mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
317 lines
8.7 KiB
317 lines
8.7 KiB
// SPDX-License-Identifier: GPL-2.0 |
|
|
|
#define pr_fmt(fmt) "rethook: " fmt |
|
|
|
#include <linux/bug.h> |
|
#include <linux/kallsyms.h> |
|
#include <linux/kprobes.h> |
|
#include <linux/preempt.h> |
|
#include <linux/rethook.h> |
|
#include <linux/slab.h> |
|
#include <linux/sort.h> |
|
|
|
/* Return hook list (shadow stack by list) */ |
|
|
|
/* |
|
* This function is called from delayed_put_task_struct() when a task is |
|
* dead and cleaned up to recycle any kretprobe instances associated with |
|
* this task. These left over instances represent probed functions that |
|
* have been called but will never return. |
|
*/ |
|
void rethook_flush_task(struct task_struct *tk) |
|
{ |
|
struct rethook_node *rhn; |
|
struct llist_node *node; |
|
|
|
node = __llist_del_all(&tk->rethooks); |
|
while (node) { |
|
rhn = container_of(node, struct rethook_node, llist); |
|
node = node->next; |
|
preempt_disable(); |
|
rethook_recycle(rhn); |
|
preempt_enable(); |
|
} |
|
} |
|
|
|
static void rethook_free_rcu(struct rcu_head *head) |
|
{ |
|
struct rethook *rh = container_of(head, struct rethook, rcu); |
|
struct rethook_node *rhn; |
|
struct freelist_node *node; |
|
int count = 1; |
|
|
|
node = rh->pool.head; |
|
while (node) { |
|
rhn = container_of(node, struct rethook_node, freelist); |
|
node = node->next; |
|
kfree(rhn); |
|
count++; |
|
} |
|
|
|
/* The rh->ref is the number of pooled node + 1 */ |
|
if (refcount_sub_and_test(count, &rh->ref)) |
|
kfree(rh); |
|
} |
|
|
|
/** |
|
* rethook_free() - Free struct rethook. |
|
* @rh: the struct rethook to be freed. |
|
* |
|
* Free the rethook. Before calling this function, user must ensure the |
|
* @rh::data is cleaned if needed (or, the handler can access it after |
|
* calling this function.) This function will set the @rh to be freed |
|
* after all rethook_node are freed (not soon). And the caller must |
|
* not touch @rh after calling this. |
|
*/ |
|
void rethook_free(struct rethook *rh) |
|
{ |
|
WRITE_ONCE(rh->handler, NULL); |
|
|
|
call_rcu(&rh->rcu, rethook_free_rcu); |
|
} |
|
|
|
/** |
|
* rethook_alloc() - Allocate struct rethook. |
|
* @data: a data to pass the @handler when hooking the return. |
|
* @handler: the return hook callback function. |
|
* |
|
* Allocate and initialize a new rethook with @data and @handler. |
|
* Return NULL if memory allocation fails or @handler is NULL. |
|
* Note that @handler == NULL means this rethook is going to be freed. |
|
*/ |
|
struct rethook *rethook_alloc(void *data, rethook_handler_t handler) |
|
{ |
|
struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL); |
|
|
|
if (!rh || !handler) |
|
return NULL; |
|
|
|
rh->data = data; |
|
rh->handler = handler; |
|
rh->pool.head = NULL; |
|
refcount_set(&rh->ref, 1); |
|
|
|
return rh; |
|
} |
|
|
|
/** |
|
* rethook_add_node() - Add a new node to the rethook. |
|
* @rh: the struct rethook. |
|
* @node: the struct rethook_node to be added. |
|
* |
|
* Add @node to @rh. User must allocate @node (as a part of user's |
|
* data structure.) The @node fields are initialized in this function. |
|
*/ |
|
void rethook_add_node(struct rethook *rh, struct rethook_node *node) |
|
{ |
|
node->rethook = rh; |
|
