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 #include <wrapper/mm.h>
  21
  22 /*
  23  * fault() vm_op implementation for ring buffer file mapping.
  24  */
  25 #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,1,0) || \
  26         LTTNG_RHEL_KERNEL_RANGE(4,18,0,193,0,0, 4,19,0,0,0,0))
  27 static vm_fault_t lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  28 #else
  29 static int lib_ring_buffer_fault_compat(struct vm_area_struct *vma, struct vm_fault *vmf)
  30 #endif
  31 {
  32         struct lttng_kernel_ring_buffer *buf = vma->vm_private_data;
  33         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
  34         const struct lttng_kernel_ring_buffer_config *config = &chan->backend.config;
  35         pgoff_t pgoff = vmf->pgoff;
  36         unsigned long *pfnp;
  37         void **virt;
  38         unsigned long offset, sb_bindex;
  39
  40         /*
  41          * Verify that faults are only done on the range of pages owned by the
  42          * reader.
  43          */
  44         offset = pgoff << PAGE_SHIFT;
  45         sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id);
  46         if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset
  47               && offset < buf->backend.array[sb_bindex]->mmap_offset +
  48                           buf->backend.chan->backend.subbuf_size))
  49                 return VM_FAULT_SIGBUS;
  50         /*
  51          * ring_buffer_read_get_pfn() gets the page frame number for the
  52          * current reader's pages.
  53          */
  54         pfnp = lib_ring_buffer_read_get_pfn(&buf->backend, offset, &virt);
  55         if (!*pfnp)
  56                 return VM_FAULT_SIGBUS;
  57         get_page(pfn_to_page(*pfnp));
  58         vmf->page = pfn_to_page(*pfnp);
  59
  60         return 0;
  61 }
  62
  63 #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,1,0) || \
  64         LTTNG_RHEL_KERNEL_RANGE(4,18,0,193,0,0, 4,19,0,0,0,0))
  65 static vm_fault_t lib_ring_buffer_fault(struct vm_fault *vmf)
  66 {
  67         struct vm_area_struct *vma = vmf->vma;
  68         return lib_ring_buffer_fault_compat(vma, vmf);
  69 }
  70 #elif (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(4,11,0))
  71 static int lib_ring_buffer_fault(struct vm_fault *vmf)
  72 {
  73         struct vm_area_struct *vma = vmf->vma;
  74         return lib_ring_buffer_fault_compat(vma, vmf);
  75 }
  76 #else /* #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(4,11,0)) */
  77 static int lib_ring_buffer_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  78 {
  79         return lib_ring_buffer_fault_compat(vma, vmf);
  80 }
  81 #endif /* #else #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(4,11,0)) */
  82
  83 /*
  84  * vm_ops for ring buffer file mappings.
  85  */
  86 static const struct vm_operations_struct lib_ring_buffer_mmap_ops = {
  87         .fault = lib_ring_buffer_fault,
  88 };
  89
  90 /**
  91  *      lib_ring_buffer_mmap_buf: - mmap channel buffer to process address space
  92  *      @buf: ring buffer to map
  93  *      @vma: vm_area_struct describing memory to be mapped
  94  *
  95  *      Returns 0 if ok, negative on error
  96  *
  97  *      Caller should already have grabbed mmap_sem.
  98  */
  99 static int lib_ring_buffer_mmap_buf(struct lttng_kernel_ring_buffer *buf,
 100                                     struct vm_area_struct *vma)
 101 {
 102         unsigned long length = vma->vm_end - vma->vm_start;
 103         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
 104         const struct lttng_kernel_ring_buffer_config *config = &chan->backend.config;
 105         unsigned long mmap_buf_len;
 106
 107         if (config->output != RING_BUFFER_MMAP)
 108                 return -EINVAL;
 109
 110         mmap_buf_len = chan->backend.buf_size;
 111         if (chan->backend.extra_reader_sb)
 112                 mmap_buf_len += chan->backend.subbuf_size;
 113
 114         if (length != mmap_buf_len)
 115                 return -EINVAL;
 116
 117         vma->vm_ops = &lib_ring_buffer_mmap_ops;
 118         wrapper_vm_flags_set(vma, VM_DONTEXPAND);
 119         vma->vm_private_data = buf;
 120
 121         return 0;
 122 }
 123
 124 int lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma,
 125                 struct lttng_kernel_ring_buffer *buf)
 126 {
 127         return lib_ring_buffer_mmap_buf(buf, vma);
 128 }
 129 EXPORT_SYMBOL_GPL(lib_ring_buffer_mmap);
 130
 131 /**
 132  *      vfs_lib_ring_buffer_mmap - mmap file op
 133  *      @filp: the file
 134  *      @vma: the vma describing what to map
 135  *
 136  *      Calls upon lib_ring_buffer_mmap_buf() to map the file into user space.
 137  */
 138 int vfs_lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma)
 139 {
 140         struct lttng_kernel_ring_buffer *buf = filp->private_data;
 141         return lib_ring_buffer_mmap(filp, vma, buf);
 142 }
 143 EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_mmap);