#include <linux/module.h>
#include <linux/glob.h>

/*
 * The only reason this code can be compiled as a module is because the
 * ATA code that depends on it can be as well.  In practice, they're
 * both usually compiled in and the module overhead goes away.
 */
MODULE_DESCRIPTION("glob(7) matching");
MODULE_LICENSE("Dual MIT/GPL");

/**
 * glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0)
 * @pat: Shell-style pattern to match, e.g. "*.[ch]".
 * @str: String to match.  The pattern must match the entire string.
 *
 * Perform shell-style glob matching, returning true (1) if the match
 * succeeds, or false (0) if it fails.  Equivalent to !fnmatch(@pat, @str, 0).
 *
 * Pattern metacharacters are ?, *, [ and \.
 * (And, inside character classes, !, - and ].)
 *
 * This is small and simple implementation intended for device blacklists
 * where a string is matched against a number of patterns.  Thus, it
 * does not preprocess the patterns.  It is non-recursive, and run-time
 * is at most quadratic: strlen(@str)*strlen(@pat).
 *
 * An example of the worst case is glob_match("*aaaaa", "aaaaaaaaaa");
 * it takes 6 passes over the pattern before matching the string.
 *
 * Like !fnmatch(@pat, @str, 0) and unlike the shell, this does NOT
 * treat / or leading . specially; it isn't actually used for pathnames.
 *
 * Note that according to glob(7) (and unlike bash), character classes
 * are complemented by a leading !; this does not support the regex-style
 * [^a-z] syntax.
 *
 * An opening bracket without a matching close is matched literally.
 */
bool __pure glob_match(char const *pat, char const *str)
{
        /*
         * Backtrack to previous * on mismatch and retry starting one
         * character later in the string.  Because * matches all characters
         * (no exception for /), it can be easily proved that there's
         * never a need to backtrack multiple levels.
         */
        char const *back_pat = NULL, *back_str = back_str;

        /*
         * Loop over each token (character or class) in pat, matching
         * it against the remaining unmatched tail of str.  Return false
         * on mismatch, or true after matching the trailing nul bytes.
         */
        for (;;) {
                unsigned char c = *str++;
                unsigned char d = *pat++;

                switch (d) {
                case '?':       /* Wildcard: anything but nul */
                        if (c == '\0')
                                return false;
                        break;
                case '*':       /* Any-length wildcard */
                        if (*pat == '\0')       /* Optimize trailing * case */
                                return true;
                        back_pat = pat;
                        back_str = --str;       /* Allow zero-length match */
                        break;
                case '[': {     /* Character class */
                        bool match = false, inverted = (*pat == '!');
                        char const *class = pat + inverted;
                        unsigned char a = *class++;

                        /*
                         * Iterate over each span in the character class.
                         * A span is either a single character a, or a
                         * range a-b.  The first span may begin with ']'.
                         */
                        do {
                                unsigned char b = a;

                                if (a == '\0')  /* Malformed */
                                        goto literal;

                                if (class[0] == '-' && class[1] != ']') {
                                        b = class[1];

                                        if (b == '\0')
                                                goto literal;

                                        class += 2;
                                        /* Any special action if a > b? */
                                }
                                match |= (a <= c && c <= b);
                        } while ((a = *class++) != ']');

                        if (match == inverted)
                                goto backtrack;
                        pat = class;
                        }
                        break;
                case '\\':
                        d = *pat++;
                        /*FALLTHROUGH*/
                default:        /* Literal character */
literal:
                        if (c == d) {
                                if (d == '\0')
                                        return true;
                                break;
                        }
backtrack:
                        if (c == '\0' || !back_pat)
                                return false;   /* No point continuing */
                        /* Try again from last *, one character later in str. */
                        pat = back_pat;
                        str = ++back_str;
                        break;
                }
        }
}
EXPORT_SYMBOL(glob_match);


#ifdef CONFIG_GLOB_SELFTEST

#include <linux/printk.h>
#include <linux/moduleparam.h>

/* Boot with "glob.verbose=1" to show successful tests, too */
static bool verbose = false;
module_param(verbose, bool, 0);

struct glob_test {
        char const *pat, *str;
        bool expected;
};

static bool __pure __init test(char const *pat, char const *str, bool expected)
{
        bool match = glob_match(pat, str);
        bool success = match == expected;

