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--- old/usr/src/uts/i86pc/ml/syscall_asm_amd64.s
+++ new/usr/src/uts/i86pc/ml/syscall_asm_amd64.s
1 1 /*
2 2 * CDDL HEADER START
3 3 *
4 4 * The contents of this file are subject to the terms of the
5 5 * Common Development and Distribution License (the "License").
6 6 * You may not use this file except in compliance with the License.
7 7 *
8 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 9 * or http://www.opensolaris.org/os/licensing.
10 10 * See the License for the specific language governing permissions
11 11 * and limitations under the License.
12 12 *
13 13 * When distributing Covered Code, include this CDDL HEADER in each
14 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 15 * If applicable, add the following below this CDDL HEADER, with the
16 16 * fields enclosed by brackets "[]" replaced with your own identifying
17 17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 18 *
19 19 * CDDL HEADER END
20 20 */
21 21 /*
22 22 * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
23 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved.
24 24 */
25 25
26 26 #include <sys/asm_linkage.h>
27 27 #include <sys/asm_misc.h>
28 28 #include <sys/regset.h>
29 29 #include <sys/privregs.h>
30 30 #include <sys/psw.h>
31 31 #include <sys/machbrand.h>
32 32
33 33 #if defined(__lint)
34 34
35 35 #include <sys/types.h>
36 36 #include <sys/thread.h>
37 37 #include <sys/systm.h>
38 38
39 39 #else /* __lint */
40 40
41 41 #include <sys/segments.h>
42 42 #include <sys/pcb.h>
43 43 #include <sys/trap.h>
44 44 #include <sys/ftrace.h>
45 45 #include <sys/traptrace.h>
46 46 #include <sys/clock.h>
47 47 #include <sys/model.h>
48 48 #include <sys/panic.h>
49 49
50 50 #if defined(__xpv)
51 51 #include <sys/hypervisor.h>
52 52 #endif
53 53
54 54 #include "assym.h"
55 55
56 56 #endif /* __lint */
57 57
58 58 /*
59 59 * We implement five flavours of system call entry points
60 60 *
61 61 * - syscall/sysretq (amd64 generic)
62 62 * - syscall/sysretl (i386 plus SYSC bit)
63 63 * - sysenter/sysexit (i386 plus SEP bit)
64 64 * - int/iret (i386 generic)
65 65 * - lcall/iret (i386 generic)
66 66 *
67 67 * The current libc included in Solaris uses int/iret as the base unoptimized
68 68 * kernel entry method. Older libc implementations and legacy binaries may use
69 69 * the lcall call gate, so it must continue to be supported.
70 70 *
71 71 * System calls that use an lcall call gate are processed in trap() via a
72 72 * segment-not-present trap, i.e. lcalls are extremely slow(!).
73 73 *
74 74 * The basic pattern used in the 32-bit SYSC handler at this point in time is
75 75 * to have the bare minimum of assembler, and get to the C handlers as
76 76 * quickly as possible.
77 77 *
78 78 * The 64-bit handler is much closer to the sparcv9 handler; that's
79 79 * because of passing arguments in registers. The 32-bit world still
80 80 * passes arguments on the stack -- that makes that handler substantially
81 81 * more complex.
82 82 *
83 83 * The two handlers share a few code fragments which are broken
84 84 * out into preprocessor macros below.
85 85 *
86 86 * XX64 come back and speed all this up later. The 32-bit stuff looks
87 87 * especially easy to speed up the argument copying part ..
88 88 *
89 89 *
90 90 * Notes about segment register usage (c.f. the 32-bit kernel)
91 91 *
92 92 * In the 32-bit kernel, segment registers are dutifully saved and
93 93 * restored on all mode transitions because the kernel uses them directly.
94 94 * When the processor is running in 64-bit mode, segment registers are
95 95 * largely ignored.
96 96 *
97 97 * %cs and %ss
98 98 * controlled by the hardware mechanisms that make mode transitions
99 99 *
100 100 * The remaining segment registers have to either be pointing at a valid
101 101 * descriptor i.e. with the 'present' bit set, or they can NULL descriptors
102 102 *
103 103 * %ds and %es
104 104 * always ignored
105 105 *
106 106 * %fs and %gs
107 107 * fsbase and gsbase are used to control the place they really point at.
108 108 * The kernel only depends on %gs, and controls its own gsbase via swapgs
109 109 *
110 110 * Note that loading segment registers is still costly because the GDT
111 111 * lookup still happens (this is because the hardware can't know that we're
112 112 * not setting up these segment registers for a 32-bit program). Thus we
113 113 * avoid doing this in the syscall path, and defer them to lwp context switch
114 114 * handlers, so the register values remain virtualized to the lwp.
115 115 */
116 116
117 117 #if defined(SYSCALLTRACE)
118 118 #define ORL_SYSCALLTRACE(r32) \
119 119 orl syscalltrace(%rip), r32
120 120 #else
121 121 #define ORL_SYSCALLTRACE(r32)
122 122 #endif
123 123
124 124 /*
125 125 * In the 32-bit kernel, we do absolutely nothing before getting into the
126 126 * brand callback checks. In 64-bit land, we do swapgs and then come here.
127 127 * We assume that the %rsp- and %r15-stashing fields in the CPU structure
128 128 * are still unused.
129 129 *
130 130 * Check if a brand_mach_ops callback is defined for the specified callback_id
131 131 * type. If so invoke it with the kernel's %gs value loaded and the following
132 132 * data on the stack:
133 133 *
134 134 * stack: --------------------------------------
135 135 * 32 | callback pointer |
136 136 * | 24 | user (or interrupt) stack pointer |
137 137 * | 16 | lwp pointer |
138 138 * v 8 | userland return address |
139 139 * 0 | callback wrapper return addr |
140 140 * --------------------------------------
141 141 *
142 142 * Since we're pushing the userland return address onto the kernel stack
143 143 * we need to get that address without accessing the user's stack (since we
144 144 * can't trust that data). There are different ways to get the userland
145 145 * return address depending on how the syscall trap was made:
146 146 *
147 147 * a) For sys_syscall and sys_syscall32 the return address is in %rcx.
148 148 * b) For sys_sysenter the return address is in %rdx.
149 149 * c) For sys_int80 and sys_syscall_int (int91), upon entry into the macro,
150 150 * the stack pointer points at the state saved when we took the interrupt:
151 151 * ------------------------
152 152 * | | user's %ss |
153 153 * | | user's %esp |
154 154 * | | EFLAGS register |
155 155 * v | user's %cs |
156 156 * | user's %eip |
157 157 * ------------------------
158 158 *
159 159 * The 2nd parameter to the BRAND_CALLBACK macro is either the
160 160 * BRAND_URET_FROM_REG or BRAND_URET_FROM_INTR_STACK macro. These macros are
161 161 * used to generate the proper code to get the userland return address for
162 162 * each syscall entry point.