freelist_add(&node->freelist, &rh->pool); |
|
refcount_inc(&rh->ref); |
|
} |
|
|
|
static void free_rethook_node_rcu(struct rcu_head *head) |
|
{ |
|
struct rethook_node *node = container_of(head, struct rethook_node, rcu); |
|
|
|
if (refcount_dec_and_test(&node->rethook->ref)) |
|
kfree(node->rethook); |
|
kfree(node); |
|
} |
|
|
|
/** |
|
* rethook_recycle() - return the node to rethook. |
|
* @node: The struct rethook_node to be returned. |
|
* |
|
* Return back the @node to @node::rethook. If the @node::rethook is already |
|
* marked as freed, this will free the @node. |
|
*/ |
|
void rethook_recycle(struct rethook_node *node) |
|
{ |
|
lockdep_assert_preemption_disabled(); |
|
|
|
if (likely(READ_ONCE(node->rethook->handler))) |
|
freelist_add(&node->freelist, &node->rethook->pool); |
|
else |
|
call_rcu(&node->rcu, free_rethook_node_rcu); |
|
} |
|
NOKPROBE_SYMBOL(rethook_recycle); |
|
|
|
/** |
|
* rethook_try_get() - get an unused rethook node. |
|
* @rh: The struct rethook which pools the nodes. |
|
* |
|
* Get an unused rethook node from @rh. If the node pool is empty, this |
|
* will return NULL. Caller must disable preemption. |
|
*/ |
|
struct rethook_node *rethook_try_get(struct rethook *rh) |
|
{ |
|
rethook_handler_t handler = READ_ONCE(rh->handler); |
|
struct freelist_node *fn; |
|
|
|
lockdep_assert_preemption_disabled(); |
|
|
|
/* Check whether @rh is going to be freed. */ |
|
if (unlikely(!handler)) |
|
return NULL; |
|
|
|
fn = freelist_try_get(&rh->pool); |
|
if (!fn) |
|
return NULL; |
|
|
|
return container_of(fn, struct rethook_node, freelist); |
|
} |
|
NOKPROBE_SYMBOL(rethook_try_get); |
|
|
|
/** |
|
* rethook_hook() - Hook the current function return. |
|
* @node: The struct rethook node to hook the function return. |
|
* @regs: The struct pt_regs for the function entry. |
|
* @mcount: True if this is called from mcount(ftrace) context. |
|
* |
|
* Hook the current running function return. This must be called when the |
|
* function entry (or at least @regs must be the registers of the function |
|
* entry.) @mcount is used for identifying the context. If this is called |
|
* from ftrace (mcount) callback, @mcount must be set true. If this is called |
|
* from the real function entry (e.g. kprobes) @mcount must be set false. |
|
* This is because the way to hook the function return depends on the context. |
|
*/ |
|
void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount) |
|
{ |
|
arch_rethook_prepare(node, regs, mcount); |
|
__llist_add(&node->llist, ¤t->rethooks); |
|
} |
|
NOKPROBE_SYMBOL(rethook_hook); |
|
|
|
/* This assumes the 'tsk' is the current task or is not running. */ |
|
static unsigned long __rethook_find_ret_addr(struct task_struct *tsk, |
|
struct llist_node **cur) |
|
{ |
|
struct rethook_node *rh = NULL; |
|
struct llist_node *node = *cur; |
|
|
|
if (!node) |
|
node = tsk->rethooks.first; |
|
else |
|
node = node->next; |
|
|
|
while (node) { |
|
rh = container_of(node, struct rethook_node, llist); |
|
if (rh->ret_addr != (unsigned long)arch_rethook_trampoline) { |
|
*cur = node; |
|
return rh->ret_addr; |
|
} |
|
node = node->next; |
|
} |
|
return 0; |
|
} |
|
NOKPROBE_SYMBOL(__rethook_find_ret_addr); |
|
|
|
/** |
|
* rethook_find_ret_addr -- Find correct return address modified by rethook |
