linux-kernel - Re: [PATCH v6 1/5] random: Blocking API for accessing nonblocking

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Date:	Tue, 19 May 2015 16:36:58 +0200
From:	Stephan Mueller <smueller@...onox.de>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Theodore Ts'o <tytso@....edu>, pebolle@...cali.nl,
	andreas.steffen@...ongswan.org, sandyinchina@...il.com,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH v6 1/5] random: Blocking API for accessing nonblocking_pool

Am Dienstag, 19. Mai 2015, 22:30:22 schrieb Herbert Xu:

Hi Herbert,

>On Tue, May 19, 2015 at 04:27:54PM +0200, Stephan Mueller wrote:
>> The current modification with patch 1 to random.c is the smallest change to
>> date. Is that then appropriate?
>> 
>> Herbert, based on your comment now, would the currently discussed patch
>> with
>> waiting in the work queue in patch 3 appropriate? Or what would you like to
>> see changed?
>
>Sorry but I have lost track as to which patch is which.  Please post
>the changes to random.c and we can all take a look.

It would be the patch from the start of the thread as follows.

The added API calls provide a synchronous function call
get_blocking_random_bytes where the caller is blocked until
the nonblocking_pool is initialized.

CC: Andreas Steffen <andreas.steffen@...ongswan.org>
CC: Theodore Ts'o <tytso@....edu>
CC: Sandy Harris <sandyinchina@...il.com>
Signed-off-by: Stephan Mueller <smueller@...onox.de>
---
 drivers/char/random.c  | 14 ++++++++++++++
 include/linux/random.h |  1 +
 2 files changed, 15 insertions(+)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 9cd6968..6f71354 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1245,6 +1245,20 @@ void get_random_bytes(void *buf, int nbytes)
 EXPORT_SYMBOL(get_random_bytes);
 
 /*
+ * Equivalent function to get_random_bytes with the difference that this
+ * function blocks the request until the nonblocking_pool is initialized.
+ */
+void get_blocking_random_bytes(void *buf, int nbytes)
+{
+       if (unlikely(nonblocking_pool.initialized == 0))
+               wait_event_interruptible(urandom_init_wait,
+                                        nonblocking_pool.initialized);
+       extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+}
+EXPORT_SYMBOL(get_blocking_random_bytes);
+
+
+/*
  * This function will use the architecture-specific hardware random
  * number generator if it is available.  The arch-specific hw RNG will
  * almost certainly be faster than what we can do in software, but it
diff --git a/include/linux/random.h b/include/linux/random.h
index b05856e..0926d78 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -14,6 +14,7 @@ extern void add_input_randomness(unsigned int type, unsigned 
int code,
 extern void add_interrupt_randomness(int irq, int irq_flags);
 
 extern void get_random_bytes(void *buf, int nbytes);
+extern void get_blocking_random_bytes(void *buf, int nbytes);
 extern void get_random_bytes_arch(void *buf, int nbytes);
 void generate_random_uuid(unsigned char uuid_out[16]);
 extern int random_int_secret_init(void);
--
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