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random: convert DEBUG_ENT to tracepoints
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Instead of using the random driver's ad-hoc DEBUG_ENT() mechanism, use
tracepoints instead.  This allows for a much more fine-grained control
of which debugging mechanism which a developer might need, and unifies
the debugging messages with all of the existing tracepoints.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Theodore Ts'o committed Oct 10, 2013
1 parent 6265e16 commit f80bbd8
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Showing 2 changed files with 144 additions and 36 deletions.
52 changes: 16 additions & 36 deletions drivers/char/random.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -404,17 +404,6 @@ static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
static struct fasync_struct *fasync;

static bool debug;
module_param(debug, bool, 0644);
#define DEBUG_ENT(fmt, arg...) do { \
if (debug) \
printk(KERN_DEBUG "random %04d %04d %04d: " \
fmt,\
input_pool.entropy_count,\
blocking_pool.entropy_count,\
nonblocking_pool.entropy_count,\
## arg); } while (0)

/**********************************************************************
*
* OS independent entropy store. Here are the functions which handle
Expand Down Expand Up @@ -612,7 +601,6 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
if (!nbits)
return;

DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
retry:
entropy_count = orig = ACCESS_ONCE(r->entropy_count);
if (nfrac < 0) {
Expand Down Expand Up @@ -655,7 +643,9 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
}

if (entropy_count < 0) {
DEBUG_ENT("negative entropy/overflow\n");
pr_warn("random: negative entropy/overflow: pool %s count %d\n",
r->name, entropy_count);
WARN_ON(1);
entropy_count = 0;
} else if (entropy_count > pool_size)
entropy_count = pool_size;
Expand Down Expand Up @@ -832,10 +822,10 @@ void add_input_randomness(unsigned int type, unsigned int code,
if (value == last_value)
return;

DEBUG_ENT("input event\n");
last_value = value;
add_timer_randomness(&input_timer_state,
(type << 4) ^ code ^ (code >> 4) ^ value);
trace_add_input_randomness(ENTROPY_BITS(&input_pool));
}
EXPORT_SYMBOL_GPL(add_input_randomness);

Expand Down Expand Up @@ -890,10 +880,8 @@ void add_disk_randomness(struct gendisk *disk)
if (!disk || !disk->random)
return;
/* first major is 1, so we get >= 0x200 here */
DEBUG_ENT("disk event %d:%d\n",
MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));

add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
}
#endif

Expand Down Expand Up @@ -941,10 +929,8 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
/* but never more than the buffer size */
bytes = min_t(int, bytes, sizeof(tmp));

DEBUG_ENT("going to reseed %s with %d bits (%zu of %d requested)\n",
r->name, bytes * 8, nbytes * 8,
r->entropy_count >> ENTROPY_SHIFT);

trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
bytes = extract_entropy(r->pull, tmp, bytes,
random_read_wakeup_thresh / 8, rsvd);
mix_pool_bytes(r, tmp, bytes, NULL);
Expand Down Expand Up @@ -992,8 +978,6 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
spin_lock_irqsave(&r->lock, flags);

BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
DEBUG_ENT("trying to extract %zu bits from %s\n",
nbytes * 8, r->name);

/* Can we pull enough? */
retry:
Expand All @@ -1019,12 +1003,9 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
< random_write_wakeup_thresh)
wakeup_write = 1;
}

DEBUG_ENT("debiting %zu entropy credits from %s%s\n",
ibytes * 8, r->name, r->limit ? "" : " (unlimited)");

spin_unlock_irqrestore(&r->lock, flags);

trace_debit_entropy(r->name, 8 * ibytes);
if (wakeup_write) {
wake_up_interruptible(&random_write_wait);
kill_fasync(&fasync, SIGIO, POLL_OUT);
Expand Down Expand Up @@ -1303,32 +1284,27 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
if (n > SEC_XFER_SIZE)
n = SEC_XFER_SIZE;

DEBUG_ENT("reading %zu bits\n", n*8);

n = extract_entropy_user(&blocking_pool, buf, n);

if (n < 0) {
retval = n;
break;
}

DEBUG_ENT("read got %zd bits (%zd still needed)\n",
n*8, (nbytes-n)*8);
trace_random_read(n*8, (nbytes-n)*8,
ENTROPY_BITS(&blocking_pool),
ENTROPY_BITS(&input_pool));

if (n == 0) {
if (file->f_flags & O_NONBLOCK) {
retval = -EAGAIN;
break;
}

DEBUG_ENT("sleeping?\n");

wait_event_interruptible(random_read_wait,
ENTROPY_BITS(&input_pool) >=
random_read_wakeup_thresh);

