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-rw-r--r--kernel/livepatch/Makefile2
-rw-r--r--kernel/livepatch/core.c437
-rw-r--r--kernel/livepatch/core.h6
-rw-r--r--kernel/livepatch/patch.c272
-rw-r--r--kernel/livepatch/patch.h33
-rw-r--r--kernel/livepatch/transition.c553
-rw-r--r--kernel/livepatch/transition.h14
7 files changed, 1043 insertions, 274 deletions
diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile
index e8780c0901d9..2b8bdb1925da 100644
--- a/kernel/livepatch/Makefile
+++ b/kernel/livepatch/Makefile
@@ -1,3 +1,3 @@
obj-$(CONFIG_LIVEPATCH) += livepatch.o
-livepatch-objs := core.o
+livepatch-objs := core.o patch.o transition.o
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 8739e9e0bdb8..b9628e43c78f 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -24,61 +24,31 @@
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/slab.h>
-#include <linux/ftrace.h>
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
#include <linux/elf.h>
#include <linux/moduleloader.h>
+#include <linux/completion.h>
#include <asm/cacheflush.h>
-
-/**
- * struct klp_ops - structure for tracking registered ftrace ops structs
- *
- * A single ftrace_ops is shared between all enabled replacement functions
- * (klp_func structs) which have the same old_addr. This allows the switch
- * between function versions to happen instantaneously by updating the klp_ops
- * struct's func_stack list. The winner is the klp_func at the top of the
- * func_stack (front of the list).
- *
- * @node: node for the global klp_ops list
- * @func_stack: list head for the stack of klp_func's (active func is on top)
- * @fops: registered ftrace ops struct
- */
-struct klp_ops {
- struct list_head node;
- struct list_head func_stack;
- struct ftrace_ops fops;
-};
+#include "core.h"
+#include "patch.h"
+#include "transition.h"
/*
- * The klp_mutex protects the global lists and state transitions of any
- * structure reachable from them. References to any structure must be obtained
- * under mutex protection (except in klp_ftrace_handler(), which uses RCU to
- * ensure it gets consistent data).
+ * klp_mutex is a coarse lock which serializes access to klp data. All
+ * accesses to klp-related variables and structures must have mutex protection,
+ * except within the following functions which carefully avoid the need for it:
+ *
+ * - klp_ftrace_handler()
+ * - klp_update_patch_state()
*/
-static DEFINE_MUTEX(klp_mutex);
+DEFINE_MUTEX(klp_mutex);
static LIST_HEAD(klp_patches);
-static LIST_HEAD(klp_ops);
static struct kobject *klp_root_kobj;
-static struct klp_ops *klp_find_ops(unsigned long old_addr)
-{
- struct klp_ops *ops;
- struct klp_func *func;
-
- list_for_each_entry(ops, &klp_ops, node) {
- func = list_first_entry(&ops->func_stack, struct klp_func,
- stack_node);
- if (func->old_addr == old_addr)
- return ops;
- }
-
- return NULL;
-}
-
static bool klp_is_module(struct klp_object *obj)
{
return obj->name;
@@ -117,7 +87,6 @@ static void klp_find_object_module(struct klp_object *obj)
mutex_unlock(&module_mutex);
}
-/* klp_mutex must be held by caller */
static bool klp_is_patch_registered(struct klp_patch *patch)
{
struct klp_patch *mypatch;
@@ -314,191 +283,30 @@ static int klp_write_object_relocations(struct module *pmod,
return ret;
}
-static void notrace klp_ftrace_handler(unsigned long ip,
- unsigned long parent_ip,
- struct ftrace_ops *fops,
- struct pt_regs *regs)
-{
- struct klp_ops *ops;
- struct klp_func *func;
-
- ops = container_of(fops, struct klp_ops, fops);
-
- rcu_read_lock();
- func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
- stack_node);
- if (WARN_ON_ONCE(!func))
- goto unlock;
-
- klp_arch_set_pc(regs, (unsigned long)func->new_func);
-unlock:
- rcu_read_unlock();
-}
-
-/*
- * Convert a function address into the appropriate ftrace location.
- *
- * Usually this is just the address of the function, but on some architectures
- * it's more complicated so allow them to provide a custom behaviour.
