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SAMA5 TRNG: /dev/random appears to be functional

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This commit is contained in:
Gregory Nutt 2013-10-20 12:08:39 -06:00
parent 0ebdbfbc88
commit dbeee18171
2 changed files with 107 additions and 70 deletions
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3
arch/arm/src/sama5/chip/sam_trng.h
View File

@ -68,7 +68,8 @@
/* Control Register */
#define TRNG_CR_ENABLE (1 << 0) /* Bit 0: nables the TRNG */
#define TRNG_CR_ENABLE (1 << 0) /* Bit 0: 1=Enables the TRNG */
# define TRNG_CR_DISABLE (0) /* Bit 0: 0=Disables the TRNG */
#define TRNG_CR_KEY_SHIFT (8) /* Bits 8-31: Security key */
#define TRNG_CR_KEY_MASK (0xffffff << TRNG_CR_KEY_SHIFT)
# define TRNG_CR_KEY (0x524e47 << TRNG_CR_KEY_SHIFT) /* RNG in ASCII */

174
arch/arm/src/sama5/sam_trng.c
View File

@ -125,84 +125,102 @@ static int sam_interrupt(int irq, void *context)
{
uint32_t odata;
/* Verify that sample data is available */
if ((getreg32(SAM_TRNG_ISR) & CONFIG_SAMA5_TRNG) == 0)
{
/* No? Then why are we here? */
return OK;
}
/* Read the random sample */
odata = getreg32(SAM_TRNG_ODATA);
/* As required by the FIPS PUB (Federal Information Processing Standard
* Publication) 140-2, the first random number generated after setting the
* RNGEN bit should not be used, but saved for comparison with the next
* generated random number. Each subsequent generated random number has to be
* compared with the previously generated number. The test fails if any two
* compared numbers are equal (continuous random number generator test).
/* Loop where there are samples available to be read and/or until the user
* buffer is filled. Each sample requires only 84 clocks it is likely
* that we will loop here.
*/
if (g_trngdev.nsamples == 0)
for (;;)
{
/* This is the first sample we have taken. Save it for subsequent
* comparison.
/* Read the random sample (before checking DATRDY -- but probably not
* necessary)
*/
g_trngdev.samples[0] = odata;
g_trngdev.nsamples = 1;
return OK;
}
odata = getreg32(SAM_TRNG_ODATA);
/* This is not the first sample. Check if the new sample differs from the
* preceding sample.
*/
/* Verify that sample data is available (DATARDY is cleared when the
* interrupt status regiser is read)
*/
if ((getreg32(SAM_TRNG_ISR) & TRNG_INT_DATRDY) == 0)
{
/* No? Then return and continue processing on the next interrupt. */
return OK;
}
/* As required by the FIPS PUB (Federal Information Processing Standard
* Publication) 140-2, the first random number generated after setting
* the RNGEN bit should not be used, but saved for comparison with the
* next generated random number. Each subsequent generated random number
* has to be compared with the previously generated number. The test
* fails if any two compared numbers are equal (continuous random number
* generator test).
*/
if (g_trngdev.nsamples == 0)
{
/* This is the first sample we have taken. Save it for subsequent
* comparison.
*/
g_trngdev.samples[0] = odata;
g_trngdev.nsamples = 1;
continue;
}
/* This is not the first sample. Check if the new sample differs from
* the preceding sample.
*/
else if (odata == g_trngdev.samples[g_trngdev.nsamples - 1])
{
/* Two ssamples with the same value. Discard this one and try again. */
else if (odata == g_trngdev.samples[g_trngdev.nsamples - 1])
{
/* Two samples with the same value. Discard this one and try again. */
return OK;
continue;
}
/* This sample differs from the previous value. Have we discarded the
* first sample yet?
*/
if (g_trngdev.first)
{
/* No, discard it now by replacing it with the new sample */
g_trngdev.samples[0] = odata;
g_trngdev.nsamples = 1;
g_trngdev.first = false;
}
/* Yes.. the first sample has been dicarded */
else
{
/* Add the new random number to the buffer */
g_trngdev.samples[g_trngdev.nsamples] = odata;
g_trngdev.nsamples++;
}
/* Have all of the requested samples been saved? */
if (g_trngdev.nsamples == g_trngdev.maxsamples)
{
/* Yes.. disable any further interrupts */
putreg32(TRNG_INT_DATRDY, SAM_TRNG_IDR);
/* Disable the TRNG */
putreg32(TRNG_CR_DISABLE | TRNG_CR_KEY, SAM_TRNG_CR);
/* And wakeup the waiting read thread. */
sem_post(&g_trngdev.waitsem);
return OK;
}
}
/* The numbers differ. Have we discarded the first sample yet? */
if (g_trngdev.first)
{
/* No, discard it now by replacing it with the new sample */
g_trngdev.samples[0] = odata;
g_trngdev.nsamples = 1;
g_trngdev.first = false;
}
/* Yes.. the first sample has been dicarded */
else
{
/* Add the new random number to the buffer */
g_trngdev.samples[g_trngdev.nsamples] = odata;
g_trngdev.nsamples++;
}
/* Have all of the requested samples been saved? */
if (g_trngdev.nsamples == g_trngdev.maxsamples)
{
/* Yes.. disable any further interrupts */
putreg32(TRNG_INT_DATRDY, SAM_TRNG_IER);
/* And wakeup the waiting read thread. */
sem_post(&g_trngdev.waitsem);
}
return OK;
}
/****************************************************************************
@ -245,6 +263,16 @@ static ssize_t sam_read(struct file *filep, char *buffer, size_t buflen)
g_trngdev.nsamples = 0;
g_trngdev.first = true;
/* Enable the TRNG */
putreg32(TRNG_CR_ENABLE | TRNG_CR_KEY, SAM_TRNG_CR);
/* Clear any pending TRNG interrupts by reading the interrupt status
* register
*/
(void)getreg32(SAM_TRNG_ISR);
/* Enable TRNG interrupts */
putreg32(TRNG_INT_DATRDY, SAM_TRNG_IER);
@ -284,6 +312,10 @@ errout:
putreg32(TRNG_INT_DATRDY, SAM_TRNG_IDR);
/* Disable the TRNG */
putreg32(TRNG_CR_DISABLE | TRNG_CR_KEY, SAM_TRNG_CR);
/* Release our lock on the TRNG hardware */
sem_post(&g_trngdev.exclsem);
@ -338,6 +370,10 @@ void up_rnginitialize(void)
putreg32(TRNG_INT_DATRDY, SAM_TRNG_IDR);
/* Disable the TRNG */
putreg32(TRNG_CR_DISABLE | TRNG_CR_KEY, SAM_TRNG_CR);
/* Register the character driver */
ret = register_driver("/dev/random", &g_trngops, 0644, NULL);