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 (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright 2018 Joyent, Inc.
24 * Copyright (c) 2016 by Delphix. All rights reserved.
25 */
26
27 #include <sys/asm_linkage.h>
28 #include <sys/asm_misc.h>
29 #include <sys/regset.h>
30 #include <sys/privregs.h>
31 #include <sys/psw.h>
32 #include <sys/machbrand.h>
33
34 #if defined(__lint)
35
36 #include <sys/types.h>
37 #include <sys/thread.h>
38 #include <sys/systm.h>
39
40 #else /* __lint */
41
42 #include <sys/segments.h>
43 #include <sys/pcb.h>
44 #include <sys/trap.h>
45 #include <sys/ftrace.h>
46 #include <sys/traptrace.h>
47 #include <sys/clock.h>
48 #include <sys/model.h>
49 #include <sys/panic.h>
50
51 #if defined(__xpv)
52 #include <sys/hypervisor.h>
53 #endif
54
55 #include "assym.h"
56
57 #endif /* __lint */
58
59 /*
60 * We implement five flavours of system call entry points
61 *
62 * - syscall/sysretq (amd64 generic)
63 * - syscall/sysretl (i386 plus SYSC bit)
64 * - sysenter/sysexit (i386 plus SEP bit)
65 * - int/iret (i386 generic)
66 * - lcall/iret (i386 generic)
67 *
68 * The current libc included in Solaris uses int/iret as the base unoptimized
69 * kernel entry method. Older libc implementations and legacy binaries may use
70 * the lcall call gate, so it must continue to be supported.
71 *
72 * System calls that use an lcall call gate are processed in trap() via a
73 * segment-not-present trap, i.e. lcalls are extremely slow(!).
74 *
75 * The basic pattern used in the 32-bit SYSC handler at this point in time is
76 * to have the bare minimum of assembler, and get to the C handlers as
77 * quickly as possible.
78 *
79 * The 64-bit handler is much closer to the sparcv9 handler; that's
80 * because of passing arguments in registers. The 32-bit world still
81 * passes arguments on the stack -- that makes that handler substantially
82 * more complex.
83 *
84 * The two handlers share a few code fragments which are broken
85 * out into preprocessor macros below.
86 *
87 * XX64 come back and speed all this up later. The 32-bit stuff looks
88 * especially easy to speed up the argument copying part ..
89 *
90 *
91 * Notes about segment register usage (c.f. the 32-bit kernel)
92 *
93 * In the 32-bit kernel, segment registers are dutifully saved and
94 * restored on all mode transitions because the kernel uses them directly.
95 * When the processor is running in 64-bit mode, segment registers are
96 * largely ignored.
97 *
98 * %cs and %ss
99 * controlled by the hardware mechanisms that make mode transitions
100 *
101 * The remaining segment registers have to either be pointing at a valid
102 * descriptor i.e. with the 'present' bit set, or they can NULL descriptors
103 *
104 * %ds and %es
105 * always ignored
106 *
107 * %fs and %gs
108 * fsbase and gsbase are used to control the place they really point at.
109 * The kernel only depends on %gs, and controls its own gsbase via swapgs
110 *
111 * Note that loading segment registers is still costly because the GDT
112 * lookup still happens (this is because the hardware can't know that we're
113 * not setting up these segment registers for a 32-bit program). Thus we
114 * avoid doing this in the syscall path, and defer them to lwp context switch
115 * handlers, so the register values remain virtualized to the lwp.
116 */
117
118 #if defined(SYSCALLTRACE)
119 #define ORL_SYSCALLTRACE(r32) \
120 orl syscalltrace(%rip), r32
121 #else
122 #define ORL_SYSCALLTRACE(r32)
123 #endif
124
125 /*
126 * In the 32-bit kernel, we do absolutely nothing before getting into the
127 * brand callback checks. In 64-bit land, we do swapgs and then come here.
128 * We assume that the %rsp- and %r15-stashing fields in the CPU structure
129 * are still unused.
130 *
131 * Check if a brand_mach_ops callback is defined for the specified callback_id
132 * type. If so invoke it with the kernel's %gs value loaded and the following
133 * data on the stack:
134 *
135 * stack: --------------------------------------
136 * 32 | callback pointer |
137 * | 24 | user (or interrupt) stack pointer |
138 * | 16 | lwp pointer |
139 * v 8 | userland return address |
140 * 0 | callback wrapper return addr |
141 * --------------------------------------
142 *
143 * Since we're pushing the userland return address onto the kernel stack
144 * we need to get that address without accessing the user's stack (since we
145 * can't trust that data). There are different ways to get the userland
146 * return address depending on how the syscall trap was made:
147 *
148 * a) For sys_syscall and sys_syscall32 the return address is in %rcx.
149 * b) For sys_sysenter the return address is in %rdx.
150 * c) For sys_int80 and sys_syscall_int (int91), upon entry into the macro,
151 * the stack pointer points at the state saved when we took the interrupt:
152 * ------------------------
153 * | | user's %ss |
154 * | | user's %esp |
155 * | | EFLAGS register |
156 * v | user's %cs |
157 * | user's %eip |
158 * ------------------------
159 *
160 * The 2nd parameter to the BRAND_CALLBACK macro is either the
161 * BRAND_URET_FROM_REG or BRAND_URET_FROM_INTR_STACK macro. These macros are
162 * used to generate the proper code to get the userland return address for
163 * each syscall entry point.
164 *
165 * The interface to the brand callbacks on the 64-bit kernel assumes %r15
166 * is available as a scratch register within the callback. If the callback
167 * returns within the kernel then this macro will restore %r15. If the
168 * callback is going to return directly to userland then it should restore
169 * %r15 before returning to userland.
170 */
171 #define BRAND_URET_FROM_REG(rip_reg) \
172 pushq rip_reg /* push the return address */
173
174 /*
175 * The interrupt stack pointer we saved on entry to the BRAND_CALLBACK macro
176 * is currently pointing at the user return address (%eip).
