1 /* Target description related code for GNU/Linux x86 (i386 and x86-64). 2 3 Copyright (C) 2024 Free Software Foundation, Inc. 4 5 This file is part of GDB. 6 7 This program is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 #include "arch/x86-linux-tdesc-features.h" 21 22 /* A structure used to describe a single xstate feature bit that might, or 23 might not, be checked for when creating a target description for one of 24 i386, amd64, or x32. 25 26 The different CPU/ABI types check for different xstate features when 27 creating a target description. 28 29 We want to cache target descriptions, and this is currently done in 30 three separate caches, one each for i386, amd64, and x32. Additionally, 31 the caching we're discussing here is Linux only, and for Linux, the only 32 thing that has an impact on target description creation is the xcr0 33 value. 34 35 In order to ensure the cache functions correctly we need to filter out 36 only those xcr0 feature bits that are relevant, we can then cache target 37 descriptions based on the relevant feature bits. Two xcr0 values might 38 be different, but have the same relevant feature bits. In this case we 39 would expect the two xcr0 values to map to the same cache entry. */ 40 41 struct x86_xstate_feature { 42 /* The xstate feature mask. This is a mask against an xcr0 value. */ 43 uint64_t feature; 44 45 /* Is this feature checked when creating an i386 target description. */ 46 bool is_i386; 47 48 /* Is this feature checked when creating an amd64 target description. */ 49 bool is_amd64; 50 51 /* Is this feature checked when creating an x32 target description. */ 52 bool is_x32; 53 }; 54 55 /* A constant table that describes all of the xstate features that are 56 checked when building a target description for i386, amd64, or x32. 57 58 If in the future, due to simplifications or refactoring, this table ever 59 ends up with 'true' for every xcr0 feature on every target type, then this 60 is an indication that this table should probably be removed, and that the 61 rest of the code in this file can be simplified. */ 62 63 static constexpr x86_xstate_feature x86_linux_all_xstate_features[] = { 64 /* Feature, i386, amd64, x32. */ 65 { X86_XSTATE_PKRU, true, true, true }, 66 { X86_XSTATE_AVX512, true, true, true }, 67 { X86_XSTATE_AVX, true, true, true }, 68 { X86_XSTATE_SSE, true, false, false }, 69 { X86_XSTATE_X87, true, false, false } 70 }; 71 72 /* Return a compile time constant which is a mask of all the xstate features 73 that are checked for when building an i386 target description. */ 74 75 static constexpr uint64_t 76 x86_linux_i386_xcr0_feature_mask_1 () 77 { 78 uint64_t mask = 0; 79 80 for (const auto &entry : x86_linux_all_xstate_features) 81 if (entry.is_i386) 82 mask |= entry.feature; 83 84 return mask; 85 } 86 87 /* Return a compile time constant which is a mask of all the xstate features 88 that are checked for when building an amd64 target description. */ 89 90 static constexpr uint64_t 91 x86_linux_amd64_xcr0_feature_mask_1 () 92 { 93 uint64_t mask = 0; 94 95 for (const auto &entry : x86_linux_all_xstate_features) 96 if (entry.is_amd64) 97 mask |= entry.feature; 98 99 return mask; 100 } 101 102 /* Return a compile time constant which is a mask of all the xstate features 103 that are checked for when building an x32 target description. */ 104 105 static constexpr uint64_t 106 x86_linux_x32_xcr0_feature_mask_1 () 107 { 108 uint64_t mask = 0; 109 110 for (const auto &entry : x86_linux_all_xstate_features) 111 if (entry.is_x32) 112 mask |= entry.feature; 113 114 return