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 xregs_state *xsave = ¤t->thread.fpu.state.xsave; 159 struct task_struct *tsk = current; 160 int ia32_fxstate = (buf != buf_fx); 161 162 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || 163 IS_ENABLED(CONFIG_IA32_EMULATION)); 164 165 if (!access_ok(VERIFY_WRITE, buf, size)) 166 return -EACCES; 167 168 if (!static_cpu_has(X86_FEATURE_FPU)) 169 return fpregs_soft_get(current, NULL, 0, 170 sizeof(struct user_i387_ia32_struct), NULL, 171 (struct _fpstate_32 __user *) buf) ? -1 : 1; 172 173 if (fpregs_active() || using_compacted_format()) { 174 /* Save the live register state to the user directly. */ 175 if (copy_fpregs_to_sigframe(buf_fx)) 176 return -1; 177 /* Update the thread's fxstate to save the fsave header. */ 178 if (ia32_fxstate) 179 copy_fxregs_to_kernel(&tsk->thread.fpu); 180 } else { 181 /* 182 * It is a *bug* if kernel uses compacted-format for xsave 183 * area and we copy it out directly to a signal frame. It 184 * should have been handled above by saving the registers 185 * directly. 186 */ 187 if (boot_cpu_has(X86_FEATURE_XSAVES)) { 188 WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n"); 189 return -1; 190 } 191 192 fpstate_sanitize_xstate(&tsk->thread.fpu); 193 if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size)) 194 return -1; 195 } 196 197 /* Save the fsave header for the 32-bit frames. */ 198 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf)) 199 return -1; 200 201 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate)) 202 return -1; 203 204 return 0; 205 } 206 207 static inline void 208 sanitize_restored_xstate(struct task_struct *tsk, 209 struct user_i387_ia32_struct *ia32_env, 210 u64 xfeatures, int fx_only) 211 { 212 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave; 213 struct xstate_header *header = &xsave->header; 214 215 if (use_xsave()) { 216 /* These bits must be zero. */ 217 memset(header->reserved, 0, 48); 218 219 /* 220 * Init the state that is not present in the memory 221 * layout and not enabled by the OS. 222 */ 223 if (fx_only) 224 header->xfeatures = XFEATURE_MASK_FPSSE; 225 else 226 header->xfeatures &= (xfeatures_mask & xfeatures); 227 } 228 229 if (use_fxsr()) { 230 /* 231 * mscsr reserved bits must be masked to zero for security 232 * reasons. 233 */ 234 xsave->i387.mxcsr &= mxcsr_feature_mask; 235 236 convert_to_fxsr(tsk, ia32_env); 237 } 238 } 239 240 /* 241 * Restore the extended state if present. Otherwise, restore the FP/SSE state. 242 */ 243 static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only) 244 { 245 if (use_xsave()) { 246 if ((unsigned long)buf % 64 || fx_only) { 247 u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE; 248 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); 249 return copy_user_to_fxregs(buf); 250 } else { 251 u64 init_bv = xfeatures_mask & ~xbv; 252 if (unlikely(init_bv)) 253 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); 254 return copy_user_to_xregs(buf, xbv); 255 } 256 } else if (use_fxsr()) { 257 return copy_user_to_fxregs(buf); 258 } else 259 return copy_user_to_fregs(buf); 260 } 261 262 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) 263 { 264 int ia32_fxstate = (buf != buf_fx); 265 struct task_struct *tsk = current; 266 struct fpu *fpu = &tsk->thread.fpu; 267 int state_size = fpu_kernel_xstate_size; 268 u64 xfeatures = 0; 269 int fx_only = 0; 270 271 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || 272 IS_ENABLED(CONFIG_IA32_EMULATION)); 273 274 if (!buf) { 275 fpu__clear(fpu); 276 return 0; 277 } 278 279 if (!access_ok(VERIFY_READ, buf, size)) 280 return -EACCES; 281 282 fpu__activate_curr(fpu); 283 284 if (!static_cpu_has(X86_FEATURE_FPU)) 285 return fpregs_soft_set(current, NULL, 286 0, sizeof(struct user_i387_ia32_struct), 287 NULL, buf) != 0; 288 289 if (use_xsave()) { 290 struct _fpx_sw_bytes fx_sw_user; 291 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) { 292 /* 293 * Couldn't find the extended state information in the 294 * memory layout. Restore just the FP/SSE and init all 295 * the other extended state. 