linux/samples/livepatch/livepatch-callbacks-demo.c

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treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 Based on 2 normalized pattern(s): 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 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 [based] [from] [clk] [highbank] [c] you should have received a copy of the gnu general public license along with this program if not see http www gnu org licenses extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 355 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com> Reviewed-by: Steve Winslow <swinslow@gmail.com> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190519154041.837383322@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-19 15:51:43 +02:00
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
*/
/*
* 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)
{
livepatch: Simplify API by removing registration step The possibility to re-enable a registered patch was useful for immediate patches where the livepatch module had to stay until the system reboot. The improved consistency model allows to achieve the same result by unloading and loading the livepatch module again. Also we are going to add a feature called atomic replace. It will allow to create a patch that would replace all already registered patches. The aim is to handle dependent patches more securely. It will obsolete the stack of patches that helped to handle the dependencies so far. Then it might be unclear when a cumulative patch re-enabling is safe. It would be complicated to support the many modes. Instead we could actually make the API and code easier to understand. Therefore, remove the two step public API. All the checks and init calls are moved from klp_register_patch() to klp_enabled_patch(). Also the patch is automatically freed, including the sysfs interface when the transition to the disabled state is completed. As a result, there is never a disabled patch on the top of the stack. Therefore we do not need to check the stack in __klp_enable_patch(). And we could simplify the check in __klp_disable_patch(). Also the API and logic is much easier. It is enough to call klp_enable_patch() in module_init() call. The patch can be disabled by writing '0' into /sys/kernel/livepatch/<patch>/enabled. Then the module can be removed once the transition finishes and sysfs interface is freed. The only problem is how to free the structures and kobjects safely. The operation is triggered from the sysfs interface. We could not put the related kobject from there because it would cause lock inversion between klp_mutex and kernfs locks, see kn->count lockdep map. Therefore, offload the free task to a workqueue. It is perfectly fine: + The patch can no longer be used in the livepatch operations. + The module could not be removed until the free operation finishes and module_put() is called. + The operation is asynchronous already when the first klp_try_complete_transition() fails and another call is queued with a delay. Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Acked-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2019-01-09 13:43:23 +01:00
return klp_enable_patch(&patch);
}
static void livepatch_callbacks_demo_exit(void)
{
}
module_init(livepatch_callbacks_demo_init);
module_exit(livepatch_callbacks_demo_exit);
MODULE_LICENSE("GPL");
MODULE_INFO(livepatch, "Y");