kdb: Replace deprecated strcpy() with helper function in kdb_defcmd()

strcpy() is deprecated; use the new helper function kdb_strdup_dequote()
instead. In addition to string duplication similar to kdb_strdup(), it
also trims surrounding quotes from the input string if present.

kdb_strdup_dequote() also checks for a trailing quote in the input
string which was previously not checked.

Link: https://github.com/KSPP/linux/issues/88
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Daniel Thompson (RISCstar) <danielt@kernel.org>

kernel/debug/kdb/kdb_support.c

@@ -255,6 +255,35 @@ char *kdb_strdup(const char *str, gfp_t type)
 	return s;
 }
 
+/*
+ * kdb_strdup_dequote - same as kdb_strdup(), but trims surrounding quotes from
+ *			the input string if present.
+ * Remarks:
+ *	Quotes are only removed if there is both a leading and a trailing quote.
+ */
+char *kdb_strdup_dequote(const char *str, gfp_t type)
+{
+	size_t len = strlen(str);
+	char *s;
+
+	if (str[0] == '"' && len > 1 && str[len - 1] == '"') {
+		/* trim both leading and trailing quotes */
+		str++;
+		len -= 2;
+	}
+
+	len++; /* add space for NUL terminator */
+
+	s = kmalloc(len, type);
+	if (!s)
+		return NULL;
+
+	memcpy(s, str, len - 1);
+	s[len - 1] = '\0';
+
+	return s;
+}
+
 /*
  * kdb_getarea_size - Read an area of data.  The kdb equivalent of
  *	copy_from_user, with kdb messages for invalid addresses.