livepatch: samples: add sample live patching module

Add a sample live patching module.

Signed-off-by: Seth Jennings <sjenning@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/MAINTAINERS b/MAINTAINERS
index df6a0784b466cf291a01c82a2d47704054b905b5..afe93ead73f7fe26ed5062e08d43277d06afce77 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5795,6 +5795,7 @@ F:        include/linux/livepatch.h
 F:     arch/x86/include/asm/livepatch.h
 F:     arch/x86/kernel/livepatch.c
 F:     Documentation/ABI/testing/sysfs-kernel-livepatch
+F:     samples/livepatch/
 L:     live-patching@vger.kernel.org
 
 LLC (802.2)

diff --git a/samples/Kconfig b/samples/Kconfig
index 6181c2cc9ca06221047025771950bfc37eb8ca7e..0aed20df5f0bc5e934b4dd0b11e04ec726be2b02 100644 (file)
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -63,4 +63,11 @@ config SAMPLE_RPMSG_CLIENT
          to communicate with an AMP-configured remote processor over
          the rpmsg bus.
 
+config SAMPLE_LIVE_PATCHING
+       tristate "Build live patching sample -- loadable modules only"
+       depends on LIVE_PATCHING && m
+       help
+         Builds a sample live patch that replaces the procfs handler
+         for /proc/cmdline to print "this has been live patched".
+
 endif # SAMPLES

diff --git a/samples/Makefile b/samples/Makefile
index 1a60c62e20454eeb8961fb9be7f80d2eaabef3fa..f00257bcc5a73570013f5a25253ed8da3e2ee629 100644 (file)
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,4 @@
 # Makefile for Linux samples code
 
-obj-$(CONFIG_SAMPLES)  += kobject/ kprobes/ trace_events/ \
+obj-$(CONFIG_SAMPLES)  += kobject/ kprobes/ trace_events/ livepatch/ \
                           hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/

diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile
new file mode 100644 (file)
index 0000000..7f1cdc1
--- /dev/null
+++ b/samples/livepatch/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_SAMPLE_LIVE_PATCHING) += livepatch-sample.o

diff --git a/samples/livepatch/livepatch-sample.c b/samples/livepatch/livepatch-sample.c
new file mode 100644 (file)
index 0000000..21f159d
--- /dev/null
+++ b/samples/livepatch/livepatch-sample.c
@@ -0,0 +1,87 @@
+/*
+ * 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/klp_sample/enabled
+ * <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");