177 */
178 #define BRAND_URET_FROM_INTR_STACK() \
179 movq %gs:CPU_RTMP_RSP, %r15 /* grab the intr. stack pointer */ ;\
180 pushq (%r15) /* push the return address */
181
182 #define BRAND_CALLBACK(callback_id, push_userland_ret) \
183 movq %rsp, %gs:CPU_RTMP_RSP /* save the stack pointer */ ;\
184 movq %r15, %gs:CPU_RTMP_R15 /* save %r15 */ ;\
185 movq %gs:CPU_THREAD, %r15 /* load the thread pointer */ ;\
186 movq T_STACK(%r15), %rsp /* switch to the kernel stack */ ;\
187 subq $16, %rsp /* save space for 2 pointers */ ;\
188 pushq %r14 /* save %r14 */ ;\
189 movq %gs:CPU_RTMP_RSP, %r14 ;\
190 movq %r14, 8(%rsp) /* stash the user stack pointer */ ;\
191 popq %r14 /* restore %r14 */ ;\
192 movq T_LWP(%r15), %r15 /* load the lwp pointer */ ;\
193 pushq %r15 /* push the lwp pointer */ ;\
194 movq LWP_PROCP(%r15), %r15 /* load the proc pointer */ ;\
195 movq P_BRAND(%r15), %r15 /* load the brand pointer */ ;\
196 movq B_MACHOPS(%r15), %r15 /* load the machops pointer */ ;\
197 movq _CONST(_MUL(callback_id, CPTRSIZE))(%r15), %r15 ;\
198 cmpq $0, %r15 ;\
199 je 1f ;\
200 movq %r15, 16(%rsp) /* save the callback pointer */ ;\
201 push_userland_ret /* push the return address */ ;\
202 call *24(%rsp) /* call callback */ ;\
203 1: movq %gs:CPU_RTMP_R15, %r15 /* restore %r15 */ ;\
204 movq %gs:CPU_RTMP_RSP, %rsp /* restore the stack pointer */
205
206 #define MSTATE_TRANSITION(from, to) \
207 movl $from, %edi; \
208 movl $to, %esi; \
209 call syscall_mstate
210
211 /*
212 * Check to see if a simple (direct) return is possible i.e.
213 *
214 * if (t->t_post_sys_ast | syscalltrace |
215 * lwp->lwp_pcb.pcb_rupdate == 1)
216 * do full version ;
217 *
218 * Preconditions:
219 * - t is curthread
220 * Postconditions:
221 * - condition code NE is set if post-sys is too complex
222 * - rtmp is zeroed if it isn't (we rely on this!)
223 * - ltmp is smashed
224 */
225 #define CHECK_POSTSYS_NE(t, ltmp, rtmp) \
226 movq T_LWP(t), ltmp; \
227 movzbl PCB_RUPDATE(ltmp), rtmp; \
228 ORL_SYSCALLTRACE(rtmp); \
229 orl T_POST_SYS_AST(t), rtmp; \
230 cmpl $0, rtmp
231
232 /*
233 * Fix up the lwp, thread, and eflags for a successful return
234 *
235 * Preconditions:
236 * - zwreg contains zero
237 */
238 #define SIMPLE_SYSCALL_POSTSYS(t, lwp, zwreg) \
239 movb $LWP_USER, LWP_STATE(lwp); \
240 movw zwreg, T_SYSNUM(t); \
241 andb $_CONST(0xffff - PS_C), REGOFF_RFL(%rsp)
242
243 /*
244 * ASSERT(lwptoregs(lwp) == rp);
245 *
246 * This may seem obvious, but very odd things happen if this
247 * assertion is false
248 *
249 * Preconditions:
250 * (%rsp is ready for normal call sequence)
251 * Postconditions (if assertion is true):
252 * %r11 is smashed
253 *
254 * ASSERT(rp->r_cs == descnum)
255 *
256 * The code selector is written into the regs structure when the
257 * lwp stack is created. We use this ASSERT to validate that
258 * the regs structure really matches how we came in.
259 *
260 * Preconditions:
261 * (%rsp is ready for normal call sequence)
262 * Postconditions (if assertion is true):
263 * -none-
264 *
265 * ASSERT(lwp->lwp_pcb.pcb_rupdate == 0);
266 *
267 * If this is false, it meant that we returned to userland without
268 * updating the segment registers as we were supposed to.
269 *
270 * Note that we must ensure no interrupts or other traps intervene
271 * between entering privileged mode and performing the assertion,
272 * otherwise we may perform a context switch on the thread, which
273 * will end up setting pcb_rupdate to 1 again.
274 */
275 #if defined(DEBUG)
276
277 #if !defined(__lint)
278
279 __lwptoregs_msg:
280 .string "syscall_asm_amd64.s:%d lwptoregs(%p) [%p] != rp [%p]"
281
282 __codesel_msg:
283 .string "syscall_asm_amd64.s:%d rp->r_cs [%ld] != %ld"
284
285 __no_rupdate_msg:
286 .string "syscall_asm_amd64.s:%d lwp %p, pcb_rupdate != 0"
287
288 #endif /* !__lint */
289
290 #define ASSERT_LWPTOREGS(lwp, rp) \
291 movq LWP_REGS(lwp), %r11; \
292 cmpq rp, %r11; \
293 je 7f; \
294 leaq __lwptoregs_msg(%rip), %rdi; \
295 movl $__LINE__, %esi; \
296 movq lwp, %rdx; \
297 movq %r11, %rcx; \
298 movq rp, %r8; \
299 xorl %eax, %eax; \
300 call panic; \
301 7:
302
303 #define ASSERT_NO_RUPDATE_PENDING(lwp) \
304 testb $0x1, PCB_RUPDATE(lwp); \
305 je 8f; \
306 movq lwp, %rdx; \
307 leaq __no_rupdate_msg(%rip), %rdi; \
308 movl $__LINE__, %esi; \
309 xorl %eax, %eax; \
310 call panic; \
311 8:
312
313 #else
314 #define ASSERT_LWPTOREGS(lwp, rp)
315 #define ASSERT_NO_RUPDATE_PENDING(lwp)
316 #endif
317
318 /*
319 * Do the traptrace thing and restore any registers we used
320 * in situ. Assumes that %rsp is pointing at the base of
321 * the struct regs, obviously ..
