rethook.c (cdd5b5a9761fd66d17586e4f4ba6588c70e640ea) rethook.c (a1461f1fd6cfdc4b8917c9d4a91e92605d1f28dc)
1// SPDX-License-Identifier: GPL-2.0
2
3#define pr_fmt(fmt) "rethook: " fmt
4
5#include <linux/bug.h>
6#include <linux/kallsyms.h>
7#include <linux/kprobes.h>
8#include <linux/preempt.h>
9#include <linux/rethook.h>
10#include <linux/slab.h>
1// SPDX-License-Identifier: GPL-2.0
2
3#define pr_fmt(fmt) "rethook: " fmt
4
5#include <linux/bug.h>
6#include <linux/kallsyms.h>
7#include <linux/kprobes.h>
8#include <linux/preempt.h>
9#include <linux/rethook.h>
10#include <linux/slab.h>
11#include <linux/sort.h>
12
13/* Return hook list (shadow stack by list) */
14
15/*
16 * This function is called from delayed_put_task_struct() when a task is
17 * dead and cleaned up to recycle any kretprobe instances associated with
18 * this task. These left over instances represent probed functions that
19 * have been called but will never return.

--- 11 unchanged lines hidden (view full) ---

31 rethook_recycle(rhn);
32 preempt_enable();
33 }
34}
35
36static void rethook_free_rcu(struct rcu_head *head)
37{
38 struct rethook *rh = container_of(head, struct rethook, rcu);
11
12/* Return hook list (shadow stack by list) */
13
14/*
15 * This function is called from delayed_put_task_struct() when a task is
16 * dead and cleaned up to recycle any kretprobe instances associated with
17 * this task. These left over instances represent probed functions that
18 * have been called but will never return.

