| Date | Sun, 09 Sep 2012 23:43:12 +0100 | From | Ben Hutchings <> | Subject | [ 82/95] random: Add comment to random_initialize() |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Tony Luck <tony.luck@intel.com>
commit cbc96b7594b5691d61eba2db8b2ea723645be9ca upstream.
Many platforms have per-machine instance data (serial numbers, asset tags, etc.) squirreled away in areas that are accessed during early system bringup. Mixing this data into the random pools has a very high value in providing better random data, so we should allow (and even encourage) architecture code to call add_device_randomness() from the setup_arch() paths.
However, this limits our options for internal structure of the random driver since random_initialize() is not called until long after setup_arch().
Add a big fat comment to rand_initialize() spelling out this requirement.
Suggested-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/char/random.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/drivers/char/random.c b/drivers/char/random.c index 9793b40..1a2dfa8 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1087,6 +1087,16 @@ static void init_std_data(struct entropy_store *r) mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); } +/* + * Note that setup_arch() may call add_device_randomness() + * long before we get here. This allows seeding of the pools + * with some platform dependent data very early in the boot + * process. But it limits our options here. We must use + * statically allocated structures that already have all + * initializations complete at compile time. We should also + * take care not to overwrite the precious per platform data + * we were given. + */ static int rand_initialize(void) { init_std_data(&input_pool);
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