| paul@93 | 1 | /* |
| paul@93 | 2 | * A flexpage abstraction. |
| paul@93 | 3 | * |
| paul@554 | 4 | * Copyright (C) 2021, 2022, 2023 Paul Boddie <paul@boddie.org.uk> |
| paul@93 | 5 | * |
| paul@93 | 6 | * This program is free software; you can redistribute it and/or |
| paul@93 | 7 | * modify it under the terms of the GNU General Public License as |
| paul@93 | 8 | * published by the Free Software Foundation; either version 2 of |
| paul@93 | 9 | * the License, or (at your option) any later version. |
| paul@93 | 10 | * |
| paul@93 | 11 | * This program is distributed in the hope that it will be useful, |
| paul@93 | 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| paul@93 | 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| paul@93 | 14 | * GNU General Public License for more details. |
| paul@93 | 15 | * |
| paul@93 | 16 | * You should have received a copy of the GNU General Public License |
| paul@93 | 17 | * along with this program; if not, write to the Free Software |
| paul@93 | 18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, |
| paul@93 | 19 | * Boston, MA 02110-1301, USA |
| paul@93 | 20 | */ |
| paul@93 | 21 | |
| paul@0 | 22 | #include <algorithm> |
| paul@0 | 23 | |
| paul@0 | 24 | #include "flexpage.h" |
| paul@554 | 25 | #include "ipc.h" |
| paul@0 | 26 | |
| paul@0 | 27 | |
| paul@0 | 28 | |
| paul@342 | 29 | /* Virtual destructor required for introspection. */ |
| paul@342 | 30 | |
| paul@342 | 31 | Flexpage::~Flexpage() |
| paul@342 | 32 | { |
| paul@342 | 33 | } |
| paul@342 | 34 | |
| paul@0 | 35 | /* Reset the flexpage using 'offset', being the file offset. */ |
| paul@0 | 36 | |
| paul@0 | 37 | void Flexpage::reset(offset_t offset) |
| paul@0 | 38 | { |
| paul@332 | 39 | if (region == NULL) |
| paul@332 | 40 | return; |
| paul@332 | 41 | |
| paul@0 | 42 | _counter = 0; |
| paul@333 | 43 | _flags = 0; |
| paul@0 | 44 | |
| paul@0 | 45 | /* By definition (see "Flexible-Sized Page Objects - Object-Orientation |
| paul@0 | 46 | in Operation Systems"), flexpages are aligned to multiples of their |
| paul@0 | 47 | size. |
| paul@0 | 48 | |
| paul@0 | 49 | The size of the flexpage depends on the amount of space around the |
| paul@0 | 50 | accessed page. It cannot exceed the size of the memory region. */ |
| paul@0 | 51 | |
| paul@0 | 52 | size = max_multiple(region->start, region->end, PAGE_SIZE); |
| paul@0 | 53 | |
| paul@0 | 54 | /* The base address of the flexpage is computed from the region start |
| paul@0 | 55 | and flexpage size. It will be no lower than the region start. |
| paul@0 | 56 | |
| paul@0 | 57 | Sent flexpages may use higher bases due to receive window constraints, |
| paul@0 | 58 | these being communicated by the "hot spot". */ |
| paul@0 | 59 | |
| paul@0 | 60 | base_addr = round(region->start, size); |
| paul@0 | 61 | |
| paul@0 | 62 | /* Get the file offset for the base of the flexpage. This will be a |
| paul@0 | 63 | multiple of the flexpage size for alignment purposes. */ |
| paul@0 | 64 | |
| paul@0 | 65 | base_offset = trunc(offset, size); |
| paul@0 | 66 | |
| paul@0 | 67 | /* The page being accessed is relative to the base. |
| paul@0 | 68 | (This is transient information recording the initialising access |
| paul@0 | 69 | details.) */ |
| paul@0 | 70 | |
| paul@0 | 71 | page_offset = trunc(offset - base_offset, PAGE_SIZE); |
