[PATCH v4 07/14] ARM: KVM: one_reg coproc set and get BE fixes

[christoffer.dall@linaro.org (Christoffer Dall)]

On Thu, Jun 12, 2014 at 09:30:06AM -0700, Victor Kamensky wrote:
> Fix code that handles KVM_SET_ONE_REG, KVM_GET_ONE_REG ioctls to work in BE
> image. Before this fix get/set_one_reg functions worked correctly only in
> LE case - reg_from_user was taking 'void *' kernel address that actually could
> be target/source memory of either 4 bytes size or 8 bytes size, and code copied
> from/to user memory that could hold either 4 bytes register, 8 byte register
> or pair of 4 bytes registers.
> 
> In order to work in endian agnostic way reg_from_user to reg_to_user functions
> should copy register value only to kernel variable with size that matches
> register size. In few place where size mismatch existed fix issue on macro
> caller side.
> 
> Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org>
> ---
>  arch/arm/kvm/coproc.c | 84 +++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 75 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
> index c58a351..bcc9a0f 100644
> --- a/arch/arm/kvm/coproc.c
> +++ b/arch/arm/kvm/coproc.c
> @@ -44,6 +44,30 @@ static u32 cache_levels;
>  /* CSSELR values; used to index KVM_REG_ARM_DEMUX_ID_CCSIDR */
>  #define CSSELR_MAX 12
>  
> +/*
> + * kvm_vcpu_arch.cp15 holds cp15 registers as an array of u32, but some
> + * of cp15 registers can be viewed either as couple of two u32 registers
> + * or one u64 register. Current u64 register encoding is that least
> + * significant u32 word is followed by most significant u32 word.
> + */
> +static inline void vcpu_cp15_reg64_set(struct kvm_vcpu *vcpu,
> +				       const struct coproc_reg *r,
> +				       u64 val)
> +{
> +	vcpu->arch.cp15[r->reg] = val & 0xffffffff;
> +	vcpu->arch.cp15[r->reg + 1] = val >> 32;
> +}
> +
> +static inline u64 vcpu_cp15_reg64_get(struct kvm_vcpu *vcpu,
> +				      const struct coproc_reg *r)
> +{
> +	u64 val;
> +	val = vcpu->arch.cp15[r->reg + 1];
> +	val = val << 32;
> +	val = val | vcpu->arch.cp15[r->reg];
> +	return val;
> +}
> +
>  int kvm_handle_cp10_id(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  {
>  	kvm_inject_undefined(vcpu);
> @@ -682,17 +706,23 @@ static struct coproc_reg invariant_cp15[] = {
>  	{ CRn( 0), CRm( 0), Op1( 1), Op2( 7), is32, NULL, get_AIDR },
>  };
>  
> +/*
> + * Reads a register value from a userspace address to a kernel
> + * variable. Make sure that register size matches sizeof(*__val).
> + */
>  static int reg_from_user(void *val, const void __user *uaddr, u64 id)
>  {
> -	/* This Just Works because we are little endian. */
>  	if (copy_from_user(val, uaddr, KVM_REG_SIZE(id)) != 0)
>  		return -EFAULT;
>  	return 0;
>  }
>  
> +/*
> + * Writes a register value to a userspace address from a kernel variable.
> + * Make sure that register size matches sizeof(*__val).
> + */
>  static int reg_to_user(void __user *uaddr, const void *val, u64 id)
>  {
> -	/* This Just Works because we are little endian. */
>  	if (copy_to_user(uaddr, val, KVM_REG_SIZE(id)) != 0)
>  		return -EFAULT;
>  	return 0;
> @@ -702,6 +732,7 @@ static int get_invariant_cp15(u64 id, void __user *uaddr)
>  {
