lib/string_helpers: introduce generic string_unescape

There are several places in kernel where modules unescapes input to convert
C-Style Escape Sequences into byte codes.

The patch provides generic implementation of such approach. Test cases are
also included into the patch.

[akpm@linux-foundation.org: clarify comment]
[akpm@linux-foundation.org: export get_random_int() to modules]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@braille.uwo.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 103 insertions, 0 deletions

diff --git a/lib/test-string_helpers.c b/lib/test-string_helpers.c
new file mode 100644
index 000000000000..6ac48de04c0e
--- /dev/null
+++ b/lib/test-string_helpers.c
@@ -0,0 +1,103 @@
+/*
+ * Test cases for lib/string_helpers.c module.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/string.h>
+#include <linux/string_helpers.h>
+
+struct test_string {
+	const char *in;
+	const char *out;
+	unsigned int flags;
+};
+
+static const struct test_string strings[] __initconst = {
+	{
+		.in = "\\f\\ \\n\\r\\t\\v",
+		.out = "\f\\ \n\r\t\v",
+		.flags = UNESCAPE_SPACE,
+	},
+	{
+		.in = "\\40\\1\\387\\0064\\05\\040\\8a\\110\\777",
+		.out = " \001\00387\0064\005 \\8aH?7",
+		.flags = UNESCAPE_OCTAL,
+	},
+	{
+		.in = "\\xv\\xa\\x2c\\xD\\x6f2",
+		.out = "\\xv\n,\ro2",
+		.flags = UNESCAPE_HEX,
+	},
+	{
+		.in = "\\h\\\\\\\"\\a\\e\\",
+		.out = "\\h\\\"\a\e\\",
+		.flags = UNESCAPE_SPECIAL,
+	},
+};
+
+static void __init test_string_unescape(unsigned int flags, bool inplace)
+{
+	char in[256];
+	char out_test[256];
+	char out_real[256];
+	int i, p = 0, q_test = 0, q_real = sizeof(out_real);
+
+	for (i = 0; i < ARRAY_SIZE(strings); i++) {
+		const char *s = strings[i].in;
+		int len = strlen(strings[i].in);
+
+		/* Copy string to in buffer */
+		memcpy(&in[p], s, len);
+		p += len;
+
+		/* Copy expected result for given flags */
+		if (flags & strings[i].flags) {
+			s = strings[i].out;
+			len = strlen(strings[i].out);
+		}
+		memcpy(&out_test[q_test], s, len);
+		q_test += len;
+	}
+	in[p++] = '\0';
+
+	/* Call string_unescape and compare result */
+	if (inplace) {
+		memcpy(out_real, in, p);
+		if (flags == UNESCAPE_ANY)
+			q_real = string_unescape_any_inplace(out_real);
+		else
+			q_real = string_unescape_inplace(out_real, flags);
+	} else if (flags == UNESCAPE_ANY) {
+		q_real = string_unescape_any(in, out_real, q_real);
+	} else {
+		q_real = string_unescape(in, out_real, q_real, flags);
+	}
+
+	if (q_real != q_test || memcmp(out_test, out_real, q_test)) {
+		pr_warn("Test failed: flags = %u\n", flags);
+		print_hex_dump(KERN_WARNING, "Input: ",
+			       DUMP_PREFIX_NONE, 16, 1, in, p - 1, true);
+		print_hex_dump(KERN_WARNING, "Expected: ",
+			       DUMP_PREFIX_NONE, 16, 1, out_test, q_test, true);
+		print_hex_dump(KERN_WARNING, "Got: ",
+			       DUMP_PREFIX_NONE, 16, 1, out_real, q_real, true);
+	}
+}
+
+static int __init test_string_helpers_init(void)
+{
+	unsigned int i;
+
+	pr_info("Running tests...\n");
+	for (i = 0; i < UNESCAPE_ANY + 1; i++)
+		test_string_unescape(i, false);
+	test_string_unescape(get_random_int() % (UNESCAPE_ANY + 1), true);
+
+	return -EINVAL;
+}
+module_init(test_string_helpers_init);
+MODULE_LICENSE("Dual BSD/GPL");