| paul@0 | 72 | page_addr = base_addr + page_offset; |
| paul@0 | 73 | } |
| paul@0 | 74 | |
| paul@332 | 75 | /* Set a region. */ |
| paul@332 | 76 | |
| paul@332 | 77 | void Flexpage::set_region(Region *region) |
| paul@332 | 78 | { |
| paul@332 | 79 | this->region = region; |
| paul@332 | 80 | } |
| paul@332 | 81 | |
| paul@110 | 82 | /* Decrement the usage counter, returning whether the flexpage is now no longer |
| paul@110 | 83 | used. */ |
| paul@110 | 84 | |
| paul@0 | 85 | bool Flexpage::decrement() |
| paul@0 | 86 | { |
| paul@0 | 87 | if (_counter) |
| paul@0 | 88 | { |
| paul@0 | 89 | _counter--; |
| paul@0 | 90 | return _counter == 0; |
| paul@0 | 91 | } |
| paul@0 | 92 | else |
| paul@0 | 93 | return 0; |
| paul@0 | 94 | } |
| paul@0 | 95 | |
| paul@110 | 96 | /* Increment the usage counter. */ |
| paul@110 | 97 | |
| paul@0 | 98 | void Flexpage::increment() |
| paul@0 | 99 | { |
| paul@0 | 100 | _counter++; |
| paul@0 | 101 | } |
| paul@0 | 102 | |
| paul@554 | 103 | /* Unmap and invalidate the flexpage, meaning that it should not now be in |
| paul@554 | 104 | use. */ |
| paul@110 | 105 | |
| paul@0 | 106 | void Flexpage::invalidate() |
| paul@0 | 107 | { |
| paul@0 | 108 | _counter = 0; |
| paul@554 | 109 | ipc_unmap_flexpage(this); |
| paul@554 | 110 | |
| paul@554 | 111 | /* Unmap and invalidate all derived flexpages. */ |
| paul@554 | 112 | |
| paul@554 | 113 | disassociate(); |
| paul@0 | 114 | } |
| paul@0 | 115 | |
| paul@110 | 116 | /* Return whether the flexpage is in use and is therefore valid. */ |
| paul@110 | 117 | |
| paul@0 | 118 | bool Flexpage::valid() |
| paul@0 | 119 | { |
| paul@0 | 120 | return _counter != 0; |
| paul@0 | 121 | } |
| paul@0 | 122 | |
| paul@0 | 123 | /* Return whether the flexpage supports the given file 'position'. */ |
| paul@0 | 124 | |
| paul@0 | 125 | bool Flexpage::supports_position(offset_t position) |
| paul@0 | 126 | { |
| paul@0 | 127 | return (base_offset <= position) && (position < (base_offset + size)); |
| paul@0 | 128 | } |
| paul@0 | 129 | |
| paul@86 | 130 | /* Upgrade the flags involved with this flexpage. This is used to track the |
| paul@86 | 131 | maximal flags employed by the different pagers, with the result being used in |
| paul@86 | 132 | unmap operations. */ |
| paul@86 | 133 | |
| paul@121 | 134 | void Flexpage::upgrade(map_flags_t flags) |
| paul@11 | 135 | { |
| paul@11 | 136 | if (flags && (flags != _flags)) |
| paul@11 | 137 | _flags |= flags; |
| paul@11 | 138 | } |
| paul@11 | 139 | |
| paul@115 | 140 | /* Return whether the flexpage has been modified due to write access having been |
| paul@115 | 141 | granted for any user of the page. */ |
| paul@115 | 142 | |
| paul@115 | 143 | bool Flexpage::modified() |
| paul@115 | 144 | { |
| paul@333 | 145 | return _flags & L4RE_DS_F_W; |
| paul@115 | 146 | } |
| paul@115 | 147 | |
| paul@0 | 148 | /* Return a "send" flexpage for an access to 'offset' by positioning it relative |
| paul@0 | 149 | to 'hot_spot' for the receive flexpage window. */ |
| paul@0 | 150 | |
| paul@86 | 151 | SendFlexpage Flexpage::to_send(offset_t offset, offset_t hot_spot, |
| paul@121 | 152 | map_flags_t flags, offset_t max_offset) |
| paul@0 | 153 | { |
| paul@0 | 154 | /* The dataspace offset of the flexpage base is a multiple of the flexpage |
