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 #include <asm/fpu/xstate.h>
  12
  13 #include <asm/sigframe.h>
  14 #include <asm/trace/fpu.h>
  15
  16 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
  17
  18 /*
  19  * Check for the presence of extended state information in the
  20  * user fpstate pointer in the sigcontext.
  21  */
  22 static inline int check_for_xstate(struct fxregs_state __user *buf,
  23                                    void __user *fpstate,
  24                                    struct _fpx_sw_bytes *fx_sw)
  25 {
  26         int min_xstate_size = sizeof(struct fxregs_state) +
  27                               sizeof(struct xstate_header);
  28         unsigned int magic2;
  29
  30         if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
  31                 return -1;
  32
  33         /* Check for the first magic field and other error scenarios. */
  34         if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
  35             fx_sw->xstate_size < min_xstate_size ||
  36             fx_sw->xstate_size > fpu_user_xstate_size ||
  37             fx_sw->xstate_size > fx_sw->extended_size)
  38                 return -1;
  39
  40         /*
  41          * Check for the presence of second magic word at the end of memory
  42          * layout. This detects the case where the user just copied the legacy
  43          * fpstate layout with out copying the extended state information
  44          * in the memory layout.
  45          */
  46         if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
  47             || magic2 != FP_XSTATE_MAGIC2)
  48                 return -1;
  49
  50         return 0;
  51 }
  52
  53 /*
  54  * Signal frame handlers.
  55  */
  56 static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
  57 {
  58         if (use_fxsr()) {
  59                 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
  60                 struct user_i387_ia32_struct env;
  61                 struct _fpstate_32 __user *fp = buf;
  62
  63                 convert_from_fxsr(&env, tsk);
  64
  65                 if (__copy_to_user(buf, &env, sizeof(env)) ||
  66                     __put_user(xsave->i387.swd, &fp->status) ||
  67                     __put_user(X86_FXSR_MAGIC, &fp->magic))
  68                         return -1;
  69         } else {
  70                 struct fregs_state __user *fp = buf;
  71                 u32 swd;
  72                 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
  73                         return -1;
  74         }
  75
  76         return 0;
  77 }
  78
  79 static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
  80 {
  81         struct xregs_state __user *x = buf;
  82         struct _fpx_sw_bytes *sw_bytes;
  83         u32 xfeatures;
  84         int err;
  85
  86         /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
  87         sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
  88         err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
  89
  90         if (!use_xsave())
  91                 return err;
  92
  93         err |= __put_user(FP_XSTATE_MAGIC2,
  94                           (__u32 *)(buf + fpu_user_xstate_size));
  95
  96         /*
  97          * Read the xfeatures which we copied (directly from the cpu or
  98          * from the state in task struct) to the user buffers.
  99          */
 100         err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures);
 101
 102         /*
 103          * For legacy compatible, we always set FP/SSE bits in the bit
 104          * vector while saving the state to the user context. This will
 105          * enable us capturing any changes(during sigreturn) to
 106          * the FP/SSE bits by the legacy applications which don't touch
 107          * xfeatures in the xsave header.
 108          *
 109          * xsave aware apps can change the xfeatures in the xsave
 110          * header as well as change any contents in the memory layout.
 111          * xrestore as part of sigreturn will capture all the changes.
 112          */
 113         xfeatures |= XFEATURE_MASK_FPSSE;
 114
 115         err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures);
 116
 117         return err;
 118 }
 119
 120 static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
 121 {
 122         int err;
 123
 124         if (use_xsave())
 125                 err = copy_xregs_to_user(buf);
 126         else if (use_fxsr())
 127                 err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
 128         else
 129                 err = copy_fregs_to_user((struct fregs_state __user *) buf);
 130
 131         if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
 132                 err = -EFAULT;
 133         return err;
 134 }
 135
 136 /*
 137  * Save the fpu, extended register state to the user signal frame.
 138  *
 139  * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
 140  *  state is copied.
 141  *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
 142  *
 143  *      buf == buf_fx for 64-bit frames and 32-bit fsave frame.
 144  *      buf != buf_fx for 32-bit frames with fxstate.
 145  *
 146  * If the fpu, extended register state is live, save the state directly
 147  * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
 148  * copy the thread's fpu state to the user frame starting at 'buf_fx'.
 149  *
 150  * If this is a 32-bit frame with fxstate, put a fsave header before
 151  * the aligned state at 'buf_fx'.
 152  *
 153  * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
 154  * indicating the absence/presence of the extended state to the user.