322 */
323 #ifdef TRAPTRACE
324 #define SYSCALL_TRAPTRACE(ttype) \
325 TRACE_PTR(%rdi, %rbx, %ebx, %rcx, ttype); \
326 TRACE_REGS(%rdi, %rsp, %rbx, %rcx); \
327 TRACE_STAMP(%rdi); /* rdtsc clobbers %eax, %edx */ \
328 movq REGOFF_RAX(%rsp), %rax; \
329 movq REGOFF_RBX(%rsp), %rbx; \
330 movq REGOFF_RCX(%rsp), %rcx; \
331 movq REGOFF_RDX(%rsp), %rdx; \
332 movl %eax, TTR_SYSNUM(%rdi); \
333 movq REGOFF_RDI(%rsp), %rdi
334
335 #define SYSCALL_TRAPTRACE32(ttype) \
336 SYSCALL_TRAPTRACE(ttype); \
337 /* paranoia: clean the top 32-bits of the registers */ \
338 orl %eax, %eax; \
339 orl %ebx, %ebx; \
340 orl %ecx, %ecx; \
341 orl %edx, %edx; \
342 orl %edi, %edi
343 #else /* TRAPTRACE */
344 #define SYSCALL_TRAPTRACE(ttype)
345 #define SYSCALL_TRAPTRACE32(ttype)
346 #endif /* TRAPTRACE */
347
348 /*
349 * The 64-bit libc syscall wrapper does this:
350 *
351 * fn(<args>)
352 * {
353 * movq %rcx, %r10 -- because syscall smashes %rcx
354 * movl $CODE, %eax
355 * syscall
356 * <error processing>
357 * }
358 *
359 * Thus when we come into the kernel:
360 *
361 * %rdi, %rsi, %rdx, %r10, %r8, %r9 contain first six args
362 * %rax is the syscall number
363 * %r12-%r15 contain caller state
364 *
365 * The syscall instruction arranges that:
366 *
367 * %rcx contains the return %rip
368 * %r11d contains bottom 32-bits of %rflags
369 * %rflags is masked (as determined by the SFMASK msr)
370 * %cs is set to UCS_SEL (as determined by the STAR msr)
371 * %ss is set to UDS_SEL (as determined by the STAR msr)
372 * %rip is set to sys_syscall (as determined by the LSTAR msr)
373 *
374 * Or in other words, we have no registers available at all.
375 * Only swapgs can save us!
376 *
377 * Under the hypervisor, the swapgs has happened already. However, the
378 * state of the world is very different from that we're familiar with.
379 *
380 * In particular, we have a stack structure like that for interrupt
381 * gates, except that the %cs and %ss registers are modified for reasons
382 * that are not entirely clear. Critically, the %rcx/%r11 values do
383 * *not* reflect the usage of those registers under a 'real' syscall[1];
384 * the stack, therefore, looks like this:
385 *
386 * 0x0(rsp) potentially junk %rcx
387 * 0x8(rsp) potentially junk %r11
388 * 0x10(rsp) user %rip
389 * 0x18(rsp) modified %cs
390 * 0x20(rsp) user %rflags
391 * 0x28(rsp) user %rsp
392 * 0x30(rsp) modified %ss
393 *
394 *
395 * and before continuing on, we must load the %rip into %rcx and the
396 * %rflags into %r11.
397 *
398 * [1] They used to, and we relied on it, but this was broken in 3.1.1.
399 * Sigh.
400 */
401 #if defined(__xpv)
402 #define XPV_SYSCALL_PROD \
403 movq 0x10(%rsp), %rcx; \
404 movq 0x20(%rsp), %r11; \
405 movq 0x28(%rsp), %rsp
406 #else
407 #define XPV_SYSCALL_PROD /* nothing */
408 #endif
409
410 #if defined(__lint)
411
412 /*ARGSUSED*/
413 void
414 sys_syscall()
415 {}
416
417 void
418 _allsyscalls()
419 {}
420
421 size_t _allsyscalls_size;
422
423 #else /* __lint */
424
425 ENTRY_NP2(brand_sys_syscall,_allsyscalls)
426 SWAPGS /* kernel gsbase */
427 XPV_SYSCALL_PROD
428 BRAND_CALLBACK(BRAND_CB_SYSCALL, BRAND_URET_FROM_REG(%rcx))
429 jmp noprod_sys_syscall
430
431 ALTENTRY(sys_syscall)
432 SWAPGS /* kernel gsbase */
433 XPV_SYSCALL_PROD
434
435 noprod_sys_syscall:
436 movq %r15, %gs:CPU_RTMP_R15
437 movq %rsp, %gs:CPU_RTMP_RSP
438
439 movq %gs:CPU_THREAD, %r15
440 movq T_STACK(%r15), %rsp /* switch from user to kernel stack */
441
442 ASSERT_UPCALL_MASK_IS_SET
443
444 movl $UCS_SEL, REGOFF_CS(%rsp)
445 movq %rcx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */
446 movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */
447 movl $UDS_SEL, REGOFF_SS(%rsp)
448
449 movl %eax, %eax /* wrapper: sysc# -> %eax */
450 movq %rdi, REGOFF_RDI(%rsp)
451 movq %rsi, REGOFF_RSI(%rsp)
452 movq %rdx, REGOFF_RDX(%rsp)
453 movq %r10, REGOFF_RCX(%rsp) /* wrapper: %rcx -> %r10 */
454 movq %r10, %rcx /* arg[3] for direct calls */
455
456 movq %r8, REGOFF_R8(%rsp)
457 movq %r9, REGOFF_R9(%rsp)
458 movq %rax, REGOFF_RAX(%rsp)
459 movq %rbx, REGOFF_RBX(%rsp)
460
461 movq %rbp, REGOFF_RBP(%rsp)
462 movq %r10, REGOFF_R10(%rsp)
463 movq %gs:CPU_RTMP_RSP, %r11
464 movq %r11, REGOFF_RSP(%rsp)
465 movq %r12, REGOFF_R12(%rsp)
466
467 movq %r13, REGOFF_R13(%rsp)
468 movq %r14, REGOFF_R14(%rsp)
469 movq %gs:CPU_RTMP_R15, %r10
470 movq %r10, REGOFF_R15(%rsp)
471 movq $0, REGOFF_SAVFP(%rsp)
472 movq $0, REGOFF_SAVPC(%rsp)
473
474 /*
475 * Copy these registers here in case we end up stopped with
476 * someone (like, say, /proc) messing with our register state.
477 * We don't -restore- them unless we have to in update_sregs.
478 *
479 * Since userland -can't- change fsbase or gsbase directly,
480 * and capturing them involves two serializing instructions,
481 * we don't bother to capture them here.
482 */
483 xorl %ebx, %ebx
484 movw %ds, %bx
485 movq %rbx, REGOFF_DS(%rsp)
486 movw %es, %bx
487 movq %rbx, REGOFF_ES(%rsp)
488 movw %fs, %bx
489 movq %rbx, REGOFF_FS(%rsp)
490 movw %gs, %bx
491 movq %rbx, REGOFF_GS(%rsp)
492
493 /*
494 * If we're trying to use TRAPTRACE though, I take that back: we're
495 * probably debugging some problem in the SWAPGS logic and want to know
496 * what the incoming gsbase was.
497 *
498 * Since we already did SWAPGS, record the KGSBASE.
