arch/x86/kernel/fpu/regset.c

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