| 1 | /* |
| 2 | * Copyright (C) 2011 Mathieu Desnoyers (mathieu.desnoyers@efficios.com) |
| 3 | * |
| 4 | * wrapper around poll_get_entry, implementing __pollwait with exclusive |
| 5 | * wakeups. Using KALLSYMS to get poll_get_entry address when available, |
| 6 | * else we need to have a kernel that exports this function to GPL |
| 7 | * modules. |
| 8 | * |
| 9 | * GPL v2 license. |
| 10 | */ |
| 11 | |
| 12 | #ifdef CONFIG_KALLSYMS |
| 13 | |
| 14 | #include <linux/kallsyms.h> |
| 15 | #include <linux/poll.h> |
| 16 | #include <linux/wait.h> |
| 17 | |
| 18 | struct poll_table_entry; |
| 19 | struct splice_pipe_desc; |
| 20 | |
| 21 | static |
| 22 | int (*pollwake_sym)(wait_queue_t *wait, unsigned mode, int sync, void *key); |
| 23 | static |
| 24 | struct poll_table_entry *(*poll_get_entry_sym)(struct poll_wqueues *p); |
| 25 | |
| 26 | /* Add a new entry */ |
| 27 | static void __pollwait_exclusive(struct file *filp, |
| 28 | wait_queue_head_t *wait_address, |
| 29 | poll_table *p) |
| 30 | { |
| 31 | struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); |
| 32 | struct poll_table_entry *entry; |
| 33 | |
| 34 | if (!poll_get_entry_sym) |
| 35 | poll_get_entry_sym = (void *) kallsyms_lookup_name("poll_get_entry"); |
| 36 | if (!poll_get_entry_sym) { |
| 37 | printk(KERN_WARNING "LTTng: poll_get_entry_sym symbol lookup failed.\n"); |
| 38 | return; |
| 39 | } |
| 40 | |
| 41 | if (!pollwake_sym) |
| 42 | pollwake_sym = (void *) kallsyms_lookup_name("pollwake"); |
| 43 | if (!pollwake_sym) { |
| 44 | printk(KERN_WARNING "LTTng: pollwake_sym symbol lookup failed.\n"); |
| 45 | return; |
| 46 | } |
| 47 | |
| 48 | entry = poll_get_entry_sym(pwq); |
| 49 | |
| 50 | if (!entry) |
| 51 | return; |
| 52 | get_file(filp); |
| 53 | entry->filp = filp; |
| 54 | entry->wait_address = wait_address; |
| 55 | entry->key = p->key; |
| 56 | init_waitqueue_func_entry(&entry->wait, pollwake_sym); |
| 57 | entry->wait.private = pwq; |
| 58 | add_wait_queue_exclusive(wait_address, &entry->wait); |
| 59 | } |
| 60 | |
| 61 | void wrapper_pollwait_exclusive(struct file *filp, |
| 62 | wait_queue_head_t *wait_address, |
| 63 | poll_table *p) |
| 64 | |
| 65 | { |
| 66 | __pollwait_exclusive(filp, wait_address, p); |
| 67 | } |
| 68 | |
| 69 | #else |
| 70 | |
| 71 | #include <linux/poll.h> |
| 72 | |
| 73 | ssize_t wrapper_pollwait_exclusive(struct file *filp, |
| 74 | wait_queue_head_t *wait_address, |
| 75 | poll_table *p) |
| 76 | { |
| 77 | return pollwait_exclusive(filp, wait_address, p); |
| 78 | } |
| 79 | |
| 80 | #endif |