>  	struct coproc_params params;
>  	const struct coproc_reg *r;
> +	int ret;
>  
>  	if (!index_to_params(id, &params))
>  		return -ENOENT;
> @@ -710,7 +741,14 @@ static int get_invariant_cp15(u64 id, void __user *uaddr)
>  	if (!r)
>  		return -ENOENT;
>  
> -	return reg_to_user(uaddr, &r->val, id);
> +	ret = -ENOENT;
> +	if (KVM_REG_SIZE(id) == 4) {
> +		u32 val = r->val;
> +		ret = reg_to_user(uaddr, &val, id);
> +	} else if (KVM_REG_SIZE(id) == 8) {
> +		ret = reg_to_user(uaddr, &r->val, id);
> +	}
> +	return ret;
>  }
>  
>  static int set_invariant_cp15(u64 id, void __user *uaddr)
> @@ -718,7 +756,7 @@ static int set_invariant_cp15(u64 id, void __user *uaddr)
>  	struct coproc_params params;
>  	const struct coproc_reg *r;
>  	int err;
> -	u64 val = 0; /* Make sure high bits are 0 for 32-bit regs */
> +	u64 val;
>  
>  	if (!index_to_params(id, &params))
>  		return -ENOENT;
> @@ -726,7 +764,15 @@ static int set_invariant_cp15(u64 id, void __user *uaddr)
>  	if (!r)
>  		return -ENOENT;
>  
> -	err = reg_from_user(&val, uaddr, id);
> +	err = -ENOENT;
> +	if (KVM_REG_SIZE(id) == 4) {
> +		u32 val32;
> +		err = reg_from_user(&val32, uaddr, id);
> +		if (!err)
> +			val = val32;
> +	} else if (KVM_REG_SIZE(id) == 8) {
> +		err = reg_from_user(&val, uaddr, id);
> +	}
>  	if (err)
>  		return err;
>  
> @@ -1004,6 +1050,7 @@ int kvm_arm_coproc_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  {
>  	const struct coproc_reg *r;
>  	void __user *uaddr = (void __user *)(long)reg->addr;
> +	int ret;
>  
>  	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_DEMUX)
>  		return demux_c15_get(reg->id, uaddr);
> @@ -1015,14 +1062,23 @@ int kvm_arm_coproc_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  	if (!r)
>  		return get_invariant_cp15(reg->id, uaddr);
>  
> -	/* Note: copies two regs if size is 64 bit. */
> -	return reg_to_user(uaddr, &vcpu->arch.cp15[r->reg], reg->id);
> +	ret = -ENOENT;
> +	if (KVM_REG_SIZE(reg->id) == 8) {
> +		u64 val;
> +		val = vcpu_cp15_reg64_get(vcpu, r);
> +		ret = reg_to_user(uaddr, &val, reg->id);
> +	} else if (KVM_REG_SIZE(reg->id) == 4) {
> +		ret = reg_to_user(uaddr, &vcpu->arch.cp15[r->reg], reg->id);
> +	}
> +
> +	return ret;
>  }
>  
>  int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  {
>  	const struct coproc_reg *r;
>  	void __user *uaddr = (void __user *)(long)reg->addr;
> +	int ret;
>  
>  	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_DEMUX)
>  		return demux_c15_set(reg->id, uaddr);
> @@ -1034,8 +1090,18 @@ int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  	if (!r)
>  		return set_invariant_cp15(reg->id, uaddr);
>  
> -	/* Note: copies two regs if size is 64 bit */
> -	return reg_from_user(&vcpu->arch.cp15[r->reg], uaddr, reg->id);
> +	ret = -ENOENT;
> +	if (KVM_REG_SIZE(reg->id) == 8) {
> +		u64 val;
> +		ret = reg_from_user(&val, uaddr, reg->id);
> +		if (!ret) {
> +			vcpu_cp15_reg64_set(vcpu, r, val);
> +		}
> +	} else if (KVM_REG_SIZE(reg->id) == 4) {
> +		ret = reg_from_user(&vcpu->arch.cp15[r->reg], uaddr, reg->id);
> +	}
> +
> +	return ret;
>  }
>  
>  static unsigned int num_demux_regs(void)
> -- 
> 1.8.1.4
> 

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>