1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21/* 22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26#include <sys/asm_linkage.h> 27#include <sys/asm_misc.h> 28#include <sys/regset.h> 29#include <sys/privregs.h> 30#include <sys/psw.h> 31#include <sys/machbrand.h> 32 33#if defined(__lint) 34 35#include <sys/types.h> 36#include <sys/thread.h> 37#include <sys/systm.h> 38 39#else /* __lint */ 40 41#include <sys/segments.h> 42#include <sys/pcb.h> 43#include <sys/trap.h> 44#include <sys/ftrace.h> 45#include <sys/traptrace.h> 46#include <sys/clock.h> 47#include <sys/model.h> 48#include <sys/panic.h> 49 50#if defined(__xpv) 51#include <sys/hypervisor.h> 52#endif 53 54#include "assym.h" 55 56#endif /* __lint */ 57 58/* 59 * We implement five flavours of system call entry points 60 * 61 * - syscall/sysretq (amd64 generic) 62 * - syscall/sysretl (i386 plus SYSC bit) 63 * - sysenter/sysexit (i386 plus SEP bit) 64 * - int/iret (i386 generic) 65 * - lcall/iret (i386 generic) 66 * 67 * The current libc included in Solaris uses int/iret as the base unoptimized 68 * kernel entry method. Older libc implementations and legacy binaries may use 69 * the lcall call gate, so it must continue to be supported. 70 * 71 * System calls that use an lcall call gate are processed in trap() via a 72 * segment-not-present trap, i.e. lcalls are extremely slow(!). 73 * 74 * The basic pattern used in the 32-bit SYSC handler at this point in time is 75 * to have the bare minimum of assembler, and get to the C handlers as 76 * quickly as possible. 77 * 78 * The 64-bit handler is much closer to the sparcv9 handler; that's 79 * because of passing arguments in registers. The 32-bit world still 80 * passes arguments on the stack -- that makes that handler substantially 81 * more complex. 82 * 83 * The two handlers share a few code fragments which are broken 84 * out into preprocessor macros below. 85 * 86 * XX64 come back and speed all this up later. The 32-bit stuff looks 87 * especially easy to speed up the argument copying part .. 88 * 89 * 90 * Notes about segment register usage (c.f. the 32-bit kernel) 91 * 92 * In the 32-bit kernel, segment registers are dutifully saved and 93 * restored on all mode transitions because the kernel uses them directly. 94 * When the processor is running in 64-bit mode, segment registers are 95 * largely ignored. 96 * 97 * %cs and %ss 98 * controlled by the hardware mechanisms that make mode transitions 99 * 100 * The remaining segment registers have to either be pointing at a valid 101 * descriptor i.e. with the 'present' bit set, or they can NULL descriptors 102 * 103 * %ds and %es 104 * always ignored 105 * 106 * %fs and %gs 107 * fsbase and gsbase are used to control the place they really point at. 108 * The kernel only depends on %gs, and controls its own gsbase via swapgs 109 * 110 * Note that loading segment registers is still costly because the GDT 111 * lookup still happens (this is because the hardware can't know that we're 112 * not setting up these segment registers for a 32-bit program). Thus we 113 * avoid doing this in the syscall path, and defer them to lwp context switch 114 * handlers, so the register values remain virtualized to the lwp. 115 */ 116 117#if defined(SYSCALLTRACE) 118#define ORL_SYSCALLTRACE(r32) \ 119 orl syscalltrace(%rip), r32 120#else 121#define ORL_SYSCALLTRACE(r32) 122#endif 123 124/* 125 * In the 32-bit kernel, we do absolutely nothing before getting into the 126 * brand callback checks. In 64-bit land, we do swapgs and then come here. 127 * We assume that the %rsp- and %r15-stashing fields in the CPU structure 128 * are still unused. 129 * 130 * Check if a brand_mach_ops callback is defined for the specified callback_id 131 * type. If so invoke it with the kernel's %gs value loaded and the following 132 * data on the stack: 133 * 134 * stack: -------------------------------------- 135 * 40 | user %gs | 136 * 32 | callback pointer | 137 * | 24 | user stack pointer | 138 * | 16 | lwp pointer | 139 * v 8 | userland return address | 140 * 0 | callback wrapper return addr | 141 * -------------------------------------- 142 * 143 */ 144#define BRAND_CALLBACK(callback_id) \ 145 movq %rsp, %gs:CPU_RTMP_RSP /* save the stack pointer */ ;\ 146 movq %r15, %gs:CPU_RTMP_R15 /* save %r15 */ ;\ 147 movq %gs:CPU_THREAD, %r15 /* load the thread pointer */ ;\ 148 movq T_STACK(%r15), %rsp /* switch to the kernel stack */ ;\ 149 subq $24, %rsp /* save space for 3 pointers */ ;\ 150 pushq %r14 /* save %r14 */ ;\ 151 movq %gs:CPU_RTMP_RSP, %r14 ;\ 152 movq %r14, 8(%rsp) /* stash the user stack pointer */ ;\ 153 popq %r14 /* restore %r14 */ ;\ 154 movq T_LWP(%r15), %r15 /* load the lwp pointer */ ;\ 155 pushq %r15 /* push the lwp pointer */ ;\ 156 movq LWP_PROCP(%r15), %r15 /* load the proc pointer */ ;\ 157 movq P_BRAND(%r15), %r15 /* load the brand pointer */ ;\ 158 movq B_MACHOPS(%r15), %r15 /* load the machops pointer */ ;\ 159 movq _CONST(_MUL(callback_id, CPTRSIZE))(%r15), %r15 ;\ 160 cmpq $0, %r15 ;\ 161 je 1f ;\ 162 movq %r15, 16(%rsp) /* save the callback pointer */ ;\ 163 movq %gs:CPU_RTMP_RSP, %r15 /* grab the user stack pointer */ ;\ 164 pushq (%r15) /* push the return address */ ;\ 165 SWAPGS /* user gsbase */ ;\ 166 mov %gs, %r15 /* get %gs */ ;\ 167 movq %r15, 32(%rsp) /* save %gs on stack */ ;\ 168 SWAPGS /* kernel gsbase */ ;\ 169 movq %gs:CPU_RTMP_R15, %r15 /* restore %r15 */ ;\ 170 call *24(%rsp) /* call callback */ ;\ 1711: movq %gs:CPU_RTMP_R15, %r15 /* restore %r15 */ ;\ 172 movq %gs:CPU_RTMP_RSP, %rsp /* restore the stack pointer */ 173 174#define MSTATE_TRANSITION(from, to) \ 175 movl $from, %edi; \ 176 movl $to, %esi; \ 177 call syscall_mstate 178 179/* 180 * Check to see if a simple (direct) return is possible i.e. 181 * 182 * if (t->t_post_sys_ast | syscalltrace | 183 * lwp->lwp_pcb.pcb_rupdate == 1) 184 * do full version ; 185 * 186 * Preconditions: 187 * - t is curthread 188 * Postconditions: 189 * - condition code NE is set if post-sys is too complex 190 * - rtmp is zeroed if it isn't (we rely on this!) 191 * - ltmp is smashed 192 */ 193#define CHECK_POSTSYS_NE(t, ltmp, rtmp) \ 194 movq T_LWP(t), ltmp; \ 195 movzbl PCB_RUPDATE(ltmp), rtmp; \ 196 ORL_SYSCALLTRACE(rtmp); \ 197 orl T_POST_SYS_AST(t), rtmp; \ 198 cmpl $0, rtmp 199 200/* 201 * Fix up the lwp, thread, and eflags for a successful return 202 * 203 * Preconditions: 204 * - zwreg contains zero 205 */ 206#define SIMPLE_SYSCALL_POSTSYS(t, lwp, zwreg) \ 207 movb $LWP_USER, LWP_STATE(lwp); \ 208 movw zwreg, T_SYSNUM(t); \ 209 andb $_CONST(0xffff - PS_C), REGOFF_RFL(%rsp) 210 211/* 212 * ASSERT(lwptoregs(lwp) == rp); 213 * 214 * This may seem obvious, but very odd things happen if this 215 * assertion is false 216 * 217 * Preconditions: 218 * (%rsp is ready for normal call sequence) 219 * Postconditions (if assertion is true): 220 * %r11 is smashed 221 * 222 * ASSERT(rp->r_cs == descnum) 223 * 224 * The code selector is written into the regs structure when the 225 * lwp stack is created. We use this ASSERT to validate that 226 * the regs structure really matches how we came in. 227 * 228 * Preconditions: 229 * (%rsp is ready for normal call sequence) 230 * Postconditions (if assertion is true): 231 * -none- 232 * 233 * ASSERT(lwp->lwp_pcb.pcb_rupdate == 0); 234 * 235 * If this is false, it meant that we returned to userland without 236 * updating the segment registers as we were supposed to. 237 * 238 * Note that we must ensure no interrupts or other traps intervene 239 * between entering privileged mode and performing the assertion, 240 * otherwise we may perform a context switch on the thread, which 241 * will end up setting pcb_rupdate to 1 again. 242 */ 243#if defined(DEBUG) 244 245#if !defined(__lint) 246 247__lwptoregs_msg: 248 .string "syscall_asm_amd64.s:%d lwptoregs(%p) [%p] != rp [%p]" 249 250__codesel_msg: 251 .string "syscall_asm_amd64.s:%d rp->r_cs [%ld] != %ld" 252 253__no_rupdate_msg: 254 .string "syscall_asm_amd64.s:%d lwp %p, pcb_rupdate != 0" 255 256#endif /* !__lint */ 257 258#define ASSERT_LWPTOREGS(lwp, rp) \ 259 movq LWP_REGS(lwp), %r11; \ 260 cmpq rp, %r11; \ 261 je 7f; \ 262 leaq __lwptoregs_msg(%rip), %rdi; \ 263 movl $__LINE__, %esi; \ 264 movq lwp, %rdx; \ 265 movq %r11, %rcx; \ 266 movq rp, %r8; \ 267 xorl %eax, %eax; \ 268 call panic; \ 2697: 270 271#define ASSERT_NO_RUPDATE_PENDING(lwp) \ 272 testb $0x1, PCB_RUPDATE(lwp); \ 273 je 8f; \ 274 movq lwp, %rdx; \ 275 leaq __no_rupdate_msg(%rip), %rdi; \ 276 movl $__LINE__, %esi; \ 277 xorl %eax, %eax; \ 278 call panic; \ 2798: 280 281#else 282#define ASSERT_LWPTOREGS(lwp, rp) 283#define ASSERT_NO_RUPDATE_PENDING(lwp) 284#endif 285 286/* 287 * Do the traptrace thing and restore any registers we used 288 * in situ. Assumes that %rsp is pointing at the base of 289 * the struct regs, obviously .. 290 */ 291#ifdef TRAPTRACE 292#define SYSCALL_TRAPTRACE(ttype) \ 293 TRACE_PTR(%rdi, %rbx, %ebx, %rcx, ttype); \ 294 TRACE_REGS(%rdi, %rsp, %rbx, %rcx); \ 295 TRACE_STAMP(%rdi); /* rdtsc clobbers %eax, %edx */ \ 296 movq REGOFF_RAX(%rsp), %rax; \ 297 movq REGOFF_RBX(%rsp), %rbx; \ 298 movq REGOFF_RCX(%rsp), %rcx; \ 299 movq REGOFF_RDX(%rsp), %rdx; \ 300 movl %eax, TTR_SYSNUM(%rdi); \ 301 movq REGOFF_RDI(%rsp), %rdi 302 303#define SYSCALL_TRAPTRACE32(ttype) \ 304 SYSCALL_TRAPTRACE(ttype); \ 305 /* paranoia: clean the top 32-bits of the registers */ \ 306 orl %eax, %eax; \ 307 orl %ebx, %ebx; \ 308 orl %ecx, %ecx; \ 309 orl %edx, %edx; \ 310 orl %edi, %edi 311#else /* TRAPTRACE */ 312#define SYSCALL_TRAPTRACE(ttype) 313#define SYSCALL_TRAPTRACE32(ttype) 314#endif /* TRAPTRACE */ 315 316/* 317 * The 64-bit libc syscall wrapper does this: 318 * 319 * fn(<args>) 320 * { 321 * movq %rcx, %r10 -- because syscall smashes %rcx 322 * movl $CODE, %eax 323 * syscall 324 * <error processing> 325 * } 326 * 327 * Thus when we come into the kernel: 328 * 329 * %rdi, %rsi, %rdx, %r10, %r8, %r9 contain first six args 330 * %rax is the syscall number 331 * %r12-%r15 contain caller state 332 * 333 * The syscall instruction arranges that: 334 * 335 * %rcx contains the return %rip 336 * %r11d contains bottom 32-bits of %rflags 337 * %rflags is masked (as determined by the SFMASK msr) 338 * %cs is set to UCS_SEL (as determined by the STAR msr) 339 * %ss is set to UDS_SEL (as determined by the STAR msr) 340 * %rip is set to sys_syscall (as determined by the LSTAR msr) 341 * 342 * Or in other words, we have no registers available at all. 343 * Only swapgs can save us! 344 * 345 * Under the hypervisor, the swapgs has happened already. However, the 346 * state of the world is very different from that we're familiar with. 347 * 348 * In particular, we have a stack structure like that for interrupt 349 * gates, except that the %cs and %ss registers are modified for reasons 350 * that are not entirely clear. Critically, the %rcx/%r11 values do 351 * *not* reflect the usage of those registers under a 'real' syscall[1]; 352 * the stack, therefore, looks like this: 353 * 354 * 0x0(rsp) potentially junk %rcx 355 * 0x8(rsp) potentially junk %r11 356 * 0x10(rsp) user %rip 357 * 0x18(rsp) modified %cs 358 * 0x20(rsp) user %rflags 359 * 0x28(rsp) user %rsp 360 * 0x30(rsp) modified %ss 361 * 362 * 363 * and before continuing on, we must load the %rip into %rcx and the 364 * %rflags into %r11. 365 * 366 * [1] They used to, and we relied on it, but this was broken in 3.1.1. 367 * Sigh. 368 */ 369#if defined(__xpv) 370#define XPV_SYSCALL_PROD \ 371 movq 0x10(%rsp), %rcx; \ 372 movq 0x20(%rsp), %r11; \ 373 movq 0x28(%rsp), %rsp 374#else 375#define XPV_SYSCALL_PROD /* nothing */ 376#endif 377 378#if defined(__lint) 379 380/*ARGSUSED*/ 381void 382sys_syscall() 383{} 384 385void 386_allsyscalls() 387{} 388 389size_t _allsyscalls_size; 390 391#else /* __lint */ 392 393 ENTRY_NP2(brand_sys_syscall,_allsyscalls) 394 SWAPGS /* kernel gsbase */ 395 XPV_SYSCALL_PROD 396 BRAND_CALLBACK(BRAND_CB_SYSCALL) 397 SWAPGS /* user gsbase */ 398 399#if defined(__xpv) 400 jmp noprod_sys_syscall 401#endif 402 403 ALTENTRY(sys_syscall) 404 SWAPGS /* kernel gsbase */ 405 XPV_SYSCALL_PROD 406 407noprod_sys_syscall: 408 ASSERT_UPCALL_MASK_IS_SET 409 410 movq %r15, %gs:CPU_RTMP_R15 411 movq %rsp, %gs:CPU_RTMP_RSP 412 413 movq %gs:CPU_THREAD, %r15 414 movq T_STACK(%r15), %rsp 415 416 movl $UCS_SEL, REGOFF_CS(%rsp) 417 movq %rcx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */ 418 movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */ 419 movl $UDS_SEL, REGOFF_SS(%rsp) 420 421 movl %eax, %eax /* wrapper: sysc# -> %eax */ 422 movq %rdi, REGOFF_RDI(%rsp) 423 movq %rsi, REGOFF_RSI(%rsp) 424 movq %rdx, REGOFF_RDX(%rsp) 425 movq %r10, REGOFF_RCX(%rsp) /* wrapper: %rcx -> %r10 */ 426 movq %r10, %rcx /* arg[3] for direct calls */ 427 428 movq %r8, REGOFF_R8(%rsp) 429 movq %r9, REGOFF_R9(%rsp) 430 movq %rax, REGOFF_RAX(%rsp) 431 movq %rbx, REGOFF_RBX(%rsp) 432 433 movq %rbp, REGOFF_RBP(%rsp) 434 movq %r10, REGOFF_R10(%rsp) 435 movq %gs:CPU_RTMP_RSP, %r11 436 movq %r11, REGOFF_RSP(%rsp) 437 movq %r12, REGOFF_R12(%rsp) 438 439 movq %r13, REGOFF_R13(%rsp) 440 movq %r14, REGOFF_R14(%rsp) 441 movq %gs:CPU_RTMP_R15, %r10 442 movq %r10, REGOFF_R15(%rsp) 443 movq $0, REGOFF_SAVFP(%rsp) 444 movq $0, REGOFF_SAVPC(%rsp) 445 446 /* 447 * Copy these registers here in case we end up stopped with 448 * someone (like, say, /proc) messing with our register state. 449 * We don't -restore- them unless we have to in update_sregs. 450 * 451 * Since userland -can't- change fsbase or gsbase directly, 452 * and capturing them involves two serializing instructions, 453 * we don't bother to capture them here. 454 */ 455 xorl %ebx, %ebx 456 movw %ds, %bx 457 movq %rbx, REGOFF_DS(%rsp) 458 movw %es, %bx 459 movq %rbx, REGOFF_ES(%rsp) 460 movw %fs, %bx 461 movq %rbx, REGOFF_FS(%rsp) 462 movw %gs, %bx 463 movq %rbx, REGOFF_GS(%rsp) 464 465 /* 466 * Machine state saved in the regs structure on the stack 467 * First six args in %rdi, %rsi, %rdx, %rcx, %r8, %r9 468 * %eax is the syscall number 469 * %rsp is the thread's stack, %r15 is curthread 470 * REG_RSP(%rsp) is the user's stack 471 */ 472 473 SYSCALL_TRAPTRACE($TT_SYSC64) 474 475 movq %rsp, %rbp 476 477 movq T_LWP(%r15), %r14 478 ASSERT_NO_RUPDATE_PENDING(%r14) 479 ENABLE_INTR_FLAGS 480 481 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM) 482 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */ 483 484 ASSERT_LWPTOREGS(%r14, %rsp) 485 486 movb $LWP_SYS, LWP_STATE(%r14) 487 incq LWP_RU_SYSC(%r14) 488 movb $NORMALRETURN, LWP_EOSYS(%r14) 489 490 incq %gs:CPU_STATS_SYS_SYSCALL 491 492 movw %ax, T_SYSNUM(%r15) 493 movzbl T_PRE_SYS(%r15), %ebx 494 ORL_SYSCALLTRACE(%ebx) 495 testl %ebx, %ebx 496 jne _syscall_pre 497 498_syscall_invoke: 499 movq REGOFF_RDI(%rbp), %rdi 500 movq REGOFF_RSI(%rbp), %rsi 501 movq REGOFF_RDX(%rbp), %rdx 502 movq REGOFF_RCX(%rbp), %rcx 503 movq REGOFF_R8(%rbp), %r8 504 movq REGOFF_R9(%rbp), %r9 505 506 cmpl $NSYSCALL, %eax 507 jae _syscall_ill 508 shll $SYSENT_SIZE_SHIFT, %eax 509 leaq sysent(%rax), %rbx 510 511 call *SY_CALLC(%rbx) 512 513 movq %rax, %r12 514 movq %rdx, %r13 515 516 /* 517 * If the handler returns two ints, then we need to split the 518 * 64-bit return value into two 32-bit values. 