linux-kernel - Re: kmemleak hexdump proposal

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Date:	Tue, 14 Jul 2009 13:57:11 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...l.by>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: kmemleak hexdump proposal

On (07/14/09 11:34), Catalin Marinas wrote:
> On Tue, 2009-07-14 at 13:33 +0300, Sergey Senozhatsky wrote:
> > On (07/14/09 11:07), Catalin Marinas wrote:
> > Am I understand correct that no way for user to on/off hexdump?
> > /* no need for atomic_t kmemleak_hex_dump */
> 
> Yes. Two lines aren't really too much so we can always have them
> displayed.
>
Agree.


diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 5aabd41..f7b74ac 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -161,6 +161,15 @@ struct kmemleak_object {
 /* flag set on newly allocated objects */
 #define OBJECT_NEW		(1 << 3)
 
+/* number of bytes to print per line; must be 16 or 32 */
+#define HEX_ROW_SIZE		16
+/* number of bytes to print at a time (1, 2, 4, 8) */
+#define HEX_GROUP_SIZE		1
+/* include ASCII after the hex output */
+#define HEX_ASCII		1
+/* max number of lines to be printed */
+#define HEX_MAX_LINES		2
+
 /* the list of all allocated objects */
 static LIST_HEAD(object_list);
 /* the list of gray-colored objects (see color_gray comment below) */
@@ -254,6 +263,35 @@ static void kmemleak_disable(void);
 	kmemleak_disable();		\
 } while (0)
 
+
+/*
+ * Printing of the objects hex dump to the seq file. The number on lines
+ * to be printed is limited to HEX_MAX_LINES to prevent seq file spamming.
+ * The actual number of printed bytes depends on HEX_ROW_SIZE.
+ * It must be called with the object->lock held.
+ */
+static void hex_dump_object(struct seq_file *seq,
+				struct kmemleak_object *object)
+{
+	const u8 *ptr = (const u8 *)object->pointer;
+	/* Limit the number of lines to HEX_MAX_LINES. */
+	int len = min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));
+	int i, remaining = len;
+	unsigned char linebuf[200];
+
+	seq_printf(seq, "  hex dump (first %d bytes):\n", len);
+
+	for (i = 0; i < len; i += HEX_ROW_SIZE) {
+		int linelen = min(remaining, HEX_ROW_SIZE);
+		remaining -= HEX_ROW_SIZE;
+		hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
+						   HEX_GROUP_SIZE, linebuf,
+						   sizeof(linebuf), HEX_ASCII);
+
+		seq_printf(seq, "    %s\n", linebuf);
+	}
+}
+
 /*
  * Object colors, encoded with count and min_count:
  * - white - orphan object, not enough references to it (count < min_count)
@@ -304,6 +342,9 @@ static void print_unreferenced(struct seq_file *seq,
 		   object->pointer, object->size);
 	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
 		   object->comm, object->pid, object->jiffies);
+
+	hex_dump_object(seq, object);
+
 	seq_printf(seq, "  backtrace:\n");
 
 	for (i = 0; i < object->trace_len; i++) {


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