1 // SPDX-License-Identifier: (GPL-2.0 OR MIT) 2 #include <linux/module.h> 3 #include <linux/glob.h> 4 #include <linux/export.h> 5 6 /* 7 * The only reason this code can be compiled as a module is because the 8 * ATA code that depends on it can be as well. In practice, they're 9 * both usually compiled in and the module overhead goes away. 10 */ 11 MODULE_DESCRIPTION("glob(7) matching"); 12 MODULE_LICENSE("Dual MIT/GPL"); 13 14 /** 15 * glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0) 16 * @pat: Shell-style pattern to match, e.g. "*.[ch]". 17 * @str: String to match. The pattern must match the entire string. 18 * 19 * Perform shell-style glob matching, returning true (1) if the match 20 * succeeds, or false (0) if it fails. Equivalent to !fnmatch(@pat, @str, 0). 21 * 22 * Pattern metacharacters are ?, *, [ and \. 23 * (And, inside character classes, !, - and ].) 24 * 25 * This is a small and simple implementation intended for device denylists 26 * where a string is matched against a number of patterns. Thus, it 27 * does not preprocess the patterns. It is non-recursive, and run-time 28 * is at most quadratic: strlen(@str)*strlen(@pat). 29 * 30 * An example of the worst case is glob_match("*aaaaa", "aaaaaaaaaa"); 31 * it takes 6 passes over the pattern before matching the string. 32 * 33 * Like !fnmatch(@pat, @str, 0) and unlike the shell, this does NOT 34 * treat / or leading . specially; it isn't actually used for pathnames. 35 * 36 * Note that according to glob(7) (and unlike bash), character classes 37 * are complemented by a leading !; this does not support the regex-style 38 * [^a-z] syntax. 39 * 40 * An opening bracket without a matching close is matched literally. 41 */ 42 bool __pure glob_match(char const *pat, char const *str) 43 { 44 /* 45 * Backtrack to previous * on mismatch and retry starting one 46 * character later in the string. Because * matches all characters 47 * (no exception for /), it can be easily proved that there's 48 * never a need to backtrack multiple levels. 49 */ 50 char const *back_pat = NULL, *back_str = NULL; 51 52 /* 53 * Loop over each token (character or class) in pat, matching 54 * it against the remaining unmatched tail of str. Return false 55 * on mismatch, or true after matching the trailing nul bytes. 56 */ 57 for (;;) { 58 unsigned char c = *str++; 59 unsigned char d = *pat++; 60 61 switch (d) { 62 case '?': /* Wildcard: anything but nul */ 63 if (c == '\0') 64 return false; 65 break; 66 case '*': /* Any-length wildcard */ 67 if (*pat == '\0') /* Optimize trailing * case */ 68 return true; 69 back_pat = pat; 70 back_str = --str; /* Allow zero-length match */ 71 break; 72 case '[': { /* Character class */ 73 if (c == '\0') /* No possible match */ 74 return false; 75 bool match = false, inverted = (*pat == '!'); 76 char const *class = inverted ? pat + 1 : pat; 77 unsigned char a = *class++; 78 79 /* 80 * Iterate over each span in the character class. 81 * A span is either a single character a, or a 82 * range a-b. The first span may begin with ']'. 83 */ 84 do { 85 unsigned char b = a; 86 87 if (a == '\0') /* Malformed */ 88 goto literal; 89 90 if (class[0] == '-' && class[1] != ']') { 91 b = class[1]; 92 93 if (b == '\0') 94 goto literal; 95 96 class += 2; 97 /* Any special action if a > b? */ 98 } 99 if (a <= c && c <= b) 100 match = true; 101 } while ((a = *class++) != ']'); 102 103 if (match == inverted) 104 goto backtrack; 105 pat = class; 106 } 107 break; 108 case '\\': 109 d = *pat++; 110 fallthrough; 111 default: /* Literal character */ 112 literal: 113 if (c == d) { 114 if (d == '\0') 115 return true; 116 break; 117 } 118 backtrack: 119 if (c == '\0' || !back_pat) 120 return false; /* No point continuing */ 121 /* Try again from last *, one character later in str. */ 122 pat = back_pat; 123 str = ++back_str; 124 break; 125 } 126 } 127 } 128 EXPORT_SYMBOL(glob_match); 129