1#include <linux/module.h>
  2#include <linux/glob.h>
  3
  4/*
  5 * The only reason this code can be compiled as a module is because the
  6 * ATA code that depends on it can be as well.  In practice, they're
  7 * both usually compiled in and the module overhead goes away.
  8 */
  9MODULE_DESCRIPTION("glob(7) matching");
 10MODULE_LICENSE("Dual MIT/GPL");
 11
 12/**
 13 * glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0)
 14 * @pat: Shell-style pattern to match, e.g. "*.[ch]".
 15 * @str: String to match.  The pattern must match the entire string.
 16 *
 17 * Perform shell-style glob matching, returning true (1) if the match
 18 * succeeds, or false (0) if it fails.  Equivalent to !fnmatch(@pat, @str, 0).
 19 *
 20 * Pattern metacharacters are ?, *, [ and \.
 21 * (And, inside character classes, !, - and ].)
 22 *
 23 * This is small and simple implementation intended for device blacklists
 24 * where a string is matched against a number of patterns.  Thus, it
 25 * does not preprocess the patterns.  It is non-recursive, and run-time
 26 * is at most quadratic: strlen(@str)*strlen(@pat).
 27 *
 28 * An example of the worst case is glob_match("*aaaaa", "aaaaaaaaaa");
 29 * it takes 6 passes over the pattern before matching the string.
 30 *
 31 * Like !fnmatch(@pat, @str, 0) and unlike the shell, this does NOT
 32 * treat / or leading . specially; it isn't actually used for pathnames.
 33 *
 34 * Note that according to glob(7) (and unlike bash), character classes
 35 * are complemented by a leading !; this does not support the regex-style
 36 * [^a-z] syntax.
 37 *
 38 * An opening bracket without a matching close is matched literally.
 39 */
 40bool __pure glob_match(char const *pat, char const *str)
 41{
 42	/*
 43	 * Backtrack to previous * on mismatch and retry starting one
 44	 * character later in the string.  Because * matches all characters
 45	 * (no exception for /), it can be easily proved that there's
 46	 * never a need to backtrack multiple levels.
 47	 */
 48	char const *back_pat = NULL, *back_str;
 49
 50	/*
 51	 * Loop over each token (character or class) in pat, matching
 52	 * it against the remaining unmatched tail of str.  Return false
 53	 * on mismatch, or true after matching the trailing nul bytes.
 54	 */
 55	for (;;) {
 56		unsigned char c = *str++;
 57		unsigned char d = *pat++;
 58
 59		switch (d) {
 60		case '?':	/* Wildcard: anything but nul */
 61			if (c == '\0')
 62				return false;
 63			break;
 64		case '*':	/* Any-length wildcard */
 65			if (*pat == '\0')	/* Optimize trailing * case */
 66				return true;
 67			back_pat = pat;
 68			back_str = --str;	/* Allow zero-length match */
 69			break;
 70		case '[': {	/* Character class */
 71			bool match = false, inverted = (*pat == '!');
 72			char const *class = pat + inverted;
 73			unsigned char a = *class++;
 74
 75			/*
 76			 * Iterate over each span in the character class.
 77			 * A span is either a single character a, or a
 78			 * range a-b.  The first span may begin with ']'.
 79			 */
 80			do {
 81				unsigned char b = a;
 82
 83				if (a == '\0')	/* Malformed */
 84					goto literal;
 85
 86				if (class[0] == '-' && class[1] != ']') {
 87					b = class[1];
 88
 89					if (b == '\0')
 90						goto literal;
 91
 92					class += 2;
 93					/* Any special action if a > b? */
 94				}
 95				match |= (a <= c && c <= b);
 96			} while ((a = *class++) != ']');
 97
 98			if (match == inverted)
 99				goto backtrack;
100			pat = class;
101			}
102			break;
103		case '\\':
104			d = *pat++;
105			fallthrough;
106		default:	/* Literal character */
107literal:
108			if (c == d) {
109				if (d == '\0')
110					return true;
111				break;
112			}
113backtrack:
114			if (c == '\0' || !back_pat)
115				return false;	/* No point continuing */
116			/* Try again from last *, one character later in str. */
117			pat = back_pat;
118			str = ++back_str;
119			break;
120		}
121	}
122}
123EXPORT_SYMBOL(glob_match);