After successful initialization of the CPU Jitter RNG as part of the Linux RNG, the two variables defining the memory size of the memory chunk used for measuring memory access times are set. In case the Jitter RNG does not successfully initialize, these variables are set to zero.
These two variables can be exported to user space to allow user space to check whether the CPU Jitter RNG is operational and which memory values are used. Note, according to tests, the size of the memory chunk has a direct impact on the execution timing variations. The exported variables are all read only and can be found at: /proc/sys/kernel/random. The files are: jent_memblocksize -- size of one memory block in bytes jent_memblocks -- number of memory blocks used Signed-off-by: Stephan Mueller <[email protected]> --- drivers/char/random.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index eb4fe99..4b2267b 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1703,6 +1703,20 @@ struct ctl_table random_table[] = { .mode = 0444, .proc_handler = proc_do_uuid, }, + { + .procname = "jent_memblocksize", + .maxlen = sizeof(int), + .mode = 0444, + .proc_handler = proc_dointvec, + .data = &input_pool.jent_ec.memblocksize, + }, + { + .procname = "jent_memblocks", + .maxlen = sizeof(int), + .mode = 0444, + .proc_handler = proc_dointvec, + .data = &input_pool.jent_ec.memblocks, + }, { } }; #endif /* CONFIG_SYSCTL */ -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