 155  */
 156 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 157 {
 158         struct fpu *fpu = &current->thread.fpu;
 159         struct xregs_state *xsave = &fpu->state.xsave;
 160         struct task_struct *tsk = current;
 161         int ia32_fxstate = (buf != buf_fx);
 162
 163         ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 164                          IS_ENABLED(CONFIG_IA32_EMULATION));
 165
 166         if (!access_ok(VERIFY_WRITE, buf, size))
 167                 return -EACCES;
 168
 169         if (!static_cpu_has(X86_FEATURE_FPU))
 170                 return fpregs_soft_get(current, NULL, 0,
 171                         sizeof(struct user_i387_ia32_struct), NULL,
 172                         (struct _fpstate_32 __user *) buf) ? -1 : 1;
 173
 174         if (fpu->fpregs_active || using_compacted_format()) {
 175                 /* Save the live register state to the user directly. */
 176                 if (copy_fpregs_to_sigframe(buf_fx))
 177                         return -1;
 178                 /* Update the thread's fxstate to save the fsave header. */
 179                 if (ia32_fxstate)
 180                         copy_fxregs_to_kernel(fpu);
 181         } else {
 182                 /*
 183                  * It is a *bug* if kernel uses compacted-format for xsave
 184                  * area and we copy it out directly to a signal frame. It
 185                  * should have been handled above by saving the registers
 186                  * directly.
 187                  */
 188                 if (boot_cpu_has(X86_FEATURE_XSAVES)) {
 189                         WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n");
 190                         return -1;
 191                 }
 192
 193                 fpstate_sanitize_xstate(fpu);
 194                 if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
 195                         return -1;
 196         }
 197
 198         /* Save the fsave header for the 32-bit frames. */
 199         if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
 200                 return -1;
 201
 202         if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
 203                 return -1;
 204
 205         return 0;
 206 }
 207
 208 static inline void
 209 sanitize_restored_xstate(struct task_struct *tsk,
 210                          struct user_i387_ia32_struct *ia32_env,
 211                          u64 xfeatures, int fx_only)
 212 {
 213         struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
 214         struct xstate_header *header = &xsave->header;
 215
 216         if (use_xsave()) {
 217                 /* These bits must be zero. */
 218                 memset(header->reserved, 0, 48);
 219
 220                 /*
 221                  * Init the state that is not present in the memory
 222                  * layout and not enabled by the OS.
 223                  */
 224                 if (fx_only)
 225                         header->xfeatures = XFEATURE_MASK_FPSSE;
 226                 else
 227                         header->xfeatures &= (xfeatures_mask & xfeatures);
 228         }
 229
 230         if (use_fxsr()) {
 231                 /*
 232                  * mscsr reserved bits must be masked to zero for security
 233                  * reasons.
 234                  */
 235                 xsave->i387.mxcsr &= mxcsr_feature_mask;
 236
 237                 convert_to_fxsr(tsk, ia32_env);
 238         }
 239 }
 240
 241 /*
 242  * Restore the extended state if present. Otherwise, restore the FP/SSE state.
 243  */
 244 static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
 245 {
 246         if (use_xsave()) {
 247                 if ((unsigned long)buf % 64 || fx_only) {
 248                         u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
 249                         copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 250                         return copy_user_to_fxregs(buf);
 251                 } else {
 252                         u64 init_bv = xfeatures_mask & ~xbv;
 253                         if (unlikely(init_bv))
 254                                 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 255                         return copy_user_to_xregs(buf, xbv);
 256                 }
 257         } else if (use_fxsr()) {
 258                 return copy_user_to_fxregs(buf);
 259         } else
 260                 return copy_user_to_fregs(buf);
 261 }
 262
 263 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 264 {
 265         int ia32_fxstate = (buf != buf_fx);
 266         struct task_struct *tsk = current;
 267         struct fpu *fpu = &tsk->thread.fpu;
 268         int state_size = fpu_kernel_xstate_size;
 269         u64 xfeatures = 0;
 270         int fx_only = 0;
 271
 272         ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 273                          IS_ENABLED(CONFIG_IA32_EMULATION));
 274
 275         if (!buf) {
 276                 fpu__clear(fpu);
 277                 return 0;
 278         }
 279
 280         if (!access_ok(VERIFY_READ, buf, size))
 281                 return -EACCES;
 282
 283         fpu__activate_curr(fpu);
 284
 285         if (!static_cpu_has(X86_FEATURE_FPU))
 286                 return fpregs_soft_set(current, NULL,
 287                                        0, sizeof(struct user_i387_ia32_struct),
 288                                        NULL, buf) != 0;
 289
 290         if (use_xsave()) {
 291                 struct _fpx_sw_bytes fx_sw_user;
 292                 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
 293                         /*
 294                          * Couldn't find the extended state information in the
 295                          * memory layout. Restore just the FP/SSE and init all
 296                          * the other extended state.