499 */
500 #if defined(DEBUG) && defined(TRAPTRACE) && !defined(__xpv)
501 movl $MSR_AMD_KGSBASE, %ecx
502 rdmsr
503 movl %eax, REGOFF_GSBASE(%rsp)
504 movl %edx, REGOFF_GSBASE+4(%rsp)
505 #endif
506
507 /*
508 * Machine state saved in the regs structure on the stack
509 * First six args in %rdi, %rsi, %rdx, %rcx, %r8, %r9
510 * %eax is the syscall number
511 * %rsp is the thread's stack, %r15 is curthread
512 * REG_RSP(%rsp) is the user's stack
513 */
514
515 SYSCALL_TRAPTRACE($TT_SYSC64)
516
517 movq %rsp, %rbp
518
519 movq T_LWP(%r15), %r14
520 ASSERT_NO_RUPDATE_PENDING(%r14)
521 ENABLE_INTR_FLAGS
522
523 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
524 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */
525
526 ASSERT_LWPTOREGS(%r14, %rsp)
527
528 movb $LWP_SYS, LWP_STATE(%r14)
529 incq LWP_RU_SYSC(%r14)
530 movb $NORMALRETURN, LWP_EOSYS(%r14)
531
532 incq %gs:CPU_STATS_SYS_SYSCALL
533
534 movw %ax, T_SYSNUM(%r15)
535 movzbl T_PRE_SYS(%r15), %ebx
536 ORL_SYSCALLTRACE(%ebx)
537 testl %ebx, %ebx
538 jne _syscall_pre
539
540 _syscall_invoke:
541 movq REGOFF_RDI(%rbp), %rdi
542 movq REGOFF_RSI(%rbp), %rsi
543 movq REGOFF_RDX(%rbp), %rdx
544 movq REGOFF_RCX(%rbp), %rcx
545 movq REGOFF_R8(%rbp), %r8
546 movq REGOFF_R9(%rbp), %r9
547
548 cmpl $NSYSCALL, %eax
549 jae _syscall_ill
550 shll $SYSENT_SIZE_SHIFT, %eax
551 leaq sysent(%rax), %rbx
552
553 call *SY_CALLC(%rbx)
554
555 movq %rax, %r12
556 movq %rdx, %r13
557
558 /*
559 * If the handler returns two ints, then we need to split the
560 * 64-bit return value into two 32-bit values.
561 */
562 testw $SE_32RVAL2, SY_FLAGS(%rbx)
563 je 5f
564 movq %r12, %r13
565 shrq $32, %r13 /* upper 32-bits into %edx */
566 movl %r12d, %r12d /* lower 32-bits into %eax */
567 5:
568 /*
569 * Optimistically assume that there's no post-syscall
570 * work to do. (This is to avoid having to call syscall_mstate()
571 * with interrupts disabled)
572 */
573 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
574
575 /*
576 * We must protect ourselves from being descheduled here;
577 * If we were, and we ended up on another cpu, or another
578 * lwp got in ahead of us, it could change the segment
579 * registers without us noticing before we return to userland.
580 */
581 CLI(%r14)
582 CHECK_POSTSYS_NE(%r15, %r14, %ebx)
583 jne _syscall_post
584
585 /*
586 * We need to protect ourselves against non-canonical return values
587 * because Intel doesn't check for them on sysret (AMD does). Canonical
588 * addresses on current amd64 processors only use 48-bits for VAs; an
589 * address is canonical if all upper bits (47-63) are identical. If we
590 * find a non-canonical %rip, we opt to go through the full
591 * _syscall_post path which takes us into an iretq which is not
592 * susceptible to the same problems sysret is.
593 *
594 * We're checking for a canonical address by first doing an arithmetic
595 * shift. This will fill in the remaining bits with the value of bit 63.
596 * If the address were canonical, the register would now have either all
597 * zeroes or all ones in it. Therefore we add one (inducing overflow)
598 * and compare against 1. A canonical address will either be zero or one
599 * at this point, hence the use of ja.
600 *
601 * At this point, r12 and r13 have the return value so we can't use
602 * those registers.
603 */
604 movq REGOFF_RIP(%rsp), %rcx
605 sarq $47, %rcx
606 incq %rcx
607 cmpq $1, %rcx
608 ja _syscall_post
609
610
611 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
612
613 movq %r12, REGOFF_RAX(%rsp)
614 movq %r13, REGOFF_RDX(%rsp)
615
616 /*
617 * To get back to userland, we need the return %rip in %rcx and
618 * the return %rfl in %r11d. The sysretq instruction also arranges
619 * to fix up %cs and %ss; everything else is our responsibility.
620 */
621 movq REGOFF_RDI(%rsp), %rdi
622 movq REGOFF_RSI(%rsp), %rsi
623 movq REGOFF_RDX(%rsp), %rdx
624 /* %rcx used to restore %rip value */
625
626 movq REGOFF_R8(%rsp), %r8
627 movq REGOFF_R9(%rsp), %r9
628 movq REGOFF_RAX(%rsp), %rax
629 movq REGOFF_RBX(%rsp), %rbx
630
631 movq REGOFF_RBP(%rsp), %rbp
632 movq REGOFF_R10(%rsp), %r10
633 /* %r11 used to restore %rfl value */
634 movq REGOFF_R12(%rsp), %r12
635
636 movq REGOFF_R13(%rsp), %r13
637 movq REGOFF_R14(%rsp), %r14
638 movq REGOFF_R15(%rsp), %r15
639
640 movq REGOFF_RIP(%rsp), %rcx
641 movl REGOFF_RFL(%rsp), %r11d
642
643 #if defined(__xpv)
644 addq $REGOFF_RIP, %rsp
645 #else
646 movq REGOFF_RSP(%rsp), %rsp
647 #endif
648
649 /*
650 * There can be no instructions between the ALTENTRY below and
651 * SYSRET or we could end up breaking brand support. See label usage
652 * in sn1_brand_syscall_callback for an example.
653 */
654 ASSERT_UPCALL_MASK_IS_SET
655 #if defined(__xpv)
656 SYSRETQ
657 ALTENTRY(nopop_sys_syscall_swapgs_sysretq)
658
659 /*
660 * We can only get here after executing a brand syscall
661 * interposition callback handler and simply need to
662 * "sysretq" back to userland. On the hypervisor this
663 * involves the iret hypercall which requires us to construct
664 * just enough of the stack needed for the hypercall.
665 * (rip, cs, rflags, rsp, ss).
