| 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); |