[PATCH 4/5] lib: Add strerror and strerror_name functions

[danielfsantos@att.net]

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
---
 include/linux/string.h |  8 +++++++
 lib/string.c           | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index ac889c5..76ce2ff 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -154,4 +154,12 @@ static inline const char *kbasename(const char *path)
 	return tail ? tail + 1 : path;
 }
 
+#ifdef CONFIG_STRERROR
+extern const char *strerror(int error);
+#endif
+
+#ifdef CONFIG_STRERROR_NAME
+extern const char *strerror_name(int error);
+#endif
+
 #endif /* _LINUX_STRING_H_ */
diff --git a/lib/string.c b/lib/string.c
index e5878de..7fd2704 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -27,6 +27,10 @@
 #include <linux/bug.h>
 #include <linux/errno.h>
 
+#if defined(CONFIG_STRERROR) || defined(CONFIG_STRERROR_NAME)
+# include <generated/error_strings.h>
+#endif
+
 #ifndef __HAVE_ARCH_STRNICMP
 /**
  * strnicmp - Case insensitive, length-limited string comparison
@@ -824,3 +828,59 @@ void *memchr_inv(const void *start, int c, size_t bytes)
 	return check_bytes8(start, value, bytes % 8);
 }
 EXPORT_SYMBOL(memchr_inv);
+
+#if defined(CONFIG_STRERROR) || defined(CONFIG_STRERROR_NAME)
+static const char *_strerror(int error, unsigned index)
+{
+	unsigned uerror = error < 0 ? -error : error;
+	const struct error_strings *es;
+	const struct error_strings *es_end = &error_strings[
+			sizeof(error_strings) / sizeof(*error_strings)];
+	const char *ret;
+	unsigned i;
+
+	for (es = error_strings; es != es_end; ++es) {
+		if (uerror >= es->first && uerror <= es->last)
+			break;
+	}
+
+	if (es == es_end)
+		return NULL;
+
+	for (i = es->first, ret = es->desc[index]; i < uerror; ++ret)
+		i += !*ret;
+
+	BUG_ON(i > es->last);
+	BUG_ON(i != uerror);
+
+	return *ret ? ret : NULL;
+}
+#endif /* defined(CONFIG_STRERROR) || defined(CONFIG_STRERROR_NAME) */
+
+#ifdef CONFIG_STRERROR
+/**
+ * strerror - Translates an error code into a description.
+ * @error:	The error to describe (may be positive or negative)
+ *
+ * Returns a pointer to the error description or NULL if none is found.
+ */
+const char *strerror(int error)
+{
+	return _strerror(error, 1);
+}
+EXPORT_SYMBOL(strerror);
+#endif
+
+#ifdef CONFIG_STRERROR_NAME
+/**
+ * strerror_name - Translates an error code into a name
+ * @error:	The error to describe (may be positive or negative)
+ *
+ * Returns a pointer to the error name or NULL if none is found.
+ */
+const char *strerror_name(int error)
+{
+	return _strerror(error, 0);
+}
+EXPORT_SYMBOL(strerror_name);
+#endif
-- 
1.8.1.5