1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * FPU signal frame handling routines. 4 */ 5 6 #include <linux/compat.h> 7 #include <linux/cpu.h> 8 9 #include <asm/fpu/internal.h> 10 #include <asm/fpu/signal.h> 11 #include <asm/fpu/regset.h> 12 #include <asm/fpu/xstate.h> 13 14 #include <asm/sigframe.h> 15 #include <asm/trace/fpu.h> 16 17 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32; 18 19 /* 20 * Check for the presence of extended state information in the 21 * user fpstate pointer in the sigcontext. 22 */ 23 static inline int check_for_xstate(struct fxregs_state __user *buf, 24 void __user *fpstate, 25 struct _fpx_sw_bytes *fx_sw) 26 { 27 int min_xstate_size = sizeof(struct fxregs_state) + 28 sizeof(struct xstate_header); 29 unsigned int magic2; 30 31 if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw))) 32 return -1; 33 34 /* Check for the first magic field and other error scenarios. */ 35 if (fx_sw->magic1 != FP_XSTATE_MAGIC1 || 36 fx_sw->xstate_size < min_xstate_size || 37 fx_sw->xstate_size > fpu_user_xstate_size || 38 fx_sw->xstate_size > fx_sw->extended_size) 39 return -1; 40 41 /* 42 * Check for the presence of second magic word at the end of memory 43 * layout. This detects the case where the user just copied the legacy 44 * fpstate layout with out copying the extended state information 45 * in the memory layout. 46 */ 47 if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size)) 48 || magic2 != FP_XSTATE_MAGIC2) 49 return -1; 50 51 return 0; 52 } 53 54 /* 55 * Signal frame handlers. 56 */ 57 static inline int save_fsave_header(struct task_struct *tsk, void __user *buf) 58 { 59 if (use_fxsr()) { 60 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave; 61 struct user_i387_ia32_struct env; 62 struct _fpstate_32 __user *fp = buf; 63 64 convert_from_fxsr(&env, tsk); 65 66 if (__copy_to_user(buf, &env, sizeof(env)) || 67 __put_user(xsave->i387.swd, &fp->status) || 68 __put_user(X86_FXSR_MAGIC, &fp->magic)) 69 return -1; 70 } else { 71 struct fregs_state __user *fp = buf; 72 u32 swd; 73 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status)) 74 return -1; 75 } 76 77 return 0; 78 } 79 80 static inline int save_xstate_epilog(void __user *buf, int ia32_frame) 81 { 82 struct xregs_state __user *x = buf; 83 struct _fpx_sw_bytes *sw_bytes; 84 u32 xfeatures; 85 int err; 86 87 /* Setup the bytes not touched by the [f]xsave and reserved for SW. */ 88 sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved; 89 err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes)); 90 91 if (!use_xsave()) 92 return err; 93 94 err |= __put_user(FP_XSTATE_MAGIC2, 95 (__u32 *)(buf + fpu_user_xstate_size)); 96 97 /* 98 * Read the xfeatures which we copied (directly from the cpu or 99 * from the state in task struct) to the user buffers. 100 */ 101 err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures); 102 103 /* 104 * For legacy compatible, we always set FP/SSE bits in the bit 105 * vector while saving the state to the user context. This will 106 * enable us capturing any changes(during sigreturn) to 107 * the FP/SSE bits by the legacy applications which don't touch 108 * xfeatures in the xsave header. 109 * 110 * xsave aware apps can change the xfeatures in the xsave 111 * header as well as change any contents in the memory layout. 112 * xrestore as part of sigreturn will capture all the changes. 113 */ 114 xfeatures |= XFEATURE_MASK_FPSSE; 115 116 err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures); 117 118 return err; 119 } 120 121 static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf) 122 { 123 int err; 124 125 if (use_xsave()) 126 err = copy_xregs_to_user(buf); 127 else if (use_fxsr()) 128 err = copy_fxregs_to_user((struct fxregs_state __user *) buf); 129 else 130 err = copy_fregs_to_user((struct fregs_state __user *) buf); 131 132 if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size)) 133 err = -EFAULT; 134 return err; 135 } 136 137 /* 138 * Save the fpu, extended register state to the user signal frame. 139 * 140 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save 141 * state is copied. 142 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'. 143 * 144 * buf == buf_fx for 64-bit frames and 32-bit fsave frame. 145 * buf != buf_fx for 32-bit frames with fxstate. 146 * 147 * If the fpu, extended register state is live, save the state directly 148 * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise, 149 * copy the thread's fpu state to the user frame starting at 'buf_fx'. 150 * 151 * If this is a 32-bit frame with fxstate, put a fsave header before 152 * the aligned state at 'buf_fx'. 153 * 154 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame 155 * indicating the absence/presence of the extended state to the user. 156 */ 157 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) 158 { 159 struct fpu *fpu = ¤t->thread.fpu; 160 struct xregs_state *xsave = &fpu->state.xsave; 161 struct task_struct *tsk = current; 162 int ia32_fxstate = (buf != buf_fx); 163 164 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || 165 IS_ENABLED(CONFIG_IA32_EMULATION)); 166 167 if (!access_ok(buf, size)) 168 return -EACCES; 169 170 if (!static_cpu_has(X86_FEATURE_FPU)) 171 return fpregs_soft_get(current, NULL, 0, 172 sizeof(struct user_i387_ia32_struct), NULL, 173 (struct _fpstate_32 __user *) buf) ? -1 : 1; 174 175 if (fpu->initialized || using_compacted_format()) { 176 /* Save the live register state to the user directly. */ 177 if (copy_fpregs_to_sigframe(buf_fx)) 178 return -1; 179 /* Update the thread's fxstate to save the fsave header. */ 180 if (ia32_fxstate) 181 copy_fxregs_to_kernel(fpu); 182 } else { 183 /* 184 * It is a *bug* if kernel uses compacted-format for xsave 185 * area and we copy it out directly to a signal frame. It 186 * should have been handled above by saving the registers 187 * directly. 188 */ 189 if (boot_cpu_has(X86_FEATURE_XSAVES)) { 190 WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n"); 191 return -1; 192 } 193 194 fpstate_sanitize_xstate(fpu); 195 if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size)) 196 return -1; 197 } 198 199 /* Save the fsave header for the 32-bit frames. */ 200 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf)) 201 return -1; 202 203 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate)) 204 return -1; 205 206 return 0; 207 } 208 209 static inline void 210 sanitize_restored_xstate(struct task_struct *tsk, 211 struct user_i387_ia32_struct *ia32_env, 212 u64 xfeatures, int fx_only) 213 { 214 struct xregs_state *xsave = &tsk->thread.fpu.state.xsave; 215 struct xstate_header *header = &xsave->header; 216 217 if (use_xsave()) { 218 /* 219 * Note: we don't need to zero the reserved bits in the 220 * xstate_header here because we either didn't copy them at all, 221 * or we checked earlier that they aren't set. 222 */ 223 224 /* 225 * Init the state that is not present in the memory 226 * layout and not enabled by the OS. 227 */ 228 if (fx_only) 229 header->xfeatures = XFEATURE_MASK_FPSSE; 230 else 231 header->xfeatures &= xfeatures; 232 } 233 234 if (use_fxsr()) { 235 /* 236 * mscsr reserved bits must be masked to zero for security 237 * reasons. 238 */ 239 xsave->i387.mxcsr &= mxcsr_feature_mask; 240 241 convert_to_fxsr(tsk, ia32_env); 242 } 243 } 244 245 /* 246 * Restore the extended state if present. Otherwise, restore the FP/SSE state. 247 */ 248 static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only) 249 { 250 if (use_xsave()) { 251 if ((unsigned long)buf % 64 || fx_only) { 252 u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE; 253 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); 254 return copy_user_to_fxregs(buf); 255 } else { 256 u64 init_bv = xfeatures_mask & ~xbv; 257 if (unlikely(init_bv)) 258 copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); 259 return copy_user_to_xregs(buf, xbv); 260 } 261 } else if (use_fxsr()) { 262 return copy_user_to_fxregs(buf); 263 } else 264 return copy_user_to_fregs(buf); 265 } 266 267 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) 268 { 269 int ia32_fxstate = (buf != buf_fx); 270 struct task_struct *tsk = current; 271 struct fpu *fpu = &tsk->thread.fpu; 272 int state_size = fpu_kernel_xstate_size; 273 u64 xfeatures = 0; 274 int fx_only = 0; 275 276 ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || 277 IS_ENABLED(CONFIG_IA32_EMULATION)); 278 279 if (!buf) { 280 fpu__clear(fpu); 281 return 0; 282 } 283 284 if (!access_ok(buf, size)) 285 return -EACCES; 286 287 fpu__initialize(fpu); 288 289 if (!static_cpu_has(X86_FEATURE_FPU)) 290 return fpregs_soft_set(current, NULL, 291 0, sizeof(struct user_i387_ia32_struct), 292 NULL, buf) != 0; 293 294 if (use_xsave()) { 295 struct _fpx_sw_bytes fx_sw_user; 296 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) { 297 /* 298 * Couldn't find the extended state information in the 299 * memory layout. Restore just the FP/SSE and init all 300 * the other extended state. 301 */ 302 state_size = sizeof(struct fxregs_state); 303 fx_only = 1; 304 trace_x86_fpu_xstate_check_failed(fpu); 305 } else { 306 state_size = fx_sw_user.xstate_size; 307 xfeatures = fx_sw_user.xfeatures; 308 } 309 } 310 311 if (ia32_fxstate) { 312 /* 313 * For 32-bit frames with fxstate, copy the user state to the 314 * thread's fpu state, reconstruct fxstate from the fsave 315 * header. Validate and sanitize the copied state. 316 */ 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 local_bh_disable(); 348 fpu->initialized = 1; 349 fpu__restore(fpu); 350 local_bh_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 } 430 431