--- 11 unchanged lines hidden (view full) ---

30 rethook_recycle(rhn);
31 preempt_enable();
32 }
33}
34
35static void rethook_free_rcu(struct rcu_head *head)
36{
37 struct rethook *rh = container_of(head, struct rethook, rcu);
39 struct rethook_node *rhn;
40 struct freelist_node *node;
41 int count = 1;
42
43 node = rh->pool.head;
44 while (node) {
45 rhn = container_of(node, struct rethook_node, freelist);
46 node = node->next;
47 kfree(rhn);
48 count++;
49 }
50
51 /* The rh->ref is the number of pooled node + 1 */
52 if (refcount_sub_and_test(count, &rh->ref))
53 kfree(rh);
38 objpool_fini(&rh->pool);
54}
55
56/**
57 * rethook_stop() - Stop using a rethook.
58 * @rh: the struct rethook to stop.
59 *
60 * Stop using a rethook to prepare for freeing it. If you want to wait for
61 * all running rethook handler before calling rethook_free(), you need to
62 * call this first and wait RCU, and call rethook_free().
63 */
64void rethook_stop(struct rethook *rh)
65{
39}
40
41/**
42 * rethook_stop() - Stop using a rethook.
43 * @rh: the struct rethook to stop.
44 *
45 * Stop using a rethook to prepare for freeing it. If you want to wait for
46 * all running rethook handler before calling rethook_free(), you need to
47 * call this first and wait RCU, and call rethook_free().
48 */
49void rethook_stop(struct rethook *rh)
50{
66 WRITE_ONCE(rh->handler, NULL);
51 rcu_assign_pointer(rh->handler, NULL);
67}
68
69/**
70 * rethook_free() - Free struct rethook.
71 * @rh: the struct rethook to be freed.
72 *
73 * Free the rethook. Before calling this function, user must ensure the
74 * @rh::data is cleaned if needed (or, the handler can access it after
75 * calling this function.) This function will set the @rh to be freed
76 * after all rethook_node are freed (not soon). And the caller must
77 * not touch @rh after calling this.
78 */
79void rethook_free(struct rethook *rh)
80{
52}
53
54/**
55 * rethook_free() - Free struct rethook.
56 * @rh: the struct rethook to be freed.
57 *
58 * Free the rethook. Before calling this function, user must ensure the
59 * @rh::data is cleaned if needed (or, the handler can access it after
60 * calling this function.) This function will set the @rh to be freed
61 * after all rethook_node are freed (not soon). And the caller must
62 * not touch @rh after calling this.
63 */
64void rethook_free(struct rethook *rh)
65{
81 WRITE_ONCE(rh->handler, NULL);
66 rethook_stop(rh);
82
83 call_rcu(&rh->rcu, rethook_free_rcu);
84}
85
67
68 call_rcu(&rh->rcu, rethook_free_rcu);
69}
70
71static int rethook_init_node(void *nod, void *context)
72{
73 struct rethook_node *node = nod;
74
75 node->rethook = context;
76 return 0;
77}
78
79static int rethook_fini_pool(struct objpool_head *head, void *context)
80{
81 kfree(context);
82 return 0;
83}
84
85static inline rethook_handler_t rethook_get_handler(struct rethook *rh)
86{
87 return (rethook_handler_t)rcu_dereference_check(rh->handler,
88 rcu_read_lock_any_held());
89}
90
86/**
87 * rethook_alloc() - Allocate struct rethook.
88 * @data: a data to pass the @handler when hooking the return.
91/**
92 * rethook_alloc() - Allocate struct rethook.
93 * @data: a data to pass the @handler when hooking the return.
89 * @handler: the return hook callback function.
94 * @handler: the return hook callback function, must NOT be NULL
95 * @size: node size: rethook node and additional data
96 * @num: number of rethook nodes to be preallocated
90 *
91 * Allocate and initialize a new rethook with @data and @handler.
97 *
98 * Allocate and initialize a new rethook with @data and @handler.
92 * Return NULL if memory allocation fails or @handler is NULL.
99 * Return pointer of new rethook, or error codes for failures.
100 *
93 * Note that @handler == NULL means this rethook is going to be freed.
94 */
101 * Note that @handler == NULL means this rethook is going to be freed.
102 */
95struct rethook *rethook_alloc(void *data, rethook_handler_t handler)
103struct rethook *rethook_alloc(void *data, rethook_handler_t handler,
104 int size, int num)
96{
105{
97 struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL);
106 struct rethook *rh;
98
107
99 if (!rh || !handler) {
100 kfree(rh);
101 return NULL;
102 }
108 if (!handler || num <= 0 || size < sizeof(struct rethook_node))
109 return ERR_PTR(-EINVAL);
103
110
111 rh = kzalloc(sizeof(struct rethook), GFP_KERNEL);
112 if (!rh)
113 return ERR_PTR(-ENOMEM);
114
104 rh->data = data;
115 rh->data = data;
105 rh->handler = handler;
106 rh->pool.head = NULL;
107 refcount_set(&rh->ref, 1);
116 rcu_assign_pointer(rh->handler, handler);
108
117
118 /* initialize the objpool for rethook nodes */
119 if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh,
120 rethook_init_node, rethook_fini_pool)) {
121 kfree(rh);
122 return ERR_PTR(-ENOMEM);
123 }
109 return rh;
110}
111
124 return rh;
125}
126
112/**
113 * rethook_add_node() - Add a new node to the rethook.
114 * @rh: the struct rethook.
115 * @node: the struct rethook_node to be added.
116 *
117 * Add @node to @rh. User must allocate @node (as a part of user's
118 * data structure.) The @node fields are initialized in this function.
119 */
120void rethook_add_node(struct rethook *rh, struct rethook_node *node)
121{
122 node->rethook = rh;
123 freelist_add(&node->freelist, &rh->pool);
124 refcount_inc(&rh->ref);
125}
126
127static void free_rethook_node_rcu(struct rcu_head *head)
128{
129 struct rethook_node *node = container_of(head, struct rethook_node, rcu);
127static void free_rethook_node_rcu(struct rcu_head *head)
128{
129 struct rethook_node *node = container_of(head, struct rethook_node, rcu);
130 struct rethook *rh = node->rethook;
130
131
131 if (refcount_dec_and_test(&node->rethook->ref))
132 kfree(node->rethook);
133 kfree(node);
132 objpool_drop(node, &rh->pool);
134}
135
136/**
137 * rethook_recycle() - return the node to rethook.
138 * @node: The struct rethook_node to be returned.
139 *
140 * Return back the @node to @node::rethook. If the @node::rethook is already
141 * marked as freed, this will free the @node.
142 */
143void rethook_recycle(struct rethook_node *node)
144{
133}
134
135/**
136 * rethook_recycle() - return the node to rethook.
137 * @node: The struct rethook_node to be returned.
138 *
139 * Return back the @node to @node::rethook. If the @node::rethook is already
140 * marked as freed, this will free the @node.
141 */
142void rethook_recycle(struct rethook_node *node)
143{
145 lockdep_assert_preemption_disabled();
144 rethook_handler_t handler;
146
145
147 if (likely(READ_ONCE(node->rethook->handler)))
148 freelist_add(&node->freelist, &node->rethook->pool);
146 handler = rethook_get_handler(node->rethook);
147 if (likely(handler))
148 objpool_push(node, &node->rethook->pool);
149 else
150 call_rcu(&node->rcu, free_rethook_node_rcu);
151}
152NOKPROBE_SYMBOL(rethook_recycle);
153
154/**
155 * rethook_try_get() - get an unused rethook node.
156 * @rh: The struct rethook which pools the nodes.
157 *
158 * Get an unused rethook node from @rh. If the node pool is empty, this
159 * will return NULL. Caller must disable preemption.
160 */
161struct rethook_node *rethook_try_get(struct rethook *rh)
162{
149 else
150 call_rcu(&node->rcu, free_rethook_node_rcu);
151}
152NOKPROBE_SYMBOL(rethook_recycle);
153
154/**
155 * rethook_try_get() - get an unused rethook node.
156 * @rh: The struct rethook which pools the nodes.
157 *
158 * Get an unused rethook node from @rh. If the node pool is empty, this
159 * will return NULL. Caller must disable preemption.
160 */
161struct rethook_node *rethook_try_get(struct rethook *rh)
162{
163 rethook_handler_t handler = READ_ONCE(rh->handler);
164 struct freelist_node *fn;
163 rethook_handler_t handler = rethook_get_handler(rh);
165
164
166 lockdep_assert_preemption_disabled();
167
168 /* Check whether @rh is going to be freed. */
169 if (unlikely(!handler))
170 return NULL;
171
172 /*
173 * This expects the caller will set up a rethook on a function entry.
174 * When the function returns, the rethook will eventually be reclaimed
175 * or released in the rethook_recycle() with call_rcu().
176 * This means the caller must be run in the RCU-availabe context.
177 */
178 if (unlikely(!rcu_is_watching()))
179 return NULL;
180
165 /* Check whether @rh is going to be freed. */
166 if (unlikely(!handler))
167 return NULL;
168
169 /*
170 * This expects the caller will set up a rethook on a function entry.
171 * When the function returns, the rethook will eventually be reclaimed
172 * or released in the rethook_recycle() with call_rcu().
173 * This means the caller must be run in the RCU-availabe context.
174 */
175 if (unlikely(!rcu_is_watching()))
176 return NULL;
177
181 fn = freelist_try_get(&rh->pool);
182 if (!fn)
183 return NULL;
184
185 return container_of(fn, struct rethook_node, freelist);
178 return (struct rethook_node *)objpool_pop(&rh->pool);
186}
187NOKPROBE_SYMBOL(rethook_try_get);
188
189/**
190 * rethook_hook() - Hook the current function return.
191 * @node: The struct rethook node to hook the function return.
192 * @regs: The struct pt_regs for the function entry.
193 * @mcount: True if this is called from mcount(ftrace) context.