- */
-#ifndef klp_get_ftrace_location
-static unsigned long klp_get_ftrace_location(unsigned long faddr)
-{
- return faddr;
-}
-#endif
-
-static void klp_disable_func(struct klp_func *func)
-{
- struct klp_ops *ops;
-
- if (WARN_ON(func->state != KLP_ENABLED))
- return;
- if (WARN_ON(!func->old_addr))
- return;
-
- ops = klp_find_ops(func->old_addr);
- if (WARN_ON(!ops))
- return;
-
- if (list_is_singular(&ops->func_stack)) {
- unsigned long ftrace_loc;
-
- ftrace_loc = klp_get_ftrace_location(func->old_addr);
- if (WARN_ON(!ftrace_loc))
- return;
-
- WARN_ON(unregister_ftrace_function(&ops->fops));
- WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
-
- list_del_rcu(&func->stack_node);
- list_del(&ops->node);
- kfree(ops);
- } else {
- list_del_rcu(&func->stack_node);
- }
-
- func->state = KLP_DISABLED;
-}
-
-static int klp_enable_func(struct klp_func *func)
-{
- struct klp_ops *ops;
- int ret;
-
- if (WARN_ON(!func->old_addr))
- return -EINVAL;
-
- if (WARN_ON(func->state != KLP_DISABLED))
- return -EINVAL;
-
- ops = klp_find_ops(func->old_addr);
- if (!ops) {
- unsigned long ftrace_loc;
-
- ftrace_loc = klp_get_ftrace_location(func->old_addr);
- if (!ftrace_loc) {
- pr_err("failed to find location for function '%s'\n",
- func->old_name);
- return -EINVAL;
- }
-
- ops = kzalloc(sizeof(*ops), GFP_KERNEL);
- if (!ops)
- return -ENOMEM;
-
- ops->fops.func = klp_ftrace_handler;
- ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
- FTRACE_OPS_FL_DYNAMIC |
- FTRACE_OPS_FL_IPMODIFY;
-
- list_add(&ops->node, &klp_ops);
-
- INIT_LIST_HEAD(&ops->func_stack);
- list_add_rcu(&func->stack_node, &ops->func_stack);
-
- ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
- if (ret) {
- pr_err("failed to set ftrace filter for function '%s' (%d)\n",
- func->old_name, ret);
- goto err;
- }
-
- ret = register_ftrace_function(&ops->fops);
- if (ret) {
- pr_err("failed to register ftrace handler for function '%s' (%d)\n",
- func->old_name, ret);
- ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
- goto err;
- }
-
-
- } else {
- list_add_rcu(&func->stack_node, &ops->func_stack);
- }
-
- func->state = KLP_ENABLED;
-
- return 0;
-
-err:
- list_del_rcu(&func->stack_node);
- list_del(&ops->node);
- kfree(ops);
- return ret;
-}
-
-static void klp_disable_object(struct klp_object *obj)
-{
- struct klp_func *func;
-
- klp_for_each_func(obj, func)
- if (func->state == KLP_ENABLED)
- klp_disable_func(func);
-
- obj->state = KLP_DISABLED;
-}
-
-static int klp_enable_object(struct klp_object *obj)
-{
- struct klp_func *func;
- int ret;
-
- if (WARN_ON(obj->state != KLP_DISABLED))
- return -EINVAL;
-
- if (WARN_ON(!klp_is_object_loaded(obj)))
- return -EINVAL;
-
- klp_for_each_func(obj, func) {
- ret = klp_enable_func(func);
- if (ret) {
- klp_disable_object(obj);
- return ret;
- }
- }
- obj->state = KLP_ENABLED;
-
- return 0;
-}
-
static int __klp_disable_patch(struct klp_patch *patch)
{
- struct klp_object *obj;
+ if (klp_transition_patch)
+ return -EBUSY;
/* enforce stacking: only the last enabled patch can be disabled */
if (!list_is_last(&patch->list, &klp_patches) &&
- list_next_entry(patch, list)->state == KLP_ENABLED)
+ list_next_entry(patch, list)->enabled)
return -EBUSY;
- pr_notice("disabling patch '%s'\n", patch->mod->name);
+ klp_init_transition(patch, KLP_UNPATCHED);
- klp_for_each_object(patch, obj) {
- if (obj->state == KLP_ENABLED)
- klp_disable_object(obj);
- }
+ /*
+ * Enforce the order of the func->transition writes in
+ * klp_init_transition() and the TIF_PATCH_PENDING writes in
+ * klp_start_transition(). In the rare case where klp_ftrace_handler()
+ * is called shortly after klp_update_patch_state() switches the task,
+ * this ensures the handler sees that func->transition is set.
+ */
+ smp_wmb();
- patch->state = KLP_DISABLED;
+ klp_start_transition();
+ klp_try_complete_transition();
+ patch->enabled = false;
return 0;
}
@@ -522,7 +330,7 @@ int klp_disable_patch(struct klp_patch *patch)
goto err;
}
- if (patch->state == KLP_DISABLED) {
+ if (!patch->enabled) {
ret = -EINVAL;
goto err;
}
@@ -540,32 +348,61 @@ static int __klp_enable_patch(struct klp_patch *patch)
struct klp_object *obj;
int ret;
- if (WARN_ON(patch->state != KLP_DISABLED))
+ if (klp_transition_patch)
+ return -EBUSY;
+
+ if (WARN_ON(patch->enabled))
return -EINVAL;
/* enforce stacking: only the first disabled patch can be enabled */
if (patch->list.prev != &klp_patches &&
- list_prev_entry(patch, list)->state == KLP_DISABLED)
+ !list_prev_entry(patch, list)->enabled)
return -EBUSY;
+ /*
+ * A reference is taken on the patch module to prevent it from being
+ * unloaded.
+ *
+ * Note: For immediate (no consistency model) patches we don't allow
+ * patch modules to unload since there is no safe/sane method to
+ * determine if a thread is still running in the patched code contained
+ * in the patch module once the ftrace registration is successful.
+ */
+ if (!try_module_get(patch->mod))
+ return -ENODEV;
+
pr_notice("enabling patch '%s'\n", patch->mod->name);
+ klp_init_transition(patch, KLP_PATCHED);
+
+ /*
+ * Enforce the order of the func->transition writes in
+ * klp_init_transition() and the ops->func_stack writes in
+ * klp_patch_object(), so that klp_ftrace_handler() will see the
+ * func->transition updates before the handler is registered and the
+ * new funcs become visible to the handler.