666 */
667 movq %rsp, %gs:CPU_RTMP_RSP /* save user's rsp */
668 movq %gs:CPU_THREAD, %r11
669 movq T_STACK(%r11), %rsp
670
671 movq %rcx, REGOFF_RIP(%rsp)
672 movl $UCS_SEL, REGOFF_CS(%rsp)
673 movq %gs:CPU_RTMP_RSP, %r11
674 movq %r11, REGOFF_RSP(%rsp)
675 pushfq
676 popq %r11 /* hypercall enables ints */
677 movq %r11, REGOFF_RFL(%rsp)
678 movl $UDS_SEL, REGOFF_SS(%rsp)
679 addq $REGOFF_RIP, %rsp
680 /*
681 * XXPV: see comment in SYSRETQ definition for future optimization
682 * we could take.
683 */
684 ASSERT_UPCALL_MASK_IS_SET
685 SYSRETQ
686 #else
687 ALTENTRY(nopop_sys_syscall_swapgs_sysretq)
688 jmp tr_sysretq
689 #endif
690 /*NOTREACHED*/
691 SET_SIZE(nopop_sys_syscall_swapgs_sysretq)
692
693 _syscall_pre:
694 call pre_syscall
695 movl %eax, %r12d
696 testl %eax, %eax
697 jne _syscall_post_call
698 /*
699 * Didn't abort, so reload the syscall args and invoke the handler.
700 */
701 movzwl T_SYSNUM(%r15), %eax
702 jmp _syscall_invoke
703
704 _syscall_ill:
705 call nosys
706 movq %rax, %r12
707 movq %rdx, %r13
708 jmp _syscall_post_call
709
710 _syscall_post:
711 STI
712 /*
713 * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM
714 * so that we can account for the extra work it takes us to finish.
715 */
716 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
717 _syscall_post_call:
718 movq %r12, %rdi
719 movq %r13, %rsi
720 call post_syscall
721 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
722 jmp _sys_rtt
723 SET_SIZE(sys_syscall)
724 SET_SIZE(brand_sys_syscall)
725
726 #endif /* __lint */
727
728 #if defined(__lint)
729
730 /*ARGSUSED*/
731 void
732 sys_syscall32()
733 {}
734
735 #else /* __lint */
736
737 ENTRY_NP(brand_sys_syscall32)
738 SWAPGS /* kernel gsbase */
739 XPV_TRAP_POP
740 BRAND_CALLBACK(BRAND_CB_SYSCALL32, BRAND_URET_FROM_REG(%rcx))
741 jmp nopop_sys_syscall32
742
743 ALTENTRY(sys_syscall32)
744 SWAPGS /* kernel gsbase */
745 XPV_TRAP_POP
746
747 nopop_sys_syscall32:
748 movl %esp, %r10d
749 movq %gs:CPU_THREAD, %r15
750 movq T_STACK(%r15), %rsp
751 movl %eax, %eax
752
753 movl $U32CS_SEL, REGOFF_CS(%rsp)
754 movl %ecx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */
755 movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */
756 movq %r10, REGOFF_RSP(%rsp)
757 movl $UDS_SEL, REGOFF_SS(%rsp)
758
759 _syscall32_save:
760 movl %edi, REGOFF_RDI(%rsp)
761 movl %esi, REGOFF_RSI(%rsp)
762 movl %ebp, REGOFF_RBP(%rsp)
763 movl %ebx, REGOFF_RBX(%rsp)
764 movl %edx, REGOFF_RDX(%rsp)
765 movl %ecx, REGOFF_RCX(%rsp)
766 movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */
767 movq $0, REGOFF_SAVFP(%rsp)
768 movq $0, REGOFF_SAVPC(%rsp)
769
770 /*
771 * Copy these registers here in case we end up stopped with
772 * someone (like, say, /proc) messing with our register state.
773 * We don't -restore- them unless we have to in update_sregs.
774 *
775 * Since userland -can't- change fsbase or gsbase directly,
776 * we don't bother to capture them here.
777 */
778 xorl %ebx, %ebx
779 movw %ds, %bx
780 movq %rbx, REGOFF_DS(%rsp)
781 movw %es, %bx
782 movq %rbx, REGOFF_ES(%rsp)
783 movw %fs, %bx
784 movq %rbx, REGOFF_FS(%rsp)
785 movw %gs, %bx
786 movq %rbx, REGOFF_GS(%rsp)
787
788 /*
789 * If we're trying to use TRAPTRACE though, I take that back: we're
790 * probably debugging some problem in the SWAPGS logic and want to know
791 * what the incoming gsbase was.
792 *
793 * Since we already did SWAPGS, record the KGSBASE.
794 */
795 #if defined(DEBUG) && defined(TRAPTRACE) && !defined(__xpv)
796 movl $MSR_AMD_KGSBASE, %ecx
797 rdmsr
798 movl %eax, REGOFF_GSBASE(%rsp)
799 movl %edx, REGOFF_GSBASE+4(%rsp)
800 #endif
801
802 /*
803 * Application state saved in the regs structure on the stack
804 * %eax is the syscall number
805 * %rsp is the thread's stack, %r15 is curthread
806 * REG_RSP(%rsp) is the user's stack
807 */
808
809 SYSCALL_TRAPTRACE32($TT_SYSC)
810
811 movq %rsp, %rbp
812
813 movq T_LWP(%r15), %r14
814 ASSERT_NO_RUPDATE_PENDING(%r14)
815
816 ENABLE_INTR_FLAGS
817
818 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
819 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */
820
821 ASSERT_LWPTOREGS(%r14, %rsp)
822
823 incq %gs:CPU_STATS_SYS_SYSCALL
824
825 /*
826 * Make some space for MAXSYSARGS (currently 8) 32-bit args placed
827 * into 64-bit (long) arg slots, maintaining 16 byte alignment. Or
828 * more succinctly:
829 *
830 * SA(MAXSYSARGS * sizeof (long)) == 64
831 */
832 #define SYS_DROP 64 /* drop for args */
833 subq $SYS_DROP, %rsp
834 movb $LWP_SYS, LWP_STATE(%r14)
835 movq %r15, %rdi
836 movq %rsp, %rsi
837 call syscall_entry
838
839 /*
840 * Fetch the arguments copied onto the kernel stack and put
841 * them in the right registers to invoke a C-style syscall handler.
842 * %rax contains the handler address.
843 *
844 * Ideas for making all this go faster of course include simply
845 * forcibly fetching 6 arguments from the user stack under lofault
846 * protection, reverting to copyin_args only when watchpoints
847 * are in effect.
848 *
849 * (If we do this, make sure that exec and libthread leave
850 * enough space at the top of the stack to ensure that we'll
851 * never do a fetch from an invalid page.)
