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-rw-r--r--kernel/fork.c3
-rw-r--r--kernel/livepatch/Makefile2
-rw-r--r--kernel/livepatch/core.c105
-rw-r--r--kernel/livepatch/patch.c59
-rw-r--r--kernel/livepatch/patch.h1
-rw-r--r--kernel/livepatch/transition.c543
-rw-r--r--kernel/livepatch/transition.h14
-rw-r--r--kernel/sched/idle.c4
8 files changed, 706 insertions, 25 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 6c463c80e93d..942cbcd07c18 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -87,6 +87,7 @@
#include <linux/compiler.h>
#include <linux/sysctl.h>
#include <linux/kcov.h>
+#include <linux/livepatch.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1797,6 +1798,8 @@ static __latent_entropy struct task_struct *copy_process(
p->parent_exec_id = current->self_exec_id;
}
+ klp_copy_process(p);
+
spin_lock(&current->sighand->siglock);
/*
diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile
index e136dad8ff7e..2b8bdb1925da 100644
--- a/kernel/livepatch/Makefile
+++ b/kernel/livepatch/Makefile
@@ -1,3 +1,3 @@
obj-$(CONFIG_LIVEPATCH) += livepatch.o
-livepatch-objs := core.o patch.o
+livepatch-objs := core.o patch.o transition.o
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 10ba3a1578bd..3dc3c9049690 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -31,22 +31,22 @@
#include <linux/moduleloader.h>
#include <asm/cacheflush.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 struct kobject *klp_root_kobj;
-/* TODO: temporary stub */
-void klp_update_patch_state(struct task_struct *task) {}
-
static bool klp_is_module(struct klp_object *obj)
{
return obj->name;
@@ -85,7 +85,6 @@ 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;
@@ -281,20 +280,27 @@ static int klp_write_object_relocations(struct module *pmod,
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)->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->patched)
- klp_unpatch_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();
+ klp_start_transition();
+ klp_try_complete_transition();
patch->enabled = false;
return 0;
@@ -337,6 +343,9 @@ static int __klp_enable_patch(struct klp_patch *patch)
struct klp_object *obj;
int ret;
+ if (klp_transition_patch)
+ return -EBUSY;
+
if (WARN_ON(patch->enabled))
return -EINVAL;
@@ -347,22 +356,36 @@ static int __klp_enable_patch(struct klp_patch *patch)
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_patch_object(obj);
- if (ret)
- goto unregister;
+ if (ret) {
+ pr_warn("failed to enable patch '%s'\n",
+ patch->mod->name);
+
+ klp_cancel_transition();
+ return ret;
+ }
}
+ klp_start_transition();
+ klp_try_complete_transition();
patch->enabled = true;
return 0;
-
-unregister:
- WARN_ON(__klp_disable_patch(patch));
- return ret;
}
/**
@@ -399,6 +422,7 @@ 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>
*/
@@ -424,7 +448,9 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
goto err;
}
- if (enabled) {
+ if (patch == klp_transition_patch) {
+ klp_reverse_transition();
+ } else if (enabled) {
ret = __klp_enable_patch(patch);
if (ret)
goto err;
@@ -452,9 +478,21 @@ static ssize_t enabled_show(struct kobject *kobj,
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
};
@@ -544,6 +582,7 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
INIT_LIST_HEAD(&func->stack_node);
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
@@ -740,6 +779,16 @@ int klp_register_patch(struct klp_patch *patch)
return -ENODEV;
/*
+ * Architectures without reliable stack traces have to set
+ * patch->immediate because there's currently no way to patch kthreads
+ * with the consistency model.
+ */
+ if (!klp_have_reliable_stack() && !patch->immediate) {
+ pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
+ return -ENOSYS;
+ }
+
+ /*
* 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
@@ -788,7 +837,11 @@ int klp_module_coming(struct module *mod)
goto err;
}
- if (!patch->enabled)
+ /*
+ * 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",
@@ -845,7 +898,11 @@ void klp_module_going(struct module *mod)
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;
- if (patch->enabled) {
+ /*
+ * 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_unpatch_object(obj);
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index 5efa2620851a..f8269036bf0b 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -29,6 +29,7 @@
#include <linux/bug.h>
#include <linux/printk.h>
#include "patch.h"
+#include "transition.h"
static LIST_HEAD(klp_ops);
@@ -54,15 +55,64 @@ static void notrace klp_ftrace_handler(unsigned long ip,
{
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();
@@ -211,3 +261,12 @@ int klp_patch_object(struct klp_object *obj)
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
index 2d0cce02dade..0db227170c36 100644
--- a/kernel/livepatch/patch.h
+++ b/kernel/livepatch/patch.h
@@ -28,5 +28,6 @@ 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..428533ec51b5
--- /dev/null
+++ b/kernel/livepatch/transition.c
@@ -0,0 +1,543 @@
+/*
+ * 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 "patch.h"
+#include "transition.h"
+#include "../sched/sched.h"
+
+#define MAX_STACK_ENTRIES 100
+#define STACK_ERR_BUF_SIZE 128
+
+extern struct mutex klp_mutex;
+
+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;
+
+ 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;
+
+ /* 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)
+{
+ klp_target_state = !klp_target_state;
+ 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 */
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index ac6d5176463d..2a25a9ec2c6e 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -10,6 +10,7 @@
#include <linux/mm.h>
#include <linux/stackprotector.h>
#include <linux/suspend.h>
+#include <linux/livepatch.h>
#include <asm/tlb.h>
@@ -265,6 +266,9 @@ static void do_idle(void)
sched_ttwu_pending();
schedule_preempt_disabled();
+
+ if (unlikely(klp_patch_pending(current)))
+ klp_update_patch_state(current);
}
bool cpu_in_idle(unsigned long pc)