+ */
+ smp_wmb();
+
klp_for_each_object(patch, obj) {
if (!klp_is_object_loaded(obj))
continue;
- ret = klp_enable_object(obj);
- if (ret)
- goto unregister;
+ ret = klp_patch_object(obj);
+ if (ret) {
+ pr_warn("failed to enable patch '%s'\n",
+ patch->mod->name);
+
+ klp_cancel_transition();
+ return ret;
+ }
}
- patch->state = KLP_ENABLED;
+ klp_start_transition();
+ klp_try_complete_transition();
+ patch->enabled = true;
return 0;
-
-unregister:
- WARN_ON(__klp_disable_patch(patch));
- return ret;
}
/**
@@ -602,6 +439,7 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
* /sys/kernel/livepatch
* /sys/kernel/livepatch/<patch>
* /sys/kernel/livepatch/<patch>/enabled
+ * /sys/kernel/livepatch/<patch>/transition
* /sys/kernel/livepatch/<patch>/<object>
* /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
*/
@@ -611,26 +449,34 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
{
struct klp_patch *patch;
int ret;
- unsigned long val;
+ bool enabled;
- ret = kstrtoul(buf, 10, &val);
+ ret = kstrtobool(buf, &enabled);
if (ret)
- return -EINVAL;
-
- if (val != KLP_DISABLED && val != KLP_ENABLED)
- return -EINVAL;
+ return ret;
patch = container_of(kobj, struct klp_patch, kobj);
mutex_lock(&klp_mutex);
- if (val == patch->state) {
+ if (!klp_is_patch_registered(patch)) {
+ /*
+ * Module with the patch could either disappear meanwhile or is
+ * not properly initialized yet.
+ */
+ ret = -EINVAL;
+ goto err;
+ }
+
+ if (patch->enabled == enabled) {
/* already in requested state */
ret = -EINVAL;
goto err;
}
- if (val == KLP_ENABLED) {
+ if (patch == klp_transition_patch) {
+ klp_reverse_transition();
+ } else if (enabled) {
ret = __klp_enable_patch(patch);
if (ret)
goto err;
@@ -655,21 +501,33 @@ static ssize_t enabled_show(struct kobject *kobj,
struct klp_patch *patch;
patch = container_of(kobj, struct klp_patch, kobj);
- return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->state);
+ return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
+}
+
+static ssize_t transition_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct klp_patch *patch;
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ return snprintf(buf, PAGE_SIZE-1, "%d\n",
+ patch == klp_transition_patch);
}
static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
+static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
static struct attribute *klp_patch_attrs[] = {
&enabled_kobj_attr.attr,
+ &transition_kobj_attr.attr,
NULL
};
static void klp_kobj_release_patch(struct kobject *kobj)
{
- /*
- * Once we have a consistency model we'll need to module_put() the
- * patch module here. See klp_register_patch() for more details.
- */
+ struct klp_patch *patch;
+
+ patch = container_of(kobj, struct klp_patch, kobj);
+ complete(&patch->finish);
}
static struct kobj_type klp_ktype_patch = {
@@ -740,7 +598,6 @@ static void klp_free_patch(struct klp_patch *patch)
klp_free_objects_limited(patch, NULL);
if (!list_empty(&patch->list))
list_del(&patch->list);
- kobject_put(&patch->kobj);
}
static int klp_init_func(struct klp_object *obj, struct klp_func *func)
@@ -749,7 +606,8 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
return -EINVAL;
INIT_LIST_HEAD(&func->stack_node);
- func->state = KLP_DISABLED;
+ func->patched = false;
+ func->transition = false;
/* The format for the sysfs directory is <function,sympos> where sympos
* is the nth occurrence of this symbol in kallsyms for the patched
@@ -790,6 +648,22 @@ static int klp_init_object_loaded(struct klp_patch *patch,
&func->old_addr);
if (ret)
return ret;
+
+ ret = kallsyms_lookup_size_offset(func->old_addr,
+ &func->old_size, NULL);
+ if (!ret) {
+ pr_err("kallsyms size lookup failed for '%s'\n",
+ func->old_name);
+ return -ENOENT;
+ }
+
+ ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
+ &func->new_size, NULL);
+ if (!ret) {
+ pr_err("kallsyms size lookup failed for '%s' replacement\n",
+ func->old_name);
+ return -ENOENT;
+ }
}
return 0;
@@ -804,7 +678,7 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
if (!obj->funcs)
return -EINVAL;
- obj->state = KLP_DISABLED;
+ obj->patched = false;
obj->mod = NULL;
klp_find_object_module(obj);
@@ -845,12 +719,15 @@ static int klp_init_patch(struct klp_patch *patch)
mutex_lock(&klp_mutex);
- patch->state = KLP_DISABLED;
+ patch->enabled = false;
+ init_completion(&patch->finish);
ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
klp_root_kobj, "%s", patch->mod->name);
- if (ret)
- goto unlock;
+ if (ret) {
+ mutex_unlock(&klp_mutex);
+ return ret;
+ }
klp_for_each_object(patch, obj) {
ret = klp_init_object(patch, obj);
@@ -866,9 +743,12 @@ static int klp_init_patch(struct klp_patch *patch)
free:
klp_free_objects_limited(patch, obj);
- kobject_put(&patch->kobj);
-unlock:
+
mutex_unlock(&klp_mutex);
+
+ kobject_put(&patch->kobj);
+ wait_for_completion(&patch->finish);
+
return ret;
}
@@ -882,23 +762,29 @@ unlock:
*/
int klp_unregister_patch(struct klp_patch *patch)
{
- int ret = 0;
+ int ret;
mutex_lock(&klp_mutex);
if (!klp_is_patch_registered(patch)) {
ret = -EINVAL;
- goto out;
+ goto err;
}
- if (patch->state == KLP_ENABLED) {
+ if (patch->enabled) {
ret = -EBUSY;
- goto out;
+ goto err;
}
klp_free_patch(patch);
-out:
+ mutex_unlock(&klp_mutex);
+
+ kobject_put(&patch->kobj);
+ wait_for_completion(&patch->finish);
+
+ return 0;
+err:
mutex_unlock(&klp_mutex);
return ret;
}
@@ -911,12 +797,13 @@ EXPORT_SYMBOL_GPL(klp_unregister_patch);
* Initializes the data structure associated with the patch and
* creates the sysfs interface.
