Re: [PATCH v16 4/5] random: introduce generic vDSO getrandom() implementation

Jason A. Donenfeld
2024-06-07T15:38:05Z

On Fri, May 31, 2024 at 12:15:16PM -0700, Randy Dunlap wrote:
>
>
> On 5/28/24 5:19 AM, Jason A. Donenfeld wrote:
> > +/**
> > + * __cvdso_getrandom_data - Generic vDSO implementation of getrandom() syscall.
> > + * @rng_info: Describes state of kernel RNG, memory shared with kernel.
> > + * @buffer: Destination buffer to fill with random bytes.
> > + * @len: Size of @buffer in bytes.
> > + * @flags: Zero or more GRND_* flags.
> > + * @opaque_state: Pointer to an opaque state area.
> > + *
> > + * This implements a "fast key erasure" RNG using ChaCha20, in the same way that the kernel's
> > + * getrandom() syscall does. It periodically reseeds its key from the kernel's RNG, at the same
> > + * schedule that the kernel's RNG is reseeded. If the kernel's RNG is not ready, then this always
> > + * calls into the syscall.
> > + *
> > + * @opaque_state *must* be allocated using the vgetrandom_alloc() syscall. Unless external locking
> > + * is used, one state must be allocated per thread, as it is not safe to call this function
> > + * concurrently with the same @opaque_state. However, it is safe to call this using the same
> > + * @opaque_state that is shared between main code and signal handling code, within the same thread.
> > + *
> > + * Returns the number of random bytes written to @buffer, or a negative value indicating an error.
>
> * Returns:

Ack. Thanks.