Re: [PATCH v2 1/3] tpm: vtpm_proxy: Add ioctl to get supported flags

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Fri, Apr 28, 2017 at 09:02:16AM -0400, Stefan Berger wrote:
> Add an ioctl to get the supported flags.
> 
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

The commit message is a bit lacking on explaining things like why we
need it.

> ---
>  drivers/char/tpm/tpm_vtpm_proxy.c | 29 +++++++++++++++++++++++++++++
>  include/uapi/linux/vtpm_proxy.h   | 11 +++++++++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
> index 751059d..fb4d207 100644
> --- a/drivers/char/tpm/tpm_vtpm_proxy.c
> +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
> @@ -592,6 +592,33 @@ static long vtpmx_ioc_new_dev(struct file *file, unsigned int ioctl,
>  	return 0;
>  }
>  
> +/**
> + * vtpmx_ioc_get_supt_flags - handler for the %VTPM_PROXY_IOC_GET_SUPT_FLAGS
> + *                            ioctl
> + * @file:	/dev/vtpmx
> + * @ioctl:	the ioctl number
> + * @arg:	pointer to the struct vtpmx_proxy_get_supt_flags
> + *
> + * Return the bitfield of supported flags
> + */
> +static long vtpmx_ioc_get_supt_flags(struct file *file, unsigned int ioctl,
> +				     unsigned long arg)
> +{
> +	void __user *argp = (void __user *)arg;
> +	struct vtpm_proxy_supt_flags __user *vtpm_supt_flags_p = argp;
> +	struct vtpm_proxy_supt_flags flags = {
> +		.flags = VTPM_PROXY_FLAGS_ALL,
> +	};
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
> +	if (copy_to_user(vtpm_supt_flags_p, &flags, sizeof(flags)))
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +
>  /*
>   * vtpmx_fops_ioctl: ioctl on /dev/vtpmx
>   *
> @@ -604,6 +631,8 @@ static long vtpmx_fops_ioctl(struct file *f, unsigned int ioctl,
>  	switch (ioctl) {
>  	case VTPM_PROXY_IOC_NEW_DEV:
>  		return vtpmx_ioc_new_dev(f, ioctl, arg);
> +	case VTPM_PROXY_IOC_GET_SUPT_FLAGS:
> +		return vtpmx_ioc_get_supt_flags(f, ioctl, arg);
>  	default:
>  		return -ENOIOCTLCMD;
>  	}
> diff --git a/include/uapi/linux/vtpm_proxy.h b/include/uapi/linux/vtpm_proxy.h
> index a69e991..83e64e7 100644
> --- a/include/uapi/linux/vtpm_proxy.h
> +++ b/include/uapi/linux/vtpm_proxy.h
> @@ -44,6 +44,17 @@ struct vtpm_proxy_new_dev {
>  	__u32 minor;         /* output */
>  };
>  
> +/**
> + * struct vtpm_proxy_supt_flags - parameter structure for the
> + *                                %VTPM_PROXY_IOC_GET_SUPT_FLAGS ioctl
> + * @flags: flags supported by the vtpm proxy driver
> + */
> +struct vtpm_proxy_supt_flags {
> +	__u32 flags;         /* output */
> +};
> +
>  #define VTPM_PROXY_IOC_NEW_DEV	_IOWR(0xa1, 0x00, struct vtpm_proxy_new_dev)
> +#define VTPM_PROXY_IOC_GET_SUPT_FLAGS \
> +				_IOR(0xa1, 0x01, struct vtpm_proxy_supt_flags)
>  
>  #endif /* _UAPI_LINUX_VTPM_PROXY_H */
> -- 
> 2.4.3
> 

/Jarkko