*
+ * There is no need to take the reference on the patch module here. It is done
+ * later when the patch is enabled.
+ *
* Return: 0 on success, otherwise error
*/
int klp_register_patch(struct klp_patch *patch)
{
- int ret;
-
if (!patch || !patch->mod)
return -EINVAL;
@@ -930,20 +817,16 @@ int klp_register_patch(struct klp_patch *patch)
return -ENODEV;
/*
- * A reference is taken on the patch module to prevent it from being
- * unloaded. Right now, we don't allow patch modules to unload since
- * there is currently no method to determine if a thread is still
- * running in the patched code contained in the patch module once
- * the ftrace registration is successful.
+ * Architectures without reliable stack traces have to set
+ * patch->immediate because there's currently no way to patch kthreads
+ * with the consistency model.
*/
- if (!try_module_get(patch->mod))
- return -ENODEV;
-
- ret = klp_init_patch(patch);
- if (ret)
- module_put(patch->mod);
+ if (!klp_have_reliable_stack() && !patch->immediate) {
+ pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
+ return -ENOSYS;
+ }
- return ret;
+ return klp_init_patch(patch);
}
EXPORT_SYMBOL_GPL(klp_register_patch);
@@ -978,13 +861,17 @@ int klp_module_coming(struct module *mod)
goto err;
}
- if (patch->state == KLP_DISABLED)
+ /*
+ * Only patch the module if the patch is enabled or is
+ * in transition.
+ */
+ if (!patch->enabled && patch != klp_transition_patch)
break;
pr_notice("applying patch '%s' to loading module '%s'\n",
patch->mod->name, obj->mod->name);
- ret = klp_enable_object(obj);
+ ret = klp_patch_object(obj);
if (ret) {
pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
patch->mod->name, obj->mod->name, ret);
@@ -1035,10 +922,14 @@ void klp_module_going(struct module *mod)
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;
- if (patch->state != KLP_DISABLED) {
+ /*
+ * Only unpatch the module if the patch is enabled or
+ * is in transition.
+ */
+ if (patch->enabled || patch == klp_transition_patch) {
pr_notice("reverting patch '%s' on unloading module '%s'\n",
patch->mod->name, obj->mod->name);
- klp_disable_object(obj);
+ klp_unpatch_object(obj);
}
klp_free_object_loaded(obj);
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
new file mode 100644
index 000000000000..c74f24c47837
--- /dev/null
+++ b/kernel/livepatch/core.h
@@ -0,0 +1,6 @@
+#ifndef _LIVEPATCH_CORE_H
+#define _LIVEPATCH_CORE_H
+
+extern struct mutex klp_mutex;
+
+#endif /* _LIVEPATCH_CORE_H */
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
new file mode 100644
index 000000000000..f8269036bf0b
--- /dev/null
+++ b/kernel/livepatch/patch.c
@@ -0,0 +1,272 @@
+/*
+ * patch.c - livepatch patching functions
+ *
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ * Copyright (C) 2014 SUSE
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@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/>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/livepatch.h>
+#include <linux/list.h>
+#include <linux/ftrace.h>
+#include <linux/rculist.h>
+#include <linux/slab.h>
+#include <linux/bug.h>
+#include <linux/printk.h>
+#include "patch.h"
+#include "transition.h"
+
+static LIST_HEAD(klp_ops);
+
+struct klp_ops *klp_find_ops(unsigned long old_addr)
+{
+ struct klp_ops *ops;
+ struct klp_func *func;
+
+ list_for_each_entry(ops, &klp_ops, node) {
+ func = list_first_entry(&ops->func_stack, struct klp_func,
+ stack_node);
+ if (func->old_addr == old_addr)
+ return ops;
+ }
+
+ return NULL;
+}
+
+static void notrace klp_ftrace_handler(unsigned long ip,
+ unsigned long parent_ip,
+ struct ftrace_ops *fops,
+ struct pt_regs *regs)
+{
+ struct klp_ops *ops;
+ struct klp_func *func;
+ int patch_state;
+
+ ops = container_of(fops, struct klp_ops, fops);
+
+ rcu_read_lock();
+
+ func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
+ stack_node);
+
+ /*
+ * func should never be NULL because preemption should be disabled here
+ * and unregister_ftrace_function() does the equivalent of a
+ * synchronize_sched() before the func_stack removal.
+ */
+ if (WARN_ON_ONCE(!func))
+ goto unlock;
+
+ /*
+ * In the enable path, enforce the order of the ops->func_stack and
+ * func->transition reads. The corresponding write barrier is in
+ * __klp_enable_patch().
+ *
+ * (Note that this barrier technically isn't needed in the disable
+ * path. In the rare case where klp_update_patch_state() runs before
+ * this handler, its TIF_PATCH_PENDING read and this func->transition
+ * read need to be ordered. But klp_update_patch_state() already
+ * enforces that.)
+ */
+ smp_rmb();
+
+ if (unlikely(func->transition)) {
+
+ /*
+ * Enforce the order of the func->transition and
+ * current->patch_state reads. Otherwise we could read an
+ * out-of-date task state and pick the wrong function. The
+ * corresponding write barrier is in klp_init_transition().
+ */
+ smp_rmb();
+
+ patch_state = current->patch_state;
+
+ WARN_ON_ONCE(patch_state == KLP_UNDEFINED);
+
+ if (patch_state == KLP_UNPATCHED) {
+ /*
+ * Use the previously patched version of the function.
