From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZoouIKDgjjw8ZAqiYwBAed4Zj4tSg2pRdL7pA8icnsFL7lMI33zdL6pTNv7tyUrTgo5cc2H ARC-Seal: i=1; a=rsa-sha256; t=1526419030; cv=none; d=google.com; s=arc-20160816; b=vE0tORAXxc5aHkXyGclMm9chxhv77adGWGSE2+X9f4LpfpS/4oqivWG++GcWk0NjzT Q5ZqTf6qkPzxQseFtJ+6S3Fzz4TetVrzeGwkcjYk3ZgESXNIrRmNDeZbJSKZ/BW/bomp JXnSg4BTLl4fW5UxlWp4dRLoc08wpTUGfunYTU6lVPsgslAT0+x/B9F7WJ+tNOOxnOWv 9cOyaMU3hw5kUY0qys/u1+bEH8m0NujogsWB0GdEhT/qZYWPJWhQCOLeHo++cQfZ+t3d hRtyaFUygnkk5hvnIBFmcWytn5GWDzkDzLecGQ9IPITS1+F9csrKk8JX1IgEjLgP2zOV DfkA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature:dkim-signature :arc-authentication-results; bh=lCUTdEzuA0OP8iIqYp2CfQyX0LIEtmC19Ss0DR9PDus=; b=uVZi0MTgkXzcVVPP3rQY2RxcpQIbOrKNQo45TBm4+YUVgm4Y8xjieMS7KQ/sijdTOn AkgikWnNw/Mje4dv8o9hIoT6U00G33eDNzj5k/IVJ/mUIkhYudnYN8B7+/Go+aqx09B0 nJuBwqEz1zRDlsN2HFpS9c4QRmlhcGLJvCi7ztPPEFC8VCWh8Z6IbHvZ+TrhSCQFtSIs hU73kixFyBN1gUaniJBXa7SprrSh4FUJTvCqYM/QAi/P46hqq47bhuq8MNe09I2MTlDa k5kBqIpZUwpK3+rCzWArBM8dZH3C0b0U4YvlJcQmhBheQWQR9H1aJOo0bfy+2YCxmXxt cLAg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@tobin.cc header.s=fm3 header.b=AoyFw4gq; dkim=pass header.i=@messagingengine.com header.s=fm2 header.b=DUCcMKAv; spf=neutral (google.com: 66.111.4.26 is neither permitted nor denied by best guess record for domain of me@tobin.cc) smtp.mailfrom=me@tobin.cc Authentication-Results: mx.google.com; dkim=pass header.i=@tobin.cc header.s=fm3 header.b=AoyFw4gq; dkim=pass header.i=@messagingengine.com header.s=fm2 header.b=DUCcMKAv; spf=neutral (google.com: 66.111.4.26 is neither permitted nor denied by best guess record for domain of me@tobin.cc) smtp.mailfrom=me@tobin.cc X-ME-Sender: Date: Wed, 16 May 2018 07:17:06 +1000 From: "Tobin C. Harding" To: Steven Rostedt Cc: Theodore Ts'o , Linus Torvalds , Randy Dunlap , Kees Cook , Anna-Maria Gleixner , Andrew Morton , Greg Kroah-Hartman , Arnd Bergmann , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/3] random: Return nbytes filled from hw RNG Message-ID: <20180515211706.GG10152@eros> References: <1526353586-30092-1-git-send-email-me@tobin.cc> <1526353586-30092-3-git-send-email-me@tobin.cc> <20180515093705.03850c5a@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180515093705.03850c5a@gandalf.local.home> X-Mailer: Mutt 1.5.24 (2015-08-30) User-Agent: Mutt/1.5.24 (2015-08-30) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1600497767242955587?= X-GMAIL-MSGID: =?utf-8?q?1600566361399860854?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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" 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 > > Acked-by: Theodore Ts'o > > Signed-off-by: Tobin C. Harding > > --- > > 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) Thanks for the review Steve, will spin again. Tobin.