From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 8 Mar 2012 15:54:13 +0000 (-0500)
Subject: Fix: power of 2 size check should apply to size_t type, not uint32_t
X-Git-Tag: v2.0.0-rc3~9
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=12bcbbdbd7eb6b3cb111ab91b316b14ac210ceb2

Fix: power of 2 size check should apply to size_t type, not uint32_t

Fix this by using the much simpler x & (x - 1) check (rather than
hweight(x) == 1).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/libringbuffer/backend_internal.h b/libringbuffer/backend_internal.h
index 36d53dfd..c4fb7604 100644
--- a/libringbuffer/backend_internal.h
+++ b/libringbuffer/backend_internal.h
@@ -475,20 +475,4 @@ static inline int get_count_order(unsigned int count)
 	return order;
 }
 
-static inline
-unsigned int hweight32(unsigned int value)
-{
-	unsigned int r;
-
-	r = value;
-	r = r - ((r >> 1) & 0x55555555);
-	r = (r & 0x33333333) + ((r >> 2) & 0x33333333);
-	r += r >> 4;
-	r &= 0x0F0F0F0F;
-	r += r >> 8;
-	r += r >> 16;
-	r &= 0x000000FF;
-	return r;
-}
-
 #endif /* _LINUX_RING_BUFFER_BACKEND_INTERNAL_H */
diff --git a/libringbuffer/ring_buffer_backend.c b/libringbuffer/ring_buffer_backend.c
index 769e24bf..e949a5e2 100644
--- a/libringbuffer/ring_buffer_backend.c
+++ b/libringbuffer/ring_buffer_backend.c
@@ -218,11 +218,12 @@ int channel_backend_init(struct channel_backend *chanb,
 		return -EINVAL;
 
 	/*
-	 * Make sure the number of subbuffers and subbuffer size are power of 2.
+	 * Make sure the number of subbuffers and subbuffer size are
+	 * power of 2, and nonzero.
 	 */
-	if (hweight32(subbuf_size) != 1)
+	if (!subbuf_size || (subbuf_size & (subbuf_size - 1)))
 		return -EINVAL;
-	if (hweight32(num_subbuf) != 1)
+	if (!num_subbuf || (num_subbuf & (num_subbuf - 1)))
 		return -EINVAL;
 
 	ret = subbuffer_id_check_index(config, num_subbuf);