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");