Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / samples / livepatch / livepatch-sample.c

diff --git a/kernel/samples/livepatch/livepatch-sample.c b/kernel/samples/livepatch/livepatch-sample.c
new file mode 100644 (file)
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+++ b/kernel/samples/livepatch/livepatch-sample.c
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+/*
+ * livepatch-sample.c - Kernel Live Patching Sample Module
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/livepatch.h>
+
+/*
+ * This (dumb) live patch overrides the function that prints the
+ * kernel boot cmdline when /proc/cmdline is read.
+ *
+ * Example:
+ *
+ * $ cat /proc/cmdline
+ * <your cmdline>
+ *
+ * $ insmod livepatch-sample.ko
+ * $ cat /proc/cmdline
+ * this has been live patched
+ *
+ * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
+ * $ cat /proc/cmdline
+ * <your cmdline>
+ */
+
+#include <linux/seq_file.h>
+static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
+{
+       seq_printf(m, "%s\n", "this has been live patched");
+       return 0;
+}
+
+static struct klp_func funcs[] = {
+       {
+               .old_name = "cmdline_proc_show",
+               .new_func = livepatch_cmdline_proc_show,
+       }, { }
+};
+
+static struct klp_object objs[] = {
+       {
+               /* name being NULL means vmlinux */
+               .funcs = funcs,
+       }, { }
+};
+
+static struct klp_patch patch = {
+       .mod = THIS_MODULE,
+       .objs = objs,
+};
+
+static int livepatch_init(void)
+{
+       int ret;
+
+       ret = klp_register_patch(&patch);
+       if (ret)
+               return ret;
+       ret = klp_enable_patch(&patch);
+       if (ret) {
+               WARN_ON(klp_unregister_patch(&patch));
+               return ret;
+       }
+       return 0;
+}
+
+static void livepatch_exit(void)
+{
+       WARN_ON(klp_disable_patch(&patch));
+       WARN_ON(klp_unregister_patch(&patch));
+}
+
+module_init(livepatch_init);
+module_exit(livepatch_exit);
+MODULE_LICENSE("GPL");