        /* Can't get string literals into a particular section, so... */
        static char const msg_error[] __initconst =
                KERN_ERR "glob: \"%s\" vs. \"%s\": %s *** ERROR ***\n";
        static char const msg_ok[] __initconst =
                KERN_DEBUG "glob: \"%s\" vs. \"%s\": %s OK\n";
        static char const mismatch[] __initconst = "mismatch";
        char const *message;

        if (!success)
                message = msg_error;
        else if (verbose)
                message = msg_ok;
        else
                return success;

        printk(message, pat, str, mismatch + 3*match);
        return success;
}

/*
 * The tests are all jammed together in one array to make it simpler
 * to place that array in the .init.rodata section.  The obvious
 * "array of structures containing char *" has no way to force the
 * pointed-to strings to be in a particular section.
 *
 * Anyway, a test consists of:
 * 1. Expected glob_match result: '1' or '0'.
 * 2. Pattern to match: null-terminated string
 * 3. String to match against: null-terminated string
 *
 * The list of tests is terminated with a final '\0' instead of
 * a glob_match result character.
 */
static char const glob_tests[] __initconst =
        /* Some basic tests */
        "1" "a\0" "a\0"
        "0" "a\0" "b\0"
        "0" "a\0" "aa\0"
        "0" "a\0" "\0"
        "1" "\0" "\0"
        "0" "\0" "a\0"
        /* Simple character class tests */
        "1" "[a]\0" "a\0"
        "0" "[a]\0" "b\0"
        "0" "[!a]\0" "a\0"
        "1" "[!a]\0" "b\0"
        "1" "[ab]\0" "a\0"
        "1" "[ab]\0" "b\0"
        "0" "[ab]\0" "c\0"
        "1" "[!ab]\0" "c\0"
        "1" "[a-c]\0" "b\0"
        "0" "[a-c]\0" "d\0"
        /* Corner cases in character class parsing */
        "1" "[a-c-e-g]\0" "-\0"
        "0" "[a-c-e-g]\0" "d\0"
        "1" "[a-c-e-g]\0" "f\0"
        "1" "[]a-ceg-ik[]\0" "a\0"
        "1" "[]a-ceg-ik[]\0" "]\0"
        "1" "[]a-ceg-ik[]\0" "[\0"
        "1" "[]a-ceg-ik[]\0" "h\0"
        "0" "[]a-ceg-ik[]\0" "f\0"
        "0" "[!]a-ceg-ik[]\0" "h\0"
        "0" "[!]a-ceg-ik[]\0" "]\0"
        "1" "[!]a-ceg-ik[]\0" "f\0"
        /* Simple wild cards */
        "1" "?\0" "a\0"
        "0" "?\0" "aa\0"
        "0" "??\0" "a\0"
        "1" "?x?\0" "axb\0"
        "0" "?x?\0" "abx\0"
        "0" "?x?\0" "xab\0"
        /* Asterisk wild cards (backtracking) */
        "0" "*??\0" "a\0"
        "1" "*??\0" "ab\0"
        "1" "*??\0" "abc\0"
        "1" "*??\0" "abcd\0"
        "0" "??*\0" "a\0"
        "1" "??*\0" "ab\0"
        "1" "??*\0" "abc\0"
        "1" "??*\0" "abcd\0"
        "0" "?*?\0" "a\0"
        "1" "?*?\0" "ab\0"
        "1" "?*?\0" "abc\0"
        "1" "?*?\0" "abcd\0"
        "1" "*b\0" "b\0"
        "1" "*b\0" "ab\0"
        "0" "*b\0" "ba\0"
        "1" "*b\0" "bb\0"
        "1" "*b\0" "abb\0"
        "1" "*b\0" "bab\0"
        "1" "*bc\0" "abbc\0"
        "1" "*bc\0" "bc\0"
        "1" "*bc\0" "bbc\0"
        "1" "*bc\0" "bcbc\0"
        /* Multiple asterisks (complex backtracking) */
        "1" "*ac*\0" "abacadaeafag\0"
        "1" "*ac*ae*ag*\0" "abacadaeafag\0"
        "1" "*a*b*[bc]*[ef]*g*\0" "abacadaeafag\0"
        "0" "*a*b*[ef]*[cd]*g*\0" "abacadaeafag\0"
        "1" "*abcd*\0" "abcabcabcabcdefg\0"
        "1" "*ab*cd*\0" "abcabcabcabcdefg\0"
        "1" "*abcd*abcdef*\0" "abcabcdabcdeabcdefg\0"
        "0" "*abcd*\0" "abcabcabcabcefg\0"
        "0" "*ab*cd*\0" "abcabcabcabcefg\0";

static int __init glob_init(void)
{
        unsigned successes = 0;
        unsigned n = 0;
        char const *p = glob_tests;
        static char const message[] __initconst =
                KERN_INFO "glob: %u self-tests passed, %u failed\n";

        /*
         * Tests are jammed together in a string.  The first byte is '1'
         * or '0' to indicate the expected outcome, or '\0' to indicate the
         * end of the tests.  Then come two null-terminated strings: the
         * pattern and the string to match it against.
         */
        while (*p) {
                bool expected = *p++ & 1;
                char const *pat = p;

                p += strlen(p) + 1;
                successes += test(pat, p, expected);
                p += strlen(p) + 1;
                n++;
        }

        n -= successes;
        printk(message, successes, n);

        /* What's the errno for "kernel bug detected"?  Guess... */
        return n ? -ECANCELED : 0;
}

/* We need a dummy exit function to allow unload */
static void __exit glob_fini(void) { }

module_init(glob_init);
module_exit(glob_fini);

#endif /* CONFIG_GLOB_SELFTEST */