163 163 *
164 164 * The interface to the brand callbacks on the 64-bit kernel assumes %r15
165 165 * is available as a scratch register within the callback. If the callback
166 166 * returns within the kernel then this macro will restore %r15. If the
167 167 * callback is going to return directly to userland then it should restore
168 168 * %r15 before returning to userland.
169 169 */
170 170 #define BRAND_URET_FROM_REG(rip_reg) \
171 171 pushq rip_reg /* push the return address */
172 172
173 173 /*
174 174 * The interrupt stack pointer we saved on entry to the BRAND_CALLBACK macro
175 175 * is currently pointing at the user return address (%eip).
176 176 */
177 177 #define BRAND_URET_FROM_INTR_STACK() \
178 178 movq %gs:CPU_RTMP_RSP, %r15 /* grab the intr. stack pointer */ ;\
179 179 pushq (%r15) /* push the return address */
180 180
181 181 #define BRAND_CALLBACK(callback_id, push_userland_ret) \
182 182 movq %rsp, %gs:CPU_RTMP_RSP /* save the stack pointer */ ;\
183 183 movq %r15, %gs:CPU_RTMP_R15 /* save %r15 */ ;\
184 184 movq %gs:CPU_THREAD, %r15 /* load the thread pointer */ ;\
185 185 movq T_STACK(%r15), %rsp /* switch to the kernel stack */ ;\
186 186 subq $16, %rsp /* save space for 2 pointers */ ;\
187 187 pushq %r14 /* save %r14 */ ;\
188 188 movq %gs:CPU_RTMP_RSP, %r14 ;\
189 189 movq %r14, 8(%rsp) /* stash the user stack pointer */ ;\
190 190 popq %r14 /* restore %r14 */ ;\
191 191 movq T_LWP(%r15), %r15 /* load the lwp pointer */ ;\
192 192 pushq %r15 /* push the lwp pointer */ ;\
193 193 movq LWP_PROCP(%r15), %r15 /* load the proc pointer */ ;\
194 194 movq P_BRAND(%r15), %r15 /* load the brand pointer */ ;\
195 195 movq B_MACHOPS(%r15), %r15 /* load the machops pointer */ ;\
196 196 movq _CONST(_MUL(callback_id, CPTRSIZE))(%r15), %r15 ;\
197 197 cmpq $0, %r15 ;\
198 198 je 1f ;\
199 199 movq %r15, 16(%rsp) /* save the callback pointer */ ;\
200 200 push_userland_ret /* push the return address */ ;\
201 201 call *24(%rsp) /* call callback */ ;\
202 202 1: movq %gs:CPU_RTMP_R15, %r15 /* restore %r15 */ ;\
203 203 movq %gs:CPU_RTMP_RSP, %rsp /* restore the stack pointer */
204 204
205 205 #define MSTATE_TRANSITION(from, to) \
206 206 movl $from, %edi; \
207 207 movl $to, %esi; \
208 208 call syscall_mstate
209 209
210 210 /*
211 211 * Check to see if a simple (direct) return is possible i.e.
212 212 *
213 213 * if (t->t_post_sys_ast | syscalltrace |
214 214 * lwp->lwp_pcb.pcb_rupdate == 1)
215 215 * do full version ;
216 216 *
217 217 * Preconditions:
218 218 * - t is curthread
219 219 * Postconditions:
220 220 * - condition code NE is set if post-sys is too complex
221 221 * - rtmp is zeroed if it isn't (we rely on this!)
222 222 * - ltmp is smashed
223 223 */
224 224 #define CHECK_POSTSYS_NE(t, ltmp, rtmp) \
225 225 movq T_LWP(t), ltmp; \
226 226 movzbl PCB_RUPDATE(ltmp), rtmp; \
227 227 ORL_SYSCALLTRACE(rtmp); \
228 228 orl T_POST_SYS_AST(t), rtmp; \
229 229 cmpl $0, rtmp
230 230
231 231 /*
232 232 * Fix up the lwp, thread, and eflags for a successful return
233 233 *
234 234 * Preconditions:
235 235 * - zwreg contains zero
236 236 */
237 237 #define SIMPLE_SYSCALL_POSTSYS(t, lwp, zwreg) \
238 238 movb $LWP_USER, LWP_STATE(lwp); \
239 239 movw zwreg, T_SYSNUM(t); \
240 240 andb $_CONST(0xffff - PS_C), REGOFF_RFL(%rsp)
241 241
242 242 /*
243 243 * ASSERT(lwptoregs(lwp) == rp);
244 244 *
245 245 * This may seem obvious, but very odd things happen if this
246 246 * assertion is false
247 247 *
248 248 * Preconditions:
249 249 * (%rsp is ready for normal call sequence)
250 250 * Postconditions (if assertion is true):
251 251 * %r11 is smashed
252 252 *
253 253 * ASSERT(rp->r_cs == descnum)
254 254 *
255 255 * The code selector is written into the regs structure when the
256 256 * lwp stack is created. We use this ASSERT to validate that
257 257 * the regs structure really matches how we came in.
258 258 *
259 259 * Preconditions:
260 260 * (%rsp is ready for normal call sequence)
261 261 * Postconditions (if assertion is true):
262 262 * -none-
263 263 *
264 264 * ASSERT(lwp->lwp_pcb.pcb_rupdate == 0);
265 265 *
266 266 * If this is false, it meant that we returned to userland without
267 267 * updating the segment registers as we were supposed to.
268 268 *
269 269 * Note that we must ensure no interrupts or other traps intervene
270 270 * between entering privileged mode and performing the assertion,
271 271 * otherwise we may perform a context switch on the thread, which
272 272 * will end up setting pcb_rupdate to 1 again.
