lib/ringbuffer/ring_buffer_mmap.c

   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) 2008-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; only version 2 of the License.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, write to the Free Software Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Re-using code from kernel/relay.c, hence the GPLv2 license for this
  22  * file.
  23  */
  24
  25 #include <linux/module.h>
  26 #include <linux/mm.h>
  27
  28 #include <wrapper/ringbuffer/backend.h>
  29 #include <wrapper/ringbuffer/frontend.h>
  30 #include <wrapper/ringbuffer/vfs.h>
  31
  32 /*
  33  * fault() vm_op implementation for ring buffer file mapping.
  34  */
  35 static int lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  36 {
  37         struct lib_ring_buffer *buf = vma->vm_private_data;
  38         struct channel *chan = buf->backend.chan;
  39         const struct lib_ring_buffer_config *config = &chan->backend.config;
  40         pgoff_t pgoff = vmf->pgoff;
  41         unsigned long *pfnp;
  42         void **virt;
  43         unsigned long offset, sb_bindex;
  44
  45         /*
  46          * Verify that faults are only done on the range of pages owned by the
  47          * reader.
  48          */
  49         offset = pgoff << PAGE_SHIFT;
  50         sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id);
  51         if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset
  52               && offset < buf->backend.array[sb_bindex]->mmap_offset +
  53                           buf->backend.chan->backend.subbuf_size))
  54                 return VM_FAULT_SIGBUS;
  55         /*
  56          * ring_buffer_read_get_pfn() gets the page frame number for the
  57          * current reader's pages.
  58          */
  59         pfnp = lib_ring_buffer_read_get_pfn(&buf->backend, offset, &virt);
  60         if (!*pfnp)
  61                 return VM_FAULT_SIGBUS;
  62         get_page(pfn_to_page(*pfnp));
  63         vmf->page = pfn_to_page(*pfnp);
  64
  65         return 0;
  66 }
  67
  68 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0))
  69 static int lib_ring_buffer_fault(struct vm_fault *vmf)
  70 {
  71         struct vm_area_struct *vma = vmf->vma;
  72         return lib_ring_buffer_fault_compat(vma, vmf);
  73 }
  74 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  75 static int lib_ring_buffer_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  76 {
  77         return lib_ring_buffer_fault_compat(vma, vmf);
  78 }
  79 #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  80
  81 /*
  82  * vm_ops for ring buffer file mappings.
  83  */
  84 static const struct vm_operations_struct lib_ring_buffer_mmap_ops = {
  85         .fault = lib_ring_buffer_fault,
  86 };
  87
  88 /**
  89  *      lib_ring_buffer_mmap_buf: - mmap channel buffer to process address space
  90  *      @buf: ring buffer to map
  91  *      @vma: vm_area_struct describing memory to be mapped
  92  *
  93  *      Returns 0 if ok, negative on error
  94  *
  95  *      Caller should already have grabbed mmap_sem.
  96  */
  97 static int lib_ring_buffer_mmap_buf(struct lib_ring_buffer *buf,
  98                                     struct vm_area_struct *vma)
  99 {
 100         unsigned long length = vma->vm_end - vma->vm_start;
 101         struct channel *chan = buf->backend.chan;
 102         const struct lib_ring_buffer_config *config = &chan->backend.config;
 103         unsigned long mmap_buf_len;
 104
 105         if (config->output != RING_BUFFER_MMAP)
 106                 return -EINVAL;
 107
 108         mmap_buf_len = chan->backend.buf_size;
 109         if (chan->backend.extra_reader_sb)
 110                 mmap_buf_len += chan->backend.subbuf_size;
 111
 112         if (length != mmap_buf_len)
 113                 return -EINVAL;
 114
 115         vma->vm_ops = &lib_ring_buffer_mmap_ops;
 116         vma->vm_flags |= VM_DONTEXPAND;
 117         vma->vm_private_data = buf;
 118
 119         return 0;
 120 }
 121
 122 int lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma,
 123                 struct lib_ring_buffer *buf)
 124 {
 125         return lib_ring_buffer_mmap_buf(buf, vma);
 126 }
 127 EXPORT_SYMBOL_GPL(lib_ring_buffer_mmap);
 128
 129 /**
 130  *      vfs_lib_ring_buffer_mmap - mmap file op
 131  *      @filp: the file
 132  *      @vma: the vma describing what to map
 133  *
 134  *      Calls upon lib_ring_buffer_mmap_buf() to map the file into user space.
 135  */
 136 int vfs_lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma)
 137 {
 138         struct lib_ring_buffer *buf = filp->private_data;
 139         return lib_ring_buffer_mmap(filp, vma, buf);
 140 }
 141 EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_mmap);