519 */ 520 testw $SE_32RVAL2, SY_FLAGS(%rbx) 521 je 5f 522 movq %r12, %r13 523 shrq $32, %r13 /* upper 32-bits into %edx */ 524 movl %r12d, %r12d /* lower 32-bits into %eax */ 5255: 526 /* 527 * Optimistically assume that there's no post-syscall 528 * work to do. (This is to avoid having to call syscall_mstate() 529 * with interrupts disabled) 530 */ 531 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER) 532 533 /* 534 * We must protect ourselves from being descheduled here; 535 * If we were, and we ended up on another cpu, or another 536 * lwp got in ahead of us, it could change the segment 537 * registers without us noticing before we return to userland. 538 */ 539 CLI(%r14) 540 CHECK_POSTSYS_NE(%r15, %r14, %ebx) 541 jne _syscall_post 542 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx) 543 544 movq %r12, REGOFF_RAX(%rsp) 545 movq %r13, REGOFF_RDX(%rsp) 546 547 /* 548 * To get back to userland, we need the return %rip in %rcx and 549 * the return %rfl in %r11d. The sysretq instruction also arranges 550 * to fix up %cs and %ss; everything else is our responsibility. 551 */ 552 movq REGOFF_RDI(%rsp), %rdi 553 movq REGOFF_RSI(%rsp), %rsi 554 movq REGOFF_RDX(%rsp), %rdx 555 /* %rcx used to restore %rip value */ 556 557 movq REGOFF_R8(%rsp), %r8 558 movq REGOFF_R9(%rsp), %r9 559 movq REGOFF_RAX(%rsp), %rax 560 movq REGOFF_RBX(%rsp), %rbx 561 562 movq REGOFF_RBP(%rsp), %rbp 563 movq REGOFF_R10(%rsp), %r10 564 /* %r11 used to restore %rfl value */ 565 movq REGOFF_R12(%rsp), %r12 566 567 movq REGOFF_R13(%rsp), %r13 568 movq REGOFF_R14(%rsp), %r14 569 movq REGOFF_R15(%rsp), %r15 570 571 movq REGOFF_RIP(%rsp), %rcx 572 movl REGOFF_RFL(%rsp), %r11d 573 574#if defined(__xpv) 575 addq $REGOFF_RIP, %rsp 576#else 577 movq REGOFF_RSP(%rsp), %rsp 578#endif 579 580 /* 581 * There can be no instructions between the ALTENTRY below and 582 * SYSRET or we could end up breaking brand support. See label usage 583 * in sn1_brand_syscall_callback for an example. 584 */ 585 ASSERT_UPCALL_MASK_IS_SET 586#if defined(__xpv) 587 SYSRETQ 588 ALTENTRY(nopop_sys_syscall_swapgs_sysretq) 589 590 /* 591 * We can only get here after executing a brand syscall 592 * interposition callback handler and simply need to 593 * "sysretq" back to userland. On the hypervisor this 594 * involves the iret hypercall which requires us to construct 595 * just enough of the stack needed for the hypercall. 596 * (rip, cs, rflags, rsp, ss). 597 */ 598 movq %rsp, %gs:CPU_RTMP_RSP /* save user's rsp */ 599 movq %gs:CPU_THREAD, %r11 600 movq T_STACK(%r11), %rsp 601 602 movq %rcx, REGOFF_RIP(%rsp) 603 movl $UCS_SEL, REGOFF_CS(%rsp) 604 movq %gs:CPU_RTMP_RSP, %r11 605 movq %r11, REGOFF_RSP(%rsp) 606 pushfq 607 popq %r11 /* hypercall enables ints */ 608 movq %r11, REGOFF_RFL(%rsp) 609 movl $UDS_SEL, REGOFF_SS(%rsp) 610 addq $REGOFF_RIP, %rsp 611 /* 612 * XXPV: see comment in SYSRETQ definition for future optimization 613 * we could take. 614 */ 615 ASSERT_UPCALL_MASK_IS_SET 616 SYSRETQ 617#else 618 ALTENTRY(nopop_sys_syscall_swapgs_sysretq) 619 SWAPGS /* user gsbase */ 620 SYSRETQ 621#endif 622 /*NOTREACHED*/ 623 SET_SIZE(nopop_sys_syscall_swapgs_sysretq) 624 625_syscall_pre: 626 call pre_syscall 627 movl %eax, %r12d 628 testl %eax, %eax 629 jne _syscall_post_call 630 /* 631 * Didn't abort, so reload the syscall args and invoke the handler. 632 */ 633 movzwl T_SYSNUM(%r15), %eax 634 jmp _syscall_invoke 635 636_syscall_ill: 637 call nosys 638 movq %rax, %r12 639 movq %rdx, %r13 640 jmp _syscall_post_call 641 642_syscall_post: 643 STI 644 /* 645 * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM 646 * so that we can account for the extra work it takes us to finish. 