1 /* 2 * Copyright (c) 1990 William Jolitz. 3 * Copyright (c) 1991 The Regents of the University of California. 4 * Copyright (c) 2006 The DragonFly Project. 5 * Copyright (c) 2006 Matthew Dillon. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in 16 * the documentation and/or other materials provided with the 17 * distribution. 18 * 3. Neither the name of The DragonFly Project nor the names of its 19 * contributors may be used to endorse or promote products derived 20 * from this software without specific, prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 30 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 31 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * from: @(#)npx.c 7.2 (Berkeley) 5/12/91 36 * $FreeBSD: src/sys/i386/isa/npx.c,v 1.80.2.3 2001/10/20 19:04:38 tegge Exp $ 37 */ 38 39 #include "opt_cpu.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/bus.h> 44 #include <sys/kernel.h> 45 #include <sys/malloc.h> 46 #include <sys/module.h> 47 #include <sys/sysctl.h> 48 #include <sys/proc.h> 49 #include <sys/rman.h> 50 #include <sys/signalvar.h> 51 52 #include <sys/thread2.h> 53 #include <sys/mplock2.h> 54 55 #include <machine/cputypes.h> 56 #include <machine/frame.h> 57 #include <machine/md_var.h> 58 #include <machine/pcb.h> 59 #include <machine/psl.h> 60 #include <machine/specialreg.h> 61 #include <machine/segments.h> 62 #include <machine/globaldata.h> 63 64 #define fldcw(addr) __asm("fldcw %0" : : "m" (*(addr))) 65 #define fnclex() __asm("fnclex") 66 #define fninit() __asm("fninit") 67 #define fnop() __asm("fnop") 68 #define fnsave(addr) __asm __volatile("fnsave %0" : "=m" (*(addr))) 69 #define fnstcw(addr) __asm __volatile("fnstcw %0" : "=m" (*(addr))) 70 #define fnstsw(addr) __asm __volatile("fnstsw %0" : "=m" (*(addr))) 71 #define frstor(addr) __asm("frstor %0" : : "m" (*(addr))) 72 #define fxrstor(addr) __asm("fxrstor %0" : : "m" (*(addr))) 73 #define fxsave(addr) __asm __volatile("fxsave %0" : "=m" (*(addr))) 74 #ifndef CPU_DISABLE_AVX 75 #define xrstor(eax,edx,addr) __asm __volatile(".byte 0x0f,0xae,0x2f" : : "D" (addr), "a" (eax), "d" (edx)) 76 #define xsave(eax,edx,addr) __asm __volatile(".byte 0x0f,0xae,0x27" : : "D" (addr), "a" (eax), "d" (edx) : "memory") 77 #endif 78 #define start_emulating() __asm("smsw %%ax; orb %0,%%al; lmsw %%ax" \ 79 : : "n" (CR0_TS) : "ax") 80 #define stop_emulating() __asm("clts") 81 82 typedef u_char bool_t; 83 static void fpu_clean_state(void); 84 #define ldmxcsr(csr) __asm __volatile("ldmxcsr %0" : : "m" (csr)) 85 86 static struct krate badfprate = { 1 }; 87 88 static void fpusave (union savefpu *); 89 static void fpurstor (union savefpu *); 90 91 uint32_t npx_mxcsr_mask = 0xFFBF; /* this is the default */ 92 93 /* 94 * Probe the npx_mxcsr_mask 95 */ 96 void npxprobemask(void) 97 { 98 /*64-Byte alignment required for xsave*/ 99 static union savefpu dummy __aligned(64); 100 101 crit_enter(); 102 stop_emulating(); 103 fxsave(&dummy); 104 npx_mxcsr_mask = ((uint32_t *)&dummy)[7]; 105 start_emulating(); 106 crit_exit(); 107 } 108 109 /* 110 * Initialize the floating point unit. 111 */ 112 void npxinit(void) 113 { 114 /*64-Byte alignment required for xsave*/ 115 static union savefpu dummy __aligned(64); 116 u_short control = __INITIAL_FPUCW__; 117 u_int mxcsr = __INITIAL_MXCSR__; 118 119 /* 120 * fninit has the same h/w bugs as fnsave. Use the detoxified 121 * fnsave to throw away any junk in the fpu. npxsave() initializes 122 * the fpu and sets npxthread = NULL as important side effects. 123 */ 124 125 npxsave(&dummy); 126 crit_enter(); 127 stop_emulating(); 128 fldcw(&control); 129 ldmxcsr(mxcsr); 130 fpusave(curthread->td_savefpu); 131 mdcpu->gd_npxthread = NULL; 132 start_emulating(); 133 crit_exit(); 134 } 135 136 /* 137 * Free coprocessor (if we have it). 138 */ 139 void 140 npxexit(void) 141 { 142 if (curthread == mdcpu->gd_npxthread) 143 npxsave(curthread->td_savefpu); 144 } 145 146 #if 0 147 /* 148 * The following mechanism is used to ensure that the FPE_... value 149 * that is passed as a trapcode to the signal handler of the user 150 * process does not have more than one bit set. 151 * 152 * Multiple bits may be set if the user process modifies the control 153 * word while a status word bit is already set. While this is a sign 154 * of bad coding, we have no choise than to narrow them down to one 155 * bit, since we must not send a trapcode that is not exactly one of 156 * the FPE_ macros. 157 * 158 * The mechanism has a static table with 127 entries. Each combination 159 * of the 7 FPU status word exception bits directly translates to a 160 * position in this table, where a single FPE_... value is stored. 161 * This FPE_... value stored there is considered the "most important" 162 * of the exception bits and will be sent as the signal code. The 163 * precedence of the bits is based upon Intel Document "Numerical 164 * Applications", Chapter "Special Computational Situations". 165 * 166 * The macro to choose one of these values does these steps: 1) Throw 167 * away status word bits that cannot be masked. 2) Throw away the bits 168 * currently masked in the control word, assuming the user isn't 169 * interested in them anymore. 3) Reinsert status word bit 7 (stack 170 * fault) if it is set, which cannot be masked but must be presered. 171 * 4) Use the remaining bits to point into the trapcode table. 172 * 173 * The 6 maskable bits in order of their preference, as stated in the 174 * above referenced Intel manual: 175 * 1 Invalid operation (FP_X_INV) 176 * 1a Stack underflow 177 * 1b Stack overflow 178 * 1c Operand of unsupported format 179 * 1d SNaN operand. 