296 */ 297 state_size = sizeof(struct fxregs_state); 298 fx_only = 1; 299 trace_x86_fpu_xstate_check_failed(fpu); 300 } else { 301 state_size = fx_sw_user.xstate_size; 302 xfeatures = fx_sw_user.xfeatures; 303 } 304 } 305 306 if (ia32_fxstate) { 307 /* 308 * For 32-bit frames with fxstate, copy the user state to the 309 * thread's fpu state, reconstruct fxstate from the fsave 310 * header. Sanitize the copied state etc. 311 */ 312 struct fpu *fpu = &tsk->thread.fpu; 313 struct user_i387_ia32_struct env; 314 int err = 0; 315 316 /* 317 * Drop the current fpu which clears fpu->fpstate_active. This ensures 318 * that any context-switch during the copy of the new state, 319 * avoids the intermediate state from getting restored/saved. 320 * Thus avoiding the new restored state from getting corrupted. 321 * We will be ready to restore/save the state only after 322 * fpu->fpstate_active is again set. 323 */ 324 fpu__drop(fpu); 325 326 if (using_compacted_format()) { 327 err = copyin_to_xsaves(NULL, buf_fx, 328 &fpu->state.xsave); 329 } else { 330 err = __copy_from_user(&fpu->state.xsave, 331 buf_fx, state_size); 332 } 333 334 if (err || __copy_from_user(&env, buf, sizeof(env))) { 335 fpstate_init(&fpu->state); 336 trace_x86_fpu_init_state(fpu); 337 err = -1; 338 } else { 339 sanitize_restored_xstate(tsk, &env, xfeatures, fx_only); 340 } 341 342 fpu->fpstate_active = 1; 343 preempt_disable(); 344 fpu__restore(fpu); 345 preempt_enable(); 346 347 return err; 348 } else { 349 /* 350 * For 64-bit frames and 32-bit fsave frames, restore the user 351 * state to the registers directly (with exceptions handled). 352 */ 353 user_fpu_begin(); 354 if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) { 355 fpu__clear(fpu); 356 return -1; 357 } 358 } 359 360 return 0; 361 } 362 363 static inline int xstate_sigframe_size(void) 364 { 365 return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE : 366 fpu_user_xstate_size; 367 } 368 369 /* 370 * Restore FPU state from a sigframe: 371 */ 372 int fpu__restore_sig(void __user *buf, int ia32_frame) 373 { 374 void __user *buf_fx = buf; 375 int size = xstate_sigframe_size(); 376 377 if (ia32_frame && use_fxsr()) { 378 buf_fx = buf + sizeof(struct fregs_state); 379 size += sizeof(struct fregs_state); 380 } 381 382 return __fpu__restore_sig(buf, buf_fx, size); 383 } 384 385 unsigned long 386 fpu__alloc_mathframe(unsigned long sp, int ia32_frame, 387 unsigned long *buf_fx, unsigned long *size) 388 { 389 unsigned long frame_size = xstate_sigframe_size(); 390 391 *buf_fx = sp = round_down(sp - frame_size, 64); 392 if (ia32_frame && use_fxsr()) { 393 frame_size += sizeof(struct fregs_state); 394 sp -= sizeof(struct fregs_state); 395 } 396 397 *size = frame_size; 398 399 return sp; 400 } 401 /* 402 * Prepare the SW reserved portion of the fxsave memory layout, indicating 403 * the presence of the extended state information in the memory layout 404 * pointed by the fpstate pointer in the sigcontext. 405 * This will be saved when ever the FP and extended state context is 406 * saved on the user stack during the signal handler delivery to the user. 407 */ 408 void fpu__init_prepare_fx_sw_frame(void) 409 { 410 int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE; 411 412 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1; 413 fx_sw_reserved.extended_size = size; 414 fx_sw_reserved.xfeatures = xfeatures_mask; 415 fx_sw_reserved.xstate_size = fpu_user_xstate_size; 416 417 if (IS_ENABLED(CONFIG_IA32_EMULATION) || 418 IS_ENABLED(CONFIG_X86_32)) { 419 int fsave_header_size = sizeof(struct fregs_state); 420 421 fx_sw_reserved_ia32 = fx_sw_reserved; 422 fx_sw_reserved_ia32.extended_size = size + fsave_header_size; 423 } 424 } 425 426