647 */ 648 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM) 649_syscall_post_call: 650 movq %r12, %rdi 651 movq %r13, %rsi 652 call post_syscall 653 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER) 654 jmp _sys_rtt 655 SET_SIZE(sys_syscall) 656 SET_SIZE(brand_sys_syscall) 657 658#endif /* __lint */ 659 660#if defined(__lint) 661 662/*ARGSUSED*/ 663void 664sys_syscall32() 665{} 666 667#else /* __lint */ 668 669 ENTRY_NP(brand_sys_syscall32) 670 SWAPGS /* kernel gsbase */ 671 XPV_TRAP_POP 672 BRAND_CALLBACK(BRAND_CB_SYSCALL32) 673 SWAPGS /* user gsbase */ 674 675#if defined(__xpv) 676 jmp nopop_sys_syscall32 677#endif 678 679 ALTENTRY(sys_syscall32) 680 SWAPGS /* kernel gsbase */ 681 682#if defined(__xpv) 683 XPV_TRAP_POP 684nopop_sys_syscall32: 685#endif 686 687 movl %esp, %r10d 688 movq %gs:CPU_THREAD, %r15 689 movq T_STACK(%r15), %rsp 690 movl %eax, %eax 691 692 movl $U32CS_SEL, REGOFF_CS(%rsp) 693 movl %ecx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */ 694 movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */ 695 movq %r10, REGOFF_RSP(%rsp) 696 movl $UDS_SEL, REGOFF_SS(%rsp) 697 698_syscall32_save: 699 movl %edi, REGOFF_RDI(%rsp) 700 movl %esi, REGOFF_RSI(%rsp) 701 movl %ebp, REGOFF_RBP(%rsp) 702 movl %ebx, REGOFF_RBX(%rsp) 703 movl %edx, REGOFF_RDX(%rsp) 704 movl %ecx, REGOFF_RCX(%rsp) 705 movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */ 706 movq $0, REGOFF_SAVFP(%rsp) 707 movq $0, REGOFF_SAVPC(%rsp) 708 709 /* 710 * Copy these registers here in case we end up stopped with 711 * someone (like, say, /proc) messing with our register state. 712 * We don't -restore- them unless we have to in update_sregs. 713 * 714 * Since userland -can't- change fsbase or gsbase directly, 715 * we don't bother to capture them here. 716 */ 717 xorl %ebx, %ebx 718 movw %ds, %bx 719 movq %rbx, REGOFF_DS(%rsp) 720 movw %es, %bx 721 movq %rbx, REGOFF_ES(%rsp) 722 movw %fs, %bx 723 movq %rbx, REGOFF_FS(%rsp) 724 movw %gs, %bx 725 movq %rbx, REGOFF_GS(%rsp) 726 727 /* 728 * Application state saved in the regs structure on the stack 729 * %eax is the syscall number 730 * %rsp is the thread's stack, %r15 is curthread 731 * REG_RSP(%rsp) is the user's stack 732 */ 733 734 SYSCALL_TRAPTRACE32($TT_SYSC) 735 736 movq %rsp, %rbp 737 738 movq T_LWP(%r15), %r14 739 ASSERT_NO_RUPDATE_PENDING(%r14) 740 741 ENABLE_INTR_FLAGS 742 743 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM) 744 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */ 745 746 ASSERT_LWPTOREGS(%r14, %rsp) 747 748 incq %gs:CPU_STATS_SYS_SYSCALL 749 750 /* 751 * Make some space for MAXSYSARGS (currently 8) 32-bit args placed 752 * into 64-bit (long) arg slots, maintaining 16 byte alignment. Or 753 * more succinctly: 754 * 755 * SA(MAXSYSARGS * sizeof (long)) == 64 756 */ 757#define SYS_DROP 64 /* drop for args */ 758 subq $SYS_DROP, %rsp 759 movb $LWP_SYS, LWP_STATE(%r14) 760 movq %r15, %rdi 761 movq %rsp, %rsi 762 call syscall_entry 763 764 /* 765 * Fetch the arguments copied onto the kernel stack and put 766 * them in the right registers to invoke a C-style syscall handler. 767 * %rax contains the handler address. 768 * 769 * Ideas for making all this go faster of course include simply 770 * forcibly fetching 6 arguments from the user stack under lofault 771 * protection, reverting to copyin_args only when watchpoints 772 * are in effect. 773 * 774 * (If we do this, make sure that exec and libthread leave 775 * enough space at the top of the stack to ensure that we'll 776 * never do a fetch from an invalid page.) 777 * 778 * Lots of ideas here, but they won't really help with bringup B-) 779 * Correctness can't wait, performance can wait a little longer .. 780 */ 781 782 movq %rax, %rbx 783 movl 0(%rsp), %edi 784 movl 8(%rsp), %esi 785 movl 0x10(%rsp), %edx 786 movl 0x18(%rsp), %ecx 787 movl 0x20(%rsp), %r8d 788 movl 0x28(%rsp), %r9d 789 790 call *SY_CALLC(%rbx) 791 792 movq %rbp, %rsp /* pop the args */ 793 794 /* 795 * amd64 syscall handlers -always- return a 64-bit value in %rax. 796 * On the 32-bit kernel, they always return that value in %eax:%edx 797 * as required by the 32-bit ABI. 798 * 799 * Simulate the same behaviour by unconditionally splitting the 800 * return value in the same way. 801 */ 802 movq %rax, %r13 803 shrq $32, %r13 /* upper 32-bits into %edx */ 804 movl %eax, %r12d /* lower 32-bits into %eax */ 805 806 /* 807 * Optimistically assume that there's no post-syscall 808 * work to do. (This is to avoid having to call syscall_mstate() 809 * with interrupts disabled) 810 */ 811 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER) 812 813 /* 814 * We must protect ourselves from being descheduled here; 815 * If we were, and we ended up on another cpu, or another 816 * lwp got in ahead of us, it could change the segment 817 * registers without us noticing before we return to userland. 818 */ 819 CLI(%r14) 820 CHECK_POSTSYS_NE(%r15, %r14, %ebx) 821 jne _full_syscall_postsys32 822 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx) 823 824 /* 825 * To get back to userland, we need to put the return %rip in %rcx and 826 * the return %rfl in %r11d. The sysret instruction also arranges 827 * to fix up %cs and %ss; everything else is our responsibility. 