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->initialized || 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                 /*
 218                  * Note: we don't need to zero the reserved bits in the
 219                  * xstate_header here because we either didn't copy them at all,
 220                  * or we checked earlier that they aren't set.
 221                  */
 222
 223                 /*
 224                  * Init the state that is not present in the memory
 225                  * layout and not enabled by the OS.
 226                  */
 227                 if (fx_only)
 228                         header->xfeatures = XFEATURE_MASK_FPSSE;
 229                 else
 230                         header->xfeatures &= xfeatures;
 231         }
 232
 233         if (use_fxsr()) {
 234                 /*
 235                  * mscsr reserved bits must be masked to zero for security
 236                  * reasons.
 237                  */
 238                 xsave->i387.mxcsr &= mxcsr_feature_mask;
 239
 240                 convert_to_fxsr(tsk, ia32_env);
 241         }
 242 }
 243
 244 /*
 245  * Restore the extended state if present. Otherwise, restore the FP/SSE state.
 246  */
 247 static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
 248 {
 249         if (use_xsave()) {
 250                 if ((unsigned long)buf % 64 || fx_only) {
 251                         u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
 252                         copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 253                         return copy_user_to_fxregs(buf);
 254                 } else {
 255                         u64 init_bv = xfeatures_mask & ~xbv;
 256                         if (unlikely(init_bv))
 257                                 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 258                         return copy_user_to_xregs(buf, xbv);
 259                 }
 260         } else if (use_fxsr()) {
 261                 return copy_user_to_fxregs(buf);
 262         } else
 263                 return copy_user_to_fregs(buf);
 264 }
 265
 266 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 267 {
 268         int ia32_fxstate = (buf != buf_fx);
 269         struct task_struct *tsk = current;
 270         struct fpu *fpu = &tsk->thread.fpu;
 271         int state_size = fpu_kernel_xstate_size;
 272         u64 xfeatures = 0;
 273         int fx_only = 0;
 274
 275         ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 276                          IS_ENABLED(CONFIG_IA32_EMULATION));
 277
 278         if (!buf) {
 279                 fpu__clear(fpu);
 280                 return 0;
 281         }
 282
 283         if (!access_ok(VERIFY_READ, buf, size))
 284                 return -EACCES;
 285
 286         fpu__initialize(fpu);
 287
 288         if (!static_cpu_has(X86_FEATURE_FPU))
 289                 return fpregs_soft_set(current, NULL,
 290                                        0, sizeof(struct user_i387_ia32_struct),
 291                                        NULL, buf) != 0;
 292
 293         if (use_xsave()) {
 294                 struct _fpx_sw_bytes fx_sw_user;
 295                 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
 296                         /*
 297                          * Couldn't find the extended state information in the
 298                          * memory layout. Restore just the FP/SSE and init all
 299                          * the other extended state.
 300                          */
 301                         state_size = sizeof(struct fxregs_state);
 302                         fx_only = 1;
 303                         trace_x86_fpu_xstate_check_failed(fpu);
 304                 } else {
 305                         state_size = fx_sw_user.xstate_size;
 306                         xfeatures = fx_sw_user.xfeatures;
 307                 }
 308         }
 309
 310         if (ia32_fxstate) {
 311                 /*
 312                  * For 32-bit frames with fxstate, copy the user state to the
 313                  * thread's fpu state, reconstruct fxstate from the fsave
 314                  * header. Validate and sanitize the copied state.
 315                  */
 316                 struct fpu *fpu = &tsk->thread.fpu;
 317                 struct user_i387_ia32_struct env;
 318                 int err = 0;
 319
 320                 /*
 321                  * Drop the current fpu which clears fpu->initialized. This ensures
 322                  * that any context-switch during the copy of the new state,
 323                  * avoids the intermediate state from getting restored/saved.
 324                  * Thus avoiding the new restored state from getting corrupted.
 325                  * We will be ready to restore/save the state only after
 326                  * fpu->initialized is again set.
 327                  */
 328                 fpu__drop(fpu);
 329
 330                 if (using_compacted_format()) {
 331                         err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
 332                 } else {
 333                         err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
 334
 335                         if (!err && state_size > offsetof(struct xregs_state, header))
 336                                 err = validate_xstate_header(&fpu->state.xsave.header);
 337                 }
 338
 339                 if (err || __copy_from_user(&env, buf, sizeof(env))) {
 340                         fpstate_init(&fpu->state);
 341                         trace_x86_fpu_init_state(fpu);
 342                         err = -1;
 343                 } else {
 344                         sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
 345                 }
 346
 347                 fpu->initialized = 1;
 348                 preempt_disable();
 349                 fpu__restore(fpu);
 350                 preempt_enable();
 351
 352                 return err;
 353         } else {
 354                 /*
 355                  * For 64-bit frames and 32-bit fsave frames, restore the user
 356                  * state to the registers directly (with exceptions handled).
 357                  */
 358                 user_fpu_begin();
 359                 if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
 360                         fpu__clear(fpu);
 361                         return -1;
 362                 }
 363         }
 364
 365         return 0;
 366 }
 367
 368 static inline int xstate_sigframe_size(void)
 369 {
 370         return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
 371                         fpu_user_xstate_size;
 372 }
 373
 374 /*
 375  * Restore FPU state from a sigframe:
 376  */
 377 int fpu__restore_sig(void __user *buf, int ia32_frame)
 378 {
 379         void __user *buf_fx = buf;
 380         int size = xstate_sigframe_size();
 381
 382         if (ia32_frame && use_fxsr()) {
 383                 buf_fx = buf + sizeof(struct fregs_state);
 384                 size += sizeof(struct fregs_state);
 385         }
 386
 387         return __fpu__restore_sig(buf, buf_fx, size);
 388 }
 389
 390 unsigned long
 391 fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
 392                      unsigned long *buf_fx, unsigned long *size)
 393 {
 394         unsigned long frame_size = xstate_sigframe_size();
 395
 396         *buf_fx = sp = round_down(sp - frame_size, 64);
 397         if (ia32_frame && use_fxsr()) {
 398                 frame_size += sizeof(struct fregs_state);
 399                 sp -= sizeof(struct fregs_state);
 400         }
 401
 402         *size = frame_size;
 403
 404         return sp;
 405 }
 406 /*
 407  * Prepare the SW reserved portion of the fxsave memory layout, indicating
 408  * the presence of the extended state information in the memory layout
 409  * pointed by the fpstate pointer in the sigcontext.
 410  * This will be saved when ever the FP and extended state context is
 411  * saved on the user stack during the signal handler delivery to the user.
 412  */
 413 void fpu__init_prepare_fx_sw_frame(void)
 414 {
 415         int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
 416
 417         fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
 418         fx_sw_reserved.extended_size = size;
 419         fx_sw_reserved.xfeatures = xfeatures_mask;
 420         fx_sw_reserved.xstate_size = fpu_user_xstate_size;
 421
 422         if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
 423             IS_ENABLED(CONFIG_X86_32)) {
 424                 int fsave_header_size = sizeof(struct fregs_state);
 425
 426                 fx_sw_reserved_ia32 = fx_sw_reserved;
 427                 fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
 428         }
 429 }
 430