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 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,1,0))
  36 static vm_fault_t lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  37 #else
  38 static int lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  39 #endif
  40 {
  41         struct lib_ring_buffer *buf = vma->vm_private_data;
  42         struct channel *chan = buf->backend.chan;
  43         const struct lib_ring_buffer_config *config = &chan->backend.config;
  44         pgoff_t pgoff = vmf->pgoff;
  45         unsigned long *pfnp;
  46         void **virt;
  47         unsigned long offset, sb_bindex;
  48
  49         /*
  50          * Verify that faults are only done on the range of pages owned by the
  51          * reader.
  52          */
  53         offset = pgoff << PAGE_SHIFT;
  54         sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id);
  55         if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset
  56               && offset < buf->backend.array[sb_bindex]->mmap_offset +
  57                           buf->backend.chan->backend.subbuf_size))
  58                 return VM_FAULT_SIGBUS;
  59         /*
  60          * ring_buffer_read_get_pfn() gets the page frame number for the
  61          * current reader's pages.
  62          */
  63         pfnp = lib_ring_buffer_read_get_pfn(&buf->backend, offset, &virt);
  64         if (!*pfnp)
  65                 return VM_FAULT_SIGBUS;
  66         get_page(pfn_to_page(*pfnp));
  67         vmf->page = pfn_to_page(*pfnp);
  68
  69         return 0;
  70 }
  71
  72 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,1,0))
  73 static vm_fault_t lib_ring_buffer_fault(struct vm_fault *vmf)
  74 {
  75         struct vm_area_struct *vma = vmf->vma;
  76         return lib_ring_buffer_fault_compat(vma, vmf);
  77 }
  78 #elif (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0))
  79 static int lib_ring_buffer_fault(struct vm_fault *vmf)
  80 {
  81         struct vm_area_struct *vma = vmf->vma;
  82         return lib_ring_buffer_fault_compat(vma, vmf);
  83 }
  84 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  85 static int lib_ring_buffer_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  86 {
  87         return lib_ring_buffer_fault_compat(vma, vmf);
  88 }
  89 #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  90
  91 /*
  92  * vm_ops for ring buffer file mappings.
  93  */
  94 static const struct vm_operations_struct lib_ring_buffer_mmap_ops = {
  95         .fault = lib_ring_buffer_fault,
  96 };
  97
  98 /**
  99  *      lib_ring_buffer_mmap_buf: - mmap channel buffer to process address space
 100  *      @buf: ring buffer to map
 101  *      @vma: vm_area_struct describing memory to be mapped
 102  *
 103  *      Returns 0 if ok, negative on error
 104  *
 105  *      Caller should already have grabbed mmap_sem.
 106  */
 107 static int lib_ring_buffer_mmap_buf(struct lib_ring_buffer *buf,
 108                                     struct vm_area_struct *vma)
 109 {
 110         unsigned long length = vma->vm_end - vma->vm_start;
 111         struct channel *chan = buf->backend.chan;
 112         const struct lib_ring_buffer_config *config = &chan->backend.config;
 113         unsigned long mmap_buf_len;
 114
 115         if (config->output != RING_BUFFER_MMAP)
 116                 return -EINVAL;
 117
 118         mmap_buf_len = chan->backend.buf_size;
 119         if (chan->backend.extra_reader_sb)
 120                 mmap_buf_len += chan->backend.subbuf_size;
 121
 122         if (length != mmap_buf_len)
 123                 return -EINVAL;
 124
 125         vma->vm_ops = &lib_ring_buffer_mmap_ops;
 126         vma->vm_flags |= VM_DONTEXPAND;
 127         vma->vm_private_data = buf;
 128
 129         return 0;
 130 }
 131
 132 int lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma,
 133                 struct lib_ring_buffer *buf)
 134 {
 135         return lib_ring_buffer_mmap_buf(buf, vma);
 136 }
 137 EXPORT_SYMBOL_GPL(lib_ring_buffer_mmap);
 138
 139 /**
 140  *      vfs_lib_ring_buffer_mmap - mmap file op
 141  *      @filp: the file
 142  *      @vma: the vma describing what to map
 143  *
 144  *      Calls upon lib_ring_buffer_mmap_buf() to map the file into user space.
 145  */
 146 int vfs_lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma)
 147 {
 148         struct lib_ring_buffer *buf = filp->private_data;
 149         return lib_ring_buffer_mmap(filp, vma, buf);
 150 }
 151 EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_mmap);