828 */ 829 830 movl %r12d, %eax /* %eax: rval1 */ 831 movl REGOFF_RBX(%rsp), %ebx 832 /* %ecx used for return pointer */ 833 movl %r13d, %edx /* %edx: rval2 */ 834 movl REGOFF_RBP(%rsp), %ebp 835 movl REGOFF_RSI(%rsp), %esi 836 movl REGOFF_RDI(%rsp), %edi 837 838 movl REGOFF_RFL(%rsp), %r11d /* %r11 -> eflags */ 839 movl REGOFF_RIP(%rsp), %ecx /* %ecx -> %eip */ 840 movl REGOFF_RSP(%rsp), %esp 841 842 ASSERT_UPCALL_MASK_IS_SET 843 ALTENTRY(nopop_sys_syscall32_swapgs_sysretl) 844 SWAPGS /* user gsbase */ 845 SYSRETL 846 SET_SIZE(nopop_sys_syscall32_swapgs_sysretl) 847 /*NOTREACHED*/ 848 849_full_syscall_postsys32: 850 STI 851 /* 852 * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM 853 * so that we can account for the extra work it takes us to finish. 854 */ 855 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM) 856 movq %r15, %rdi 857 movq %r12, %rsi /* rval1 - %eax */ 858 movq %r13, %rdx /* rval2 - %edx */ 859 call syscall_exit 860 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER) 861 jmp _sys_rtt 862 SET_SIZE(sys_syscall32) 863 SET_SIZE(brand_sys_syscall32) 864 865#endif /* __lint */ 866 867/* 868 * System call handler via the sysenter instruction 869 * Used only for 32-bit system calls on the 64-bit kernel. 870 * 871 * The caller in userland has arranged that: 872 * 873 * - %eax contains the syscall number 874 * - %ecx contains the user %esp 875 * - %edx contains the return %eip 876 * - the user stack contains the args to the syscall 877 * 878 * Hardware and (privileged) initialization code have arranged that by 879 * the time the sysenter instructions completes: 880 * 881 * - %rip is pointing to sys_sysenter (below). 882 * - %cs and %ss are set to kernel text and stack (data) selectors. 883 * - %rsp is pointing at the lwp's stack 884 * - interrupts have been disabled. 885 * 886 * Note that we are unable to return both "rvals" to userland with 887 * this call, as %edx is used by the sysexit instruction. 888 * 889 * One final complication in this routine is its interaction with 890 * single-stepping in a debugger. For most of the system call mechanisms, 891 * the CPU automatically clears the single-step flag before we enter the 892 * kernel. The sysenter mechanism does not clear the flag, so a user 893 * single-stepping through a libc routine may suddenly find him/herself 894 * single-stepping through the kernel. To detect this, kmdb compares the 895 * trap %pc to the [brand_]sys_enter addresses on each single-step trap. 896 * If it finds that we have single-stepped to a sysenter entry point, it 897 * explicitly clears the flag and executes the sys_sysenter routine. 898 * 899 * One final complication in this final complication is the fact that we 900 * have two different entry points for sysenter: brand_sys_sysenter and 901 * sys_sysenter. If we enter at brand_sys_sysenter and start single-stepping 902 * through the kernel with kmdb, we will eventually hit the instruction at 903 * sys_sysenter. kmdb cannot distinguish between that valid single-step 904 * and the undesirable one mentioned above. To avoid this situation, we 905 * simply add a jump over the instruction at sys_sysenter to make it 906 * impossible to single-step to it. 907 */ 908#if defined(__lint) 909 910void 911sys_sysenter() 912{} 913 914#else /* __lint */ 915 916 ENTRY_NP(brand_sys_sysenter) 917 SWAPGS /* kernel gsbase */ 918 ALTENTRY(_brand_sys_sysenter_post_swapgs) 919 BRAND_CALLBACK(BRAND_CB_SYSENTER) 920 /* 921 * Jump over sys_sysenter to allow single-stepping as described 922 * above. 923 */ 924 jmp _sys_sysenter_post_swapgs 925 926 ALTENTRY(sys_sysenter) 927 SWAPGS /* kernel gsbase */ 928 929 ALTENTRY(_sys_sysenter_post_swapgs) 930 movq %gs:CPU_THREAD, %r15 931 932 movl $U32CS_SEL, REGOFF_CS(%rsp) 933 movl %ecx, REGOFF_RSP(%rsp) /* wrapper: %esp -> %ecx */ 934 movl %edx, REGOFF_RIP(%rsp) /* wrapper: %eip -> %edx */ 935 pushfq 936 popq %r10 937 movl $UDS_SEL, REGOFF_SS(%rsp) 938 939 /* 940 * Set the interrupt flag before storing the flags to the 941 * flags image on the stack so we can return to user with 942 * interrupts enabled if we return via sys_rtt_syscall32 943 */ 944 orq $PS_IE, %r10 945 movq %r10, REGOFF_RFL(%rsp) 946 947 movl %edi, REGOFF_RDI(%rsp) 948 movl %esi, REGOFF_RSI(%rsp) 949 movl %ebp, REGOFF_RBP(%rsp) 950 movl %ebx, REGOFF_RBX(%rsp) 951 movl %edx, REGOFF_RDX(%rsp) 952 movl %ecx, REGOFF_RCX(%rsp) 953 movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */ 954 movq $0, REGOFF_SAVFP(%rsp) 955 movq $0, REGOFF_SAVPC(%rsp) 956 957 /* 958 * Copy these registers here in case we end up stopped with 959 * someone (like, say, /proc) messing with our register state. 960 * We don't -restore- them unless we have to in update_sregs. 