+ * If no previous patches exist, continue with the
+ * original function.
+ */
+ func = list_entry_rcu(func->stack_node.next,
+ struct klp_func, stack_node);
+
+ if (&func->stack_node == &ops->func_stack)
+ goto unlock;
+ }
+ }
+
+ klp_arch_set_pc(regs, (unsigned long)func->new_func);
+unlock:
+ rcu_read_unlock();
+}
+
+/*
+ * Convert a function address into the appropriate ftrace location.
+ *
+ * Usually this is just the address of the function, but on some architectures
+ * it's more complicated so allow them to provide a custom behaviour.
+ */
+#ifndef klp_get_ftrace_location
+static unsigned long klp_get_ftrace_location(unsigned long faddr)
+{
+ return faddr;
+}
+#endif
+
+static void klp_unpatch_func(struct klp_func *func)
+{
+ struct klp_ops *ops;
+
+ if (WARN_ON(!func->patched))
+ return;
+ if (WARN_ON(!func->old_addr))
+ return;
+
+ ops = klp_find_ops(func->old_addr);
+ if (WARN_ON(!ops))
+ return;
+
+ if (list_is_singular(&ops->func_stack)) {
+ unsigned long ftrace_loc;
+
+ ftrace_loc = klp_get_ftrace_location(func->old_addr);
+ if (WARN_ON(!ftrace_loc))
+ return;
+
+ WARN_ON(unregister_ftrace_function(&ops->fops));
+ WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
+
+ list_del_rcu(&func->stack_node);
+ list_del(&ops->node);
+ kfree(ops);
+ } else {
+ list_del_rcu(&func->stack_node);
+ }
+
+ func->patched = false;
+}
+
+static int klp_patch_func(struct klp_func *func)
+{
+ struct klp_ops *ops;
+ int ret;
+
+ if (WARN_ON(!func->old_addr))
+ return -EINVAL;
+
+ if (WARN_ON(func->patched))
+ return -EINVAL;
+
+ ops = klp_find_ops(func->old_addr);
+ if (!ops) {
+ unsigned long ftrace_loc;
+
+ ftrace_loc = klp_get_ftrace_location(func->old_addr);
+ if (!ftrace_loc) {
+ pr_err("failed to find location for function '%s'\n",
+ func->old_name);
+ return -EINVAL;
+ }
+
+ ops = kzalloc(sizeof(*ops), GFP_KERNEL);
+ if (!ops)
+ return -ENOMEM;
+
+ ops->fops.func = klp_ftrace_handler;
+ ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
+ FTRACE_OPS_FL_DYNAMIC |
+ FTRACE_OPS_FL_IPMODIFY;
+
+ list_add(&ops->node, &klp_ops);
+
+ INIT_LIST_HEAD(&ops->func_stack);
+ list_add_rcu(&func->stack_node, &ops->func_stack);
+
+ ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
+ if (ret) {
+ pr_err("failed to set ftrace filter for function '%s' (%d)\n",
+ func->old_name, ret);
+ goto err;
+ }
+
+ ret = register_ftrace_function(&ops->fops);
+ if (ret) {
+ pr_err("failed to register ftrace handler for function '%s' (%d)\n",
+ func->old_name, ret);
+ ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
+ goto err;
+ }
+
+
+ } else {
+ list_add_rcu(&func->stack_node, &ops->func_stack);
+ }
+
+ func->patched = true;
+
+ return 0;
+
+err:
+ list_del_rcu(&func->stack_node);
+ list_del(&ops->node);
+ kfree(ops);
+ return ret;
+}
+
+void klp_unpatch_object(struct klp_object *obj)
+{
+ struct klp_func *func;
+
+ klp_for_each_func(obj, func)
+ if (func->patched)
+ klp_unpatch_func(func);
+
+ obj->patched = false;
+}
+
+int klp_patch_object(struct klp_object *obj)
+{
+ struct klp_func *func;
+ int ret;
+
+ if (WARN_ON(obj->patched))
+ return -EINVAL;
+
+ klp_for_each_func(obj, func) {
+ ret = klp_patch_func(func);
+ if (ret) {
+ klp_unpatch_object(obj);
+ return ret;
+ }
+ }
+ obj->patched = true;
+
+ return 0;
+}
+
+void klp_unpatch_objects(struct klp_patch *patch)
+{
+ struct klp_object *obj;
+
+ klp_for_each_object(patch, obj)
+ if (obj->patched)
+ klp_unpatch_object(obj);
+}
diff --git a/kernel/livepatch/patch.h b/kernel/livepatch/patch.h
new file mode 100644
index 000000000000..0db227170c36
--- /dev/null
+++ b/kernel/livepatch/patch.h
@@ -0,0 +1,33 @@
+#ifndef _LIVEPATCH_PATCH_H
+#define _LIVEPATCH_PATCH_H
+
+#include <linux/livepatch.h>
+#include <linux/list.h>
+#include <linux/ftrace.h>
+
+/**
+ * struct klp_ops - structure for tracking registered ftrace ops structs
+ *
+ * A single ftrace_ops is shared between all enabled replacement functions
+ * (klp_func structs) which have the same old_addr. This allows the switch
+ * between function versions to happen instantaneously by updating the klp_ops
+ * struct's func_stack list. The winner is the klp_func at the top of the
+ * func_stack (front of the list).
