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x86_64: Fix /dev/random rdrand implementation

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rdrand was checking the wrong return value for the intrinsics
so it would block forever.  The read function was also not returning
the actual number of bytes read.

This was tested by running the rand example application
NuttShell (NSH) NuttX-9.0.0
nsh>rand
Reading 8 random numbers
Random values (0x101584f70):
0000: 019a172df7d539f2df8550362e2d3f74 9b467c51ebe30b9f6510e540e34fabcc ...-..9...P6.-?t .F|Q....e..@.O..

Signed-off-by: Brennan Ashton <bashton@brennanashton.com>
This commit is contained in:
Brennan Ashton 2020-05-04 20:57:15 -07:00 committed by Xiang Xiao
parent 521e6354b6
commit 093aa040eb
1 changed files with 7 additions and 5 deletions
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12
arch/x86_64/src/intel64/intel64_rng.c
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@ -107,9 +107,10 @@ static int x86_rng_initialize(void)
static ssize_t x86_rngread(struct file *filep, char *buffer, size_t buflen)
{
size_t reqlen = buflen;
for (; buflen > 8; buflen -= 8)
{
while (_rdrand64_step((unsigned long long *)buffer))
while (_rdrand64_step((unsigned long long *)buffer) == 0)
{
sched_yield();
}
@ -119,7 +120,7 @@ static ssize_t x86_rngread(struct file *filep, char *buffer, size_t buflen)
for (; buflen > 4; buflen -= 4)
{
while (_rdrand32_step((unsigned int *)buffer))
while (_rdrand32_step((unsigned int *)buffer) == 0)
{
sched_yield();
}
@ -129,7 +130,7 @@ static ssize_t x86_rngread(struct file *filep, char *buffer, size_t buflen)
for (; buflen > 2; buflen -= 2)
{
while (_rdrand16_step((unsigned short *)buffer))
while (_rdrand16_step((unsigned short *)buffer) == 0)
{
sched_yield();
}
@ -141,15 +142,16 @@ static ssize_t x86_rngread(struct file *filep, char *buffer, size_t buflen)
{
unsigned short temp = 0;
while (_rdrand16_step(&temp))
while (_rdrand16_step(&temp) == 0)
{
sched_yield();
}
*buffer = (temp & 0xff);
buffer++;
}
return buflen;
return reqlen;
}
/****************************************************************************