852 *
853 * Lots of ideas here, but they won't really help with bringup B-)
854 * Correctness can't wait, performance can wait a little longer ..
855 */
856
857 movq %rax, %rbx
858 movl 0(%rsp), %edi
859 movl 8(%rsp), %esi
860 movl 0x10(%rsp), %edx
861 movl 0x18(%rsp), %ecx
862 movl 0x20(%rsp), %r8d
863 movl 0x28(%rsp), %r9d
864
865 call *SY_CALLC(%rbx)
866
867 movq %rbp, %rsp /* pop the args */
868
869 /*
870 * amd64 syscall handlers -always- return a 64-bit value in %rax.
871 * On the 32-bit kernel, they always return that value in %eax:%edx
872 * as required by the 32-bit ABI.
873 *
874 * Simulate the same behaviour by unconditionally splitting the
875 * return value in the same way.
876 */
877 movq %rax, %r13
878 shrq $32, %r13 /* upper 32-bits into %edx */
879 movl %eax, %r12d /* lower 32-bits into %eax */
880
881 /*
882 * Optimistically assume that there's no post-syscall
883 * work to do. (This is to avoid having to call syscall_mstate()
884 * with interrupts disabled)
885 */
886 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
887
888 /*
889 * We must protect ourselves from being descheduled here;
890 * If we were, and we ended up on another cpu, or another
891 * lwp got in ahead of us, it could change the segment
892 * registers without us noticing before we return to userland.
893 */
894 CLI(%r14)
895 CHECK_POSTSYS_NE(%r15, %r14, %ebx)
896 jne _full_syscall_postsys32
897 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
898
899 /*
900 * To get back to userland, we need to put the return %rip in %rcx and
901 * the return %rfl in %r11d. The sysret instruction also arranges
902 * to fix up %cs and %ss; everything else is our responsibility.
903 */
904
905 movl %r12d, %eax /* %eax: rval1 */
906 movl REGOFF_RBX(%rsp), %ebx
907 /* %ecx used for return pointer */
908 movl %r13d, %edx /* %edx: rval2 */
909 movl REGOFF_RBP(%rsp), %ebp
910 movl REGOFF_RSI(%rsp), %esi
911 movl REGOFF_RDI(%rsp), %edi
912
913 movl REGOFF_RFL(%rsp), %r11d /* %r11 -> eflags */
914 movl REGOFF_RIP(%rsp), %ecx /* %ecx -> %eip */
915 movl REGOFF_RSP(%rsp), %esp
916
917 ASSERT_UPCALL_MASK_IS_SET
918 ALTENTRY(nopop_sys_syscall32_swapgs_sysretl)
919 jmp tr_sysretl
920 SET_SIZE(nopop_sys_syscall32_swapgs_sysretl)
921 /*NOTREACHED*/
922
923 _full_syscall_postsys32:
924 STI
925 /*
926 * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM
927 * so that we can account for the extra work it takes us to finish.
928 */
929 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
930 movq %r15, %rdi
931 movq %r12, %rsi /* rval1 - %eax */
932 movq %r13, %rdx /* rval2 - %edx */
933 call syscall_exit
934 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
935 jmp _sys_rtt
936 SET_SIZE(sys_syscall32)
937 SET_SIZE(brand_sys_syscall32)
938
939 #endif /* __lint */
940
941 /*
942 * System call handler via the sysenter instruction
943 * Used only for 32-bit system calls on the 64-bit kernel.
944 *
945 * The caller in userland has arranged that:
946 *
947 * - %eax contains the syscall number
948 * - %ecx contains the user %esp
949 * - %edx contains the return %eip
950 * - the user stack contains the args to the syscall
951 *
952 * Hardware and (privileged) initialization code have arranged that by
953 * the time the sysenter instructions completes:
954 *
955 * - %rip is pointing to sys_sysenter (below).
956 * - %cs and %ss are set to kernel text and stack (data) selectors.
957 * - %rsp is pointing at the lwp's stack
958 * - interrupts have been disabled.
959 *
960 * Note that we are unable to return both "rvals" to userland with
961 * this call, as %edx is used by the sysexit instruction.
962 *
963 * One final complication in this routine is its interaction with
964 * single-stepping in a debugger. For most of the system call mechanisms, the
965 * CPU automatically clears the single-step flag before we enter the kernel.
966 * The sysenter mechanism does not clear the flag, so a user single-stepping
967 * through a libc routine may suddenly find themself single-stepping through the
968 * kernel. To detect this, kmdb and trap() both compare the trap %pc to the
969 * [brand_]sys_enter addresses on each single-step trap. If it finds that we
970 * have single-stepped to a sysenter entry point, it explicitly clears the flag
971 * and executes the sys_sysenter routine.
972 *
973 * One final complication in this final complication is the fact that we have
974 * two different entry points for sysenter: brand_sys_sysenter and sys_sysenter.
975 * If we enter at brand_sys_sysenter and start single-stepping through the
976 * kernel with kmdb, we will eventually hit the instruction at sys_sysenter.
977 * kmdb cannot distinguish between that valid single-step and the undesirable
978 * one mentioned above. To avoid this situation, we simply add a jump over the
979 * instruction at sys_sysenter to make it impossible to single-step to it.
980 */
981 #if defined(__lint)
982
983 void
984 sys_sysenter()
985 {}
986
987 #else /* __lint */
988
989 ENTRY_NP(brand_sys_sysenter)
990 SWAPGS /* kernel gsbase */
991 ALTENTRY(_brand_sys_sysenter_post_swapgs)
992
993 BRAND_CALLBACK(BRAND_CB_SYSENTER, BRAND_URET_FROM_REG(%rdx))
994 /*
995 * Jump over sys_sysenter to allow single-stepping as described
996 * above.
997 */
998 jmp _sys_sysenter_post_swapgs
999
1000 ALTENTRY(sys_sysenter)
1001 SWAPGS /* kernel gsbase */
1002 ALTENTRY(_sys_sysenter_post_swapgs)
1003
1004 movq %gs:CPU_THREAD, %r15
1005
1006 movl $U32CS_SEL, REGOFF_CS(%rsp)
1007 movl %ecx, REGOFF_RSP(%rsp) /* wrapper: %esp -> %ecx */
1008 movl %edx, REGOFF_RIP(%rsp) /* wrapper: %eip -> %edx */
1009 /*
1010 * NOTE: none of the instructions that run before we get here should
1011 * clobber bits in (R)FLAGS! This includes the kpti trampoline.