+ *
+ * @node: node for the global klp_ops list
+ * @func_stack: list head for the stack of klp_func's (active func is on top)
+ * @fops: registered ftrace ops struct
+ */
+struct klp_ops {
+ struct list_head node;
+ struct list_head func_stack;
+ struct ftrace_ops fops;
+};
+
+struct klp_ops *klp_find_ops(unsigned long old_addr);
+
+int klp_patch_object(struct klp_object *obj);
+void klp_unpatch_object(struct klp_object *obj);
+void klp_unpatch_objects(struct klp_patch *patch);
+
+#endif /* _LIVEPATCH_PATCH_H */
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
new file mode 100644
index 000000000000..adc0cc64aa4b
--- /dev/null
+++ b/kernel/livepatch/transition.c
@@ -0,0 +1,553 @@
+/*
+ * transition.c - Kernel Live Patching transition functions
+ *
+ * Copyright (C) 2015-2016 Josh Poimboeuf <jpoimboe@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/>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cpu.h>
+#include <linux/stacktrace.h>
+#include "core.h"
+#include "patch.h"
+#include "transition.h"
+#include "../sched/sched.h"
+
+#define MAX_STACK_ENTRIES 100
+#define STACK_ERR_BUF_SIZE 128
+
+struct klp_patch *klp_transition_patch;
+
+static int klp_target_state = KLP_UNDEFINED;
+
+/*
+ * This work can be performed periodically to finish patching or unpatching any
+ * "straggler" tasks which failed to transition in the first attempt.
+ */
+static void klp_transition_work_fn(struct work_struct *work)
+{
+ mutex_lock(&klp_mutex);
+
+ if (klp_transition_patch)
+ klp_try_complete_transition();
+
+ mutex_unlock(&klp_mutex);
+}
+static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn);
+
+/*
+ * The transition to the target patch state is complete. Clean up the data
+ * structures.
+ */
+static void klp_complete_transition(void)
+{
+ struct klp_object *obj;
+ struct klp_func *func;
+ struct task_struct *g, *task;
+ unsigned int cpu;
+ bool immediate_func = false;
+
+ if (klp_target_state == KLP_UNPATCHED) {
+ /*
+ * All tasks have transitioned to KLP_UNPATCHED so we can now
+ * remove the new functions from the func_stack.
+ */
+ klp_unpatch_objects(klp_transition_patch);
+
+ /*
+ * Make sure klp_ftrace_handler() can no longer see functions
+ * from this patch on the ops->func_stack. Otherwise, after
+ * func->transition gets cleared, the handler may choose a
+ * removed function.
+ */
+ synchronize_rcu();
+ }
+
+ if (klp_transition_patch->immediate)
+ goto done;
+
+ klp_for_each_object(klp_transition_patch, obj) {
+ klp_for_each_func(obj, func) {
+ func->transition = false;
+ if (func->immediate)
+ immediate_func = true;
+ }
+ }
+
+ if (klp_target_state == KLP_UNPATCHED && !immediate_func)
+ module_put(klp_transition_patch->mod);
+
+ /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */
+ if (klp_target_state == KLP_PATCHED)
+ synchronize_rcu();
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task) {
+ WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING));
+ task->patch_state = KLP_UNDEFINED;
+ }
+ read_unlock(&tasklist_lock);
+
+ for_each_possible_cpu(cpu) {
+ task = idle_task(cpu);
+ WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING));
+ task->patch_state = KLP_UNDEFINED;
+ }
+
+done:
+ klp_target_state = KLP_UNDEFINED;
+ klp_transition_patch = NULL;
+}
+
+/*
+ * This is called in the error path, to cancel a transition before it has
+ * started, i.e. klp_init_transition() has been called but
+ * klp_start_transition() hasn't. If the transition *has* been started,
+ * klp_reverse_transition() should be used instead.
+ */
+void klp_cancel_transition(void)
+{
+ if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED))
+ return;
+
+ klp_target_state = KLP_UNPATCHED;
+ klp_complete_transition();
+}
+
+/*
+ * Switch the patched state of the task to the set of functions in the target
+ * patch state.
+ *
+ * NOTE: If task is not 'current', the caller must ensure the task is inactive.
+ * Otherwise klp_ftrace_handler() might read the wrong 'patch_state' value.
+ */
+void klp_update_patch_state(struct task_struct *task)
+{
+ rcu_read_lock();
+
+ /*
+ * This test_and_clear_tsk_thread_flag() call also serves as a read
+ * barrier (smp_rmb) for two cases:
+ *
+ * 1) Enforce the order of the TIF_PATCH_PENDING read and the
+ * klp_target_state read. The corresponding write barrier is in
+ * klp_init_transition().
+ *
+ * 2) Enforce the order of the TIF_PATCH_PENDING read and a future read
+ * of func->transition, if klp_ftrace_handler() is called later on
+ * the same CPU. See __klp_disable_patch().
+ */
+ if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING))
+ task->patch_state = READ_ONCE(klp_target_state);
+
+ rcu_read_unlock();
+}
+
+/*
+ * Determine whether the given stack trace includes any references to a
+ * to-be-patched or to-be-unpatched function.
+ */
+static int klp_check_stack_func(struct klp_func *func,
+ struct stack_trace *trace)
+{
+ unsigned long func_addr, func_size, address;
+ struct klp_ops *ops;
+ int i;
+
+ if (func->immediate)
+ return 0;
+
+ for (i = 0; i < trace->nr_entries; i++) {
+ address = trace->entries[i];
+
+ if (klp_target_state == KLP_UNPATCHED) {
+ /*
+ * Check for the to-be-unpatched function
+ * (the func itself).
+ */
+ func_addr = (unsigned long)func->new_func;
+ func_size = func->new_size;
+ } else {
+ /*
+ * Check for the to-be-patched function
+ * (the previous func).
