[incubator-nuttx] branch master updated: x86_64: Fix /dev/random rdrand implementation

[xiaoxiang]

This is an automated email from the ASF dual-hosted git repository.

xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 093aa04  x86_64: Fix /dev/random rdrand implementation
093aa04 is described below

commit 093aa040ebf9f346de4e982f600f73aece2b060a
Author: Brennan Ashton <bash...@brennanashton.com>
AuthorDate: Mon May 4 20:57:15 2020 -0700

    x86_64: Fix /dev/random rdrand implementation
    
    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 <bash...@brennanashton.com>
---
 arch/x86_64/src/intel64/intel64_rng.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86_64/src/intel64/intel64_rng.c 
b/arch/x86_64/src/intel64/intel64_rng.c
index a68d6c3..e602f61 100644
--- a/arch/x86_64/src/intel64/intel64_rng.c
+++ b/arch/x86_64/src/intel64/intel64_rng.c
@@ -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;
 }
 
 /****************************************************************************