mask; 115 } 116 117 /* See arch/x86-linux-tdesc-features.h. */ 118 119 uint64_t 120 x86_linux_i386_xcr0_feature_mask () 121 { 122 return x86_linux_i386_xcr0_feature_mask_1 (); 123 } 124 125 /* See arch/x86-linux-tdesc-features.h. */ 126 127 uint64_t 128 x86_linux_amd64_xcr0_feature_mask () 129 { 130 return x86_linux_amd64_xcr0_feature_mask_1 (); 131 } 132 133 /* See arch/x86-linux-tdesc-features.h. */ 134 135 uint64_t 136 x86_linux_x32_xcr0_feature_mask () 137 { 138 return x86_linux_x32_xcr0_feature_mask_1 (); 139 } 140 141 #ifdef GDBSERVER 142 143 /* See arch/x86-linux-tdesc-features.h. */ 144 145 int 146 x86_linux_xcr0_to_tdesc_idx (uint64_t xcr0) 147 { 148 /* The following table shows which features are checked for when creating 149 the target descriptions (see nat/x86-linux-tdesc.c), the feature order 150 represents the bit order within the generated index number. 151 152 i386 | x87 sse avx avx512 pkru 153 amd64 | avx avx512 pkru 154 i32 | avx avx512 pkru 155 156 The features are ordered so that for each mode (i386, amd64, i32) the 157 generated index will form a continuous range. */ 158 159 int idx = 0; 160 161 for (int i = 0; i < ARRAY_SIZE (x86_linux_all_xstate_features); ++i) 162 { 163 if ((xcr0 & x86_linux_all_xstate_features[i].feature) 164 == x86_linux_all_xstate_features[i].feature) 165 idx |= (1 << i); 166 } 167 168 return idx; 169 } 170 171 #endif /* GDBSERVER */ 172 173 #ifdef IN_PROCESS_AGENT 174 175 /* Return a compile time constant which is a count of the number of xstate 176 features that are checked for when building an i386 target description. */ 177 178 static constexpr int 179 x86_linux_i386_tdesc_count_1 () 180 { 181 uint64_t count = 0; 182 183 for (const auto &entry : x86_linux_all_xstate_features) 184 if (entry.is_i386) 185 ++count; 186 187 gdb_assert (count > 0); 188 189 return (1 << count); 190 } 191 192 /* Return a compile time constant which is a count of the number of xstate 193 features that are checked for when building an amd64 target description. */ 194 195 static constexpr int 196 x86_linux_amd64_tdesc_count_1 () 197 { 198 uint64_t count = 0; 199 200 for (const auto &entry : x86_linux_all_xstate_features) 201 if (entry.is_amd64) 202 ++count; 203 204 gdb_assert (count > 0); 205 206 return (1 << count); 207 } 208 209 /* Return a compile time constant which is a count of the number of xstate 210 features that are checked for when building an x32 target description. */ 211 212 static constexpr int 213 x86_linux_x32_tdesc_count_1 () 214 { 215 uint64_t count = 0; 216 217 for (const auto &entry : x86_linux_all_xstate_features) 218 if (entry.is_x32) 219 ++count; 220 221 gdb_assert (count > 0); 222 223 return (1 << count); 224 } 225 226 /* See arch/x86-linux-tdesc-features.h. */ 227 228 int 229 x86_linux_amd64_tdesc_count () 230 { 231 return x86_linux_amd64_tdesc_count_1 (); 232 } 233 234 /* See arch/x86-linux-tdesc-features.h. */ 235 236 int 237 x86_linux_x32_tdesc_count () 238 { 239 return x86_linux_x32_tdesc_count_1 (); 240 } 241 242 /* See arch/x86-linux-tdesc-features.h. */ 243 244 int 245 x86_linux_i386_tdesc_count () 246 { 247 return x86_linux_i386_tdesc_count_1 (); 248 } 249 250 /* See arch/x86-linux-tdesc-features.h. */ 251 252 uint64_t 253 x86_linux_tdesc_idx_to_xcr0 (int idx) 254 { 255 uint64_t xcr0 = 0; 256 257 for (int i = 0; i < ARRAY_SIZE (x86_linux_all_xstate_features); ++i) 258 { 259 if ((idx & (1 << i)) != 0) 260 xcr0 |= x86_linux_all_xstate_features[i].feature; 261 } 262 263 return xcr0; 264 } 265 266 #endif /* IN_PROCESS_AGENT */ 267
Indexes created Mon Mar 30 00:23:01 UTC 2026