+ */
+ ops = klp_find_ops(func->old_addr);
+
+ if (list_is_singular(&ops->func_stack)) {
+ /* original function */
+ func_addr = func->old_addr;
+ func_size = func->old_size;
+ } else {
+ /* previously patched function */
+ struct klp_func *prev;
+
+ prev = list_next_entry(func, stack_node);
+ func_addr = (unsigned long)prev->new_func;
+ func_size = prev->new_size;
+ }
+ }
+
+ if (address >= func_addr && address < func_addr + func_size)
+ return -EAGAIN;
+ }
+
+ return 0;
+}
+
+/*
+ * Determine whether it's safe to transition the task to the target patch state
+ * by looking for any to-be-patched or to-be-unpatched functions on its stack.
+ */
+static int klp_check_stack(struct task_struct *task, char *err_buf)
+{
+ static unsigned long entries[MAX_STACK_ENTRIES];
+ struct stack_trace trace;
+ struct klp_object *obj;
+ struct klp_func *func;
+ int ret;
+
+ trace.skip = 0;
+ trace.nr_entries = 0;
+ trace.max_entries = MAX_STACK_ENTRIES;
+ trace.entries = entries;
+ ret = save_stack_trace_tsk_reliable(task, &trace);
+ WARN_ON_ONCE(ret == -ENOSYS);
+ if (ret) {
+ snprintf(err_buf, STACK_ERR_BUF_SIZE,
+ "%s: %s:%d has an unreliable stack\n",
+ __func__, task->comm, task->pid);
+ return ret;
+ }
+
+ klp_for_each_object(klp_transition_patch, obj) {
+ if (!obj->patched)
+ continue;
+ klp_for_each_func(obj, func) {
+ ret = klp_check_stack_func(func, &trace);
+ if (ret) {
+ snprintf(err_buf, STACK_ERR_BUF_SIZE,
+ "%s: %s:%d is sleeping on function %s\n",
+ __func__, task->comm, task->pid,
+ func->old_name);
+ return ret;
+ }
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Try to safely switch a task to the target patch state. If it's currently
+ * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or
+ * if the stack is unreliable, return false.
+ */
+static bool klp_try_switch_task(struct task_struct *task)
+{
+ struct rq *rq;
+ struct rq_flags flags;
+ int ret;
+ bool success = false;
+ char err_buf[STACK_ERR_BUF_SIZE];
+
+ err_buf[0] = '\0';
+
+ /* check if this task has already switched over */
+ if (task->patch_state == klp_target_state)
+ return true;
+
+ /*
+ * For arches which don't have reliable stack traces, we have to rely
+ * on other methods (e.g., switching tasks at kernel exit).
+ */
+ if (!klp_have_reliable_stack())
+ return false;
+
+ /*
+ * Now try to check the stack for any to-be-patched or to-be-unpatched
+ * functions. If all goes well, switch the task to the target patch
+ * state.
+ */
+ rq = task_rq_lock(task, &flags);
+
+ if (task_running(rq, task) && task != current) {
+ snprintf(err_buf, STACK_ERR_BUF_SIZE,
+ "%s: %s:%d is running\n", __func__, task->comm,
+ task->pid);
+ goto done;
+ }
+
+ ret = klp_check_stack(task, err_buf);
+ if (ret)
+ goto done;
+
+ success = true;
+
+ clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
+ task->patch_state = klp_target_state;
+
+done:
+ task_rq_unlock(rq, task, &flags);
+
+ /*
+ * Due to console deadlock issues, pr_debug() can't be used while
+ * holding the task rq lock. Instead we have to use a temporary buffer
+ * and print the debug message after releasing the lock.
+ */
+ if (err_buf[0] != '\0')
+ pr_debug("%s", err_buf);
+
+ return success;
+
+}
+
+/*
+ * Try to switch all remaining tasks to the target patch state by walking the
+ * stacks of sleeping tasks and looking for any to-be-patched or
+ * to-be-unpatched functions. If such functions are found, the task can't be
+ * switched yet.
+ *
+ * If any tasks are still stuck in the initial patch state, schedule a retry.
+ */
+void klp_try_complete_transition(void)
+{
+ unsigned int cpu;
+ struct task_struct *g, *task;
+ bool complete = true;
+
+ WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED);
+
+ /*
+ * If the patch can be applied or reverted immediately, skip the
+ * per-task transitions.
+ */
+ if (klp_transition_patch->immediate)
+ goto success;
+
+ /*
+ * Try to switch the tasks to the target patch state by walking their
+ * stacks and looking for any to-be-patched or to-be-unpatched
+ * functions. If such functions are found on a stack, or if the stack
+ * is deemed unreliable, the task can't be switched yet.
+ *
+ * Usually this will transition most (or all) of the tasks on a system
+ * unless the patch includes changes to a very common function.
+ */
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task)
+ if (!klp_try_switch_task(task))
+ complete = false;
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Ditto for the idle "swapper" tasks.
+ */
+ get_online_cpus();
+ for_each_possible_cpu(cpu) {
+ task = idle_task(cpu);
+ if (cpu_online(cpu)) {
+ if (!klp_try_switch_task(task))
+ complete = false;
+ } else if (task->patch_state != klp_target_state) {
+ /* offline idle tasks can be switched immediately */
+ clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
+ task->patch_state = klp_target_state;
+ }
+ }
+ put_online_cpus();
+
+ if (!complete) {
+ /*
+ * Some tasks weren't able to be switched over. Try again
+ * later and/or wait for other methods like kernel exit
+ * switching.
