#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;
}
-static bool klp_is_object_loaded(struct klp_object *obj)
-{
- return !obj->name || obj->mod;
-}
-
/* sets obj->mod if object is not vmlinux and module is found */
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;
};
mutex_lock(&module_mutex);
- kallsyms_on_each_symbol(klp_find_callback, &args);
+ if (objname)
+ module_kallsyms_on_each_symbol(klp_find_callback, &args);
+ else
+ kallsyms_on_each_symbol(klp_find_callback, &args);
mutex_unlock(&module_mutex);
/*
for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
if (sym->st_shndx != SHN_LIVEPATCH) {
- pr_err("symbol %s is not marked as a livepatch symbol",
+ pr_err("symbol %s is not marked as a livepatch symbol\n",
strtab + sym->st_name);
return -EINVAL;
}
".klp.sym.%55[^.].%127[^,],%lu",
objname, symname, &sympos);
if (cnt != 3) {
- pr_err("symbol %s has an incorrectly formatted name",
+ pr_err("symbol %s has an incorrectly formatted name\n",
strtab + sym->st_name);
return -EINVAL;
}
*/
cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
if (cnt != 1) {
- pr_err("section %s has an incorrectly formatted name",
+ pr_err("section %s has an incorrectly formatted name\n",
secname);
ret = -EINVAL;
break;
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)
+static int __klp_disable_patch(struct klp_patch *patch)
{
- struct klp_func *func;
- int ret;
-
- if (WARN_ON(obj->state != KLP_DISABLED))
- return -EINVAL;
+ struct klp_object *obj;
- if (WARN_ON(!klp_is_object_loaded(obj)))
+ if (WARN_ON(!patch->enabled))
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);
- }
+ klp_for_each_object(patch, obj)
+ if (obj->patched)
+ klp_pre_unpatch_callback(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;
}
goto err;
}
- if (patch->state == KLP_DISABLED) {
+ if (!patch->enabled) {
ret = -EINVAL;
goto err;
}
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_pre_patch_callback(obj);
+ if (ret) {
+ pr_warn("pre-patch callback failed for object '%s'\n",
+ klp_is_module(obj) ? obj->name : "vmlinux");
+ goto err;
+ }
+
+ ret = klp_patch_object(obj);
+ if (ret) {
+ pr_warn("failed to patch object '%s'\n",
+ klp_is_module(obj) ? obj->name : "vmlinux");
+ goto err;
+ }
}
- patch->state = KLP_ENABLED;
+ klp_start_transition();
+ klp_try_complete_transition();
+ patch->enabled = true;
return 0;
+err:
+ pr_warn("failed to enable patch '%s'\n", patch->mod->name);
-unregister:
- WARN_ON(__klp_disable_patch(patch));
+ klp_cancel_transition();
return ret;
}
* /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>
*/
{
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;
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 = {
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)
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
&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;
if (!obj->funcs)
return -EINVAL;
- obj->state = KLP_DISABLED;
+ obj->patched = false;
obj->mod = NULL;
klp_find_object_module(obj);
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);
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;
}
*/
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;
}
* 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;
if (!is_livepatch_module(patch->mod)) {
- pr_err("module %s is not marked as a livepatch module",
+ pr_err("module %s is not marked as a livepatch module\n",
patch->mod->name);
return -EINVAL;
}
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);
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_pre_patch_callback(obj);
+ if (ret) {
+ pr_warn("pre-patch callback failed for object '%s'\n",
+ obj->name);
+ goto err;
+ }
+
+ 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);
+
+ klp_post_unpatch_callback(obj);
goto err;
}
+ if (patch != klp_transition_patch)
+ klp_post_patch_callback(obj);
+
break;
}
}
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) {
+
+ if (patch != klp_transition_patch)
+ klp_pre_unpatch_callback(obj);
+
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_post_unpatch_callback(obj);
}
klp_free_object_loaded(obj);
git.samba.org / sfrench / cifs-2.6.git / blobdiff