273 273 */
274 274 #if defined(DEBUG)
275 275
276 276 #if !defined(__lint)
277 277
278 278 __lwptoregs_msg:
279 279 .string "syscall_asm_amd64.s:%d lwptoregs(%p) [%p] != rp [%p]"
280 280
281 281 __codesel_msg:
282 282 .string "syscall_asm_amd64.s:%d rp->r_cs [%ld] != %ld"
283 283
284 284 __no_rupdate_msg:
285 285 .string "syscall_asm_amd64.s:%d lwp %p, pcb_rupdate != 0"
286 286
287 287 #endif /* !__lint */
288 288
289 289 #define ASSERT_LWPTOREGS(lwp, rp) \
290 290 movq LWP_REGS(lwp), %r11; \
291 291 cmpq rp, %r11; \
292 292 je 7f; \
293 293 leaq __lwptoregs_msg(%rip), %rdi; \
294 294 movl $__LINE__, %esi; \
295 295 movq lwp, %rdx; \
296 296 movq %r11, %rcx; \
297 297 movq rp, %r8; \
298 298 xorl %eax, %eax; \
299 299 call panic; \
300 300 7:
301 301
302 302 #define ASSERT_NO_RUPDATE_PENDING(lwp) \
303 303 testb $0x1, PCB_RUPDATE(lwp); \
304 304 je 8f; \
305 305 movq lwp, %rdx; \
306 306 leaq __no_rupdate_msg(%rip), %rdi; \
307 307 movl $__LINE__, %esi; \
308 308 xorl %eax, %eax; \
309 309 call panic; \
310 310 8:
311 311
312 312 #else
313 313 #define ASSERT_LWPTOREGS(lwp, rp)
314 314 #define ASSERT_NO_RUPDATE_PENDING(lwp)
315 315 #endif
316 316
317 317 /*
318 318 * Do the traptrace thing and restore any registers we used
319 319 * in situ. Assumes that %rsp is pointing at the base of
320 320 * the struct regs, obviously ..
321 321 */
322 322 #ifdef TRAPTRACE
323 323 #define SYSCALL_TRAPTRACE(ttype) \
324 324 TRACE_PTR(%rdi, %rbx, %ebx, %rcx, ttype); \
325 325 TRACE_REGS(%rdi, %rsp, %rbx, %rcx); \
326 326 TRACE_STAMP(%rdi); /* rdtsc clobbers %eax, %edx */ \
327 327 movq REGOFF_RAX(%rsp), %rax; \
328 328 movq REGOFF_RBX(%rsp), %rbx; \
329 329 movq REGOFF_RCX(%rsp), %rcx; \
330 330 movq REGOFF_RDX(%rsp), %rdx; \
331 331 movl %eax, TTR_SYSNUM(%rdi); \
332 332 movq REGOFF_RDI(%rsp), %rdi
333 333
334 334 #define SYSCALL_TRAPTRACE32(ttype) \
335 335 SYSCALL_TRAPTRACE(ttype); \
336 336 /* paranoia: clean the top 32-bits of the registers */ \
337 337 orl %eax, %eax; \
338 338 orl %ebx, %ebx; \
339 339 orl %ecx, %ecx; \
340 340 orl %edx, %edx; \
341 341 orl %edi, %edi
342 342 #else /* TRAPTRACE */
343 343 #define SYSCALL_TRAPTRACE(ttype)
344 344 #define SYSCALL_TRAPTRACE32(ttype)
345 345 #endif /* TRAPTRACE */
346 346
347 347 /*
348 348 * The 64-bit libc syscall wrapper does this:
349 349 *
350 350 * fn(<args>)
351 351 * {
352 352 * movq %rcx, %r10 -- because syscall smashes %rcx
353 353 * movl $CODE, %eax
354 354 * syscall
355 355 * <error processing>
356 356 * }
357 357 *
358 358 * Thus when we come into the kernel:
359 359 *
360 360 * %rdi, %rsi, %rdx, %r10, %r8, %r9 contain first six args
361 361 * %rax is the syscall number
362 362 * %r12-%r15 contain caller state
363 363 *
364 364 * The syscall instruction arranges that:
365 365 *
366 366 * %rcx contains the return %rip
367 367 * %r11d contains bottom 32-bits of %rflags
368 368 * %rflags is masked (as determined by the SFMASK msr)
369 369 * %cs is set to UCS_SEL (as determined by the STAR msr)
370 370 * %ss is set to UDS_SEL (as determined by the STAR msr)
371 371 * %rip is set to sys_syscall (as determined by the LSTAR msr)
372 372 *
373 373 * Or in other words, we have no registers available at all.
374 374 * Only swapgs can save us!
375 375 *
376 376 * Under the hypervisor, the swapgs has happened already. However, the
377 377 * state of the world is very different from that we're familiar with.
378 378 *
379 379 * In particular, we have a stack structure like that for interrupt
380 380 * gates, except that the %cs and %ss registers are modified for reasons
381 381 * that are not entirely clear. Critically, the %rcx/%r11 values do
382 382 * *not* reflect the usage of those registers under a 'real' syscall[1];
383 383 * the stack, therefore, looks like this:
384 384 *
385 385 * 0x0(rsp) potentially junk %rcx
386 386 * 0x8(rsp) potentially junk %r11
387 387 * 0x10(rsp) user %rip
388 388 * 0x18(rsp) modified %cs
389 389 * 0x20(rsp) user %rflags
390 390 * 0x28(rsp) user %rsp
391 391 * 0x30(rsp) modified %ss
392 392 *
393 393 *
394 394 * and before continuing on, we must load the %rip into %rcx and the
395 395 * %rflags into %r11.
396 396 *
397 397 * [1] They used to, and we relied on it, but this was broken in 3.1.1.
398 398 * Sigh.
