arch/x86/kernel/fpu/regset.c

   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         struct fpu *target_fpu = &target->thread.fpu;
  19
  20         return target_fpu->initialized ? regset->n : 0;
  21 }
  22
  23 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
  24 {
  25         struct fpu *target_fpu = &target->thread.fpu;
  26
  27         if (boot_cpu_has(X86_FEATURE_FXSR) && target_fpu->initialized)
  28                 return regset->n;
  29         else
  30                 return 0;
  31 }
  32
  33 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
  34                 unsigned int pos, unsigned int count,
  35                 void *kbuf, void __user *ubuf)
  36 {
  37         struct fpu *fpu = &target->thread.fpu;
  38
  39         if (!boot_cpu_has(X86_FEATURE_FXSR))
  40                 return -ENODEV;
  41
  42         fpu__prepare_read(fpu);
  43         fpstate_sanitize_xstate(fpu);
  44
  45         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
  46                                    &fpu->state.fxsave, 0, -1);
  47 }
  48
  49 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
  50                 unsigned int pos, unsigned int count,
  51                 const void *kbuf, const void __user *ubuf)
  52 {
  53         struct fpu *fpu = &target->thread.fpu;
  54         int ret;
  55
  56         if (!boot_cpu_has(X86_FEATURE_FXSR))
  57                 return -ENODEV;
  58
  59         fpu__prepare_write(fpu);
  60         fpstate_sanitize_xstate(fpu);
  61
  62         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
  63                                  &fpu->state.fxsave, 0, -1);
  64
  65         /*
  66          * mxcsr reserved bits must be masked to zero for security reasons.
  67          */
  68         fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
  69
  70         /*
  71          * update the header bits in the xsave header, indicating the
  72          * presence of FP and SSE state.
  73          */
  74         if (boot_cpu_has(X86_FEATURE_XSAVE))
  75                 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
  76
  77         return ret;
  78 }
  79
  80 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
  81                 unsigned int pos, unsigned int count,
  82                 void *kbuf, void __user *ubuf)
  83 {
  84         struct fpu *fpu = &target->thread.fpu;
  85         struct xregs_state *xsave;
  86         int ret;
  87
  88         if (!boot_cpu_has(X86_FEATURE_XSAVE))
  89                 return -ENODEV;
  90
  91         xsave = &fpu->state.xsave;
  92
  93         fpu__prepare_read(fpu);
  94
  95         if (using_compacted_format()) {
  96                 if (kbuf)
  97                         ret = copy_xstate_to_kernel(kbuf, xsave, pos, count);
  98                 else
  99                         ret = copy_xstate_to_user(ubuf, xsave, pos, count);
 100         } else {
 101                 fpstate_sanitize_xstate(fpu);
 102                 /*
 103                  * Copy the 48 bytes defined by the software into the xsave
 104                  * area in the thread struct, so that we can copy the whole
 105                  * area to user using one user_regset_copyout().
 106                  */
 107                 memcpy(&xsave->i387.sw_reserved, xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
 108
 109                 /*
 110                  * Copy the xstate memory layout.
 111                  */
 112                 ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 113         }
 114         return ret;
 115 }
 116
 117 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 118                   unsigned int pos, unsigned int count,
 119                   const void *kbuf, const void __user *ubuf)
 120 {
 121         struct fpu *fpu = &target->thread.fpu;
 122         struct xregs_state *xsave;
 123         int ret;
 124
 125         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 126                 return -ENODEV;
 127
 128         /*
 129          * A whole standard-format XSAVE buffer is needed:
 130          */
 131         if ((pos != 0) || (count < fpu_user_xstate_size))
 132                 return -EFAULT;
 133
 134         xsave = &fpu->state.xsave;
 135
 136         fpu__prepare_write(fpu);
 137
 138         if (using_compacted_format()) {
 139                 if (kbuf)
 140                         ret = copy_kernel_to_xstate(xsave, kbuf);
 141                 else
 142                         ret = copy_user_to_xstate(xsave, ubuf);
 143         } else {
 144                 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 145                 if (!ret)
 146                         ret = validate_xstate_header(&xsave->header);
 147         }
 148
 149         /*
 150          * mxcsr reserved bits must be masked to zero for security reasons.
 151          */
 152         xsave->i387.mxcsr &= mxcsr_feature_mask;
 153
 154         /*
 155          * In case of failure, mark all states as init:
 156          */
 157         if (ret)
 158                 fpstate_init(&fpu->state);
 159
 160         return ret;
 161 }
 162
 163 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 164
 165 /*
 166  * FPU tag word conversions.
 167  */
 168
 169 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 170 {
 171         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 172
 173         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 174         tmp = ~twd;
 175         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 176         /* and move the valid bits to the lower byte. */
 177         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 178         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 179         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 180
 181         return tmp;
 182 }
 183
 184 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16)
 185 #define FP_EXP_TAG_VALID        0
 186 #define FP_EXP_TAG_ZERO         1
 187 #define FP_EXP_TAG_SPECIAL      2
 188 #define FP_EXP_TAG_EMPTY        3
 189
 190 static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave)
 191 {
 192         struct _fpxreg *st;
 193         u32 tos = (fxsave->swd >> 11) & 7;
 194         u32 twd = (unsigned long) fxsave->twd;
 195         u32 tag;
 196         u32 ret = 0xffff0000u;
 197         int i;
 198
 199         for (i = 0; i < 8; i++, twd >>= 1) {
 200                 if (twd & 0x1) {
 201                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 202
 203                         switch (st->exponent & 0x7fff) {
 204                         case 0x7fff:
 205                                 tag = FP_EXP_TAG_SPECIAL;
 206                                 break;
 207                         case 0x0000:
 208                                 if (!st->significand[0] &&
 209                                     !st->significand[1] &&
 210                                     !st->significand[2] &&
 211                                     !st->significand[3])
 212                                         tag = FP_EXP_TAG_ZERO;
 213                                 else
 214                                         tag = FP_EXP_TAG_SPECIAL;
 215                                 break;
 216                         default:
 217                                 if (st->significand[3] & 0x8000)
 218                                         tag = FP_EXP_TAG_VALID;
 219                                 else
 220                                         tag = FP_EXP_TAG_SPECIAL;
 221                                 break;
 222                         }
 223                 } else {
 224                         tag = FP_EXP_TAG_EMPTY;
 225                 }
 226                 ret |= tag << (2 * i);
 227         }
 228         return ret;
 229 }
 230
 231 /*
 232  * FXSR floating point environment conversions.