DEBUG_ENT("awake\n");

if (signal_pending(current)) {
retval = -ERESTARTSYS;
break;
Expand All @@ -1350,7 +1326,11 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
static ssize_t
urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
return extract_entropy_user(&nonblocking_pool, buf, nbytes);
int ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);

trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
ENTROPY_BITS(&input_pool));
return ret;
}

static unsigned int
Expand Down
128 changes: 128 additions & 0 deletions include/trace/events/random.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,89 @@ TRACE_EVENT(push_to_pool,
__entry->input_bits)
);

TRACE_EVENT(debit_entropy,
TP_PROTO(const char *pool_name, int debit_bits),

TP_ARGS(pool_name, debit_bits),

TP_STRUCT__entry(
__field( const char *, pool_name )
__field( int, debit_bits )
),

TP_fast_assign(
__entry->pool_name = pool_name;
__entry->debit_bits = debit_bits;
),

TP_printk("%s: debit_bits %d", __entry->pool_name,
__entry->debit_bits)
);

TRACE_EVENT(add_input_randomness,
TP_PROTO(int input_bits),

TP_ARGS(input_bits),

TP_STRUCT__entry(
__field( int, input_bits )
),

TP_fast_assign(
__entry->input_bits = input_bits;
),

TP_printk("input_pool_bits %d", __entry->input_bits)
);

TRACE_EVENT(add_disk_randomness,
TP_PROTO(dev_t dev, int input_bits),

TP_ARGS(dev, input_bits),

TP_STRUCT__entry(
__field( dev_t, dev )
__field( int, input_bits )
),

TP_fast_assign(
__entry->dev = dev;
__entry->input_bits = input_bits;
),

TP_printk("dev %d,%d input_pool_bits %d", MAJOR(__entry->dev),
MINOR(__entry->dev), __entry->input_bits)
);

TRACE_EVENT(xfer_secondary_pool,
TP_PROTO(const char *pool_name, int xfer_bits, int request_bits,
int pool_entropy, int input_entropy),

TP_ARGS(pool_name, xfer_bits, request_bits, pool_entropy,
input_entropy),

TP_STRUCT__entry(
__field( const char *, pool_name )
__field( int, xfer_bits )
__field( int, request_bits )
__field( int, pool_entropy )
__field( int, input_entropy )
),

TP_fast_assign(
__entry->pool_name = pool_name;
__entry->xfer_bits = xfer_bits;
__entry->request_bits = request_bits;
__entry->pool_entropy = pool_entropy;
__entry->input_entropy = input_entropy;
),

TP_printk("pool %s xfer_bits %d request_bits %d pool_entropy %d "
"input_entropy %d", __entry->pool_name, __entry->xfer_bits,
__entry->request_bits, __entry->pool_entropy,
__entry->input_entropy)
);

DECLARE_EVENT_CLASS(random__get_random_bytes,
TP_PROTO(int nbytes, unsigned long IP),

Expand Down Expand Up @@ -179,7 +262,52 @@ DEFINE_EVENT(random__extract_entropy, extract_entropy_user,
TP_ARGS(pool_name, nbytes, entropy_count, IP)
);

TRACE_EVENT(random_read,
TP_PROTO(int got_bits, int need_bits, int pool_left, int input_left),

TP_ARGS(got_bits, need_bits, pool_left, input_left),

TP_STRUCT__entry(
__field( int, got_bits )
__field( int, need_bits )
__field( int, pool_left )
__field( int, input_left )
),

TP_fast_assign(
__entry->got_bits = got_bits;
__entry->need_bits = need_bits;
__entry->pool_left = pool_left;
__entry->input_left = input_left;
),

TP_printk("got_bits %d still_needed_bits %d "
"blocking_pool_entropy_left %d input_entropy_left %d",
__entry->got_bits, __entry->got_bits, __entry->pool_left,
__entry->input_left)
);

TRACE_EVENT(urandom_read,
TP_PROTO(int got_bits, int pool_left, int input_left),

TP_ARGS(got_bits, pool_left, input_left),

TP_STRUCT__entry(
__field( int, got_bits )
__field( int, pool_left )
__field( int, input_left )
),

TP_fast_assign(
__entry->got_bits = got_bits;
__entry->pool_left = pool_left;
__entry->input_left = input_left;
),

TP_printk("got_bits %d nonblocking_pool_entropy_left %d "
"input_entropy_left %d", __entry->got_bits,
__entry->pool_left, __entry->input_left)
);

#endif /* _TRACE_RANDOM_H */

Expand Down

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