1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <litmus/litmus.h>
/* only one page for now, but we might want to add a RO version at some point */
#define CTRL_NAME "litmus/ctrl"
/* allocate t->rt_param.ctrl_page*/
static int alloc_ctrl_page(struct task_struct *t)
{
int err = 0;
/* only allocate if the task doesn't have one yet */
if (!tsk_rt(t)->ctrl_page) {
tsk_rt(t)->ctrl_page = (void*) get_zeroed_page(GFP_KERNEL);
if (!tsk_rt(t)->ctrl_page)
err = -ENOMEM;
/* will get de-allocated in task teardown */
TRACE_TASK(t, "%s ctrl_page = %p\n", __FUNCTION__,
tsk_rt(t)->ctrl_page);
}
return err;
}
static int map_ctrl_page(struct task_struct *t, struct vm_area_struct* vma)
{
int err;
unsigned long pfn;
struct page* ctrl = virt_to_page(tsk_rt(t)->ctrl_page);
/* Increase ref count. Is decreased when vma is destroyed. */
get_page(ctrl);
/* compute page frame number */
pfn = page_to_pfn(ctrl);
TRACE_CUR(CTRL_NAME
": mapping %p (pfn:%lx, %lx) to 0x%lx (prot:%lx)\n",
tsk_rt(t)->ctrl_page, pfn, page_to_pfn(ctrl), vma->vm_start,
vma->vm_page_prot);
/* Map it into the vma. Make sure to use PAGE_SHARED, otherwise
* userspace actually gets a copy-on-write page. */
err = remap_pfn_range(vma, vma->vm_start, pfn, PAGE_SIZE, PAGE_SHARED);
if (err)
TRACE_CUR(CTRL_NAME ": remap_pfn_range() failed (%d)\n", err);
return err;
}
static void litmus_ctrl_vm_close(struct vm_area_struct* vma)
{
TRACE_CUR("%s flags=0x%x prot=0x%x\n", __FUNCTION__,
vma->vm_flags, vma->vm_page_prot);
TRACE_CUR(CTRL_NAME
": %p:%p vma:%p vma->vm_private_data:%p closed.\n",
(void*) vma->vm_start, (void*) vma->vm_end, vma,
vma->vm_private_data, current->comm,
current->pid);
}
static int litmus_ctrl_vm_fault(struct vm_area_struct* vma,
struct vm_fault* vmf)
{
/* This function should never be called, since
* all pages should have been mapped by mmap()
* already. */
TRACE_CUR("%s flags=0x%x\n", __FUNCTION__, vma->vm_flags);
/* nope, you only get one page */
return VM_FAULT_SIGBUS;
}
static struct vm_operations_struct litmus_ctrl_vm_ops = {
.close = litmus_ctrl_vm_close,
.fault = litmus_ctrl_vm_fault,
};
static int litmus_ctrl_mmap(struct file* filp, struct vm_area_struct* vma)
{
int err = 0;
/* first make sure mapper knows what he's doing */
/* you can only get one page */
if (vma->vm_end - vma->vm_start != PAGE_SIZE)
return -EINVAL;
/* you can only map the "first" page */
if (vma->vm_pgoff != 0)
return -EINVAL;
/* you can't share it with anyone */
if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
return -EINVAL;
vma->vm_ops = &litmus_ctrl_vm_ops;
/* this mapping should not be kept across forks,
* and cannot be expanded */
vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND;
err = alloc_ctrl_page(current);
if (!err)
err = map_ctrl_page(current, vma);
TRACE_CUR("%s flags=0x%x prot=0x%lx\n",
__FUNCTION__, vma->vm_flags, vma->vm_page_prot);
return err;
}
static struct file_operations litmus_ctrl_fops = {
.owner = THIS_MODULE,
.mmap = litmus_ctrl_mmap,
};
static struct miscdevice litmus_ctrl_dev = {
.name = CTRL_NAME,
.minor = MISC_DYNAMIC_MINOR,
.fops = &litmus_ctrl_fops,
};
static int __init init_litmus_ctrl_dev(void)
{
int err;
BUILD_BUG_ON(sizeof(struct control_page) > PAGE_SIZE);
printk("Initializing LITMUS^RT control device.\n");
err = misc_register(&litmus_ctrl_dev);
if (err)
printk("Could not allocate %s device (%d).\n", CTRL_NAME, err);
return err;
}
static void __exit exit_litmus_ctrl_dev(void)
{
misc_deregister(&litmus_ctrl_dev);
}
module_init(init_litmus_ctrl_dev);
module_exit(exit_litmus_ctrl_dev);
|