180 * 2 QNaN operand (not an exception, irrelavant here) 181 * 3 Any other invalid-operation not mentioned above or zero divide 182 * (FP_X_INV, FP_X_DZ) 183 * 4 Denormal operand (FP_X_DNML) 184 * 5 Numeric over/underflow (FP_X_OFL, FP_X_UFL) 185 * 6 Inexact result (FP_X_IMP) 186 */ 187 static char fpetable[128] = { 188 0, 189 FPE_FLTINV, /* 1 - INV */ 190 FPE_FLTUND, /* 2 - DNML */ 191 FPE_FLTINV, /* 3 - INV | DNML */ 192 FPE_FLTDIV, /* 4 - DZ */ 193 FPE_FLTINV, /* 5 - INV | DZ */ 194 FPE_FLTDIV, /* 6 - DNML | DZ */ 195 FPE_FLTINV, /* 7 - INV | DNML | DZ */ 196 FPE_FLTOVF, /* 8 - OFL */ 197 FPE_FLTINV, /* 9 - INV | OFL */ 198 FPE_FLTUND, /* A - DNML | OFL */ 199 FPE_FLTINV, /* B - INV | DNML | OFL */ 200 FPE_FLTDIV, /* C - DZ | OFL */ 201 FPE_FLTINV, /* D - INV | DZ | OFL */ 202 FPE_FLTDIV, /* E - DNML | DZ | OFL */ 203 FPE_FLTINV, /* F - INV | DNML | DZ | OFL */ 204 FPE_FLTUND, /* 10 - UFL */ 205 FPE_FLTINV, /* 11 - INV | UFL */ 206 FPE_FLTUND, /* 12 - DNML | UFL */ 207 FPE_FLTINV, /* 13 - INV | DNML | UFL */ 208 FPE_FLTDIV, /* 14 - DZ | UFL */ 209 FPE_FLTINV, /* 15 - INV | DZ | UFL */ 210 FPE_FLTDIV, /* 16 - DNML | DZ | UFL */ 211 FPE_FLTINV, /* 17 - INV | DNML | DZ | UFL */ 212 FPE_FLTOVF, /* 18 - OFL | UFL */ 213 FPE_FLTINV, /* 19 - INV | OFL | UFL */ 214 FPE_FLTUND, /* 1A - DNML | OFL | UFL */ 215 FPE_FLTINV, /* 1B - INV | DNML | OFL | UFL */ 216 FPE_FLTDIV, /* 1C - DZ | OFL | UFL */ 217 FPE_FLTINV, /* 1D - INV | DZ | OFL | UFL */ 218 FPE_FLTDIV, /* 1E - DNML | DZ | OFL | UFL */ 219 FPE_FLTINV, /* 1F - INV | DNML | DZ | OFL | UFL */ 220 FPE_FLTRES, /* 20 - IMP */ 221 FPE_FLTINV, /* 21 - INV | IMP */ 222 FPE_FLTUND, /* 22 - DNML | IMP */ 223 FPE_FLTINV, /* 23 - INV | DNML | IMP */ 224 FPE_FLTDIV, /* 24 - DZ | IMP */ 225 FPE_FLTINV, /* 25 - INV | DZ | IMP */ 226 FPE_FLTDIV, /* 26 - DNML | DZ | IMP */ 227 FPE_FLTINV, /* 27 - INV | DNML | DZ | IMP */ 228 FPE_FLTOVF, /* 28 - OFL | IMP */ 229 FPE_FLTINV, /* 29 - INV | OFL | IMP */ 230 FPE_FLTUND, /* 2A - DNML | OFL | IMP */ 231 FPE_FLTINV, /* 2B - INV | DNML | OFL | IMP */ 232 FPE_FLTDIV, /* 2C - DZ | OFL | IMP */ 233 FPE_FLTINV, /* 2D - INV | DZ | OFL | IMP */ 234 FPE_FLTDIV, /* 2E - DNML | DZ | OFL | IMP */ 235 FPE_FLTINV, /* 2F - INV | DNML | DZ | OFL | IMP */ 236 FPE_FLTUND, /* 30 - UFL | IMP */ 237 FPE_FLTINV, /* 31 - INV | UFL | IMP */ 238 FPE_FLTUND, /* 32 - DNML | UFL | IMP */ 239 FPE_FLTINV, /* 33 - INV | DNML | UFL | IMP */ 240 FPE_FLTDIV, /* 34 - DZ | UFL | IMP */ 241 FPE_FLTINV, /* 35 - INV | DZ | UFL | IMP */ 242 FPE_FLTDIV, /* 36 - DNML | DZ | UFL | IMP */ 243 FPE_FLTINV, /* 37 - INV | DNML | DZ | UFL | IMP */ 244 FPE_FLTOVF, /* 38 - OFL | UFL | IMP */ 245 FPE_FLTINV, /* 39 - INV | OFL | UFL | IMP */ 246 FPE_FLTUND, /* 3A - DNML | OFL | UFL | IMP */ 247 FPE_FLTINV, /* 3B - INV | DNML | OFL | UFL | IMP */ 248 FPE_FLTDIV, /* 3C - DZ | OFL | UFL | IMP */ 249 FPE_FLTINV, /* 3D - INV | DZ | OFL | UFL | IMP */ 250 FPE_FLTDIV, /* 3E - DNML | DZ | OFL | UFL | IMP */ 251 FPE_FLTINV, /* 