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authorMatt Mackall <mpm@selenic.com>2008-04-29 01:03:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 08:06:25 -0700
commit993ba2114c554c1561a018e5c63a771ec8e1c469 (patch)
tree75df2f882845b12b698c305625f01dc6ef227147 /drivers
parent6d38b827400d7c02bce391f90d044e4c57d5bc1e (diff)
random: simplify add_ptr logic
The add_ptr variable wasn't used in a sensible way, use only i instead. i got reused later for a different purpose, use j instead. While we're here, put tap0 first in the tap list and add a comment. Signed-off-by: Matt Mackall <mpm@selenic.com> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/char/random.c21
1 files changed, 10 insertions, 11 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index a754132336b..ba0d7030538 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -454,7 +454,7 @@ static void __add_entropy_words(struct entropy_store *r, const __u32 *in,
static __u32 const twist_table[8] = {
0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
- unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5;
+ unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
int input_rotate;
int wordmask = r->poolinfo->poolwords - 1;
__u32 w;
@@ -469,19 +469,21 @@ static void __add_entropy_words(struct entropy_store *r, const __u32 *in,
spin_lock_irqsave(&r->lock, flags);
input_rotate = r->input_rotate;
- add_ptr = r->add_ptr;
+ i = r->add_ptr;
while (nwords--) {
w = rol32(*in++, input_rotate & 31);
- i = add_ptr = (add_ptr - 1) & wordmask;
+ i = (i - 1) & wordmask;
/* XOR in the various taps */
+ w ^= r->pool[i];
w ^= r->pool[(i + tap1) & wordmask];
w ^= r->pool[(i + tap2) & wordmask];
w ^= r->pool[(i + tap3) & wordmask];
w ^= r->pool[(i + tap4) & wordmask];
w ^= r->pool[(i + tap5) & wordmask];
- w ^= r->pool[i];
+
+ /* Mix the result back in with a twist */
r->pool[i] = (w >> 3) ^ twist_table[w & 7];
/*
@@ -494,14 +496,11 @@ static void __add_entropy_words(struct entropy_store *r, const __u32 *in,
}
r->input_rotate = input_rotate;
- r->add_ptr = add_ptr;
+ r->add_ptr = i;
- if (out) {
- for (i = 0; i < 16; i++) {
- out[i] = r->pool[add_ptr];
- add_ptr = (add_ptr - 1) & wordmask;
- }
- }
+ if (out)
+ for (j = 0; j < 16; j++)
+ out[j] = r->pool[(i - j) & wordmask];
spin_unlock_irqrestore(&r->lock, flags);
}