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livepatch: separate enabled and patched states
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Once we have a consistency model, patches and their objects will be
enabled and disabled at different times.  For example, when a patch is
disabled, its loaded objects' funcs can remain registered with ftrace
indefinitely until the unpatching operation is complete and they're no
longer in use.

It's less confusing if we give them different names: patches can be
enabled or disabled; objects (and their funcs) can be patched or
unpatched:

- Enabled means that a patch is logically enabled (but not necessarily
  fully applied).

- Patched means that an object's funcs are registered with ftrace and
  added to the klp_ops func stack.

Also, since these states are binary, represent them with booleans
instead of ints.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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Josh Poimboeuf authored and Jiri Kosina committed Mar 8, 2017
1 parent 2f09ca6 commit 0dade9f
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Showing 2 changed files with 42 additions and 47 deletions.
17 changes: 6 additions & 11 deletions include/linux/livepatch.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -28,11 +28,6 @@

#include <asm/livepatch.h>

enum klp_state {
KLP_DISABLED,
KLP_ENABLED
};

/**
* struct klp_func - function structure for live patching
* @old_name: name of the function to be patched
Expand All @@ -41,8 +36,8 @@ enum klp_state {
* can be found (optional)
* @old_addr: the address of the function being patched
* @kobj: kobject for sysfs resources
* @state: tracks function-level patch application state
* @stack_node: list node for klp_ops func_stack list
* @patched: the func has been added to the klp_ops list
*/
struct klp_func {
/* external */
Expand All @@ -60,8 +55,8 @@ struct klp_func {
/* internal */
unsigned long old_addr;
struct kobject kobj;
enum klp_state state;
struct list_head stack_node;
bool patched;
};

/**
Expand All @@ -71,7 +66,7 @@ struct klp_func {
* @kobj: kobject for sysfs resources
* @mod: kernel module associated with the patched object
* (NULL for vmlinux)
* @state: tracks object-level patch application state
* @patched: the object's funcs have been added to the klp_ops list
*/
struct klp_object {
/* external */
Expand All @@ -81,7 +76,7 @@ struct klp_object {
/* internal */
struct kobject kobj;
struct module *mod;
enum klp_state state;
bool patched;
};

/**
Expand All @@ -90,7 +85,7 @@ struct klp_object {
* @objs: object entries for kernel objects to be patched
* @list: list node for global list of registered patches
* @kobj: kobject for sysfs resources
* @state: tracks patch-level application state
* @enabled: the patch is enabled (but operation may be incomplete)
*/
struct klp_patch {
/* external */
Expand All @@ -100,7 +95,7 @@ struct klp_patch {
/* internal */
struct list_head list;
struct kobject kobj;
enum klp_state state;
bool enabled;
};

#define klp_for_each_object(patch, obj) \
Expand Down
72 changes: 36 additions & 36 deletions kernel/livepatch/core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -348,11 +348,11 @@ static unsigned long klp_get_ftrace_location(unsigned long faddr)
}
#endif

static void klp_disable_func(struct klp_func *func)
static void klp_unpatch_func(struct klp_func *func)
{
struct klp_ops *ops;

if (WARN_ON(func->state != KLP_ENABLED))
if (WARN_ON(!func->patched))
return;
if (WARN_ON(!func->old_addr))
return;
Expand All @@ -378,18 +378,18 @@ static void klp_disable_func(struct klp_func *func)
list_del_rcu(&func->stack_node);
}

func->state = KLP_DISABLED;
func->patched = false;
}

static int klp_enable_func(struct klp_func *func)
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->state != KLP_DISABLED))
if (WARN_ON(func->patched))
return -EINVAL;

ops = klp_find_ops(func->old_addr);
Expand Down Expand Up @@ -437,7 +437,7 @@ static int klp_enable_func(struct klp_func *func)
list_add_rcu(&func->stack_node, &ops->func_stack);
}

func->state = KLP_ENABLED;
func->patched = true;

return 0;