|
* @tsk: Target task |
|
* @frame: A frame pointer |
|
* @cur: a storage of the loop cursor llist_node pointer for next call |
|
* |
|
* Find the correct return address modified by a rethook on @tsk in unsigned |
|
* long type. |
|
* The @tsk must be 'current' or a task which is not running. @frame is a hint |
|
* to get the currect return address - which is compared with the |
|
* rethook::frame field. The @cur is a loop cursor for searching the |
|
* kretprobe return addresses on the @tsk. The '*@cur' should be NULL at the |
|
* first call, but '@cur' itself must NOT NULL. |
|
* |
|
* Returns found address value or zero if not found. |
|
*/ |
|
unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame, |
|
struct llist_node **cur) |
|
{ |
|
struct rethook_node *rhn = NULL; |
|
unsigned long ret; |
|
|
|
if (WARN_ON_ONCE(!cur)) |
|
return 0; |
|
|
|
if (WARN_ON_ONCE(tsk != current && task_is_running(tsk))) |
|
return 0; |
|
|
|
do { |
|
ret = __rethook_find_ret_addr(tsk, cur); |
|
if (!ret) |
|
break; |
|
rhn = container_of(*cur, struct rethook_node, llist); |
|
} while (rhn->frame != frame); |
|
|
|
return ret; |
|
} |
|
NOKPROBE_SYMBOL(rethook_find_ret_addr); |
|
|
|
void __weak arch_rethook_fixup_return(struct pt_regs *regs, |
|
unsigned long correct_ret_addr) |
|
{ |
|
/* |
|
* Do nothing by default. If the architecture which uses a |
|
* frame pointer to record real return address on the stack, |
|
* it should fill this function to fixup the return address |
|
* so that stacktrace works from the rethook handler. |
|
*/ |
|
} |
|
|
|
/* This function will be called from each arch-defined trampoline. */ |
|
unsigned long rethook_trampoline_handler(struct pt_regs *regs, |
|
unsigned long frame) |
|
{ |
|
struct llist_node *first, *node = NULL; |
|
unsigned long correct_ret_addr; |
|
rethook_handler_t handler; |
|
struct rethook_node *rhn; |
|
|
|
correct_ret_addr = __rethook_find_ret_addr(current, &node); |
|
if (!correct_ret_addr) { |
|
pr_err("rethook: Return address not found! Maybe there is a bug in the kernel\n"); |
|
BUG_ON(1); |
|
} |
|
|
|
instruction_pointer_set(regs, correct_ret_addr); |
|
|
|
/* |
|
* These loops must be protected from rethook_free_rcu() because those |
|
* are accessing 'rhn->rethook'. |
|
*/ |
|
preempt_disable(); |
|
|
|
/* |
|
* Run the handler on the shadow stack. Do not unlink the list here because |
|
* stackdump inside the handlers needs to decode it. |
|
*/ |
|
first = current->rethooks.first; |
|
while (first) { |
|
rhn = container_of(first, struct rethook_node, llist); |
|
if (WARN_ON_ONCE(rhn->frame != frame)) |
|
break; |
|
handler = READ_ONCE(rhn->rethook->handler); |
|
if (handler) |
|
handler(rhn, rhn->rethook->data, regs); |
|
|
|
if (first == node) |
|
break; |
|
first = first->next; |
|
} |
|
|
|
/* Fixup registers for returning to correct address. */ |
|
arch_rethook_fixup_return(regs, correct_ret_addr); |
|
|
|
/* Unlink used shadow stack */ |
|
first = current->rethooks.first; |
|
current->rethooks.first = node->next; |
|
node->next = NULL; |
|
|
|
while (first) { |
|
rhn = container_of(first, struct rethook_node, llist); |
|
first = first->next; |
|
rethook_recycle(rhn); |
|
} |
|
preempt_enable(); |
|
|
|
return correct_ret_addr; |
|
} |
|
NOKPROBE_SYMBOL(rethook_trampoline_handler);
|
|
|