Re: [PATCH v3 02/13] random: add get_random_{bytes,u32,u64,int,long,once}_wait family

[Jeffrey Walton]

On Mon, Jun 5, 2017 at 8:50 PM, Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
> These functions are simple convenience wrappers that call
> wait_for_random_bytes before calling the respective get_random_*
> function.

It may be advantageous to add a timeout, too.

There's been a number of times I did not want to wait an INFINITE
amount of time for a completion. (In another context).

Jeff

> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> ---
>  include/linux/net.h    |  2 ++
>  include/linux/once.h   |  2 ++
>  include/linux/random.h | 25 +++++++++++++++++++++++++
>  3 files changed, 29 insertions(+)
>
> diff --git a/include/linux/net.h b/include/linux/net.h
> index abcfa46a2bd9..dda2cc939a53 100644
> --- a/include/linux/net.h
> +++ b/include/linux/net.h
> @@ -274,6 +274,8 @@ do {                                                                        \
>
>  #define net_get_random_once(buf, nbytes)                       \
>         get_random_once((buf), (nbytes))
> +#define net_get_random_once_wait(buf, nbytes)                  \
> +       get_random_once_wait((buf), (nbytes))
>
>  int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec,
>                    size_t num, size_t len);
> diff --git a/include/linux/once.h b/include/linux/once.h
> index 285f12cb40e6..9c98aaa87cbc 100644
> --- a/include/linux/once.h
> +++ b/include/linux/once.h
> @@ -53,5 +53,7 @@ void __do_once_done(bool *done, struct static_key *once_key,
>
>  #define get_random_once(buf, nbytes)                                        \
>         DO_ONCE(get_random_bytes, (buf), (nbytes))
> +#define get_random_once_wait(buf, nbytes)                                    \
> +       DO_ONCE(get_random_bytes_wait, (buf), (nbytes))                      \
>
>  #endif /* _LINUX_ONCE_H */
> diff --git a/include/linux/random.h b/include/linux/random.h
> index e29929347c95..4aecc339558d 100644
> --- a/include/linux/random.h
> +++ b/include/linux/random.h
> @@ -58,6 +58,31 @@ static inline unsigned long get_random_long(void)
>  #endif
>  }
>
> +/* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes).
> + * Returns the result of the call to wait_for_random_bytes. */
> +static inline int get_random_bytes_wait(void *buf, int nbytes)
> +{
> +       int ret = wait_for_random_bytes();
> +       if (unlikely(ret))
> +               return ret;
> +       get_random_bytes(buf, nbytes);
> +       return 0;
> +}
> +
> +#define declare_get_random_var_wait(var) \
> +       static inline int get_random_ ## var ## _wait(var *out) { \
> +               int ret = wait_for_random_bytes(); \
> +               if (unlikely(ret)) \
> +                       return ret; \
> +               *out = get_random_ ## var(); \
> +               return 0; \
> +       }
> +declare_get_random_var_wait(u32)
> +declare_get_random_var_wait(u64)
> +declare_get_random_var_wait(int)
> +declare_get_random_var_wait(long)
> +#undef declare_get_random_var
> +
>  unsigned long randomize_page(unsigned long start, unsigned long range);
>
>  u32 prandom_u32(void);