arch/x86/kernel/fpu/signal.c

   1 /*
   2  * FPU signal frame handling routines.
   3  */
   4
   5 #include <linux/compat.h>
   6 #include <linux/cpu.h>
   7
   8 #include <asm/fpu/internal.h>
   9 #include <asm/fpu/signal.h>
  10 #include <asm/fpu/regset.h>
  11
  12 #include <asm/sigframe.h>
  13
  14 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
  15
  16 /*
  17  * Check for the presence of extended state information in the
  18  * user fpstate pointer in the sigcontext.
  19  */
  20 static inline int check_for_xstate(struct fxregs_state __user *buf,
  21                                    void __user *fpstate,
  22                                    struct _fpx_sw_bytes *fx_sw)
  23 {
  24         int min_xstate_size = sizeof(struct fxregs_state) +
  25                               sizeof(struct xstate_header);
  26         unsigned int magic2;
  27
  28         if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
  29                 return -1;
  30
  31         /* Check for the first magic field and other error scenarios. */
  32         if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
  33             fx_sw->xstate_size < min_xstate_size ||
  34             fx_sw->xstate_size > xstate_size ||
  35             fx_sw->xstate_size > fx_sw->extended_size)
  36                 return -1;
  37
  38         /*
  39          * Check for the presence of second magic word at the end of memory
  40          * layout. This detects the case where the user just copied the legacy
  41          * fpstate layout with out copying the extended state information
  42          * in the memory layout.
  43          */
  44         if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
  45             || magic2 != FP_XSTATE_MAGIC2)
  46                 return -1;
  47
  48         return 0;
  49 }
  50
  51 /*
  52  * Signal frame handlers.
  53  */
  54 static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
  55 {
  56         if (use_fxsr()) {
  57                 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
  58                 struct user_i387_ia32_struct env;
  59                 struct _fpstate_32 __user *fp = buf;
  60
  61                 convert_from_fxsr(&env, tsk);
  62
  63                 if (__copy_to_user(buf, &env, sizeof(env)) ||
  64                     __put_user(xsave->i387.swd, &fp->status) ||
  65                     __put_user(X86_FXSR_MAGIC, &fp->magic))
  66                         return -1;
  67         } else {
  68                 struct fregs_state __user *fp = buf;
  69                 u32 swd;
  70                 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
  71                         return -1;
  72         }
  73
  74         return 0;
  75 }
  76
  77 static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
  78 {
  79         struct xregs_state __user *x = buf;
  80         struct _fpx_sw_bytes *sw_bytes;
  81         u32 xfeatures;
  82         int err;
  83
  84         /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
  85         sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
  86         err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
  87
  88         if (!use_xsave())
  89                 return err;
  90
  91         err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size));
  92
  93         /*
  94          * Read the xfeatures which we copied (directly from the cpu or
  95          * from the state in task struct) to the user buffers.
  96          */
  97         err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures);
  98
  99         /*
 100          * For legacy compatible, we always set FP/SSE bits in the bit
 101          * vector while saving the state to the user context. This will
 102          * enable us capturing any changes(during sigreturn) to
 103          * the FP/SSE bits by the legacy applications which don't touch
 104          * xfeatures in the xsave header.
 105          *
 106          * xsave aware apps can change the xfeatures in the xsave
 107          * header as well as change any contents in the memory layout.
 108          * xrestore as part of sigreturn will capture all the changes.
 109          */
 110         xfeatures |= XFEATURE_MASK_FPSSE;
 111
 112         err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures);
 113
 114         return err;
 115 }
 116
 117 static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
 118 {
 119         int err;
 120
 121         if (use_xsave())
 122                 err = copy_xregs_to_user(buf);
 123         else if (use_fxsr())
 124                 err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
 125         else
 126                 err = copy_fregs_to_user((struct fregs_state __user *) buf);
 127
 128         if (unlikely(err) && __clear_user(buf, xstate_size))
 129                 err = -EFAULT;
 130         return err;
 131 }
 132
 133 /*
 134  * Save the fpu, extended register state to the user signal frame.
 135  *
 136  * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
 137  *  state is copied.
 138  *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
 139  *
 140  *      buf == buf_fx for 64-bit frames and 32-bit fsave frame.
 141  *      buf != buf_fx for 32-bit frames with fxstate.
 142  *
 143  * If the fpu, extended register state is live, save the state directly
 144  * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
 145  * copy the thread's fpu state to the user frame starting at 'buf_fx'.