1012 */
1013 pushfq
1014 popq %r10
1015 movl $UDS_SEL, REGOFF_SS(%rsp)
1016
1017 /*
1018 * Set the interrupt flag before storing the flags to the
1019 * flags image on the stack so we can return to user with
1020 * interrupts enabled if we return via sys_rtt_syscall32
1021 */
1022 orq $PS_IE, %r10
1023 movq %r10, REGOFF_RFL(%rsp)
1024
1025 movl %edi, REGOFF_RDI(%rsp)
1026 movl %esi, REGOFF_RSI(%rsp)
1027 movl %ebp, REGOFF_RBP(%rsp)
1028 movl %ebx, REGOFF_RBX(%rsp)
1029 movl %edx, REGOFF_RDX(%rsp)
1030 movl %ecx, REGOFF_RCX(%rsp)
1031 movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */
1032 movq $0, REGOFF_SAVFP(%rsp)
1033 movq $0, REGOFF_SAVPC(%rsp)
1034
1035 /*
1036 * Copy these registers here in case we end up stopped with
1037 * someone (like, say, /proc) messing with our register state.
1038 * We don't -restore- them unless we have to in update_sregs.
1039 *
1040 * Since userland -can't- change fsbase or gsbase directly,
1041 * we don't bother to capture them here.
1042 */
1043 xorl %ebx, %ebx
1044 movw %ds, %bx
1045 movq %rbx, REGOFF_DS(%rsp)
1046 movw %es, %bx
1047 movq %rbx, REGOFF_ES(%rsp)
1048 movw %fs, %bx
1049 movq %rbx, REGOFF_FS(%rsp)
1050 movw %gs, %bx
1051 movq %rbx, REGOFF_GS(%rsp)
1052
1053 /*
1054 * If we're trying to use TRAPTRACE though, I take that back: we're
1055 * probably debugging some problem in the SWAPGS logic and want to know
1056 * what the incoming gsbase was.
1057 *
1058 * Since we already did SWAPGS, record the KGSBASE.
1059 */
1060 #if defined(DEBUG) && defined(TRAPTRACE) && !defined(__xpv)
1061 movl $MSR_AMD_KGSBASE, %ecx
1062 rdmsr
1063 movl %eax, REGOFF_GSBASE(%rsp)
1064 movl %edx, REGOFF_GSBASE+4(%rsp)
1065 #endif
1066
1067 /*
1068 * Application state saved in the regs structure on the stack
1069 * %eax is the syscall number
1070 * %rsp is the thread's stack, %r15 is curthread
1071 * REG_RSP(%rsp) is the user's stack
1072 */
1073
1074 SYSCALL_TRAPTRACE($TT_SYSENTER)
1075
1076 movq %rsp, %rbp
1077
1078 movq T_LWP(%r15), %r14
1079 ASSERT_NO_RUPDATE_PENDING(%r14)
1080
1081 ENABLE_INTR_FLAGS
1082
1083 /*
1084 * Catch 64-bit process trying to issue sysenter instruction
1085 * on Nocona based systems.
1086 */
1087 movq LWP_PROCP(%r14), %rax
1088 cmpq $DATAMODEL_ILP32, P_MODEL(%rax)
1089 je 7f
1090
1091 /*
1092 * For a non-32-bit process, simulate a #ud, since that's what
1093 * native hardware does. The traptrace entry (above) will
1094 * let you know what really happened.
1095 */
1096 movq $T_ILLINST, REGOFF_TRAPNO(%rsp)
1097 movq REGOFF_CS(%rsp), %rdi
1098 movq %rdi, REGOFF_ERR(%rsp)
1099 movq %rsp, %rdi
1100 movq REGOFF_RIP(%rsp), %rsi
1101 movl %gs:CPU_ID, %edx
1102 call trap
1103 jmp _sys_rtt
1104 7:
1105
1106 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
1107 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate calls) */
1108
1109 ASSERT_LWPTOREGS(%r14, %rsp)
1110
1111 incq %gs:CPU_STATS_SYS_SYSCALL
1112
1113 /*
1114 * Make some space for MAXSYSARGS (currently 8) 32-bit args
1115 * placed into 64-bit (long) arg slots, plus one 64-bit
1116 * (long) arg count, maintaining 16 byte alignment.
1117 */
1118 subq $SYS_DROP, %rsp
1119 movb $LWP_SYS, LWP_STATE(%r14)
1120 movq %r15, %rdi
1121 movq %rsp, %rsi
1122 call syscall_entry
1123
1124 /*
1125 * Fetch the arguments copied onto the kernel stack and put
1126 * them in the right registers to invoke a C-style syscall handler.
1127 * %rax contains the handler address.
1128 */
1129 movq %rax, %rbx
1130 movl 0(%rsp), %edi
1131 movl 8(%rsp), %esi
1132 movl 0x10(%rsp), %edx
1133 movl 0x18(%rsp), %ecx
1134 movl 0x20(%rsp), %r8d
1135 movl 0x28(%rsp), %r9d
1136
1137 call *SY_CALLC(%rbx)
1138
1139 movq %rbp, %rsp /* pop the args */
1140
1141 /*
1142 * amd64 syscall handlers -always- return a 64-bit value in %rax.
1143 * On the 32-bit kernel, the always return that value in %eax:%edx
1144 * as required by the 32-bit ABI.
1145 *
1146 * Simulate the same behaviour by unconditionally splitting the
1147 * return value in the same way.
1148 */
1149 movq %rax, %r13
1150 shrq $32, %r13 /* upper 32-bits into %edx */
1151 movl %eax, %r12d /* lower 32-bits into %eax */
1152
1153 /*
1154 * Optimistically assume that there's no post-syscall
1155 * work to do. (This is to avoid having to call syscall_mstate()
1156 * with interrupts disabled)
1157 */
1158 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
1159
1160 /*
1161 * We must protect ourselves from being descheduled here;
1162 * If we were, and we ended up on another cpu, or another
1163 * lwp got int ahead of us, it could change the segment
1164 * registers without us noticing before we return to userland.
1165 *
1166 * This cli is undone in the tr_sysexit trampoline code.
1167 */
1168 cli
1169 CHECK_POSTSYS_NE(%r15, %r14, %ebx)
1170 jne _full_syscall_postsys32
1171 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
1172
1173 /*
1174 * To get back to userland, load up the 32-bit registers and
1175 * sysexit back where we came from.
1176 */
1177
1178 /*
1179 * Interrupts will be turned on by the 'sti' executed just before
1180 * sysexit. The following ensures that restoring the user's rflags
1181 * doesn't enable interrupts too soon.
