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);
124