1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * FPU register's regset abstraction, for ptrace, core dumps, etc. 4 */ 5 #include <asm/fpu/internal.h> 6 #include <asm/fpu/signal.h> 7 #include <asm/fpu/regset.h> 8 #include <asm/fpu/xstate.h> 9 #include <linux/sched/task_stack.h> 10 11 /* 12 * The xstateregs_active() routine is the same as the regset_fpregs_active() routine, 13 * as the "regset->n" for the xstate regset will be updated based on the feature 14 * capabilities supported by the xsave. 15 */ 16 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset) 17 { 18 return regset->n; 19 } 20 21 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset) 22 { 23 if (boot_cpu_has(X86_FEATURE_FXSR)) 24 return regset->n; 25 else 26 return 0; 27 } 28 29 int xfpregs_get(struct task_struct *target, const struct user_regset *regset, 30 unsigned int pos, unsigned int count, 31 void *kbuf, void __user *ubuf) 32 { 33 struct fpu *fpu = &target->thread.fpu; 34 35 if (!boot_cpu_has(X86_FEATURE_FXSR)) 36 return -ENODEV; 37 38 fpu__prepare_read(fpu); 39 fpstate_sanitize_xstate(fpu); 40 41 return user_regset_copyout(&pos, &count, &kbuf, &ubuf, 42 &fpu->state.fxsave, 0, -1); 43 } 44 45 int xfpregs_set(struct task_struct *target, const struct user_regset *regset, 46 unsigned int pos, unsigned int count, 47 const void *kbuf, const void __user *ubuf) 48 { 49 struct fpu *fpu = &target->thread.fpu; 50 int ret; 51 52 if (!boot_cpu_has(X86_FEATURE_FXSR)) 53 return -ENODEV; 54 55 fpu__prepare_write(fpu); 56 fpstate_sanitize_xstate(fpu); 57 58 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, 59 &fpu->state.fxsave, 0, -1); 60 61 /* 62 * mxcsr reserved bits must be masked to zero for security reasons. 63 */ 64 fpu->state.fxsave.mxcsr &= mxcsr_feature_mask; 65 66 /* 67 * update the header bits in the xsave header, indicating the 68 * presence of FP and SSE state. 69 */ 70 if (boot_cpu_has(X86_FEATURE_XSAVE)) 71 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE; 72 73 return ret; 74 } 75 76 int xstateregs_get(struct task_struct *target, const struct user_regset *regset, 77 unsigned int pos, unsigned int count, 78 void *kbuf, void __user *ubuf) 79 { 80 struct fpu *fpu = &target->thread.fpu; 81 struct xregs_state *xsave; 82 int ret; 83 84 if (!boot_cpu_has(X86_FEATURE_XSAVE)) 85 return -ENODEV; 86 87 xsave = &fpu->state.xsave; 88 89 fpu__prepare_read(fpu); 90 91 if (using_compacted_format()) { 92 if (kbuf) 93 ret = copy_xstate_to_kernel(kbuf, xsave, pos, count); 94 else 95 ret = copy_xstate_to_user(ubuf, xsave, pos, count); 96 } else { 97 fpstate_sanitize_xstate(fpu); 98 /* 99 * Copy the 48 bytes defined by the software into the xsave 100 * area in the thread struct, so that we can copy the whole 101 * area to user using one user_regset_copyout(). 102 */ 103 memcpy(&xsave->i387.sw_reserved, xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes)); 104 105 /* 106 * Copy the xstate memory layout. 