lib/ringbuffer/ring_buffer_mmap.c

   1 /* SPDX-License-Identifier: GPL-2.0-only
   2  *
   3  * ring_buffer_mmap.c
   4  *
   5  * Copyright (C) 2002-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp
   6  * Copyright (C) 1999-2005 - Karim Yaghmour <karim@opersys.com>
   7  * Copyright (C) 2008-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Re-using code from kernel/relay.c, hence the GPL-2.0-only license for this
  10  * file.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/mm.h>
  15
  16 #include <ringbuffer/backend.h>
  17 #include <ringbuffer/frontend.h>
  18 #include <ringbuffer/vfs.h>
  19
  20 /*
  21  * fault() vm_op implementation for ring buffer file mapping.
  22  */
  23 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,1,0))
  24 static vm_fault_t lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  25 #else
  26 static int lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  27 #endif
  28 {
  29         struct lib_ring_buffer *buf = vma->vm_private_data;
  30         struct channel *chan = buf->backend.chan;
  31         const struct lib_ring_buffer_config *config = &chan->backend.config;
  32         pgoff_t pgoff = vmf->pgoff;
  33         unsigned long *pfnp;
  34         void **virt;
  35         unsigned long offset, sb_bindex;
  36
  37         /*
  38          * Verify that faults are only done on the range of pages owned by the
  39          * reader.
  40          */
  41         offset = pgoff << PAGE_SHIFT;
  42         sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id);
  43         if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset
  44               && offset < buf->backend.array[sb_bindex]->mmap_offset +
  45                           buf->backend.chan->backend.subbuf_size))
  46                 return VM_FAULT_SIGBUS;
  47         /*
  48          * ring_buffer_read_get_pfn() gets the page frame number for the
  49          * current reader's pages.
  50          */
  51         pfnp = lib_ring_buffer_read_get_pfn(&buf->backend, offset, &virt);
  52         if (!*pfnp)
  53                 return VM_FAULT_SIGBUS;
  54         get_page(pfn_to_page(*pfnp));
  55         vmf->page = pfn_to_page(*pfnp);
  56
  57         return 0;
  58 }
  59
  60 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,1,0))
  61 static vm_fault_t lib_ring_buffer_fault(struct vm_fault *vmf)
  62 {
  63         struct vm_area_struct *vma = vmf->vma;
  64         return lib_ring_buffer_fault_compat(vma, vmf);
  65 }
  66 #elif (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0))
  67 static int lib_ring_buffer_fault(struct vm_fault *vmf)
  68 {
  69         struct vm_area_struct *vma = vmf->vma;
  70         return lib_ring_buffer_fault_compat(vma, vmf);
  71 }
  72 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  73 static int lib_ring_buffer_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  74 {
  75         return lib_ring_buffer_fault_compat(vma, vmf);
  76 }
  77 #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  78
  79 /*
  80  * vm_ops for ring buffer file mappings.
  81  */
  82 static const struct vm_operations_struct lib_ring_buffer_mmap_ops = {
  83         .fault = lib_ring_buffer_fault,
  84 };
  85
  86 /**
  87  *      lib_ring_buffer_mmap_buf: - mmap channel buffer to process address space
  88  *      @buf: ring buffer to map
  89  *      @vma: vm_area_struct describing memory to be mapped
  90  *
  91  *      Returns 0 if ok, negative on error
  92  *
  93  *      Caller should already have grabbed mmap_sem.
  94  */
  95 static int lib_ring_buffer_mmap_buf(struct lib_ring_buffer *buf,
  96                                     struct vm_area_struct *vma)
  97 {
  98         unsigned long length = vma->vm_end - vma->vm_start;
  99         struct channel *chan = buf->backend.chan;
 100         const struct lib_ring_buffer_config *config = &chan->backend.config;
 101         unsigned long mmap_buf_len;
 102
 103         if (config->output != RING_BUFFER_MMAP)
 104                 return -EINVAL;
 105
 106         mmap_buf_len = chan->backend.buf_size;
 107         if (chan->backend.extra_reader_sb)
 108                 mmap_buf_len += chan->backend.subbuf_size;
 109
 110         if (length != mmap_buf_len)
 111                 return -EINVAL;
 112
 113         vma->vm_ops = &lib_ring_buffer_mmap_ops;
 114         vma->vm_flags |= VM_DONTEXPAND;
 115         vma->vm_private_data = buf;
 116
 117         return 0;
 118 }
 119
 120 int lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma,
 121                 struct lib_ring_buffer *buf)
 122 {
 123         return lib_ring_buffer_mmap_buf(buf, vma);
 124 }
 125 EXPORT_SYMBOL_GPL(lib_ring_buffer_mmap);
 126
 127 /**
 128  *      vfs_lib_ring_buffer_mmap - mmap file op
 129  *      @filp: the file
 130  *      @vma: the vma describing what to map
 131  *
 132  *      Calls upon lib_ring_buffer_mmap_buf() to map the file into user space.
 133  */
 134 int vfs_lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma)
 135 {
 136         struct lib_ring_buffer *buf = filp->private_data;
 137         return lib_ring_buffer_mmap(filp, vma, buf);
 138 }
 139 EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_mmap);