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livepatch: add (un)patch callbacks

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Provide livepatch modules a klp_object (un)patching notification
mechanism.  Pre and post-(un)patch callbacks allow livepatch modules to
setup or synchronize changes that would be difficult to support in only
patched-or-unpatched code contexts.

Callbacks can be registered for target module or vmlinux klp_objects,
but each implementation is klp_object specific.

  - Pre-(un)patch callbacks run before any (un)patching transition
    starts.

  - Post-(un)patch callbacks run once an object has been (un)patched and
    the klp_patch fully transitioned to its target state.

Example use cases include modification of global data and registration
of newly available services/handlers.

See Documentation/livepatch/callbacks.txt for details and
samples/livepatch/ for examples.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Joe Lawrence
2017-10-13 15:08:41 -04:00
committed by Jiri Kosina
parent 19205da6a0
commit 93862e385d
10 changed files with 1091 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
samples/livepatch/Makefile
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@@ -2,3 +2,6 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-mod.o
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix1.o
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o

72
samples/livepatch/livepatch-callbacks-busymod.c Normal file
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@@ -0,0 +1,72 @@
/*
* 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-busymod.c - (un)patching callbacks demo support module
*
*
* Purpose
* -------
*
* Simple module to demonstrate livepatch (un)patching callbacks.
*
*
* Usage
* -----
*
* This module is not intended to be standalone. See the "Usage"
* section of livepatch-callbacks-mod.c.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
static int sleep_secs;
module_param(sleep_secs, int, 0644);
MODULE_PARM_DESC(sleep_secs, "sleep_secs (default=0)");
static void busymod_work_func(struct work_struct *work);
static DECLARE_DELAYED_WORK(work, busymod_work_func);
static void busymod_work_func(struct work_struct *work)
{
pr_info("%s, sleeping %d seconds ...\n", __func__, sleep_secs);
msleep(sleep_secs * 1000);
pr_info("%s exit\n", __func__);
}
static int livepatch_callbacks_mod_init(void)
{
pr_info("%s\n", __func__);
schedule_delayed_work(&work,
msecs_to_jiffies(1000 * 0));
return 0;
}
static void livepatch_callbacks_mod_exit(void)
{
cancel_delayed_work_sync(&work);
pr_info("%s\n", __func__);
}
module_init(livepatch_callbacks_mod_init);
module_exit(livepatch_callbacks_mod_exit);
MODULE_LICENSE("GPL");

234
samples/livepatch/livepatch-callbacks-demo.c Normal file
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@@ -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");

53
samples/livepatch/livepatch-callbacks-mod.c Normal file
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@@ -0,0 +1,53 @@
/*
* 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-mod.c - (un)patching callbacks demo support module
*
*
* Purpose
* -------
*
* Simple module to demonstrate livepatch (un)patching callbacks.
*
*
* Usage
* -----
*
* This module is not intended to be standalone. See the "Usage"
* section of livepatch-callbacks-demo.c.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
static int livepatch_callbacks_mod_init(void)
{
pr_info("%s\n", __func__);
return 0;
}
static void livepatch_callbacks_mod_exit(void)
{
pr_info("%s\n", __func__);
}
module_init(livepatch_callbacks_mod_init);
module_exit(livepatch_callbacks_mod_exit);
MODULE_LICENSE("GPL");