399 399 */
400 400 #if defined(__xpv)
401 401 #define XPV_SYSCALL_PROD \
402 402 movq 0x10(%rsp), %rcx; \
403 403 movq 0x20(%rsp), %r11; \
404 404 movq 0x28(%rsp), %rsp
405 405 #else
406 406 #define XPV_SYSCALL_PROD /* nothing */
407 407 #endif
408 408
409 409 #if defined(__lint)
410 410
411 411 /*ARGSUSED*/
412 412 void
413 413 sys_syscall()
414 414 {}
415 415
416 416 void
417 417 _allsyscalls()
418 418 {}
419 419
420 420 size_t _allsyscalls_size;
421 421
422 422 #else /* __lint */
423 423
424 424 ENTRY_NP2(brand_sys_syscall,_allsyscalls)
425 425 SWAPGS /* kernel gsbase */
426 426 XPV_SYSCALL_PROD
427 427 BRAND_CALLBACK(BRAND_CB_SYSCALL, BRAND_URET_FROM_REG(%rcx))
428 428 jmp noprod_sys_syscall
429 429
430 430 ALTENTRY(sys_syscall)
431 431 SWAPGS /* kernel gsbase */
432 432 XPV_SYSCALL_PROD
433 433
434 434 noprod_sys_syscall:
435 435 movq %r15, %gs:CPU_RTMP_R15
436 436 movq %rsp, %gs:CPU_RTMP_RSP
437 437
438 438 movq %gs:CPU_THREAD, %r15
439 439 movq T_STACK(%r15), %rsp /* switch from user to kernel stack */
440 440
441 441 ASSERT_UPCALL_MASK_IS_SET
442 442
443 443 movl $UCS_SEL, REGOFF_CS(%rsp)
444 444 movq %rcx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */
445 445 movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */
446 446 movl $UDS_SEL, REGOFF_SS(%rsp)
447 447
448 448 movl %eax, %eax /* wrapper: sysc# -> %eax */
449 449 movq %rdi, REGOFF_RDI(%rsp)
450 450 movq %rsi, REGOFF_RSI(%rsp)
451 451 movq %rdx, REGOFF_RDX(%rsp)
452 452 movq %r10, REGOFF_RCX(%rsp) /* wrapper: %rcx -> %r10 */
453 453 movq %r10, %rcx /* arg[3] for direct calls */
454 454
455 455 movq %r8, REGOFF_R8(%rsp)
456 456 movq %r9, REGOFF_R9(%rsp)
457 457 movq %rax, REGOFF_RAX(%rsp)
458 458 movq %rbx, REGOFF_RBX(%rsp)
459 459
460 460 movq %rbp, REGOFF_RBP(%rsp)
461 461 movq %r10, REGOFF_R10(%rsp)
462 462 movq %gs:CPU_RTMP_RSP, %r11
463 463 movq %r11, REGOFF_RSP(%rsp)
464 464 movq %r12, REGOFF_R12(%rsp)
465 465
466 466 movq %r13, REGOFF_R13(%rsp)
467 467 movq %r14, REGOFF_R14(%rsp)
468 468 movq %gs:CPU_RTMP_R15, %r10
469 469 movq %r10, REGOFF_R15(%rsp)
470 470 movq $0, REGOFF_SAVFP(%rsp)
471 471 movq $0, REGOFF_SAVPC(%rsp)
472 472
473 473 /*
474 474 * Copy these registers here in case we end up stopped with
475 475 * someone (like, say, /proc) messing with our register state.
476 476 * We don't -restore- them unless we have to in update_sregs.
477 477 *
478 478 * Since userland -can't- change fsbase or gsbase directly,
479 479 * and capturing them involves two serializing instructions,
480 480 * we don't bother to capture them here.
481 481 */
482 482 xorl %ebx, %ebx
483 483 movw %ds, %bx
484 484 movq %rbx, REGOFF_DS(%rsp)
485 485 movw %es, %bx
486 486 movq %rbx, REGOFF_ES(%rsp)
487 487 movw %fs, %bx
488 488 movq %rbx, REGOFF_FS(%rsp)
489 489 movw %gs, %bx
490 490 movq %rbx, REGOFF_GS(%rsp)
491 491
492 492 /*
493 493 * Machine state saved in the regs structure on the stack
494 494 * First six args in %rdi, %rsi, %rdx, %rcx, %r8, %r9
495 495 * %eax is the syscall number
496 496 * %rsp is the thread's stack, %r15 is curthread
497 497 * REG_RSP(%rsp) is the user's stack
498 498 */
499 499
500 500 SYSCALL_TRAPTRACE($TT_SYSC64)
501 501
502 502 movq %rsp, %rbp
503 503
504 504 movq T_LWP(%r15), %r14
505 505 ASSERT_NO_RUPDATE_PENDING(%r14)
506 506 ENABLE_INTR_FLAGS
507 507
508 508 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
509 509 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */
510 510
511 511 ASSERT_LWPTOREGS(%r14, %rsp)
512 512
513 513 movb $LWP_SYS, LWP_STATE(%r14)
514 514 incq LWP_RU_SYSC(%r14)
515 515 movb $NORMALRETURN, LWP_EOSYS(%r14)
516 516
517 517 incq %gs:CPU_STATS_SYS_SYSCALL
518 518
519 519 movw %ax, T_SYSNUM(%r15)
520 520 movzbl T_PRE_SYS(%r15), %ebx
521 521 ORL_SYSCALLTRACE(%ebx)
522 522 testl %ebx, %ebx
523 523 jne _syscall_pre
524 524
525 525 _syscall_invoke:
526 526 movq REGOFF_RDI(%rbp), %rdi
527 527 movq REGOFF_RSI(%rbp), %rsi
528 528 movq REGOFF_RDX(%rbp), %rdx
529 529 movq REGOFF_RCX(%rbp), %rcx
530 530 movq REGOFF_R8(%rbp), %r8
531 531 movq REGOFF_R9(%rbp), %r9
532 532
533 533 cmpl $NSYSCALL, %eax
534 534 jae _syscall_ill
535 535 shll $SYSENT_SIZE_SHIFT, %eax
536 536 leaq sysent(%rax), %rbx
537 537
538 538 call *SY_CALLC(%rbx)
539 539
540 540 movq %rax, %r12
541 541 movq %rdx, %r13
542 542
543 543 /*
544 544 * If the handler returns two ints, then we need to split the
545 545 * 64-bit return value into two 32-bit values.
546 546 */
547 547 testw $SE_32RVAL2, SY_FLAGS(%rbx)
548 548 je 5f
549 549 movq %r12, %r13
550 550 shrq $32, %r13 /* upper 32-bits into %edx */
551 551 movl %r12d, %r12d /* lower 32-bits into %eax */
552 552 5:
553 553 /*
554 554 * Optimistically assume that there's no post-syscall
555 555 * work to do. (This is to avoid having to call syscall_mstate()
556 556 * with interrupts disabled)
557 557 */
558 558 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
559 559
560 560 /*
561 561 * We must protect ourselves from being descheduled here;
562 562 * If we were, and we ended up on another cpu, or another
563 563 * lwp got in ahead of us, it could change the segment
564 564 * registers without us noticing before we return to userland.
565 565 */
566 566 CLI(%r14)
567 567 CHECK_POSTSYS_NE(%r15, %r14, %ebx)
568 568 jne _syscall_post
569 569
570 570 /*
571 571 * We need to protect ourselves against non-canonical return values
572 572 * because Intel doesn't check for them on sysret (AMD does). Canonical
573 573 * addresses on current amd64 processors only use 48-bits for VAs; an
574 574 * address is canonical if all upper bits (47-63) are identical. If we
575 575 * find a non-canonical %rip, we opt to go through the full
576 576 * _syscall_post path which takes us into an iretq which is not
577 577 * susceptible to the same problems sysret is.
578 578 *
579 579 * We're checking for a canonical address by first doing an arithmetic
580 580 * shift. This will fill in the remaining bits with the value of bit 63.
581 581 * If the address were canonical, the register would now have either all
582 582 * zeroes or all ones in it. Therefore we add one (inducing overflow)
583 583 * and compare against 1. A canonical address will either be zero or one
584 584 * at this point, hence the use of ja.