107 */ 108 ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1); 109 } 110 return ret; 111 } 112 113 int xstateregs_set(struct task_struct *target, const struct user_regset *regset, 114 unsigned int pos, unsigned int count, 115 const void *kbuf, const void __user *ubuf) 116 { 117 struct fpu *fpu = &target->thread.fpu; 118 struct xregs_state *xsave; 119 int ret; 120 121 if (!boot_cpu_has(X86_FEATURE_XSAVE)) 122 return -ENODEV; 123 124 /* 125 * A whole standard-format XSAVE buffer is needed: 126 */ 127 if ((pos != 0) || (count < fpu_user_xstate_size)) 128 return -EFAULT; 129 130 xsave = &fpu->state.xsave; 131 132 fpu__prepare_write(fpu); 133 134 if (using_compacted_format()) { 135 if (kbuf) 136 ret = copy_kernel_to_xstate(xsave, kbuf); 137 else 138 ret = copy_user_to_xstate(xsave, ubuf); 139 } else { 140 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1); 141 if (!ret) 142 ret = validate_user_xstate_header(&xsave->header); 143 } 144 145 /* 146 * mxcsr reserved bits must be masked to zero for security reasons. 147 */ 148 xsave->i387.mxcsr &= mxcsr_feature_mask; 149 150 /* 151 * In case of failure, mark all states as init: 152 */ 153 if (ret) 154 fpstate_init(&fpu->state); 155 156 return ret; 157 } 158 159 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION 160 161 /* 162 * FPU tag word conversions. 163 */ 164 165 static inline unsigned short twd_i387_to_fxsr(unsigned short twd) 166 { 167 unsigned int tmp; /* to avoid 16 bit prefixes in the code */ 168 169 /* Transform each pair of bits into 01 (valid) or 00 (empty) */ 170 tmp = ~twd; 171 tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */ 172 /* and move the valid bits to the lower byte. */ 173 tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */ 174 tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */ 175 tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */ 176 177 return tmp; 178 } 179 180 #define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16) 181 #define FP_EXP_TAG_VALID 0 182 #define FP_EXP_TAG_ZERO 1 183 #define FP_EXP_TAG_SPECIAL 2 184 #define FP_EXP_TAG_EMPTY 3 185 186 static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave) 187 { 188 struct _fpxreg *st; 189 u32 tos = (fxsave->swd >> 11) & 7; 190 u32 twd = (unsigned long) fxsave->twd; 191 u32 tag; 192 u32 ret = 0xffff0000u; 193 int i; 194 195 for (i = 0; i < 8; i++, twd >>= 1) { 196 if (twd & 0x1) { 197 st = FPREG_ADDR(fxsave, (i - tos) & 7); 198 199 switch (st->exponent & 0x7fff) { 200 case 0x7fff: 201 tag = FP_EXP_TAG_SPECIAL; 202 break; 203 case 0x0000: 204 if (!st->significand[0] && 205 !st->significand[1] && 206 !st->significand[2] && 207 !st->significand[3]) 208 tag = FP_EXP_TAG_ZERO; 209 else 210 tag = FP_EXP_TAG_SPECIAL; 211 break; 212 default: 213 if (st->significand[3] & 0x8000) 214 tag = FP_EXP_TAG_VALID; 215 else 216 tag = FP_EXP_TAG_SPECIAL; 217 break; 218 } 219 } else { 220 tag = FP_EXP_TAG_EMPTY; 221 } 222 ret |= tag << (2 * i); 223 } 224 return ret; 225 } 226 227 /* 228 * FXSR floating point environment conversions. 229 */ 230 231 void 232 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk) 233 { 234 struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave; 235 struct _fpreg *to = (struct _fpreg *) &env->st_space[0]; 236 struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0]; 237 int i; 238 239 env->cwd = fxsave->cwd | 0xffff0000u; 240 env->swd = fxsave->swd | 0xffff0000u; 241 env->twd = twd_fxsr_to_i387(fxsave); 242 243 #ifdef CONFIG_X86_64 244 env->fip = fxsave->rip; 245 env->foo = fxsave->rdp; 246 /* 247 * should be actually ds/cs at fpu exception time, but 248 * that information is not available in 64bit mode. 249 */ 250 env->fcs = task_pt_regs(tsk)->cs; 251 if (tsk == current) { 252 savesegment(ds, env->fos); 253 } else { 254 env->fos = tsk->thread.ds; 255 } 256 env->fos |= 0xffff0000; 257 #else 258 env->fip = fxsave->fip; 259 env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16); 260 env->foo = fxsave->foo; 261 env->fos = fxsave->fos; 262 #endif 263 264 for (i = 0; i < 8; ++i) 265 memcpy(&to[i], &from[i], sizeof(to[0])); 266 } 267 268 void convert_to_fxsr(struct fxregs_state *fxsave, 269 const struct user_i387_ia32_struct *env) 270 271 { 272 struct _fpreg *from = (struct _fpreg *) &env->st_space[0]; 273 struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0]; 274 int i; 275 276 fxsave->cwd = env->cwd; 277 fxsave->swd = env->swd; 278 fxsave->twd = twd_i387_to_fxsr(env->twd); 279 fxsave->fop = (u16) ((u32) env->fcs >> 16); 280 #ifdef CONFIG_X86_64 281 fxsave->rip = env->fip; 282 fxsave->rdp = env->foo; 283 /* cs and ds ignored */ 284 #else 285 fxsave->fip = env->fip; 286 fxsave->fcs = (env->fcs & 0xffff); 287 fxsave->foo = env->foo; 288 fxsave->fos = env->fos; 289 #endif 290 291 for (i = 0; i < 8; ++i) 292 memcpy(&to[i], &from[i], sizeof(from[0])); 293 } 294 295 int fpregs_get(struct task_struct *target, const struct user_regset *regset, 296 unsigned int pos, unsigned int count, 297 void *kbuf, void __user *ubuf) 298 { 299 struct fpu *fpu = &target->thread.fpu; 300 struct user_i387_ia32_struct env; 301 302 fpu__prepare_read(fpu); 303 304 if (!boot_cpu_has(X86_FEATURE_FPU)) 305 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf); 306 307 if (!boot_cpu_has(X86_FEATURE_FXSR)) 308 return user_regset_copyout(&pos, &count, &kbuf, &ubuf, 309 &fpu->state.fsave, 0, 310 -1); 311 312 fpstate_sanitize_xstate(fpu); 313 314 if (kbuf && pos == 0 && count == sizeof(env)) { 315 convert_from_fxsr(kbuf, target); 316 return 0; 317 } 318 319 convert_from_fxsr(&env, target); 320 321 return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1); 322 } 323 324 int fpregs_set(struct task_struct *target, const struct user_regset *regset, 325 unsigned int pos, unsigned int count, 326 const void *kbuf, const void __user *ubuf) 327 { 328 struct fpu *fpu = &target->thread.fpu; 329 struct user_i387_ia32_struct env; 330 int ret; 331 332 fpu__prepare_write(fpu); 333 fpstate_sanitize_xstate(fpu); 334 335 if (!boot_cpu_has(X86_FEATURE_FPU)) 336 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf); 337 338 if (!boot_cpu_has(X86_FEATURE_FXSR)) 339 return user_regset_copyin(&pos, &count, &kbuf, &ubuf, 340 &fpu->state.fsave, 0, 341 -1); 342 343 if (pos > 0 || count < sizeof(env)) 344 convert_from_fxsr(&env, target); 345 346 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1); 347 if (!ret) 348 convert_to_fxsr(&target->thread.fpu.state.fxsave, &env); 349 350 /* 351 * update the header bit in the xsave header, indicating the 352 * presence of FP. 353 */ 354 if (boot_cpu_has(X86_FEATURE_XSAVE)) 355 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FP; 356 return ret; 357 } 358 359 /* 360 * FPU state for core dumps. 361 * This is only used for a.out dumps now. 362 * It is declared generically using elf_fpregset_t (which is 363 * struct user_i387_struct) but is in fact only used for 32-bit 364 * dumps, so on 64-bit it is really struct user_i387_ia32_struct. 365 */ 366 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu) 367 { 368 struct task_struct *tsk = current; 369 370 return !fpregs_get(tsk, NULL, 0, sizeof(struct user_i387_ia32_struct), 371 ufpu, NULL); 372 } 373 EXPORT_SYMBOL(dump_fpu); 374 375 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */ 376