test_hexdump: define FILL_CHAR constant

Define a character to fill the test buffers.  Though the character should
be printable since it's used when errors are reported.  It should neither
be from hex digit [a-fA-F0-9] dictionary nor space.  It is recommended not
to use one which is present in ASCII part of the test data.  Later on we
might switch to unprintable character to make test case more robust.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_hexdump.c

@@ -42,6 +42,8 @@ static const char * const test_data_8_le[] __initconst = {
 	"e9ac0f9cad319ca6", "0cafb1439919d14c",
 };
 
+#define FILL_CHAR	'#'
+
 static void __init test_hexdump_prepare_test(size_t len, int rowsize,
 					     int groupsize, char *test,
 					     size_t testlen, bool ascii)
@@ -70,7 +72,7 @@ static void __init test_hexdump_prepare_test(size_t len, int rowsize,
 	else
 		result = test_data_1_le;
 
-	memset(test, ' ', testlen);
+	memset(test, FILL_CHAR, testlen);
 
 	/* hex dump */
 	p = test;
@@ -79,14 +81,19 @@ static void __init test_hexdump_prepare_test(size_t len, int rowsize,
 		size_t amount = strlen(q);
 
 		strncpy(p, q, amount);
-		p += amount + 1;
+		p += amount;
+
+		*p++ = ' ';
 	}
 	if (i)
 		p--;
 
 	/* ASCII part */
 	if (ascii) {
-		p = test + rs * 2 + rs / gs + 1;
+		do {
+			*p++ = ' ';
+		} while (p < test + rs * 2 + rs / gs + 1);
+
 		strncpy(p, data_a, l);
 		p += l;
 	}
@@ -134,7 +141,7 @@ static void __init test_hexdump_overflow(bool ascii)
 	bool a;
 	int e, r;
 
-	memset(buf, ' ', sizeof(buf));
+	memset(buf, FILL_CHAR, sizeof(buf));
 
 	r = hex_dump_to_buffer(data_b, 1, 16, 1, buf, l, ascii);
 
@@ -145,14 +152,14 @@ static void __init test_hexdump_overflow(bool ascii)
 	buf[e + 2] = '\0';
 
 	if (!l) {
-		a = r == e && buf[0] == ' ';
+		a = r == e && buf[0] == FILL_CHAR;
 	} else if (l < 3) {
 		a = r == e && buf[0] == '\0';
 	} else if (l < 4) {
 		a = r == e && !strcmp(buf, t);
 	} else if (ascii) {
 		if (l < 51)
-			a = r == e && buf[l - 1] == '\0' && buf[l - 2] == ' ';
+			a = r == e && buf[l - 1] == '\0' && buf[l - 2] == FILL_CHAR;
 		else
 			a = r == e && buf[50] == '\0' && buf[49] == '.';
 	} else {