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f3bc08c5 MD |
1 | /* |
2 | * ring_buffer_mmap.c | |
3 | * | |
4 | * Copyright (C) 2002-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp | |
5 | * Copyright (C) 1999-2005 - Karim Yaghmour <karim@opersys.com> | |
6 | * Copyright (C) 2008-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * | |
8 | * Re-using content from kernel/relay.c. | |
9 | * | |
10 | * This file is released under the GPL v2. | |
11 | */ | |
12 | ||
13 | #include <linux/module.h> | |
14 | #include <linux/mm.h> | |
15 | ||
16 | #include "../../wrapper/ringbuffer/backend.h" | |
17 | #include "../../wrapper/ringbuffer/frontend.h" | |
18 | #include "../../wrapper/ringbuffer/vfs.h" | |
19 | ||
20 | /* | |
21 | * fault() vm_op implementation for ring buffer file mapping. | |
22 | */ | |
23 | static int lib_ring_buffer_fault(struct vm_area_struct *vma, struct vm_fault *vmf) | |
24 | { | |
25 | struct lib_ring_buffer *buf = vma->vm_private_data; | |
26 | struct channel *chan = buf->backend.chan; | |
27 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
28 | pgoff_t pgoff = vmf->pgoff; | |
29 | struct page **page; | |
30 | void **virt; | |
31 | unsigned long offset, sb_bindex; | |
32 | ||
33 | if (!buf) | |
34 | return VM_FAULT_OOM; | |
35 | ||
36 | /* | |
37 | * Verify that faults are only done on the range of pages owned by the | |
38 | * reader. | |
39 | */ | |
40 | offset = pgoff << PAGE_SHIFT; | |
41 | sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id); | |
42 | if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset | |
43 | && offset < buf->backend.array[sb_bindex]->mmap_offset + | |
44 | buf->backend.chan->backend.subbuf_size)) | |
45 | return VM_FAULT_SIGBUS; | |
46 | /* | |
47 | * ring_buffer_read_get_page() gets the page in the current reader's | |
48 | * pages. | |
49 | */ | |
50 | page = lib_ring_buffer_read_get_page(&buf->backend, offset, &virt); | |
51 | if (!*page) | |
52 | return VM_FAULT_SIGBUS; | |
53 | get_page(*page); | |
54 | vmf->page = *page; | |
55 | ||
56 | return 0; | |
57 | } | |
58 | ||
59 | /* | |
60 | * vm_ops for ring buffer file mappings. | |
61 | */ | |
62 | static const struct vm_operations_struct lib_ring_buffer_mmap_ops = { | |
63 | .fault = lib_ring_buffer_fault, | |
64 | }; | |
65 | ||
66 | /** | |
67 | * lib_ring_buffer_mmap_buf: - mmap channel buffer to process address space | |
68 | * @buf: ring buffer to map | |
69 | * @vma: vm_area_struct describing memory to be mapped | |
70 | * | |
71 | * Returns 0 if ok, negative on error | |
72 | * | |
73 | * Caller should already have grabbed mmap_sem. | |
74 | */ | |
75 | static int lib_ring_buffer_mmap_buf(struct lib_ring_buffer *buf, | |
76 | struct vm_area_struct *vma) | |
77 | { | |
78 | unsigned long length = vma->vm_end - vma->vm_start; | |
79 | struct channel *chan = buf->backend.chan; | |
80 | const struct lib_ring_buffer_config *config = chan->backend.config; | |
81 | unsigned long mmap_buf_len; | |
82 | ||
83 | if (config->output != RING_BUFFER_MMAP) | |
84 | return -EINVAL; | |
85 | ||
86 | if (!buf) | |
87 | return -EBADF; | |
88 | ||
89 | mmap_buf_len = chan->backend.buf_size; | |
90 | if (chan->backend.extra_reader_sb) | |
91 | mmap_buf_len += chan->backend.subbuf_size; | |
92 | ||
93 | if (length != mmap_buf_len) | |
94 | return -EINVAL; | |
95 | ||
96 | vma->vm_ops = &lib_ring_buffer_mmap_ops; | |
97 | vma->vm_flags |= VM_DONTEXPAND; | |
98 | vma->vm_private_data = buf; | |
99 | ||
100 | return 0; | |
101 | } | |
102 | ||
103 | /** | |
104 | * lib_ring_buffer_mmap - mmap file op | |
105 | * @filp: the file | |
106 | * @vma: the vma describing what to map | |
107 | * | |
108 | * Calls upon lib_ring_buffer_mmap_buf() to map the file into user space. | |
109 | */ | |
110 | int lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma) | |
111 | { | |
112 | struct lib_ring_buffer *buf = filp->private_data; | |
113 | return lib_ring_buffer_mmap_buf(buf, vma); | |
114 | } | |
115 | EXPORT_SYMBOL_GPL(lib_ring_buffer_mmap); |