 146  *
 147  * If this is a 32-bit frame with fxstate, put a fsave header before
 148  * the aligned state at 'buf_fx'.
 149  *
 150  * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
 151  * indicating the absence/presence of the extended state to the user.
 152  */
 153 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 154 {
 155         struct xregs_state *xsave = &current->thread.fpu.state.xsave;
 156         struct task_struct *tsk = current;
 157         int ia32_fxstate = (buf != buf_fx);
 158
 159         ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
 160                          config_enabled(CONFIG_IA32_EMULATION));
 161
 162         if (!access_ok(VERIFY_WRITE, buf, size))
 163                 return -EACCES;
 164
 165         if (!static_cpu_has(X86_FEATURE_FPU))
 166                 return fpregs_soft_get(current, NULL, 0,
 167                         sizeof(struct user_i387_ia32_struct), NULL,
 168                         (struct _fpstate_32 __user *) buf) ? -1 : 1;
 169
 170         if (fpregs_active()) {
 171                 /* Save the live register state to the user directly. */
 172                 if (copy_fpregs_to_sigframe(buf_fx))
 173                         return -1;
 174                 /* Update the thread's fxstate to save the fsave header. */
 175                 if (ia32_fxstate)
 176                         copy_fxregs_to_kernel(&tsk->thread.fpu);
 177         } else {
 178                 fpstate_sanitize_xstate(&tsk->thread.fpu);
 179                 if (__copy_to_user(buf_fx, xsave, xstate_size))
 180                         return -1;
 181         }
 182
 183         /* Save the fsave header for the 32-bit frames. */
 184         if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
 185                 return -1;
 186
 187         if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
 188                 return -1;
 189
 190         return 0;
 191 }
 192
 193 static inline void
 194 sanitize_restored_xstate(struct task_struct *tsk,
 195                          struct user_i387_ia32_struct *ia32_env,
 196                          u64 xfeatures, int fx_only)
 197 {
 198         struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
 199         struct xstate_header *header = &xsave->header;
 200
 201         if (use_xsave()) {
 202                 /* These bits must be zero. */
 203                 memset(header->reserved, 0, 48);
 204
 205                 /*
 206                  * Init the state that is not present in the memory
 207                  * layout and not enabled by the OS.
 208                  */
 209                 if (fx_only)
 210                         header->xfeatures = XFEATURE_MASK_FPSSE;
 211                 else
 212                         header->xfeatures &= (xfeatures_mask & xfeatures);
 213         }
 214
 215         if (use_fxsr()) {
 216                 /*
 217                  * mscsr reserved bits must be masked to zero for security
 218                  * reasons.
 219                  */
 220                 xsave->i387.mxcsr &= mxcsr_feature_mask;
 221
 222                 convert_to_fxsr(tsk, ia32_env);
 223         }
 224 }
 225
 226 /*
 227  * Restore the extended state if present. Otherwise, restore the FP/SSE state.
 228  */
 229 static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
 230 {
 231         if (use_xsave()) {
 232                 if ((unsigned long)buf % 64 || fx_only) {
 233                         u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
 234                         copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 235                         return copy_user_to_fxregs(buf);
 236                 } else {
 237                         u64 init_bv = xfeatures_mask & ~xbv;
 238                         if (unlikely(init_bv))
 239                                 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 240                         return copy_user_to_xregs(buf, xbv);
 241                 }
 242         } else if (use_fxsr()) {
 243                 return copy_user_to_fxregs(buf);
 244         } else
 245                 return copy_user_to_fregs(buf);
 246 }
 247
 248 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 249 {
 250         int ia32_fxstate = (buf != buf_fx);
 251         struct task_struct *tsk = current;
 252         struct fpu *fpu = &tsk->thread.fpu;
 253         int state_size = xstate_size;
 254         u64 xfeatures = 0;
 255         int fx_only = 0;
 256
 257         ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
 258                          config_enabled(CONFIG_IA32_EMULATION));
 259
 260         if (!buf) {
 261                 fpu__clear(fpu);
 262                 return 0;
 263         }
 264
 265         if (!access_ok(VERIFY_READ, buf, size))
 266                 return -EACCES;
 267
 268         fpu__activate_curr(fpu);
 269
 270         if (!static_cpu_has(X86_FEATURE_FPU))
 271                 return fpregs_soft_set(current, NULL,
 272                                        0, sizeof(struct user_i387_ia32_struct),
 273                                        NULL, buf) != 0;
 274
 275         if (use_xsave()) {
 276                 struct _fpx_sw_bytes fx_sw_user;
 277                 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
 278                         /*
 279                          * Couldn't find the extended state information in the
 280                          * memory layout. Restore just the FP/SSE and init all
 281                          * the other extended state.