585 585 *
586 586 * At this point, r12 and r13 have the return value so we can't use
587 587 * those registers.
588 588 */
589 589 movq REGOFF_RIP(%rsp), %rcx
590 590 sarq $47, %rcx
591 591 incq %rcx
592 592 cmpq $1, %rcx
593 593 ja _syscall_post
594 594
595 595
596 596 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
597 597
598 598 movq %r12, REGOFF_RAX(%rsp)
599 599 movq %r13, REGOFF_RDX(%rsp)
600 600
601 601 /*
602 602 * To get back to userland, we need the return %rip in %rcx and
603 603 * the return %rfl in %r11d. The sysretq instruction also arranges
604 604 * to fix up %cs and %ss; everything else is our responsibility.
605 605 */
606 606 movq REGOFF_RDI(%rsp), %rdi
607 607 movq REGOFF_RSI(%rsp), %rsi
608 608 movq REGOFF_RDX(%rsp), %rdx
609 609 /* %rcx used to restore %rip value */
610 610
611 611 movq REGOFF_R8(%rsp), %r8
612 612 movq REGOFF_R9(%rsp), %r9
613 613 movq REGOFF_RAX(%rsp), %rax
614 614 movq REGOFF_RBX(%rsp), %rbx
615 615
616 616 movq REGOFF_RBP(%rsp), %rbp
617 617 movq REGOFF_R10(%rsp), %r10
618 618 /* %r11 used to restore %rfl value */
619 619 movq REGOFF_R12(%rsp), %r12
620 620
621 621 movq REGOFF_R13(%rsp), %r13
622 622 movq REGOFF_R14(%rsp), %r14
623 623 movq REGOFF_R15(%rsp), %r15
624 624
625 625 movq REGOFF_RIP(%rsp), %rcx
626 626 movl REGOFF_RFL(%rsp), %r11d
627 627
628 628 #if defined(__xpv)
629 629 addq $REGOFF_RIP, %rsp
630 630 #else
631 631 movq REGOFF_RSP(%rsp), %rsp
632 632 #endif
633 633
634 634 /*
635 635 * There can be no instructions between the ALTENTRY below and
636 636 * SYSRET or we could end up breaking brand support. See label usage
637 637 * in sn1_brand_syscall_callback for an example.
638 638 */
639 639 ASSERT_UPCALL_MASK_IS_SET
640 640 #if defined(__xpv)
641 641 SYSRETQ
642 642 ALTENTRY(nopop_sys_syscall_swapgs_sysretq)
643 643
644 644 /*
645 645 * We can only get here after executing a brand syscall
646 646 * interposition callback handler and simply need to
647 647 * "sysretq" back to userland. On the hypervisor this
648 648 * involves the iret hypercall which requires us to construct
649 649 * just enough of the stack needed for the hypercall.
650 650 * (rip, cs, rflags, rsp, ss).
651 651 */
652 652 movq %rsp, %gs:CPU_RTMP_RSP /* save user's rsp */
653 653 movq %gs:CPU_THREAD, %r11
654 654 movq T_STACK(%r11), %rsp
655 655
656 656 movq %rcx, REGOFF_RIP(%rsp)
657 657 movl $UCS_SEL, REGOFF_CS(%rsp)
658 658 movq %gs:CPU_RTMP_RSP, %r11
659 659 movq %r11, REGOFF_RSP(%rsp)
660 660 pushfq
661 661 popq %r11 /* hypercall enables ints */
662 662 movq %r11, REGOFF_RFL(%rsp)
663 663 movl $UDS_SEL, REGOFF_SS(%rsp)
664 664 addq $REGOFF_RIP, %rsp
665 665 /*
666 666 * XXPV: see comment in SYSRETQ definition for future optimization
667 667 * we could take.
668 668 */
669 669 ASSERT_UPCALL_MASK_IS_SET
670 670 SYSRETQ
671 671 #else
672 672 ALTENTRY(nopop_sys_syscall_swapgs_sysretq)
673 673 SWAPGS /* user gsbase */
674 674 SYSRETQ
675 675 #endif
676 676 /*NOTREACHED*/
677 677 SET_SIZE(nopop_sys_syscall_swapgs_sysretq)
678 678
679 679 _syscall_pre:
680 680 call pre_syscall
681 681 movl %eax, %r12d
682 682 testl %eax, %eax
683 683 jne _syscall_post_call
684 684 /*
685 685 * Didn't abort, so reload the syscall args and invoke the handler.
686 686 */
687 687 movzwl T_SYSNUM(%r15), %eax
688 688 jmp _syscall_invoke
689 689
690 690 _syscall_ill:
691 691 call nosys
692 692 movq %rax, %r12
693 693 movq %rdx, %r13
694 694 jmp _syscall_post_call
695 695
696 696 _syscall_post:
697 697 STI
698 698 /*
699 699 * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM
700 700 * so that we can account for the extra work it takes us to finish.
701 701 */
702 702 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
703 703 _syscall_post_call:
704 704 movq %r12, %rdi
705 705 movq %r13, %rsi
706 706 call post_syscall
707 707 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
708 708 jmp _sys_rtt
709 709 SET_SIZE(sys_syscall)
710 710 SET_SIZE(brand_sys_syscall)
711 711
712 712 #endif /* __lint */
713 713
714 714 #if defined(__lint)
715 715
716 716 /*ARGSUSED*/
717 717 void
718 718 sys_syscall32()
719 719 {}
720 720
721 721 #else /* __lint */
722 722
723 723 ENTRY_NP(brand_sys_syscall32)
724 724 SWAPGS /* kernel gsbase */
725 725 XPV_TRAP_POP
726 726 BRAND_CALLBACK(BRAND_CB_SYSCALL32, BRAND_URET_FROM_REG(%rcx))
727 727 jmp nopop_sys_syscall32
728 728
729 729 ALTENTRY(sys_syscall32)
730 730 SWAPGS /* kernel gsbase */
731 731 XPV_TRAP_POP
732 732
733 733 nopop_sys_syscall32:
734 734 movl %esp, %r10d
735 735 movq %gs:CPU_THREAD, %r15
736 736 movq T_STACK(%r15), %rsp
737 737 movl %eax, %eax
738 738
739 739 movl $U32CS_SEL, REGOFF_CS(%rsp)
740 740 movl %ecx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */
741 741 movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */
742 742 movq %r10, REGOFF_RSP(%rsp)
743 743 movl $UDS_SEL, REGOFF_SS(%rsp)
744 744
745 745 _syscall32_save:
746 746 movl %edi, REGOFF_RDI(%rsp)
747 747 movl %esi, REGOFF_RSI(%rsp)
748 748 movl %ebp, REGOFF_RBP(%rsp)
749 749 movl %ebx, REGOFF_RBX(%rsp)
750 750 movl %edx, REGOFF_RDX(%rsp)
751 751 movl %ecx, REGOFF_RCX(%rsp)
752 752 movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */
753 753 movq $0, REGOFF_SAVFP(%rsp)
754 754 movq $0, REGOFF_SAVPC(%rsp)
755 755
756 756 /*
757 757 * Copy these registers here in case we end up stopped with
758 758 * someone (like, say, /proc) messing with our register state.
