kmemleak: Printing of the objects hex dump

Introducing printing of the objects hex dump to the seq file.
The number of lines to be printed is limited to HEX_MAX_LINES
to prevent seq file spamming. The actual number of printed
bytes is less than or equal to (HEX_MAX_LINES * HEX_ROW_SIZE).

(slight adjustments by Catalin Marinas)

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@mail.by>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 8172154502a6..1d7645b0a97c 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -162,6 +162,15 @@ 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) */
@@ -259,6 +268,35 @@ static void kmemleak_disable(void);
 } while (0)
 
 /*
+ * Printing of the objects hex dump to the seq file. The number of 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;
+        int i, len, remaining;
+        unsigned char linebuf[HEX_ROW_SIZE * 5];
+
+        /* limit the number of lines to HEX_MAX_LINES */
+        remaining = len =
+                min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));
+
+        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)
  * - gray  - not orphan, not marked as false positive (min_count == 0) or
@@ -308,6 +346,7 @@ 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++) {