Expand All @@ -448,36 +448,36 @@ static int klp_enable_func(struct klp_func *func)
return ret;
}

static void klp_disable_object(struct klp_object *obj)
static void klp_unpatch_object(struct klp_object *obj)
{
struct klp_func *func;

klp_for_each_func(obj, func)
if (func->state == KLP_ENABLED)
klp_disable_func(func);
if (func->patched)
klp_unpatch_func(func);

obj->state = KLP_DISABLED;
obj->patched = false;
}

static int klp_enable_object(struct klp_object *obj)
static int klp_patch_object(struct klp_object *obj)
{
struct klp_func *func;
int ret;

if (WARN_ON(obj->state != KLP_DISABLED))
if (WARN_ON(obj->patched))
return -EINVAL;

if (WARN_ON(!klp_is_object_loaded(obj)))
return -EINVAL;

klp_for_each_func(obj, func) {
ret = klp_enable_func(func);
ret = klp_patch_func(func);
if (ret) {
klp_disable_object(obj);
klp_unpatch_object(obj);
return ret;
}
}
obj->state = KLP_ENABLED;
obj->patched = true;

return 0;
}
Expand All @@ -488,17 +488,17 @@ static int __klp_disable_patch(struct klp_patch *patch)

/* 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_for_each_object(patch, obj) {
if (obj->state == KLP_ENABLED)
klp_disable_object(obj);
if (obj->patched)
klp_unpatch_object(obj);
}

patch->state = KLP_DISABLED;
patch->enabled = false;

return 0;
}
Expand All @@ -522,7 +522,7 @@ int klp_disable_patch(struct klp_patch *patch)
goto err;
}

if (patch->state == KLP_DISABLED) {
if (!patch->enabled) {
ret = -EINVAL;
goto err;
}
Expand All @@ -540,12 +540,12 @@ static int __klp_enable_patch(struct klp_patch *patch)
struct klp_object *obj;
int ret;

if (WARN_ON(patch->state != KLP_DISABLED))
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;

pr_notice("enabling patch '%s'\n", patch->mod->name);
Expand All @@ -554,12 +554,12 @@ static int __klp_enable_patch(struct klp_patch *patch)
if (!klp_is_object_loaded(obj))
continue;

ret = klp_enable_object(obj);
ret = klp_patch_object(obj);
if (ret)
goto unregister;
}

patch->state = KLP_ENABLED;
patch->enabled = true;

return 0;

Expand Down Expand Up @@ -617,20 +617,20 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
if (ret)
return -EINVAL;

if (val != KLP_DISABLED && val != KLP_ENABLED)
if (val > 1)
return -EINVAL;

patch = container_of(kobj, struct klp_patch, kobj);

mutex_lock(&klp_mutex);

if (val == patch->state) {
if (patch->enabled == val) {
/* already in requested state */
ret = -EINVAL;
goto err;
}

if (val == KLP_ENABLED) {
if (val) {
ret = __klp_enable_patch(patch);
if (ret)
goto err;
Expand All @@ -655,7 +655,7 @@ 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 struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
Expand Down Expand Up @@ -749,7 +749,7 @@ 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;

/* The format for the sysfs directory is <function,sympos> where sympos
* is the nth occurrence of this symbol in kallsyms for the patched
Expand Down Expand Up @@ -804,7 +804,7 @@ 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);
Expand Down Expand Up @@ -845,7 +845,7 @@ static int klp_init_patch(struct klp_patch *patch)

mutex_lock(&klp_mutex);

patch->state = KLP_DISABLED;
patch->enabled = false;

ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
klp_root_kobj, "%s", patch->mod->name);
Expand Down Expand Up @@ -891,7 +891,7 @@ int klp_unregister_patch(struct klp_patch *patch)
goto out;
}

if (patch->state == KLP_ENABLED) {
if (patch->enabled) {
ret = -EBUSY;
goto out;
}
Expand Down Expand Up @@ -978,13 +978,13 @@ int klp_module_coming(struct module *mod)
goto err;
}

if (patch->state == KLP_DISABLED)
if (!patch->enabled)
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);
Expand Down Expand Up @@ -1035,10 +1035,10 @@ void klp_module_going(struct module *mod)
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;

if (patch->state != KLP_DISABLED) {
if (patch->enabled) {
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);
Expand Down

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