759 759 * We don't -restore- them unless we have to in update_sregs.
760 760 *
761 761 * Since userland -can't- change fsbase or gsbase directly,
762 762 * we don't bother to capture them here.
763 763 */
764 764 xorl %ebx, %ebx
765 765 movw %ds, %bx
766 766 movq %rbx, REGOFF_DS(%rsp)
767 767 movw %es, %bx
768 768 movq %rbx, REGOFF_ES(%rsp)
769 769 movw %fs, %bx
770 770 movq %rbx, REGOFF_FS(%rsp)
771 771 movw %gs, %bx
772 772 movq %rbx, REGOFF_GS(%rsp)
773 773
774 774 /*
775 775 * Application state saved in the regs structure on the stack
776 776 * %eax is the syscall number
777 777 * %rsp is the thread's stack, %r15 is curthread
778 778 * REG_RSP(%rsp) is the user's stack
779 779 */
780 780
781 781 SYSCALL_TRAPTRACE32($TT_SYSC)
782 782
783 783 movq %rsp, %rbp
784 784
785 785 movq T_LWP(%r15), %r14
786 786 ASSERT_NO_RUPDATE_PENDING(%r14)
787 787
788 788 ENABLE_INTR_FLAGS
789 789
790 790 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
791 791 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */
792 792
793 793 ASSERT_LWPTOREGS(%r14, %rsp)
794 794
795 795 incq %gs:CPU_STATS_SYS_SYSCALL
796 796
797 797 /*
798 798 * Make some space for MAXSYSARGS (currently 8) 32-bit args placed
799 799 * into 64-bit (long) arg slots, maintaining 16 byte alignment. Or
800 800 * more succinctly:
801 801 *
802 802 * SA(MAXSYSARGS * sizeof (long)) == 64
803 803 */
804 804 #define SYS_DROP 64 /* drop for args */
805 805 subq $SYS_DROP, %rsp
806 806 movb $LWP_SYS, LWP_STATE(%r14)
807 807 movq %r15, %rdi
808 808 movq %rsp, %rsi
809 809 call syscall_entry
810 810
811 811 /*
812 812 * Fetch the arguments copied onto the kernel stack and put
813 813 * them in the right registers to invoke a C-style syscall handler.
814 814 * %rax contains the handler address.
815 815 *
816 816 * Ideas for making all this go faster of course include simply
817 817 * forcibly fetching 6 arguments from the user stack under lofault
818 818 * protection, reverting to copyin_args only when watchpoints
819 819 * are in effect.
820 820 *
821 821 * (If we do this, make sure that exec and libthread leave
822 822 * enough space at the top of the stack to ensure that we'll
823 823 * never do a fetch from an invalid page.)
824 824 *
825 825 * Lots of ideas here, but they won't really help with bringup B-)
826 826 * Correctness can't wait, performance can wait a little longer ..
827 827 */
828 828
829 829 movq %rax, %rbx
830 830 movl 0(%rsp), %edi
831 831 movl 8(%rsp), %esi
832 832 movl 0x10(%rsp), %edx
833 833 movl 0x18(%rsp), %ecx
834 834 movl 0x20(%rsp), %r8d
835 835 movl 0x28(%rsp), %r9d
836 836
837 837 call *SY_CALLC(%rbx)
838 838
839 839 movq %rbp, %rsp /* pop the args */
840 840
841 841 /*
842 842 * amd64 syscall handlers -always- return a 64-bit value in %rax.
843 843 * On the 32-bit kernel, they always return that value in %eax:%edx
844 844 * as required by the 32-bit ABI.
845 845 *
846 846 * Simulate the same behaviour by unconditionally splitting the
847 847 * return value in the same way.
848 848 */
849 849 movq %rax, %r13
850 850 shrq $32, %r13 /* upper 32-bits into %edx */
851 851 movl %eax, %r12d /* lower 32-bits into %eax */
852 852
853 853 /*
854 854 * Optimistically assume that there's no post-syscall
855 855 * work to do. (This is to avoid having to call syscall_mstate()
856 856 * with interrupts disabled)
857 857 */
858 858 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
859 859
860 860 /*
861 861 * We must protect ourselves from being descheduled here;
862 862 * If we were, and we ended up on another cpu, or another
863 863 * lwp got in ahead of us, it could change the segment
864 864 * registers without us noticing before we return to userland.
865 865 */
866 866 CLI(%r14)
867 867 CHECK_POSTSYS_NE(%r15, %r14, %ebx)
868 868 jne _full_syscall_postsys32
869 869 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
870 870
871 871 /*
872 872 * To get back to userland, we need to put the return %rip in %rcx and
873 873 * the return %rfl in %r11d. The sysret instruction also arranges
874 874 * to fix up %cs and %ss; everything else is our responsibility.
875 875 */
876 876
877 877 movl %r12d, %eax /* %eax: rval1 */
878 878 movl REGOFF_RBX(%rsp), %ebx
879 879 /* %ecx used for return pointer */
880 880 movl %r13d, %edx /* %edx: rval2 */
881 881 movl REGOFF_RBP(%rsp), %ebp
882 882 movl REGOFF_RSI(%rsp), %esi
883 883 movl REGOFF_RDI(%rsp), %edi
884 884
885 885 movl REGOFF_RFL(%rsp), %r11d /* %r11 -> eflags */
886 886 movl REGOFF_RIP(%rsp), %ecx /* %ecx -> %eip */
887 887 movl REGOFF_RSP(%rsp), %esp
888 888
889 889 ASSERT_UPCALL_MASK_IS_SET
890 890 ALTENTRY(nopop_sys_syscall32_swapgs_sysretl)
891 891 SWAPGS /* user gsbase */
892 892 SYSRETL
893 893 SET_SIZE(nopop_sys_syscall32_swapgs_sysretl)
894 894 /*NOTREACHED*/
895 895
896 896 _full_syscall_postsys32:
897 897 STI
898 898 /*
899 899 * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM
900 900 * so that we can account for the extra work it takes us to finish.
