[PATCH 06/19] KVM: arm64: Get rid of reg_from/to_user()

[Oliver Upton]

On Wed, Jul 06, 2022 at 05:42:51PM +0100, Marc Zyngier wrote:
> These helpers are only used by the invariant stuff now, and while
> they pretend to support non-64bit registers, this only serves as
> a way to scare the casual reviewer...
> 
> Replace these helpers with our good friends get/put_user(), and
> don't look back.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>

Reviewed-by: Oliver Upton <oliver.upton at linux.dev>

> ---
>  arch/arm64/kvm/sys_regs.c | 33 +++++++++------------------------
>  1 file changed, 9 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 1ce439eed3d8..b66be9df7a02 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -44,8 +44,6 @@
>   * 64bit interface.
>   */
>  
> -static int reg_from_user(u64 *val, const void __user *uaddr, u64 id);
> -static int reg_to_user(void __user *uaddr, const u64 *val, u64 id);
>  static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
>  
>  static bool read_from_write_only(struct kvm_vcpu *vcpu,
> @@ -2661,21 +2659,7 @@ static struct sys_reg_desc invariant_sys_regs[] = {
>  	{ SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 },
>  };
>  
> -static int reg_from_user(u64 *val, const void __user *uaddr, u64 id)
> -{
> -	if (copy_from_user(val, uaddr, KVM_REG_SIZE(id)) != 0)
> -		return -EFAULT;
> -	return 0;
> -}
> -
> -static int reg_to_user(void __user *uaddr, const u64 *val, u64 id)
> -{
> -	if (copy_to_user(uaddr, val, KVM_REG_SIZE(id)) != 0)
> -		return -EFAULT;
> -	return 0;
> -}
> -
> -static int get_invariant_sys_reg(u64 id, void __user *uaddr)
> +static int get_invariant_sys_reg(u64 id, u64 __user *uaddr)
>  {
>  	const struct sys_reg_desc *r;
>  
> @@ -2684,23 +2668,24 @@ static int get_invariant_sys_reg(u64 id, void __user *uaddr)
>  	if (!r)
>  		return -ENOENT;
>  
> -	return reg_to_user(uaddr, &r->val, id);
> +	if (put_user(r->val, uaddr))
> +		return -EFAULT;
> +
> +	return 0;
>  }
>  
> -static int set_invariant_sys_reg(u64 id, void __user *uaddr)
> +static int set_invariant_sys_reg(u64 id, u64 __user *uaddr)
>  {
>  	const struct sys_reg_desc *r;
> -	int err;
> -	u64 val = 0; /* Make sure high bits are 0 for 32-bit regs */
> +	u64 val;
>  
>  	r = get_reg_by_id(id, invariant_sys_regs,
>  			  ARRAY_SIZE(invariant_sys_regs));
>  	if (!r)
>  		return -ENOENT;
>  
> -	err = reg_from_user(&val, uaddr, id);
> -	if (err)
> -		return err;
> +	if (get_user(val, uaddr))
> +		return -EFAULT;
>  
>  	/* This is what we mean by invariant: you can't change it. */
>  	if (r->val != val)
> -- 
> 2.34.1
>