961 * 962 * Since userland -can't- change fsbase or gsbase directly, 963 * we don't bother to capture them here. 964 */ 965 xorl %ebx, %ebx 966 movw %ds, %bx 967 movq %rbx, REGOFF_DS(%rsp) 968 movw %es, %bx 969 movq %rbx, REGOFF_ES(%rsp) 970 movw %fs, %bx 971 movq %rbx, REGOFF_FS(%rsp) 972 movw %gs, %bx 973 movq %rbx, REGOFF_GS(%rsp) 974 975 /* 976 * Application state saved in the regs structure on the stack 977 * %eax is the syscall number 978 * %rsp is the thread's stack, %r15 is curthread 979 * REG_RSP(%rsp) is the user's stack 980 */ 981 982 SYSCALL_TRAPTRACE($TT_SYSENTER) 983 984 movq %rsp, %rbp 985 986 movq T_LWP(%r15), %r14 987 ASSERT_NO_RUPDATE_PENDING(%r14) 988 989 ENABLE_INTR_FLAGS 990 991 /* 992 * Catch 64-bit process trying to issue sysenter instruction 993 * on Nocona based systems. 994 */ 995 movq LWP_PROCP(%r14), %rax 996 cmpq $DATAMODEL_ILP32, P_MODEL(%rax) 997 je 7f 998 999 /* 1000 * For a non-32-bit process, simulate a #ud, since that's what 1001 * native hardware does. The traptrace entry (above) will 1002 * let you know what really happened. 1003 */ 1004 movq $T_ILLINST, REGOFF_TRAPNO(%rsp) 1005 movq REGOFF_CS(%rsp), %rdi 1006 movq %rdi, REGOFF_ERR(%rsp) 1007 movq %rsp, %rdi 1008 movq REGOFF_RIP(%rsp), %rsi 1009 movl %gs:CPU_ID, %edx 1010 call trap 1011 jmp _sys_rtt 10127: 1013 1014 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM) 1015 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate calls) */ 1016 1017 ASSERT_LWPTOREGS(%r14, %rsp) 1018 1019 incq %gs:CPU_STATS_SYS_SYSCALL 1020 1021 /* 1022 * Make some space for MAXSYSARGS (currently 8) 32-bit args 1023 * placed into 64-bit (long) arg slots, plus one 64-bit 1024 * (long) arg count, maintaining 16 byte alignment. 1025 */ 1026 subq $SYS_DROP, %rsp 1027 movb $LWP_SYS, LWP_STATE(%r14) 1028 movq %r15, %rdi 1029 movq %rsp, %rsi 1030 call syscall_entry 1031 1032 /* 1033 * Fetch the arguments copied onto the kernel stack and put 1034 * them in the right registers to invoke a C-style syscall handler. 1035 * %rax contains the handler address. 1036 */ 1037 movq %rax, %rbx 1038 movl 0(%rsp), %edi 1039 movl 8(%rsp), %esi 1040 movl 0x10(%rsp), %edx 1041 movl 0x18(%rsp), %ecx 1042 movl 0x20(%rsp), %r8d 1043 movl 0x28(%rsp), %r9d 1044 1045 call *SY_CALLC(%rbx) 1046 1047 movq %rbp, %rsp /* pop the args */ 1048 1049 /* 1050 * amd64 syscall handlers -always- return a 64-bit value in %rax. 1051 * On the 32-bit kernel, the always return that value in %eax:%edx 1052 * as required by the 32-bit ABI. 1053 * 1054 * Simulate the same behaviour by unconditionally splitting the 1055 * return value in the same way. 1056 */ 1057 movq %rax, %r13 1058 shrq $32, %r13 /* upper 32-bits into %edx */ 1059 movl %eax, %r12d /* lower 32-bits into %eax */ 1060 1061 /* 1062 * Optimistically assume that there's no post-syscall 1063 * work to do. (This is to avoid having to call syscall_mstate() 1064 * with interrupts disabled) 1065 */ 1066 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER) 1067 1068 /* 1069 * We must protect ourselves from being descheduled here; 1070 * If we were, and we ended up on another cpu, or another 1071 * lwp got int ahead of us, it could change the segment 1072 * registers without us noticing before we return to userland. 1073 */ 1074 cli 1075 CHECK_POSTSYS_NE(%r15, %r14, %ebx) 1076 jne _full_syscall_postsys32 1077 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx) 1078 1079 /* 1080 * To get back to userland, load up the 32-bit registers and 1081 * sysexit back where we came from. 1082 */ 1083 1084 /* 1085 * Interrupts will be turned on by the 'sti' executed just before 1086 * sysexit. The following ensures that restoring the user's rflags 1087 * doesn't enable interrupts too soon. 1088 */ 1089 andq $_BITNOT(PS_IE), REGOFF_RFL(%rsp) 1090 1091 /* 1092 * (There's no point in loading up %edx because the sysexit 1093 * mechanism smashes it.) 1094 */ 1095 movl %r12d, %eax 1096 movl REGOFF_RBX(%rsp), %ebx 1097 movl REGOFF_RBP(%rsp), %ebp 1098 movl REGOFF_RSI(%rsp), %esi 1099 movl REGOFF_RDI(%rsp), %edi 1100 1101 movl REGOFF_RIP(%rsp), %edx /* sysexit: %edx -> %eip */ 1102 pushq REGOFF_RFL(%rsp) 1103 popfq 1104 movl REGOFF_RSP(%rsp), %ecx /* sysexit: %ecx -> %esp */ 1105 ALTENTRY(sys_sysenter_swapgs_sysexit) 1106 swapgs 1107 sti 1108 sysexit 1109 SET_SIZE(sys_sysenter_swapgs_sysexit) 1110 SET_SIZE(sys_sysenter) 1111 SET_SIZE(_sys_sysenter_post_swapgs) 1112 SET_SIZE(brand_sys_sysenter) 1113 1114#endif /* __lint */ 1115 1116#if defined(__lint) 1117/* 1118 * System call via an int80. This entry point is only used by the Linux 1119 * application environment. Unlike the other entry points, there is no 1120 * default action to take if no callback is registered for this process. 1121 */ 1122void 1123sys_int80() 1124{} 1125 1126#else /* __lint */ 1127 1128 ENTRY_NP(brand_sys_int80) 1129 SWAPGS /* kernel gsbase */ 1130 XPV_TRAP_POP 1131 BRAND_CALLBACK(BRAND_CB_INT80) 1132 SWAPGS /* user gsbase */ 1133#if defined(__xpv) 1134 jmp nopop_int80 1135#endif 1136 1137 ENTRY_NP(sys_int80) 1138 /* 1139 * We hit an int80, but this process isn't of a brand with an int80 1140 * handler. Bad process! Make it look as if the INT failed. 