3F - INV | DNML | DZ | OFL | UFL | IMP */ 252 FPE_FLTSUB, /* 40 - STK */ 253 FPE_FLTSUB, /* 41 - INV | STK */ 254 FPE_FLTUND, /* 42 - DNML | STK */ 255 FPE_FLTSUB, /* 43 - INV | DNML | STK */ 256 FPE_FLTDIV, /* 44 - DZ | STK */ 257 FPE_FLTSUB, /* 45 - INV | DZ | STK */ 258 FPE_FLTDIV, /* 46 - DNML | DZ | STK */ 259 FPE_FLTSUB, /* 47 - INV | DNML | DZ | STK */ 260 FPE_FLTOVF, /* 48 - OFL | STK */ 261 FPE_FLTSUB, /* 49 - INV | OFL | STK */ 262 FPE_FLTUND, /* 4A - DNML | OFL | STK */ 263 FPE_FLTSUB, /* 4B - INV | DNML | OFL | STK */ 264 FPE_FLTDIV, /* 4C - DZ | OFL | STK */ 265 FPE_FLTSUB, /* 4D - INV | DZ | OFL | STK */ 266 FPE_FLTDIV, /* 4E - DNML | DZ | OFL | STK */ 267 FPE_FLTSUB, /* 4F - INV | DNML | DZ | OFL | STK */ 268 FPE_FLTUND, /* 50 - UFL | STK */ 269 FPE_FLTSUB, /* 51 - INV | UFL | STK */ 270 FPE_FLTUND, /* 52 - DNML | UFL | STK */ 271 FPE_FLTSUB, /* 53 - INV | DNML | UFL | STK */ 272 FPE_FLTDIV, /* 54 - DZ | UFL | STK */ 273 FPE_FLTSUB, /* 55 - INV | DZ | UFL | STK */ 274 FPE_FLTDIV, /* 56 - DNML | DZ | UFL | STK */ 275 FPE_FLTSUB, /* 57 - INV | DNML | DZ | UFL | STK */ 276 FPE_FLTOVF, /* 58 - OFL | UFL | STK */ 277 FPE_FLTSUB, /* 59 - INV | OFL | UFL | STK */ 278 FPE_FLTUND, /* 5A - DNML | OFL | UFL | STK */ 279 FPE_FLTSUB, /* 5B - INV | DNML | OFL | UFL | STK */ 280 FPE_FLTDIV, /* 5C - DZ | OFL | UFL | STK */ 281 FPE_FLTSUB, /* 5D - INV | DZ | OFL | UFL | STK */ 282 FPE_FLTDIV, /* 5E - DNML | DZ | OFL | UFL | STK */ 283 FPE_FLTSUB, /* 5F - INV | DNML | DZ | OFL | UFL | STK */ 284 FPE_FLTRES, /* 60 - IMP | STK */ 285 FPE_FLTSUB, /* 61 - INV | IMP | STK */ 286 FPE_FLTUND, /* 62 - DNML | IMP | STK */ 287 FPE_FLTSUB, /* 63 - INV | DNML | IMP | STK */ 288 FPE_FLTDIV, /* 64 - DZ | IMP | STK */ 289 FPE_FLTSUB, /* 65 - INV | DZ | IMP | STK */ 290 FPE_FLTDIV, /* 66 - DNML | DZ | IMP | STK */ 291 FPE_FLTSUB, /* 67 - INV | DNML | DZ | IMP | STK */ 292 FPE_FLTOVF, /* 68 - OFL | IMP | STK */ 293 FPE_FLTSUB, /* 69 - INV | OFL | IMP | STK */ 294 FPE_FLTUND, /* 6A - DNML | OFL | IMP | STK */ 295 FPE_FLTSUB, /* 6B - INV | DNML | OFL | IMP | STK */ 296 FPE_FLTDIV, /* 6C - DZ | OFL | IMP | STK */ 297 FPE_FLTSUB, /* 6D - INV | DZ | OFL | IMP | STK */ 298 FPE_FLTDIV, /* 6E - DNML | DZ | OFL | IMP | STK */ 299 FPE_FLTSUB, /* 6F - INV | DNML | DZ | OFL | IMP | STK */ 300 FPE_FLTUND, /* 70 - UFL | IMP | STK */ 301 FPE_FLTSUB, /* 71 - INV | UFL | IMP | STK */ 302 FPE_FLTUND, /* 72 - DNML | UFL | IMP | STK */ 303 FPE_FLTSUB, /* 73 - INV | DNML | UFL | IMP | STK */ 304 FPE_FLTDIV, /* 74 - DZ | UFL | IMP | STK */ 305 FPE_FLTSUB, /* 75 - INV | DZ | UFL | IMP | STK */ 306 FPE_FLTDIV, /* 76 - DNML | DZ | UFL | IMP | STK */ 307 FPE_FLTSUB, /* 77 - INV | DNML | DZ | UFL | IMP | STK */ 308 FPE_FLTOVF, /* 78 - OFL | UFL | IMP | STK */ 309 FPE_FLTSUB, /* 79 - INV | OFL | UFL | IMP | STK */ 310 FPE_FLTUND, /* 7A - DNML | OFL | UFL | IMP | STK */ 311 