+ */
+ schedule_delayed_work(&klp_transition_work,
+ round_jiffies_relative(HZ));
+ return;
+ }
+
+success:
+ pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name,
+ klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
+
+ /* we're done, now cleanup the data structures */
+ klp_complete_transition();
+}
+
+/*
+ * Start the transition to the specified target patch state so tasks can begin
+ * switching to it.
+ */
+void klp_start_transition(void)
+{
+ struct task_struct *g, *task;
+ unsigned int cpu;
+
+ WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED);
+
+ pr_notice("'%s': %s...\n", klp_transition_patch->mod->name,
+ klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
+
+ /*
+ * If the patch can be applied or reverted immediately, skip the
+ * per-task transitions.
+ */
+ if (klp_transition_patch->immediate)
+ return;
+
+ /*
+ * Mark all normal tasks as needing a patch state update. They'll
+ * switch either in klp_try_complete_transition() or as they exit the
+ * kernel.
+ */
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task)
+ if (task->patch_state != klp_target_state)
+ set_tsk_thread_flag(task, TIF_PATCH_PENDING);
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Mark all idle tasks as needing a patch state update. They'll switch
+ * either in klp_try_complete_transition() or at the idle loop switch
+ * point.
+ */
+ for_each_possible_cpu(cpu) {
+ task = idle_task(cpu);
+ if (task->patch_state != klp_target_state)
+ set_tsk_thread_flag(task, TIF_PATCH_PENDING);
+ }
+}
+
+/*
+ * Initialize the global target patch state and all tasks to the initial patch
+ * state, and initialize all function transition states to true in preparation
+ * for patching or unpatching.
+ */
+void klp_init_transition(struct klp_patch *patch, int state)
+{
+ struct task_struct *g, *task;
+ unsigned int cpu;
+ struct klp_object *obj;
+ struct klp_func *func;
+ int initial_state = !state;
+
+ WARN_ON_ONCE(klp_target_state != KLP_UNDEFINED);
+
+ klp_transition_patch = patch;
+
+ /*
+ * Set the global target patch state which tasks will switch to. This
+ * has no effect until the TIF_PATCH_PENDING flags get set later.
+ */
+ klp_target_state = state;
+
+ /*
+ * If the patch can be applied or reverted immediately, skip the
+ * per-task transitions.
+ */
+ if (patch->immediate)
+ return;
+
+ /*
+ * Initialize all tasks to the initial patch state to prepare them for
+ * switching to the target state.
+ */
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task) {
+ WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED);
+ task->patch_state = initial_state;
+ }
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Ditto for the idle "swapper" tasks.
+ */
+ for_each_possible_cpu(cpu) {
+ task = idle_task(cpu);
+ WARN_ON_ONCE(task->patch_state != KLP_UNDEFINED);
+ task->patch_state = initial_state;
+ }
+
+ /*
+ * Enforce the order of the task->patch_state initializations and the
+ * func->transition updates to ensure that klp_ftrace_handler() doesn't
+ * see a func in transition with a task->patch_state of KLP_UNDEFINED.
+ *
+ * Also enforce the order of the klp_target_state write and future
+ * TIF_PATCH_PENDING writes to ensure klp_update_patch_state() doesn't
+ * set a task->patch_state to KLP_UNDEFINED.
+ */
+ smp_wmb();
+
+ /*
+ * Set the func transition states so klp_ftrace_handler() will know to
+ * switch to the transition logic.
+ *
+ * When patching, the funcs aren't yet in the func_stack and will be
+ * made visible to the ftrace handler shortly by the calls to
+ * klp_patch_object().
+ *
+ * When unpatching, the funcs are already in the func_stack and so are
+ * already visible to the ftrace handler.
+ */
+ klp_for_each_object(patch, obj)
+ klp_for_each_func(obj, func)
+ func->transition = true;
+}
+
+/*
+ * This function can be called in the middle of an existing transition to
+ * reverse the direction of the target patch state. This can be done to
+ * effectively cancel an existing enable or disable operation if there are any
+ * tasks which are stuck in the initial patch state.
+ */
+void klp_reverse_transition(void)
+{
+ unsigned int cpu;
+ struct task_struct *g, *task;
+
+ klp_transition_patch->enabled = !klp_transition_patch->enabled;
+
+ klp_target_state = !klp_target_state;
+
+ /*
+ * Clear all TIF_PATCH_PENDING flags to prevent races caused by
+ * klp_update_patch_state() running in parallel with
+ * klp_start_transition().
+ */
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, task)
+ clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
+ read_unlock(&tasklist_lock);
+
+ for_each_possible_cpu(cpu)
+ clear_tsk_thread_flag(idle_task(cpu), TIF_PATCH_PENDING);
+
+ /* Let any remaining calls to klp_update_patch_state() complete */
+ synchronize_rcu();
+
+ klp_start_transition();
+}
+
+/* Called from copy_process() during fork */
+void klp_copy_process(struct task_struct *child)
+{
+ child->patch_state = current->patch_state;
+
+ /* TIF_PATCH_PENDING gets copied in setup_thread_stack() */
+}
diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h
new file mode 100644
index 000000000000..ce09b326546c
--- /dev/null
+++ b/kernel/livepatch/transition.h
@@ -0,0 +1,14 @@
+#ifndef _LIVEPATCH_TRANSITION_H
+#define _LIVEPATCH_TRANSITION_H
+
+#include <linux/livepatch.h>
+
+extern struct klp_patch *klp_transition_patch;
+
+void klp_init_transition(struct klp_patch *patch, int state);
+void klp_cancel_transition(void);
+void klp_start_transition(void);
+void klp_try_complete_transition(void);
+void klp_reverse_transition(void);
+
+#endif /* _LIVEPATCH_TRANSITION_H */