1 files changed, 234 insertions, 0 deletions

diff --git a/samples/livepatch/livepatch-callbacks-demo.c b/samples/livepatch/livepatch-callbacks-demo.c
new file mode 100644
index 000000000000..3d115bd68442
--- /dev/null
+++ b/samples/livepatch/livepatch-callbacks-demo.c
@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2017 Joe Lawrence <joe.lawrence@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/>.
+ */
+
+/*
+ * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo
+ *
+ *
+ * Purpose
+ * -------
+ *
+ * Demonstration of registering livepatch (un)patching callbacks.
+ *
+ *
+ * Usage
+ * -----
+ *
+ * Step 1 - load the simple module
+ *
+ *   insmod samples/livepatch/livepatch-callbacks-mod.ko
+ *
+ *
+ * Step 2 - load the demonstration livepatch (with callbacks)
+ *
+ *   insmod samples/livepatch/livepatch-callbacks-demo.ko
+ *
+ *
+ * Step 3 - cleanup
+ *
+ *   echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
+ *   rmmod livepatch_callbacks_demo
+ *   rmmod livepatch_callbacks_mod
+ *
+ * Watch dmesg output to see livepatch enablement, callback execution
+ * and patching operations for both vmlinux and module targets.
+ *
+ * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and
+ *       livepatch-callbacks-demo.ko to observe what happens when a
+ *       target module is loaded after a livepatch with callbacks.
+ *
+ * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch
+ *       callback return status.  Try setting up a non-zero status
+ *       such as -19 (-ENODEV):
+ *
+ *       # Load demo livepatch, vmlinux is patched
+ *       insmod samples/livepatch/livepatch-callbacks-demo.ko
+ *
+ *       # Setup next pre-patch callback to return -ENODEV
+ *       echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret
+ *
+ *       # Module loader refuses to load the target module
+ *       insmod samples/livepatch/livepatch-callbacks-mod.ko
+ *       insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device
+ *
+ * NOTE: There is a second target module,
+ *       livepatch-callbacks-busymod.ko, available for experimenting
+ *       with livepatch (un)patch callbacks.  This module contains
+ *       a 'sleep_secs' parameter that parks the module on one of the
+ *       functions that the livepatch demo module wants to patch.
+ *       Modifying this value and tweaking the order of module loads can
+ *       effectively demonstrate stalled patch transitions:
+ *
+ *       # Load a target module, let it park on 'busymod_work_func' for
+ *       # thirty seconds
+ *       insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30
+ *
+ *       # Meanwhile load the livepatch
+ *       insmod samples/livepatch/livepatch-callbacks-demo.ko
+ *
+ *       # ... then load and unload another target module while the
+ *       # transition is in progress
+ *       insmod samples/livepatch/livepatch-callbacks-mod.ko
+ *       rmmod samples/livepatch/livepatch-callbacks-mod.ko
+ *
+ *       # Finally cleanup
+ *       echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
+ *       rmmod samples/livepatch/livepatch-callbacks-demo.ko
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/livepatch.h>
+
+static int pre_patch_ret;
+module_param(pre_patch_ret, int, 0644);
+MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)");
+
+static const char *const module_state[] = {
+        [MODULE_STATE_LIVE]     = "[MODULE_STATE_LIVE] Normal state",
+        [MODULE_STATE_COMING]   = "[MODULE_STATE_COMING] Full formed, running module_init",
+        [MODULE_STATE_GOING]    = "[MODULE_STATE_GOING] Going away",
+        [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up",
+};
+
+static void callback_info(const char *callback, struct klp_object *obj)
+{
+        if (obj->mod)
+                pr_info("%s: %s -> %s\n", callback, obj->mod->name,
+                        module_state[obj->mod->state]);
+        else
+                pr_info("%s: vmlinux\n", callback);
+}
+
+/* Executed on object patching (ie, patch enablement) */
+static int pre_patch_callback(struct klp_object *obj)
+{
+        callback_info(__func__, obj);
+        return pre_patch_ret;
+}
+
+/* Executed on object unpatching (ie, patch disablement) */
+static void post_patch_callback(struct klp_object *obj)
+{
+        callback_info(__func__, obj);
+}
+
+/* Executed on object unpatching (ie, patch disablement) */
+static void pre_unpatch_callback(struct klp_object *obj)
+{
+        callback_info(__func__, obj);
+}
+
+/* Executed on object unpatching (ie, patch disablement) */
+static void post_unpatch_callback(struct klp_object *obj)
+{
+        callback_info(__func__, obj);
+}
+
+static void patched_work_func(struct work_struct *work)
+{
+        pr_info("%s\n", __func__);
+}
+
+static struct klp_func no_funcs[] = {
+        { }
+};
+
+static struct klp_func busymod_funcs[] = {
+        {
+                .old_name = "busymod_work_func",
+                .new_func = patched_work_func,
+        }, { }
+};
+
+static struct klp_object objs[] = {
+        {
+                .name = NULL,   /* vmlinux */
+                .funcs = no_funcs,
+                .callbacks = {
+                        .pre_patch = pre_patch_callback,
+                        .post_patch = post_patch_callback,
+                        .pre_unpatch = pre_unpatch_callback,
+                        .post_unpatch = post_unpatch_callback,
+                },
+        },      {
+                .name = "livepatch_callbacks_mod",
+                .funcs = no_funcs,
+                .callbacks = {
+                        .pre_patch = pre_patch_callback,
+                        .post_patch = post_patch_callback,
+                        .pre_unpatch = pre_unpatch_callback,
+                        .post_unpatch = post_unpatch_callback,
+                },
+        },      {
+                .name = "livepatch_callbacks_busymod",
+                .funcs = busymod_funcs,
+                .callbacks = {
+                        .pre_patch = pre_patch_callback,
+                        .post_patch = post_patch_callback,
+                        .pre_unpatch = pre_unpatch_callback,
+                        .post_unpatch = post_unpatch_callback,
+                },
+        }, { }
+};
+
+static struct klp_patch patch = {
+        .mod = THIS_MODULE,
+        .objs = objs,
+};
+
+static int livepatch_callbacks_demo_init(void)
+{
+        int ret;
+
+        if (!klp_have_reliable_stack() && !patch.immediate) {
+                /*
+                 * WARNING: Be very careful when using 'patch.immediate' in
+                 * your patches.  It's ok to use it for simple patches like
+                 * this, but for more complex patches which change function
+                 * semantics, locking semantics, or data structures, it may not
+                 * be safe.  Use of this option will also prevent removal of
+                 * the patch.
+                 *
+                 * See Documentation/livepatch/livepatch.txt for more details.
+                 */
+                patch.immediate = true;
+                pr_notice("The consistency model isn't supported for your architecture.  Bypassing safety mechanisms and applying the patch immediately.\n");
+        }
+
+        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_callbacks_demo_exit(void)
+{
+        WARN_ON(klp_unregister_patch(&patch));
+}
+
+module_init(livepatch_callbacks_demo_init);
+module_exit(livepatch_callbacks_demo_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");