FPE_FLTSUB, /* 7B - INV | DNML | OFL | UFL | IMP | STK */ 312 FPE_FLTDIV, /* 7C - DZ | OFL | UFL | IMP | STK */ 313 FPE_FLTSUB, /* 7D - INV | DZ | OFL | UFL | IMP | STK */ 314 FPE_FLTDIV, /* 7E - DNML | DZ | OFL | UFL | IMP | STK */ 315 FPE_FLTSUB, /* 7F - INV | DNML | DZ | OFL | UFL | IMP | STK */ 316 }; 317 318 #endif 319 320 /* 321 * Implement the device not available (DNA) exception. gd_npxthread had 322 * better be NULL. Restore the current thread's FP state and set gd_npxthread 323 * to curthread. 324 * 325 * Interrupts are enabled and preemption can occur. Enter a critical 326 * section to stabilize the FP state. 327 */ 328 int 329 npxdna(void) 330 { 331 thread_t td = curthread; 332 int didinit = 0; 333 334 if (mdcpu->gd_npxthread != NULL) { 335 kprintf("npxdna: npxthread = %p, curthread = %p\n", 336 mdcpu->gd_npxthread, curthread); 337 panic("npxdna"); 338 } 339 340 /* 341 * Setup the initial saved state if the thread has never before 342 * used the FP unit. This also occurs when a thread pushes a 343 * signal handler and uses FP in the handler. 344 */ 345 crit_enter(); 346 if ((td->td_flags & (TDF_USINGFP | TDF_KERNELFP)) == 0) { 347 td->td_flags |= TDF_USINGFP; 348 npxinit(); 349 didinit = 1; 350 } 351 352 /* 353 * The setting of gd_npxthread and the call to fpurstor() must not 354 * be preempted by an interrupt thread or we will take an npxdna 355 * trap and potentially save our current fpstate (which is garbage) 356 * and then restore the garbage rather then the originally saved 357 * fpstate. 358 */ 359 stop_emulating(); 360 /* 361 * Record new context early in case frstor causes an IRQ13. 362 */ 363 mdcpu->gd_npxthread = td; 364 /* 365 * The following frstor may cause an IRQ13 when the state being 366 * restored has a pending error. The error will appear to have been 367 * triggered by the current (npx) user instruction even when that 368 * instruction is a no-wait instruction that should not trigger an 369 * error (e.g., fnclex). On at least one 486 system all of the 370 * no-wait instructions are broken the same as frstor, so our 371 * treatment does not amplify the breakage. On at least one 372 * 386/Cyrix 387 system, fnclex works correctly while frstor and 373 * fnsave are broken, so our treatment breaks fnclex if it is the 374 * first FPU instruction after a context switch. 375 */ 376 if ((td->td_savefpu->sv_xmm.sv_env.en_mxcsr & ~npx_mxcsr_mask) && 377 cpu_fxsr) { 378 krateprintf(&badfprate, 379 "%s: FXRSTR: illegal FP MXCSR %08x didinit = %d\n", 380 td->td_comm, td->td_savefpu->sv_xmm.sv_env.en_mxcsr, 381 didinit); 382 td->td_savefpu->sv_xmm.sv_env.en_mxcsr &= npx_mxcsr_mask; 383 lwpsignal(curproc, curthread->td_lwp, SIGFPE); 384 } 385 fpurstor(td->td_savefpu); 386 crit_exit(); 387 388 return (1); 389 } 390 391 /* 392 * Wrapper for the fnsave instruction to handle h/w bugs. If there is an error 393 * pending, then fnsave generates a bogus IRQ13 on some systems. Force 394 * any IRQ13 to be handled immediately, and then ignore it. This routine is 395 * often called at splhigh so it must not use many system services. In 396 * particular, it's much easier to install a special handler than to 397 * guarantee that it's safe to use npxintr() and its supporting code. 398 * 399 * WARNING! This call is made during a switch and the MP lock will be 400 * setup for the new target thread rather then the current thread, so we 401 * cannot do anything here that depends on the *_mplock() functions as 402 * we may trip over their assertions. 403 * 404 * WARNING! When using fxsave we MUST fninit after saving the FP state. The 405 * kernel will always assume that the FP state is 'safe' (will not cause 406 * exceptions) for mmx/xmm use if npxthread is NULL. The kernel must still 407 * setup a custom save area before actually using the FP unit, but it will 408 * not bother calling fninit. This greatly improves kernel performance when 409 * it wishes to use the FP unit. 410 */ 411 void 412 npxsave(union savefpu *addr) 413 { 414 crit_enter(); 415 stop_emulating(); 416 fpusave(addr); 417 mdcpu->gd_npxthread = NULL; 418 fninit(); 419 start_emulating(); 420 crit_exit(); 421 } 422 423 static void 424 fpusave(union savefpu *addr) 425 { 426 #ifndef CPU_DISABLE_AVX 427 if (cpu_xsave) 428 xsave(CPU_XFEATURE_X87 | CPU_XFEATURE_SSE | CPU_XFEATURE_YMM, 0, addr); 429 else 430 #endif 431 if (cpu_fxsr) 432 fxsave(addr); 433 else 434 fnsave(addr); 435 } 436 437 /* 438 * Save the FP state to the mcontext structure. 439 * 440 * WARNING: If you want to try to npxsave() directly to mctx->mc_fpregs, 441 * then it MUST be 16-byte aligned. Currently this is not guarenteed. 442 */ 443 void 444 npxpush(mcontext_t *mctx) 445 { 446 thread_t td = curthread; 447 448 KKASSERT((td->td_flags & TDF_KERNELFP) == 0); 449 450 if (td->td_flags & TDF_USINGFP) { 451 if (mdcpu->gd_npxthread == td) { 452 /* 453 * XXX Note: This is a bit inefficient if the signal 454 * handler uses floating point, extra faults will 455 * occur. 456 */ 457 mctx->mc_ownedfp = _MC_FPOWNED_FPU; 458 npxsave(td->td_savefpu); 459 } else { 460 mctx->mc_ownedfp = _MC_FPOWNED_PCB; 461 } 462 KKASSERT(sizeof(*td->td_savefpu) <= sizeof(mctx->mc_fpregs)); 463 bcopy(td->td_savefpu, mctx->mc_fpregs, sizeof(*td->td_savefpu)); 464 td->td_flags &= ~TDF_USINGFP; 465 #ifndef CPU_DISABLE_AVX 466 if (cpu_xsave) 467 mctx->mc_fpformat = _MC_FPFMT_YMM; 468 else 469 #endif 470 { 471 if (cpu_fxsr) 472 mctx->mc_fpformat = _MC_FPFMT_XMM; 473 else 474 mctx->mc_fpformat = _MC_FPFMT_387; 475 } 476 } else { 477 mctx->mc_ownedfp = _MC_FPOWNED_NONE; 478 mctx->mc_fpformat = _MC_FPFMT_NODEV; 479 } 480 } 481 482 /* 483 * Restore the FP state from the mcontext structure. 