Re: [PATCH, RFC 03/12] random: Allow fractional bits to be tracked

[Theodore Ts'o]

I've added the following changes to this patch since upon testing,
there were some uses of r->entropy_count that were not properly
converted from using fractional bits to bits.

                                        - Ted

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 1547338..8654b7e 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -286,6 +286,7 @@
  * entropy_count, trickle_thresh
  */
 #define ENTROPY_SHIFT 3
+#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 
 /*
  * The minimum number of bits of entropy before we wake up a read on
@@ -618,7 +619,8 @@ retry:
                        r->initialized = 1;
        }
 
-       trace_credit_entropy_bits(r->name, nbits, entropy_count,
+       trace_credit_entropy_bits(r->name, nbits,
+                                 entropy_count >> ENTROPY_SHIFT,
                                  r->entropy_total, _RET_IP_);
 
        /* should we wake readers? */
@@ -695,7 +697,7 @@ static void add_timer_randomness(struct timer_rand_state 
*state, unsigned num)
 
        preempt_disable();
        /* if over the trickle threshold, use only 1 in 4096 samples */
-       if (input_pool.entropy_count > trickle_thresh &&
+       if (ENTROPY_BITS(&input_pool) > trickle_thresh &&
            ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
                goto out;
 
@@ -999,7 +1001,7 @@ static ssize_t extract_entropy(struct entropy_store *r, 
void *buf,
                        r->last_data_init = true;
                        spin_unlock_irqrestore(&r->lock, flags);
                        trace_extract_entropy(r->name, EXTRACT_SIZE,
-                                             r->entropy_count, _RET_IP_);
+                                             ENTROPY_BITS(r), _RET_IP_);
                        xfer_secondary_pool(r, EXTRACT_SIZE);
                        extract_buf(r, tmp);
                        spin_lock_irqsave(&r->lock, flags);
@@ -1008,7 +1010,7 @@ static ssize_t extract_entropy(struct entropy_store *r, 
void *buf,
                spin_unlock_irqrestore(&r->lock, flags);
        }
 
-       trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
+       trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
        xfer_secondary_pool(r, nbytes);
        nbytes = account(r, nbytes, min, reserved);
 
@@ -1041,7 +1043,7 @@ static ssize_t extract_entropy_user(struct entropy_store 
*r, void __user *buf,
        ssize_t ret = 0, i;
        __u8 tmp[EXTRACT_SIZE];
 
-       trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
+       trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
        xfer_secondary_pool(r, nbytes);
        nbytes = account(r, nbytes, 0, 0);
 
@@ -1213,8 +1215,8 @@ random_read(struct file *file, char __user *buf, size_t 
nbytes, loff_t *ppos)
                        DEBUG_ENT("sleeping?\n");
 
                        wait_event_interruptible(random_read_wait,
-                               input_pool.entropy_count >=
-                                                random_read_wakeup_thresh);
+                               ENTROPY_BITS(&input_pool) >=
+                               random_read_wakeup_thresh);
 
                        DEBUG_ENT("awake\n");
 
@@ -1250,9 +1252,9 @@ random_poll(struct file *file, poll_table * wait)
        poll_wait(file, &random_read_wait, wait);
        poll_wait(file, &random_write_wait, wait);
        mask = 0;
-       if (input_pool.entropy_count >= random_read_wakeup_thresh)
+       if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_thresh)
                mask |= POLLIN | POLLRDNORM;
-       if (input_pool.entropy_count < random_write_wakeup_thresh)
+       if (ENTROPY_BITS(&input_pool) < random_write_wakeup_thresh)
                mask |= POLLOUT | POLLWRNORM;
        return mask;
 }
@@ -1303,7 +1305,7 @@ static long random_ioctl(struct file *f, unsigned int 
cmd, unsigned long arg)
        switch (cmd) {
        case RNDGETENTCNT:
                /* inherently racy, no point locking */
-               ent_count = input_pool.entropy_count >> ENTROPY_SHIFT;
+               ent_count = ENTROPY_BITS(&input_pool);
                if (put_user(ent_count, p))
                        return -EFAULT;
                return 0;
--
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