test_hexdump: check all bytes in real buffer

After processing by hex_dump_to_buffer() check all the parts to be expected.

Part 1. The actual expected hex dump with or without ASCII part.

Part 2. Check if the buffer is dirty beyond needed.

Part 3. Return code should be as expected.

This is done by using comparison of the return code and memcmp() against
the test buffer.  We fill the buffer by FILL_CHAR ('#') characters, so, we
expect to have a tail of the buffer will be left untouched.  The
terminating NUL is also checked by memcmp().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: 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

@@ -135,11 +135,10 @@ static void __init test_hexdump_set(int rowsize, bool ascii)
 
 static void __init test_hexdump_overflow(size_t buflen, bool ascii)
 {
+	char test[TEST_HEXDUMP_BUF_SIZE];
 	char buf[TEST_HEXDUMP_BUF_SIZE];
-	const char *t = test_data_1_le[0];
-	size_t len = 1;
-	int rs = 16, gs = 1;
-	int ae, he, e, r;
+	int rs = rowsize, gs = groupsize;
+	int ae, he, e, f, r;
 	bool a;
 
 	memset(buf, FILL_CHAR, sizeof(buf));
@@ -157,26 +156,23 @@ static void __init test_hexdump_overflow(size_t buflen, bool ascii)
 		e = ae;
 	else
 		e = he;
-	buf[e + 2] = '\0';
-
-	if (!buflen) {
-		a = r == e && buf[0] == FILL_CHAR;
-	} else if (buflen < 3) {
-		a = r == e && buf[0] == '\0';
-	} else if (buflen < 4) {
-		a = r == e && !strcmp(buf, t);
-	} else if (ascii) {
-		if (buflen < 51)
-			a = r == e && buf[buflen - 1] == '\0' && buf[buflen - 2] == FILL_CHAR;
-		else
-			a = r == e && buf[50] == '\0' && buf[49] == '.';
-	} else {
-		a = r == e && buf[e] == '\0';
+
+	f = min_t(int, e + 1, buflen);
+	if (buflen) {
+		test_hexdump_prepare_test(len, rs, gs, test, sizeof(test), ascii);
+		test[f - 1] = '\0';
 	}
+	memset(test + f, FILL_CHAR, sizeof(test) - f);
+
+	a = r == e && !memcmp(test, buf, TEST_HEXDUMP_BUF_SIZE);
+
+	buf[sizeof(buf) - 1] = '\0';
 
 	if (!a) {
-		pr_err("Len: %zu rc: %u strlen: %zu\n", buflen, r, strlen(buf));
-		pr_err("Result: '%s'\n", buf);
+		pr_err("Len: %zu buflen: %zu strlen: %zu\n",
+			len, buflen, strnlen(buf, sizeof(buf)));
+		pr_err("Result: %d '%s'\n", r, buf);
+		pr_err("Expect: %d '%s'\n", e, test);
 	}
 }