 233  */
 234
 235 void
 236 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 237 {
 238         struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
 239         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 240         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 241         int i;
 242
 243         env->cwd = fxsave->cwd | 0xffff0000u;
 244         env->swd = fxsave->swd | 0xffff0000u;
 245         env->twd = twd_fxsr_to_i387(fxsave);
 246
 247 #ifdef CONFIG_X86_64
 248         env->fip = fxsave->rip;
 249         env->foo = fxsave->rdp;
 250         /*
 251          * should be actually ds/cs at fpu exception time, but
 252          * that information is not available in 64bit mode.
 253          */
 254         env->fcs = task_pt_regs(tsk)->cs;
 255         if (tsk == current) {
 256                 savesegment(ds, env->fos);
 257         } else {
 258                 env->fos = tsk->thread.ds;
 259         }
 260         env->fos |= 0xffff0000;
 261 #else
 262         env->fip = fxsave->fip;
 263         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 264         env->foo = fxsave->foo;
 265         env->fos = fxsave->fos;
 266 #endif
 267
 268         for (i = 0; i < 8; ++i)
 269                 memcpy(&to[i], &from[i], sizeof(to[0]));
 270 }
 271
 272 void convert_to_fxsr(struct task_struct *tsk,
 273                      const struct user_i387_ia32_struct *env)
 274
 275 {
 276         struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
 277         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 278         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 279         int i;
 280
 281         fxsave->cwd = env->cwd;
 282         fxsave->swd = env->swd;
 283         fxsave->twd = twd_i387_to_fxsr(env->twd);
 284         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 285 #ifdef CONFIG_X86_64
 286         fxsave->rip = env->fip;
 287         fxsave->rdp = env->foo;
 288         /* cs and ds ignored */
 289 #else
 290         fxsave->fip = env->fip;
 291         fxsave->fcs = (env->fcs & 0xffff);
 292         fxsave->foo = env->foo;
 293         fxsave->fos = env->fos;
 294 #endif
 295
 296         for (i = 0; i < 8; ++i)
 297                 memcpy(&to[i], &from[i], sizeof(from[0]));
 298 }
 299
 300 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 301                unsigned int pos, unsigned int count,
 302                void *kbuf, void __user *ubuf)
 303 {
 304         struct fpu *fpu = &target->thread.fpu;
 305         struct user_i387_ia32_struct env;
 306
 307         fpu__prepare_read(fpu);
 308
 309         if (!boot_cpu_has(X86_FEATURE_FPU))
 310                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 311
 312         if (!boot_cpu_has(X86_FEATURE_FXSR))
 313                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 314                                            &fpu->state.fsave, 0,
 315                                            -1);
 316
 317         fpstate_sanitize_xstate(fpu);
 318
 319         if (kbuf && pos == 0 && count == sizeof(env)) {
 320                 convert_from_fxsr(kbuf, target);
 321                 return 0;
 322         }
 323
 324         convert_from_fxsr(&env, target);
 325
 326         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 327 }
 328
 329 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 330                unsigned int pos, unsigned int count,
 331                const void *kbuf, const void __user *ubuf)
 332 {
 333         struct fpu *fpu = &target->thread.fpu;
 334         struct user_i387_ia32_struct env;
 335         int ret;
 336
 337         fpu__prepare_write(fpu);
 338         fpstate_sanitize_xstate(fpu);
 339
 340         if (!boot_cpu_has(X86_FEATURE_FPU))
 341                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 342
 343         if (!boot_cpu_has(X86_FEATURE_FXSR))
 344                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 345                                           &fpu->state.fsave, 0,
 346                                           -1);
 347
 348         if (pos > 0 || count < sizeof(env))
 349                 convert_from_fxsr(&env, target);
 350
 351         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 352         if (!ret)
 353                 convert_to_fxsr(target, &env);
 354
 355         /*
 356          * update the header bit in the xsave header, indicating the
 357          * presence of FP.
 358          */
 359         if (boot_cpu_has(X86_FEATURE_XSAVE))
 360                 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FP;
 361         return ret;
 362 }
 363
 364 /*
 365  * FPU state for core dumps.
 366  * This is only used for a.out dumps now.
 367  * It is declared generically using elf_fpregset_t (which is
 368  * struct user_i387_struct) but is in fact only used for 32-bit
 369  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 370  */
 371 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
 372 {
 373         struct task_struct *tsk = current;
 374         struct fpu *fpu = &tsk->thread.fpu;
 375         int fpvalid;
 376
 377         fpvalid = fpu->initialized;
 378         if (fpvalid)
 379                 fpvalid = !fpregs_get(tsk, NULL,
 380                                       0, sizeof(struct user_i387_ia32_struct),
 381                                       ufpu, NULL);
 382
 383         return fpvalid;
 384 }
 385 EXPORT_SYMBOL(dump_fpu);
 386
 387 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */