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 = ¤t->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 } 403 404