 297                          */
 298                         state_size = sizeof(struct fxregs_state);
 299                         fx_only = 1;
 300                         trace_x86_fpu_xstate_check_failed(fpu);
 301                 } else {
 302                         state_size = fx_sw_user.xstate_size;
 303                         xfeatures = fx_sw_user.xfeatures;
 304                 }
 305         }
 306
 307         if (ia32_fxstate) {
 308                 /*
 309                  * For 32-bit frames with fxstate, copy the user state to the
 310                  * thread's fpu state, reconstruct fxstate from the fsave
 311                  * header. Sanitize the copied state etc.
 312                  */
 313                 struct fpu *fpu = &tsk->thread.fpu;
 314                 struct user_i387_ia32_struct env;
 315                 int err = 0;
 316
 317                 /*
 318                  * Drop the current fpu which clears fpu->fpstate_active. This ensures
 319                  * that any context-switch during the copy of the new state,
 320                  * avoids the intermediate state from getting restored/saved.
 321                  * Thus avoiding the new restored state from getting corrupted.
 322                  * We will be ready to restore/save the state only after
 323                  * fpu->fpstate_active is again set.
 324                  */
 325                 fpu__drop(fpu);
 326
 327                 if (using_compacted_format())
 328                         err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
 329                 else
 330                         err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
 331
 332                 if (err || __copy_from_user(&env, buf, sizeof(env))) {
 333                         fpstate_init(&fpu->state);
 334                         trace_x86_fpu_init_state(fpu);
 335                         err = -1;
 336                 } else {
 337                         sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
 338                 }
 339
 340                 fpu->fpstate_active = 1;
 341                 preempt_disable();
 342                 fpu__restore(fpu);
 343                 preempt_enable();
 344
 345                 return err;
 346         } else {
 347                 /*
 348                  * For 64-bit frames and 32-bit fsave frames, restore the user
 349                  * state to the registers directly (with exceptions handled).
 350                  */
 351                 user_fpu_begin();
 352                 if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
 353                         fpu__clear(fpu);
 354                         return -1;
 355                 }
 356         }
 357
 358         return 0;
 359 }
 360
 361 static inline int xstate_sigframe_size(void)
 362 {
 363         return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
 364                         fpu_user_xstate_size;
 365 }
 366
 367 /*
 368  * Restore FPU state from a sigframe:
 369  */
 370 int fpu__restore_sig(void __user *buf, int ia32_frame)
 371 {
 372         void __user *buf_fx = buf;
 373         int size = xstate_sigframe_size();
 374
 375         if (ia32_frame && use_fxsr()) {
 376                 buf_fx = buf + sizeof(struct fregs_state);
 377                 size += sizeof(struct fregs_state);
 378         }
 379
 380         return __fpu__restore_sig(buf, buf_fx, size);
 381 }
 382
 383 unsigned long
 384 fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
 385                      unsigned long *buf_fx, unsigned long *size)
 386 {
 387         unsigned long frame_size = xstate_sigframe_size();
 388
 389         *buf_fx = sp = round_down(sp - frame_size, 64);
 390         if (ia32_frame && use_fxsr()) {
 391                 frame_size += sizeof(struct fregs_state);
 392                 sp -= sizeof(struct fregs_state);
 393         }
 394
 395         *size = frame_size;
 396
 397         return sp;
 398 }
 399 /*
 400  * Prepare the SW reserved portion of the fxsave memory layout, indicating
 401  * the presence of the extended state information in the memory layout
 402  * pointed by the fpstate pointer in the sigcontext.
 403  * This will be saved when ever the FP and extended state context is
 404  * saved on the user stack during the signal handler delivery to the user.
 405  */
 406 void fpu__init_prepare_fx_sw_frame(void)
 407 {
 408         int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
 409
 410         fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
 411         fx_sw_reserved.extended_size = size;
 412         fx_sw_reserved.xfeatures = xfeatures_mask;
 413         fx_sw_reserved.xstate_size = fpu_user_xstate_size;
 414
 415         if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
 416             IS_ENABLED(CONFIG_X86_32)) {
 417                 int fsave_header_size = sizeof(struct fregs_state);
 418
 419                 fx_sw_reserved_ia32 = fx_sw_reserved;
 420                 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
 421         }
 422 }
 423