--- 113 unchanged lines hidden (view full) ---

307 * Run the handler on the shadow stack. Do not unlink the list here because
308 * stackdump inside the handlers needs to decode it.
309 */
310 first = current->rethooks.first;
311 while (first) {
312 rhn = container_of(first, struct rethook_node, llist);
313 if (WARN_ON_ONCE(rhn->frame != frame))
314 break;
179}
180NOKPROBE_SYMBOL(rethook_try_get);
181
182/**
183 * rethook_hook() - Hook the current function return.
184 * @node: The struct rethook node to hook the function return.
185 * @regs: The struct pt_regs for the function entry.
186 * @mcount: True if this is called from mcount(ftrace) context.

--- 113 unchanged lines hidden (view full) ---

300 * Run the handler on the shadow stack. Do not unlink the list here because
301 * stackdump inside the handlers needs to decode it.
302 */
303 first = current->rethooks.first;
304 while (first) {
305 rhn = container_of(first, struct rethook_node, llist);
306 if (WARN_ON_ONCE(rhn->frame != frame))
307 break;
315 handler = READ_ONCE(rhn->rethook->handler);
308 handler = rethook_get_handler(rhn->rethook);
316 if (handler)
317 handler(rhn, rhn->rethook->data,
318 correct_ret_addr, regs);
319
320 if (first == node)
321 break;
322 first = first->next;
323 }

--- 19 unchanged lines hidden --- 		309 if (handler)
310 handler(rhn, rhn->rethook->data,
311 correct_ret_addr, regs);
312
313 if (first == node)
314 break;
315 first = first->next;
316 }

--- 19 unchanged lines hidden ---