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/include/linux/glob.h b/include/linux/glob.h
new file mode 100644 (file)
index 0000000..861d834
--- /dev/null
+++ b/include/linux/glob.h
@@ -0,0 +1,9 @@
+#ifndef _LINUX_GLOB_H
+#define _LINUX_GLOB_H
+
+#include <linux/types.h>       /* For bool */
+#include <linux/compiler.h>    /* For __pure */
+
+bool __pure glob_match(char const *pat, char const *str);
+
+#endif /* _LINUX_GLOB_H */

diff --git a/lib/Kconfig b/lib/Kconfig
index a8a7757..41bfeec 100644 (file)
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -396,6 +396,25 @@ config CPU_RMAP
 config DQL
        bool
 
+config GLOB
+       bool
+#      This actually supports modular compilation, but the module overhead
+#      is ridiculous for the amount of code involved.  Until an out-of-tree
+#      driver asks for it, we'll just link it directly it into the kernel
+#      when required.  Since we're ignoring out-of-tree users, there's also
+#      no need bother prompting for a manual decision:
+#      prompt "glob_match() function"
+       help
+         This option provides a glob_match function for performing
+         simple text pattern matching.  It originated in the ATA code
+         to blacklist particular drive models, but other device drivers
+         may need similar functionality.
+
+         All drivers in the Linux kernel tree that require this function
+         should automatically select this option.  Say N unless you
+         are compiling an out-of tree driver which tells you that it
+         depends on this.
+
 #
 # Netlink attribute parsing support is select'ed if needed
 #

diff --git a/lib/Makefile b/lib/Makefile
index 8427df9..d6b4bc4 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -137,6 +137,8 @@ obj-$(CONFIG_CORDIC) += cordic.o
 
 obj-$(CONFIG_DQL) += dynamic_queue_limits.o
 
+obj-$(CONFIG_GLOB) += glob.o
+
 obj-$(CONFIG_MPILIB) += mpi/
 obj-$(CONFIG_SIGNATURE) += digsig.o
 

diff --git a/lib/glob.c b/lib/glob.c
new file mode 100644 (file)
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);