Messages in this thread | | | Date | Wed, 16 May 2018 07:17:06 +1000 | From | "Tobin C. Harding" <> | Subject | Re: [PATCH v4 2/3] random: Return nbytes filled from hw RNG |
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On Tue, May 15, 2018 at 09:37:05AM -0400, Steven Rostedt wrote: > On Tue, 15 May 2018 13:06:25 +1000 > "Tobin C. Harding" <me@tobin.cc> wrote: > > > Currently the function get_random_bytes_arch() has return value 'void'. > > If the hw RNG fails we currently fall back to using get_random_bytes(). > > This defeats the purpose of requesting random material from the hw RNG > > in the first place. > > > > There are currently no intree users of get_random_bytes_arch(). > > > > Only get random bytes from the hw RNG, make function return the number > > of bytes retrieved from the hw RNG. > > > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > > Acked-by: Theodore Ts'o <tytso@mit.edu> > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > > --- > > drivers/char/random.c | 16 +++++++++------- > > include/linux/random.h | 2 +- > > 2 files changed, 10 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/char/random.c b/drivers/char/random.c > > index 031d18b31e0f..4b0ec597e783 100644 > > --- a/drivers/char/random.c > > +++ b/drivers/char/random.c > > @@ -1725,26 +1725,28 @@ EXPORT_SYMBOL(del_random_ready_callback); > > * key known by the NSA). So it's useful if we need the speed, but > > * only if we're willing to trust the hardware manufacturer not to > > * have put in a back door. > > + * > > + * Return number of bytes filled in. > > */ > > -void get_random_bytes_arch(void *buf, int nbytes) > > +int __must_check get_random_bytes_arch(void *buf, int nbytes) > > { > > char *p = buf; > > + int left = nbytes; > > Just a nit, but I know some kernel devs prefer "upside-down-xmas-tree" > style of declarations. Which would make the above: > > int left = nbytes; > char *p = buf;
Super specific coding style and rigorous code cleanliness is a big part of why I love kernel dev. Thanks for pointing this one out.
While we are on these code lines, whats the typical kernel variable name for a loop counter that is going to be counted down? 'left', 'remaining', 'to_go', 'still'???
> > > > - trace_get_random_bytes_arch(nbytes, _RET_IP_); > > - while (nbytes) { > > + trace_get_random_bytes_arch(left, _RET_IP_); > > Nothing to do with this patch series, but I wonder if we should move > the trace event below, and record how much was done.
I don't fully understand trace events, I just left this line in tact and hoped for the best :(
/me adds 'trace events' to list of things to learn more about
> > + while (left) { > > unsigned long v; > > - int chunk = min(nbytes, (int)sizeof(unsigned long)); > > + int chunk = min_t(int, left, (int)sizeof(unsigned long)); > > > > if (!arch_get_random_long(&v)) > > break; > > > > memcpy(p, &v, chunk); > > p += chunk; > > - nbytes -= chunk; > > + left -= chunk; > > } > > > > - if (nbytes) > > - get_random_bytes(p, nbytes); > > + return nbytes - left; > > } > > EXPORT_SYMBOL(get_random_bytes_arch); > > > > diff --git a/include/linux/random.h b/include/linux/random.h > > index 2ddf13b4281e..f1c9bc5cd231 100644 > > --- a/include/linux/random.h > > +++ b/include/linux/random.h > > @@ -38,7 +38,7 @@ extern void get_random_bytes(void *buf, int nbytes); > > extern int wait_for_random_bytes(void); > > extern int add_random_ready_callback(struct random_ready_callback *rdy); > > extern void del_random_ready_callback(struct random_ready_callback *rdy); > > -extern void get_random_bytes_arch(void *buf, int nbytes); > > +extern int __must_check get_random_bytes_arch(void *buf, int nbytes); > > > > #ifndef MODULE > > extern const struct file_operations random_fops, urandom_fops; > > Other than that... > > Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Thanks for the review Steve, will spin again.
Tobin.
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