901 901 */
902 902 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
903 903 movq %r15, %rdi
904 904 movq %r12, %rsi /* rval1 - %eax */
905 905 movq %r13, %rdx /* rval2 - %edx */
906 906 call syscall_exit
907 907 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
908 908 jmp _sys_rtt
909 909 SET_SIZE(sys_syscall32)
910 910 SET_SIZE(brand_sys_syscall32)
911 911
912 912 #endif /* __lint */
913 913
914 914 /*
915 915 * System call handler via the sysenter instruction
916 916 * Used only for 32-bit system calls on the 64-bit kernel.
917 917 *
918 918 * The caller in userland has arranged that:
919 919 *
920 920 * - %eax contains the syscall number
921 921 * - %ecx contains the user %esp
922 922 * - %edx contains the return %eip
923 923 * - the user stack contains the args to the syscall
924 924 *
925 925 * Hardware and (privileged) initialization code have arranged that by
926 926 * the time the sysenter instructions completes:
927 927 *
928 928 * - %rip is pointing to sys_sysenter (below).
929 929 * - %cs and %ss are set to kernel text and stack (data) selectors.
930 930 * - %rsp is pointing at the lwp's stack
931 931 * - interrupts have been disabled.
932 932 *
933 933 * Note that we are unable to return both "rvals" to userland with
934 934 * this call, as %edx is used by the sysexit instruction.
935 935 *
936 936 * One final complication in this routine is its interaction with
937 937 * single-stepping in a debugger. For most of the system call mechanisms,
938 938 * the CPU automatically clears the single-step flag before we enter the
939 939 * kernel. The sysenter mechanism does not clear the flag, so a user
940 940 * single-stepping through a libc routine may suddenly find him/herself
941 941 * single-stepping through the kernel. To detect this, kmdb compares the
942 942 * trap %pc to the [brand_]sys_enter addresses on each single-step trap.
943 943 * If it finds that we have single-stepped to a sysenter entry point, it
944 944 * explicitly clears the flag and executes the sys_sysenter routine.
945 945 *
946 946 * One final complication in this final complication is the fact that we
947 947 * have two different entry points for sysenter: brand_sys_sysenter and
948 948 * sys_sysenter. If we enter at brand_sys_sysenter and start single-stepping
949 949 * through the kernel with kmdb, we will eventually hit the instruction at
950 950 * sys_sysenter. kmdb cannot distinguish between that valid single-step
951 951 * and the undesirable one mentioned above. To avoid this situation, we
952 952 * simply add a jump over the instruction at sys_sysenter to make it
953 953 * impossible to single-step to it.
954 954 */
955 955 #if defined(__lint)
956 956
957 957 void
958 958 sys_sysenter()
959 959 {}
960 960
961 961 #else /* __lint */
962 962
963 963 ENTRY_NP(brand_sys_sysenter)
964 964 SWAPGS /* kernel gsbase */
965 965 ALTENTRY(_brand_sys_sysenter_post_swapgs)
966 966 BRAND_CALLBACK(BRAND_CB_SYSENTER, BRAND_URET_FROM_REG(%rdx))
967 967 /*
968 968 * Jump over sys_sysenter to allow single-stepping as described
969 969 * above.
970 970 */
971 971 jmp _sys_sysenter_post_swapgs
972 972
973 973 ALTENTRY(sys_sysenter)
974 974 SWAPGS /* kernel gsbase */
975 975
976 976 ALTENTRY(_sys_sysenter_post_swapgs)
977 977 movq %gs:CPU_THREAD, %r15
978 978
979 979 movl $U32CS_SEL, REGOFF_CS(%rsp)
980 980 movl %ecx, REGOFF_RSP(%rsp) /* wrapper: %esp -> %ecx */
981 981 movl %edx, REGOFF_RIP(%rsp) /* wrapper: %eip -> %edx */
982 982 pushfq
983 983 popq %r10
984 984 movl $UDS_SEL, REGOFF_SS(%rsp)
985 985
986 986 /*
987 987 * Set the interrupt flag before storing the flags to the
988 988 * flags image on the stack so we can return to user with
989 989 * interrupts enabled if we return via sys_rtt_syscall32
990 990 */
991 991 orq $PS_IE, %r10
992 992 movq %r10, REGOFF_RFL(%rsp)
993 993
994 994 movl %edi, REGOFF_RDI(%rsp)
995 995 movl %esi, REGOFF_RSI(%rsp)
996 996 movl %ebp, REGOFF_RBP(%rsp)
997 997 movl %ebx, REGOFF_RBX(%rsp)
998 998 movl %edx, REGOFF_RDX(%rsp)
999 999 movl %ecx, REGOFF_RCX(%rsp)
1000 1000 movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */
1001 1001 movq $0, REGOFF_SAVFP(%rsp)
1002 1002 movq $0, REGOFF_SAVPC(%rsp)
1003 1003
1004 1004 /*
1005 1005 * Copy these registers here in case we end up stopped with
1006 1006 * someone (like, say, /proc) messing with our register state.
1007 1007 * We don't -restore- them unless we have to in update_sregs.
1008 1008 *
1009 1009 * Since userland -can't- change fsbase or gsbase directly,
1010 1010 * we don't bother to capture them here.
1011 1011 */
1012 1012 xorl %ebx, %ebx
1013 1013 movw %ds, %bx
1014 1014 movq %rbx, REGOFF_DS(%rsp)
1015 1015 movw %es, %bx
1016 1016 movq %rbx, REGOFF_ES(%rsp)
1017 1017 movw %fs, %bx
1018 1018 movq %rbx, REGOFF_FS(%rsp)
1019 1019 movw %gs, %bx
1020 1020 movq %rbx, REGOFF_GS(%rsp)
1021 1021
1022 1022 /*
1023 1023 * Application state saved in the regs structure on the stack
1024 1024 * %eax is the syscall number
1025 1025 * %rsp is the thread's stack, %r15 is curthread
1026 1026 * REG_RSP(%rsp) is the user's stack
1027 1027 */
1028 1028
1029 1029 SYSCALL_TRAPTRACE($TT_SYSENTER)
1030 1030
1031 1031 movq %rsp, %rbp
1032 1032
1033 1033 movq T_LWP(%r15), %r14
1034 1034 ASSERT_NO_RUPDATE_PENDING(%r14)
1035 1035
1036 1036 ENABLE_INTR_FLAGS
1037 1037
1038 1038 /*
1039 1039 * Catch 64-bit process trying to issue sysenter instruction
1040 1040 * on Nocona based systems.
