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author | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2017-11-17 09:43:17 +0100 |
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committer | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2017-11-20 07:53:08 +0100 |
commit | 3d374d90f8f2814a7ae6549d4c0fb83d4cc75511 (patch) | |
tree | 3d6cd39782a2eb2677bea2611eff13b6d9349edd /c/src/lib/libbsp/shared | |
parent | bsp/atsam: Add timing for RAM mt48lc16m16a2p-6a. (diff) | |
download | rtems-3d374d90f8f2814a7ae6549d4c0fb83d4cc75511.tar.bz2 |
bsps: Use a state in default getentropy()
Use the boot time to initialize the state. Use the state, the current
CPU counter and a very simple pseudo random number generator for
getentropy(). At least, this enables to pass the test "GETENTROPY 1" on
ERC32.
Update #3239.
Diffstat (limited to 'c/src/lib/libbsp/shared')
-rw-r--r-- | c/src/lib/libbsp/shared/getentropy-cpucounter.c | 65 |
1 files changed, 40 insertions, 25 deletions
diff --git a/c/src/lib/libbsp/shared/getentropy-cpucounter.c b/c/src/lib/libbsp/shared/getentropy-cpucounter.c index 15c8648047..8ef05df85c 100644 --- a/c/src/lib/libbsp/shared/getentropy-cpucounter.c +++ b/c/src/lib/libbsp/shared/getentropy-cpucounter.c @@ -20,35 +20,50 @@ * you need for example a strong crypto. */ +#include <sys/param.h> #include <unistd.h> #include <string.h> -#include <rtems/sysinit.h> +#include <rtems/bsd.h> #include <rtems/counter.h> +#include <rtems/sysinit.h> + +static uint32_t state; int getentropy(void *ptr, size_t n) { - uint8_t *dest = ptr; - - while (n > 0) { - rtems_counter_ticks ticks; - - ticks = rtems_counter_read(); - - if (n >= sizeof(ticks)) { - memcpy(dest, &ticks, sizeof(ticks)); - n -= sizeof(ticks); - dest += sizeof(ticks); - } else { - /* - * Fill the remaining bytes with only the least - * significant byte of the time. That is the byte with - * the most changes. - */ - *dest = ticks & 0xFF; - --n; - ++dest; - } - } - - return 0; + uint8_t *dest = ptr; + + state ^= rtems_counter_read(); + state *= 25169206; + state += 1679610226; + + while (n > 0) { + size_t m; + + m = MIN(n, sizeof(state)); + memcpy(dest, &state, m); + n -= m; + dest += m; + state *= 85236167; + state += 30557471; + } + + return 0; +} + +static void getentropy_init(void) +{ + struct bintime bt; + + rtems_bsd_bintime(&bt); + state = (uint32_t) bt.frac; + state ^= (uint32_t) (bt.frac >> 32); + state ^= (uint32_t) bt.sec; + state ^= (uint32_t) (bt.sec >> 32); } + +RTEMS_SYSINIT_ITEM( + getentropy_init, + RTEMS_SYSINIT_DEVICE_DRIVERS, + RTEMS_SYSINIT_ORDER_LAST +); |