 282                          */
 283                         state_size = sizeof(struct fxregs_state);
 284                         fx_only = 1;
 285                 } else {
 286                         state_size = fx_sw_user.xstate_size;
 287                         xfeatures = fx_sw_user.xfeatures;
 288                 }
 289         }
 290
 291         if (ia32_fxstate) {
 292                 /*
 293                  * For 32-bit frames with fxstate, copy the user state to the
 294                  * thread's fpu state, reconstruct fxstate from the fsave
 295                  * header. Sanitize the copied state etc.
 296                  */
 297                 struct fpu *fpu = &tsk->thread.fpu;
 298                 struct user_i387_ia32_struct env;
 299                 int err = 0;
 300
 301                 /*
 302                  * Drop the current fpu which clears fpu->fpstate_active. This ensures
 303                  * that any context-switch during the copy of the new state,
 304                  * avoids the intermediate state from getting restored/saved.
 305                  * Thus avoiding the new restored state from getting corrupted.
 306                  * We will be ready to restore/save the state only after
 307                  * fpu->fpstate_active is again set.
 308                  */
 309                 fpu__drop(fpu);
 310
 311                 if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) ||
 312                     __copy_from_user(&env, buf, sizeof(env))) {
 313                         fpstate_init(&fpu->state);
 314                         err = -1;
 315                 } else {
 316                         sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
 317                 }
 318
 319                 fpu->fpstate_active = 1;
 320                 if (use_eager_fpu()) {
 321                         preempt_disable();
 322                         fpu__restore(fpu);
 323                         preempt_enable();
 324                 }
 325
 326                 return err;
 327         } else {
 328                 /*
 329                  * For 64-bit frames and 32-bit fsave frames, restore the user
 330                  * state to the registers directly (with exceptions handled).
 331                  */
 332                 user_fpu_begin();
 333                 if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
 334                         fpu__clear(fpu);
 335                         return -1;
 336                 }
 337         }
 338
 339         return 0;
 340 }
 341
 342 static inline int xstate_sigframe_size(void)
 343 {
 344         return use_xsave() ? xstate_size + FP_XSTATE_MAGIC2_SIZE : xstate_size;
 345 }
 346
 347 /*
 348  * Restore FPU state from a sigframe:
 349  */
 350 int fpu__restore_sig(void __user *buf, int ia32_frame)
 351 {
 352         void __user *buf_fx = buf;
 353         int size = xstate_sigframe_size();
 354
 355         if (ia32_frame && use_fxsr()) {
 356                 buf_fx = buf + sizeof(struct fregs_state);
 357                 size += sizeof(struct fregs_state);
 358         }
 359
 360         return __fpu__restore_sig(buf, buf_fx, size);
 361 }
 362
 363 unsigned long
 364 fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
 365                      unsigned long *buf_fx, unsigned long *size)
 366 {
 367         unsigned long frame_size = xstate_sigframe_size();
 368
 369         *buf_fx = sp = round_down(sp - frame_size, 64);
 370         if (ia32_frame && use_fxsr()) {
 371                 frame_size += sizeof(struct fregs_state);
 372                 sp -= sizeof(struct fregs_state);
 373         }
 374
 375         *size = frame_size;
 376
 377         return sp;
 378 }
 379 /*
 380  * Prepare the SW reserved portion of the fxsave memory layout, indicating
 381  * the presence of the extended state information in the memory layout
 382  * pointed by the fpstate pointer in the sigcontext.
 383  * This will be saved when ever the FP and extended state context is
 384  * saved on the user stack during the signal handler delivery to the user.
 385  */
 386 void fpu__init_prepare_fx_sw_frame(void)
 387 {
 388         int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;
 389
 390         fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
 391         fx_sw_reserved.extended_size = size;
 392         fx_sw_reserved.xfeatures = xfeatures_mask;
 393         fx_sw_reserved.xstate_size = xstate_size;
 394
 395         if (config_enabled(CONFIG_IA32_EMULATION) ||
 396             config_enabled(CONFIG_X86_32)) {
 397                 int fsave_header_size = sizeof(struct fregs_state);
 398
 399                 fx_sw_reserved_ia32 = fx_sw_reserved;
 400                 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
 401         }
 402 }
 403