 at 10:08:33AM +0100, Julien Thierry wrote:
> When saving the ARM integer registers, use __copy_to_user() to
> copy them into user signal frame, rather than __put_user_error().
> This has the benefit of disabling/enabling PAN once for the whole copy
> intead of once per write.
> 
> Signed-off-by: Julien Thierry <julien.thierry@arm.com>
> ---
>  arch/arm/kernel/signal.c | 49 ++++++++++++++++++++++++++----------------------
>  1 file changed, 27 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> index b8f766c..76fe75d 100644
> --- a/arch/arm/kernel/signal.c
> +++ b/arch/arm/kernel/signal.c
> @@ -288,30 +288,35 @@ asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
>  setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
>  {
>  	struct aux_sigframe __user *aux;
> +	struct sigcontext context;
>  	int err = 0;
>  
> -	__put_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
> -	__put_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
> -	__put_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
> -	__put_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
> -	__put_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
> -	__put_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
> -	__put_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
> -	__put_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
> -	__put_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
> -	__put_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
> -	__put_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
> -	__put_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
> -	__put_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
> -	__put_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
> -	__put_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
> -	__put_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
> -	__put_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);
> -
> -	__put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no, err);
> -	__put_user_error(current->thread.error_code, &sf->uc.uc_mcontext.error_code, err);
> -	__put_user_error(current->thread.address, &sf->uc.uc_mcontext.fault_address, err);
> -	__put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);
> +	context = (struct sigcontext) {
> +		.arm_r0        = regs->ARM_r0,
> +		.arm_r1        = regs->ARM_r1,
> +		.arm_r2        = regs->ARM_r2,
> +		.arm_r3        = regs->ARM_r3,
> +		.arm_r4        = regs->ARM_r4,
> +		.arm_r5        = regs->ARM_r5,
> +		.arm_r6        = regs->ARM_r6,
> +		.arm_r7        = regs->ARM_r7,
> +		.arm_r8        = regs->ARM_r8,
> +		.arm_r9        = regs->ARM_r9,
> +		.arm_r10       = regs->ARM_r10,
> +		.arm_fp        = regs->ARM_fp,
> +		.arm_ip        = regs->ARM_ip,
> +		.arm_sp        = regs->ARM_sp,
> +		.arm_lr        = regs->ARM_lr,
> +		.arm_pc        = regs->ARM_pc,
> +		.arm_cpsr      = regs->ARM_cpsr,
> +
> +		.trap_no       = current->thread.trap_no,
> +		.error_code    = current->thread.error_code,
> +		.fault_address = current->thread.address,
> +		.oldmask       = set->sig[0],
> +	};
> +
> +	err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
>  
>  	err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
>  
> -- 
> 1.9.1
> 

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