| paul@0 | 155 | size. */ |
| paul@0 | 156 | |
| paul@0 | 157 | offset_t receive_base_offset = trunc(offset, size); |
| paul@0 | 158 | |
| paul@0 | 159 | /* The offset of the accessed page within the flexpage is constrained by the |
| paul@0 | 160 | current flexpage size. */ |
| paul@0 | 161 | |
| paul@0 | 162 | offset_t page_offset = trunc(offset - receive_base_offset, PAGE_SIZE); |
| paul@0 | 163 | |
| paul@0 | 164 | /* The receive flexpage offset (hot spot) must be constrained to the |
| paul@0 | 165 | flexpage, both the size and the start. */ |
| paul@0 | 166 | |
| paul@0 | 167 | offset_t receive_size; |
| paul@0 | 168 | |
| paul@0 | 169 | if (max_offset) |
| paul@23 | 170 | { |
| paul@23 | 171 | receive_size = trunc_multiple(max_offset - receive_base_offset, PAGE_SIZE); |
| paul@23 | 172 | receive_size = std::min(size, receive_size); |
| paul@23 | 173 | } |
| paul@0 | 174 | else |
| paul@0 | 175 | receive_size = size; |
| paul@0 | 176 | |
| paul@3 | 177 | if (!receive_size) |
| paul@86 | 178 | return SendFlexpage(base_addr, page_order(0), flags); |
| paul@3 | 179 | |
| paul@374 | 180 | /* Employ the page-aligned hot spot for compatibility with the page |
| paul@374 | 181 | offset, thus handling any non-aligned values sent in map requests. */ |
| paul@374 | 182 | |
| paul@374 | 183 | offset_t hot_spot_page = trunc(hot_spot, PAGE_SIZE); |
| paul@374 | 184 | offset_t receive_page_offset = hot_spot_page % receive_size; |
| paul@0 | 185 | |
| paul@0 | 186 | while ((receive_size > PAGE_SIZE) && (receive_page_offset != page_offset)) |
| paul@0 | 187 | { |
| paul@0 | 188 | receive_size /= 2; |
| paul@374 | 189 | receive_page_offset = hot_spot_page % receive_size; |
| paul@0 | 190 | } |
| paul@0 | 191 | |
| paul@0 | 192 | /* The flexpage base address is adjusted using the difference in page |
| paul@0 | 193 | offsets. Where the receive flexpage offset is constained further, the |
| paul@0 | 194 | base address will be raised to become closer to the accessed page. */ |
| paul@0 | 195 | |
| paul@0 | 196 | offset_t adjustment = page_offset - receive_page_offset; |
| paul@0 | 197 | |
| paul@86 | 198 | return SendFlexpage(base_addr + adjustment, page_order(receive_size), flags); |
| paul@0 | 199 | } |
| paul@0 | 200 | |
| paul@0 | 201 | /* Return a representation of the flexpage for unmapping. */ |
| paul@0 | 202 | |
| paul@0 | 203 | SendFlexpage Flexpage::to_unmap() |
| paul@0 | 204 | { |
| paul@450 | 205 | return SendFlexpage(base_addr, page_order(size), L4_FPAGE_RWX); |
| paul@0 | 206 | } |
| paul@0 | 207 | |
| paul@332 | 208 | /* Associate another flexpage with this flexpage. */ |
| paul@332 | 209 | |
| paul@332 | 210 | void Flexpage::associate(Flexpage *flexpage) |
| paul@332 | 211 | { |
| paul@332 | 212 | derived.push_back(flexpage); |
| paul@332 | 213 | } |
| paul@332 | 214 | |
| paul@554 | 215 | /* Invalidate and unmap all derived flexpages. */ |
| paul@554 | 216 | |
| paul@332 | 217 | void Flexpage::disassociate() |
| paul@332 | 218 | { |
| paul@554 | 219 | DerivedFlexpages::iterator it; |
| paul@554 | 220 | |
| paul@554 | 221 | for (it = derived.begin(); it != derived.end(); it++) |
| paul@554 | 222 | (*it)->invalidate(); |
| paul@554 | 223 | |
| paul@332 | 224 | derived.clear(); |
| paul@332 | 225 | } |
| paul@332 | 226 | |
| paul@0 | 227 | // vim: tabstop=4 expandtab shiftwidth=4 |
