Re: [Minios-devel] [UNIKRAFT PATCH 1/1] lib/ukswrand: Add /dev/random and /dev/urandom

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

Hi Vlad,

"Vlad-Andrei BĂDOIU (78692)" <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
writes:

> This patch adds the /dev/random and
> /dev/urandom devices. Since we
> do not currenly have any entropy generating
> function they share the same handlers. The
> registration of the devices is guarded
> by the config option CONFIG_DEV_RANDOM.
>
> The devfs patch series is required.
>
> Signed-off-by: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
> ---
>  lib/ukswrand/Config.uk |  5 ++++
>  lib/ukswrand/mwc.c     | 65 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 70 insertions(+)
>
> diff --git a/lib/ukswrand/Config.uk b/lib/ukswrand/Config.uk
> index 44f6ee50..d694b61d 100644
> --- a/lib/ukswrand/Config.uk
> +++ b/lib/ukswrand/Config.uk
> @@ -14,6 +14,11 @@ config LIBUKSWRAND_MWC
>               Use multiply-with-carry algorithm
>  endchoice
>  
> +
> +config DEV_RANDOM
> +     bool "/dev/random device"
> +     select LIBDEVFS
> +
>  config LIBUKSWRAND_INITIALSEED
>       int "Initial random seed"
>       default 23
> diff --git a/lib/ukswrand/mwc.c b/lib/ukswrand/mwc.c
> index 199247d3..a276d657 100644
> --- a/lib/ukswrand/mwc.c
> +++ b/lib/ukswrand/mwc.c
> @@ -37,6 +37,7 @@
>  #include <uk/print.h>
>  #include <uk/assert.h>
>  #include <uk/ctors.h>
> +#include <uk/config.h>
>  
>  /* 
> https://stackoverflow.com/questions/9492581/c-random-number-generation-pure-c-code-no-libraries-or-functions
>  */
>  #define PHI 0x9e3779b9
> @@ -97,3 +98,67 @@ static void _uk_swrand_ctor(void)
>  }
>  
>  UK_CTOR_FUNC(UK_SWRAND_CTOR_PRIO, _uk_swrand_ctor);
> +
> +#ifdef CONFIG_DEV_RANDOM
> +
> +#include <vfscore/device.h>
> +#include <vfscore/uio.h>
> +#include <stdlib.h>
> +
> +static const char dev_name[] = "urandom";
> +
> +int dev_random_read(struct device *dev, struct uio *uio, int flags)
> +{
> +     char *buf;
> +     size_t count;
> +
> +     buf = uio->uio_iov->iov_base;
> +     count = uio->uio_iov->iov_len;
It can be multiple vectors here. At least add assertion. But better to
iterate all of them.

> +
> +     for (int i = 0; i < count; ++i)
> +             buf[i] = uk_swrand_randr_r(&uk_swrand_def);
The uk_swrand_randr_r gives you 4 bytes, only one of them is used. I
think this inefficiency needs fixing.

> +
> +     uio->uio_resid = 0;
> +     return 0;
> +}
> +
> +int dev_random_open(const char *c, int i, struct device **dev)
> +{
> +     return 0;
> +}
> +
> +
> +int dev_random_close(const char *c, int i, struct device **dev)
> +{
> +     return 0;
> +}
> +
> +static struct devops random_devops = {
> +     .read = dev_random_read,
> +     .open = dev_random_open,
> +     .close = dev_random_close,
> +};
> +
> +static struct driver drv = {
> +     .devops = &random_devops,
> +     .devsz = 0,
> +     .name = dev_name
> +};
> +
> +__constructor_prio(102) static void _uk_dev_swrand_ctor(void)
> +{
> +     struct device *dev;
> +
> +     uk_pr_info("Add /dev/random and /dev/urandom\n");
Sounds more like uk_pr_debug to me

> +
> +     /* register /dev/urandom */
> +     dev = device_create(&drv, dev_name, D_CHR);
> +     if (dev == NULL)
> +             uk_pr_info("Failed to register /dev/urandom\n");
> +
> +     /* register /dev/random */
> +     dev = device_create(&drv, dev_name + 1, D_CHR);
> +     if (dev == NULL)
> +             uk_pr_info("Failed to register /dev/random\n");
> +}
> +#endif
> -- 
> 2.20.1
>

-- 
Yuri Volchkov
Software Specialist

NEC Europe Ltd
Kurfürsten-Anlage 36
D-69115 Heidelberg

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