1182 */
1183 andq $_BITNOT(PS_IE), REGOFF_RFL(%rsp)
1184
1185 /*
1186 * (There's no point in loading up %edx because the sysexit
1187 * mechanism smashes it.)
1188 */
1189 movl %r12d, %eax
1190 movl REGOFF_RBX(%rsp), %ebx
1191 movl REGOFF_RBP(%rsp), %ebp
1192 movl REGOFF_RSI(%rsp), %esi
1193 movl REGOFF_RDI(%rsp), %edi
1194
1195 movl REGOFF_RIP(%rsp), %edx /* sysexit: %edx -> %eip */
1196 pushq REGOFF_RFL(%rsp)
1197 popfq
1198 movl REGOFF_RSP(%rsp), %ecx /* sysexit: %ecx -> %esp */
1199 ALTENTRY(sys_sysenter_swapgs_sysexit)
1200 jmp tr_sysexit
1201 SET_SIZE(sys_sysenter_swapgs_sysexit)
1202 SET_SIZE(sys_sysenter)
1203 SET_SIZE(_sys_sysenter_post_swapgs)
1204 SET_SIZE(brand_sys_sysenter)
1205
1206 #endif /* __lint */
1207
1208 /*
1209 * This is the destination of the "int $T_SYSCALLINT" interrupt gate, used by
1210 * the generic i386 libc to do system calls. We do a small amount of setup
1211 * before jumping into the existing sys_syscall32 path.
1212 */
1213 #if defined(__lint)
1214
1215 /*ARGSUSED*/
1216 void
1217 sys_syscall_int()
1218 {}
1219
1220 #else /* __lint */
1221
1222 ENTRY_NP(brand_sys_syscall_int)
1223 SWAPGS /* kernel gsbase */
1224 XPV_TRAP_POP
1225 call smap_enable
1226 BRAND_CALLBACK(BRAND_CB_INT91, BRAND_URET_FROM_INTR_STACK())
1227 jmp nopop_syscall_int
1228
1229 ALTENTRY(sys_syscall_int)
1230 SWAPGS /* kernel gsbase */
1231 XPV_TRAP_POP
1232 call smap_enable
1233
1234 nopop_syscall_int:
1235 movq %gs:CPU_THREAD, %r15
1236 movq T_STACK(%r15), %rsp
1237 movl %eax, %eax
1238 /*
1239 * Set t_post_sys on this thread to force ourselves out via the slow
1240 * path. It might be possible at some later date to optimize this out
1241 * and use a faster return mechanism.
1242 */
1243 movb $1, T_POST_SYS(%r15)
1244 CLEAN_CS
1245 jmp _syscall32_save
1246 /*
1247 * There should be no instructions between this label and SWAPGS/IRET
1248 * or we could end up breaking branded zone support. See the usage of
1249 * this label in lx_brand_int80_callback and sn1_brand_int91_callback
1250 * for examples.
1251 *
1252 * We want to swapgs to maintain the invariant that all entries into
1253 * tr_iret_user are done on the user gsbase.
1254 */
1255 ALTENTRY(sys_sysint_swapgs_iret)
1256 SWAPGS
1257 jmp tr_iret_user
1258 /*NOTREACHED*/
1259 SET_SIZE(sys_sysint_swapgs_iret)
1260 SET_SIZE(sys_syscall_int)
1261 SET_SIZE(brand_sys_syscall_int)
1262
1263 #endif /* __lint */
1264
1265 /*
1266 * Legacy 32-bit applications and old libc implementations do lcalls;
1267 * we should never get here because the LDT entry containing the syscall
1268 * segment descriptor has the "segment present" bit cleared, which means
1269 * we end up processing those system calls in trap() via a not-present trap.
1270 *
1271 * We do it this way because a call gate unhelpfully does -nothing- to the
1272 * interrupt flag bit, so an interrupt can run us just after the lcall
1273 * completes, but just before the swapgs takes effect. Thus the INTR_PUSH and
1274 * INTR_POP paths would have to be slightly more complex to dance around
1275 * this problem, and end up depending explicitly on the first
1276 * instruction of this handler being either swapgs or cli.
1277 */
1278
1279 #if defined(__lint)
1280
1281 /*ARGSUSED*/
1282 void
1283 sys_lcall32()
1284 {}
1285
1286 #else /* __lint */
1287
1288 ENTRY_NP(sys_lcall32)
1289 SWAPGS /* kernel gsbase */
1290 pushq $0
1291 pushq %rbp
1292 movq %rsp, %rbp
1293 leaq __lcall_panic_str(%rip), %rdi
1294 xorl %eax, %eax
1295 call panic
1296 SET_SIZE(sys_lcall32)
1297
1298 __lcall_panic_str:
1299 .string "sys_lcall32: shouldn't be here!"
1300
1301 /*
1302 * Declare a uintptr_t which covers the entire pc range of syscall
1303 * handlers for the stack walkers that need this.
1304 */
1305 .align CPTRSIZE
1306 .globl _allsyscalls_size
1307 .type _allsyscalls_size, @object
1308 _allsyscalls_size:
1309 .NWORD . - _allsyscalls
1310 SET_SIZE(_allsyscalls_size)
1311
1312 #endif /* __lint */
1313
1314 /*
1315 * These are the thread context handlers for lwps using sysenter/sysexit.
1316 */
1317
1318 #if defined(__lint)
1319
1320 /*ARGSUSED*/
1321 void
1322 sep_save(void *ksp)
1323 {}
1324
1325 /*ARGSUSED*/
1326 void
1327 sep_restore(void *ksp)
1328 {}
1329
1330 #else /* __lint */
1331
1332 /*
1333 * setting this value to zero as we switch away causes the
1334 * stack-pointer-on-sysenter to be NULL, ensuring that we
1335 * don't silently corrupt another (preempted) thread stack
1336 * when running an lwp that (somehow) didn't get sep_restore'd
1337 */
1338 ENTRY_NP(sep_save)
1339 xorl %edx, %edx
1340 xorl %eax, %eax
1341 movl $MSR_INTC_SEP_ESP, %ecx
1342 wrmsr
1343 ret
1344 SET_SIZE(sep_save)
1345
1346 /*
1347 * Update the kernel stack pointer as we resume onto this cpu.
1348 */
1349 ENTRY_NP(sep_restore)
1350 movq %rdi, %rdx
1351 shrq $32, %rdx
1352 movl %edi, %eax
1353 movl $MSR_INTC_SEP_ESP, %ecx
1354 wrmsr
1355 ret
1356 SET_SIZE(sep_restore)
1357
1358 #endif /* __lint */