484 */ 485 void 486 npxpop(mcontext_t *mctx) 487 { 488 thread_t td = curthread; 489 490 switch(mctx->mc_ownedfp) { 491 case _MC_FPOWNED_NONE: 492 /* 493 * If the signal handler used the FP unit but the interrupted 494 * code did not, release the FP unit. Clear TDF_USINGFP will 495 * force the FP unit to reinit so the interrupted code sees 496 * a clean slate. 497 */ 498 if (td->td_flags & TDF_USINGFP) { 499 if (td == mdcpu->gd_npxthread) 500 npxsave(td->td_savefpu); 501 td->td_flags &= ~TDF_USINGFP; 502 } 503 break; 504 case _MC_FPOWNED_FPU: 505 case _MC_FPOWNED_PCB: 506 /* 507 * Clear ownership of the FP unit and restore our saved state. 508 * 509 * NOTE: The signal handler may have set-up some FP state and 510 * enabled the FP unit, so we have to restore no matter what. 511 * 512 * XXX: This is bit inefficient, if the code being returned 513 * to is actively using the FP this results in multiple 514 * kernel faults. 515 * 516 * WARNING: The saved state was exposed to userland and may 517 * have to be sanitized to avoid a GP fault in the kernel. 518 */ 519 if (td == mdcpu->gd_npxthread) 520 npxsave(td->td_savefpu); 521 KKASSERT(sizeof(*td->td_savefpu) <= sizeof(mctx->mc_fpregs)); 522 bcopy(mctx->mc_fpregs, td->td_savefpu, sizeof(*td->td_savefpu)); 523 if ((td->td_savefpu->sv_xmm.sv_env.en_mxcsr & ~npx_mxcsr_mask) && 524 cpu_fxsr) { 525 krateprintf(&badfprate, 526 "pid %d (%s) signal return from user: " 527 "illegal FP MXCSR %08x\n", 528 td->td_proc->p_pid, 529 td->td_proc->p_comm, 530 td->td_savefpu->sv_xmm.sv_env.en_mxcsr); 531 } 532 td->td_flags |= TDF_USINGFP; 533 break; 534 } 535 } 536 537 538 /* 539 * On AuthenticAMD processors, the fxrstor instruction does not restore 540 * the x87's stored last instruction pointer, last data pointer, and last 541 * opcode values, except in the rare case in which the exception summary 542 * (ES) bit in the x87 status word is set to 1. 543 * 544 * In order to avoid leaking this information across processes, we clean 545 * these values by performing a dummy load before executing fxrstor(). 546 */ 547 static double dummy_variable = 0.0; 548 static void 549 fpu_clean_state(void) 550 { 551 u_short status; 552 553 /* 554 * Clear the ES bit in the x87 status word if it is currently 555 * set, in order to avoid causing a fault in the upcoming load. 556 */ 557 fnstsw(&status); 558 if (status & 0x80) 559 fnclex(); 560 561 /* 562 * Load the dummy variable into the x87 stack. This mangles 563 * the x87 stack, but we don't care since we're about to call 564 * fxrstor() anyway. 565 */ 566 __asm __volatile("ffree %%st(7); flds %0" : : "m" (dummy_variable)); 567 } 568 569 static void 570 fpurstor(union savefpu *addr) 571 { 572 #ifndef CPU_DISABLE_AVX 573 if (cpu_xsave) 574 xrstor(CPU_XFEATURE_X87 | CPU_XFEATURE_SSE | CPU_XFEATURE_YMM, 0, addr); 575 else 576 #endif 577 if (cpu_fxsr) { 578 fpu_clean_state(); 579 fxrstor(addr); 580 } else { 581 frstor(addr); 582 } 583 } 584 585