lib: add lib/glob.c
This is a helper function from drivers/ata/libata_core.c, where it is
used to blacklist particular device models. It's being moved to lib/ so
other drivers may use it for the same purpose.
This implementation in non-recursive, so is safe for the kernel stack.
[akpm@linux-foundation.org: fix sparse warning]
Signed-off-by: George Spelvin <linux@horizon.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/glob.c b/lib/glob.c
new file mode 100644
index 0000000..0ba3ea8
--- /dev/null
+++ b/lib/glob.c
@@ -0,0 +1,123 @@
+#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);