src/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 (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,1,0) || \
  24         LTTNG_RHEL_KERNEL_RANGE(4,18,0,193,0,0, 4,19,0,0,0,0))
  25 static vm_fault_t lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  26 #else
  27 static int lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  28 #endif
  29 {
  30         struct lttng_kernel_ring_buffer *buf = vma->vm_private_data;
  31         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
  32         const struct lttng_kernel_ring_buffer_config *config = &chan->backend.config;
  33         pgoff_t pgoff = vmf->pgoff;
  34         unsigned long *pfnp;
  35         void **virt;
  36         unsigned long offset, sb_bindex;
  37
  38         /*
  39          * Verify that faults are only done on the range of pages owned by the
  40          * reader.
  41          */
  42         offset = pgoff << PAGE_SHIFT;
  43         sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id);
  44         if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset
  45               && offset < buf->backend.array[sb_bindex]->mmap_offset +
  46                           buf->backend.chan->backend.subbuf_size))
  47                 return VM_FAULT_SIGBUS;
  48         /*
  49          * ring_buffer_read_get_pfn() gets the page frame number for the
  50          * current reader's pages.
  51          */
  52         pfnp = lib_ring_buffer_read_get_pfn(&buf->backend, offset, &virt);
  53         if (!*pfnp)
  54                 return VM_FAULT_SIGBUS;
  55         get_page(pfn_to_page(*pfnp));
  56         vmf->page = pfn_to_page(*pfnp);
  57
  58         return 0;
  59 }
  60
  61 #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,1,0) || \
  62         LTTNG_RHEL_KERNEL_RANGE(4,18,0,193,0,0, 4,19,0,0,0,0))
  63 static vm_fault_t lib_ring_buffer_fault(struct vm_fault *vmf)
  64 {
  65         struct vm_area_struct *vma = vmf->vma;
  66         return lib_ring_buffer_fault_compat(vma, vmf);
  67 }
  68 #elif (LTTNG_LINUX_VERSION_CODE >= LTTNG_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 (LTTNG_LINUX_VERSION_CODE >= LTTNG_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 (LTTNG_LINUX_VERSION_CODE >= LTTNG_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 lttng_kernel_ring_buffer *buf,
  98                                     struct vm_area_struct *vma)
  99 {
 100         unsigned long length = vma->vm_end - vma->vm_start;
 101         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
 102         const struct lttng_kernel_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 lttng_kernel_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 lttng_kernel_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);