1141 * Modify %rip to point before the INT, push the expected error 1142 * code and fake a GP fault. Note on 64-bit hypervisor we need 1143 * to undo the XPV_TRAP_POP and push rcx and r11 back on the stack 1144 * because gptrap will pop them again with its own XPV_TRAP_POP. 1145 */ 1146#if defined(__xpv) 1147 XPV_TRAP_POP 1148nopop_int80: 1149#endif 1150 subq $2, (%rsp) /* int insn 2-bytes */ 1151 pushq $_CONST(_MUL(T_INT80, GATE_DESC_SIZE) + 2) 1152#if defined(__xpv) 1153 push %r11 1154 push %rcx 1155#endif 1156 jmp gptrap / GP fault 1157 SET_SIZE(sys_int80) 1158 SET_SIZE(brand_sys_int80) 1159#endif /* __lint */ 1160 1161 1162/* 1163 * This is the destination of the "int $T_SYSCALLINT" interrupt gate, used by 1164 * the generic i386 libc to do system calls. We do a small amount of setup 1165 * before jumping into the existing sys_syscall32 path. 1166 */ 1167#if defined(__lint) 1168 1169/*ARGSUSED*/ 1170void 1171sys_syscall_int() 1172{} 1173 1174#else /* __lint */ 1175 1176 ENTRY_NP(brand_sys_syscall_int) 1177 SWAPGS /* kernel gsbase */ 1178 XPV_TRAP_POP 1179 BRAND_CALLBACK(BRAND_CB_INT91) 1180 SWAPGS /* user gsbase */ 1181 1182#if defined(__xpv) 1183 jmp nopop_syscall_int 1184#endif 1185 1186 ALTENTRY(sys_syscall_int) 1187 SWAPGS /* kernel gsbase */ 1188 1189#if defined(__xpv) 1190 XPV_TRAP_POP 1191nopop_syscall_int: 1192#endif 1193 1194 movq %gs:CPU_THREAD, %r15 1195 movq T_STACK(%r15), %rsp 1196 movl %eax, %eax 1197 /* 1198 * Set t_post_sys on this thread to force ourselves out via the slow 1199 * path. It might be possible at some later date to optimize this out 1200 * and use a faster return mechanism. 1201 */ 1202 movb $1, T_POST_SYS(%r15) 1203 CLEAN_CS 1204 jmp _syscall32_save 1205 /* 1206 * There should be no instructions between this label and SWAPGS/IRET 1207 * or we could end up breaking branded zone support. See the usage of 1208 * this label in lx_brand_int80_callback and sn1_brand_int91_callback 1209 * for examples. 1210 */ 1211 ALTENTRY(sys_sysint_swapgs_iret) 1212 SWAPGS /* user gsbase */ 1213 IRET 1214 /*NOTREACHED*/ 1215 SET_SIZE(sys_sysint_swapgs_iret) 1216 SET_SIZE(sys_syscall_int) 1217 SET_SIZE(brand_sys_syscall_int) 1218 1219#endif /* __lint */ 1220 1221/* 1222 * Legacy 32-bit applications and old libc implementations do lcalls; 1223 * we should never get here because the LDT entry containing the syscall 1224 * segment descriptor has the "segment present" bit cleared, which means 1225 * we end up processing those system calls in trap() via a not-present trap. 1226 * 1227 * We do it this way because a call gate unhelpfully does -nothing- to the 1228 * interrupt flag bit, so an interrupt can run us just after the lcall 1229 * completes, but just before the swapgs takes effect. Thus the INTR_PUSH and 1230 * INTR_POP paths would have to be slightly more complex to dance around 1231 * this problem, and end up depending explicitly on the first 1232 * instruction of this handler being either swapgs or cli. 1233 */ 1234 1235#if defined(__lint) 1236 1237/*ARGSUSED*/ 1238void 1239sys_lcall32() 1240{} 1241 1242#else /* __lint */ 1243 1244 ENTRY_NP(sys_lcall32) 1245 SWAPGS /* kernel gsbase */ 1246 pushq $0 1247 pushq %rbp 1248 movq %rsp, %rbp 1249 leaq __lcall_panic_str(%rip), %rdi 1250 xorl %eax, %eax 1251 call panic 1252 SET_SIZE(sys_lcall32) 1253 1254__lcall_panic_str: 1255 .string "sys_lcall32: shouldn't be here!" 1256 1257/* 1258 * Declare a uintptr_t which covers the entire pc range of syscall 1259 * handlers for the stack walkers that need this. 1260 */ 1261 .align CPTRSIZE 1262 .globl _allsyscalls_size 1263 .type _allsyscalls_size, @object 1264_allsyscalls_size: 1265 .NWORD . - _allsyscalls 1266 SET_SIZE(_allsyscalls_size) 1267 1268#endif /* __lint */ 1269 1270/* 1271 * These are the thread context handlers for lwps using sysenter/sysexit. 1272 */ 1273 1274#if defined(__lint) 1275 1276/*ARGSUSED*/ 1277void 1278sep_save(void *ksp) 1279{} 1280 1281/*ARGSUSED*/ 1282void 1283sep_restore(void *ksp) 1284{} 1285 1286#else /* __lint */ 1287 1288 /* 1289 * setting this value to zero as we switch away causes the 1290 * stack-pointer-on-sysenter to be NULL, ensuring that we 1291 * don't silently corrupt another (preempted) thread stack 1292 * when running an lwp that (somehow) didn't get sep_restore'd 1293 */ 1294 ENTRY_NP(sep_save) 1295 xorl %edx, %edx 1296 xorl %eax, %eax 1297 movl $MSR_INTC_SEP_ESP, %ecx 1298 wrmsr 1299 ret 1300 SET_SIZE(sep_save) 1301 1302 /* 1303 * Update the kernel stack pointer as we resume onto this cpu. 1304 */ 1305 ENTRY_NP(sep_restore) 1306 movq %rdi, %rdx 1307 shrq $32, %rdx 1308 movl %edi, %eax 1309 movl $MSR_INTC_SEP_ESP, %ecx 1310 wrmsr 1311 ret 1312 SET_SIZE(sep_restore) 1313 1314#endif /* __lint */ 1315