1041 1041 */
1042 1042 movq LWP_PROCP(%r14), %rax
1043 1043 cmpq $DATAMODEL_ILP32, P_MODEL(%rax)
1044 1044 je 7f
1045 1045
1046 1046 /*
1047 1047 * For a non-32-bit process, simulate a #ud, since that's what
1048 1048 * native hardware does. The traptrace entry (above) will
1049 1049 * let you know what really happened.
1050 1050 */
1051 1051 movq $T_ILLINST, REGOFF_TRAPNO(%rsp)
1052 1052 movq REGOFF_CS(%rsp), %rdi
1053 1053 movq %rdi, REGOFF_ERR(%rsp)
1054 1054 movq %rsp, %rdi
1055 1055 movq REGOFF_RIP(%rsp), %rsi
1056 1056 movl %gs:CPU_ID, %edx
1057 1057 call trap
1058 1058 jmp _sys_rtt
1059 1059 7:
1060 1060
1061 1061 MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
1062 1062 movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate calls) */
1063 1063
1064 1064 ASSERT_LWPTOREGS(%r14, %rsp)
1065 1065
1066 1066 incq %gs:CPU_STATS_SYS_SYSCALL
1067 1067
1068 1068 /*
1069 1069 * Make some space for MAXSYSARGS (currently 8) 32-bit args
1070 1070 * placed into 64-bit (long) arg slots, plus one 64-bit
1071 1071 * (long) arg count, maintaining 16 byte alignment.
1072 1072 */
1073 1073 subq $SYS_DROP, %rsp
1074 1074 movb $LWP_SYS, LWP_STATE(%r14)
1075 1075 movq %r15, %rdi
1076 1076 movq %rsp, %rsi
1077 1077 call syscall_entry
1078 1078
1079 1079 /*
1080 1080 * Fetch the arguments copied onto the kernel stack and put
1081 1081 * them in the right registers to invoke a C-style syscall handler.
1082 1082 * %rax contains the handler address.
1083 1083 */
1084 1084 movq %rax, %rbx
1085 1085 movl 0(%rsp), %edi
1086 1086 movl 8(%rsp), %esi
1087 1087 movl 0x10(%rsp), %edx
1088 1088 movl 0x18(%rsp), %ecx
1089 1089 movl 0x20(%rsp), %r8d
1090 1090 movl 0x28(%rsp), %r9d
1091 1091
1092 1092 call *SY_CALLC(%rbx)
1093 1093
1094 1094 movq %rbp, %rsp /* pop the args */
1095 1095
1096 1096 /*
1097 1097 * amd64 syscall handlers -always- return a 64-bit value in %rax.
1098 1098 * On the 32-bit kernel, the always return that value in %eax:%edx
1099 1099 * as required by the 32-bit ABI.
1100 1100 *
1101 1101 * Simulate the same behaviour by unconditionally splitting the
1102 1102 * return value in the same way.
1103 1103 */
1104 1104 movq %rax, %r13
1105 1105 shrq $32, %r13 /* upper 32-bits into %edx */
1106 1106 movl %eax, %r12d /* lower 32-bits into %eax */
1107 1107
1108 1108 /*
1109 1109 * Optimistically assume that there's no post-syscall
1110 1110 * work to do. (This is to avoid having to call syscall_mstate()
1111 1111 * with interrupts disabled)
1112 1112 */
1113 1113 MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
1114 1114
1115 1115 /*
1116 1116 * We must protect ourselves from being descheduled here;
1117 1117 * If we were, and we ended up on another cpu, or another
1118 1118 * lwp got int ahead of us, it could change the segment
1119 1119 * registers without us noticing before we return to userland.
1120 1120 */
1121 1121 cli
1122 1122 CHECK_POSTSYS_NE(%r15, %r14, %ebx)
1123 1123 jne _full_syscall_postsys32
1124 1124 SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
1125 1125
1126 1126 /*
1127 1127 * To get back to userland, load up the 32-bit registers and
1128 1128 * sysexit back where we came from.
1129 1129 */
1130 1130
1131 1131 /*
1132 1132 * Interrupts will be turned on by the 'sti' executed just before
1133 1133 * sysexit. The following ensures that restoring the user's rflags
1134 1134 * doesn't enable interrupts too soon.
1135 1135 */
1136 1136 andq $_BITNOT(PS_IE), REGOFF_RFL(%rsp)
1137 1137
1138 1138 /*
1139 1139 * (There's no point in loading up %edx because the sysexit
1140 1140 * mechanism smashes it.)
1141 1141 */
1142 1142 movl %r12d, %eax
1143 1143 movl REGOFF_RBX(%rsp), %ebx
1144 1144 movl REGOFF_RBP(%rsp), %ebp
1145 1145 movl REGOFF_RSI(%rsp), %esi
1146 1146 movl REGOFF_RDI(%rsp), %edi
1147 1147
1148 1148 movl REGOFF_RIP(%rsp), %edx /* sysexit: %edx -> %eip */
1149 1149 pushq REGOFF_RFL(%rsp)
1150 1150 popfq
1151 1151 movl REGOFF_RSP(%rsp), %ecx /* sysexit: %ecx -> %esp */
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1152 1152 ALTENTRY(sys_sysenter_swapgs_sysexit)
1153 1153 swapgs
1154 1154 sti
1155 1155 sysexit
1156 1156 SET_SIZE(sys_sysenter_swapgs_sysexit)
1157 1157 SET_SIZE(sys_sysenter)
1158 1158 SET_SIZE(_sys_sysenter_post_swapgs)
1159 1159 SET_SIZE(brand_sys_sysenter)
1160 1160
1161 1161 #endif /* __lint */
1162 +
1163 +#if defined(__lint)
1164 +/*
1165 + * System call via an int80. This entry point is only used by the Linux
1166 + * application environment. Unlike the other entry points, there is no
1167 + * default action to take if no callback is registered for this process.
1168 + */
1169 +void
1170 +sys_int80()
1171 +{}
1172 +
1173 +#else /* __lint */
1174 +
1175 + ENTRY_NP(brand_sys_int80)
1176 + SWAPGS /* kernel gsbase */
1177 + XPV_TRAP_POP
1178 + BRAND_CALLBACK(BRAND_CB_INT80, BRAND_URET_FROM_INTR_STACK())
1179 + SWAPGS /* user gsbase */
1180 + jmp nopop_int80
1181 +
1182 + ENTRY_NP(sys_int80)
1183 + /*
1184 + * We hit an int80, but this process isn't of a brand with an int80
1185 + * handler. Bad process! Make it look as if the INT failed.
1186 + * Modify %rip to point before the INT, push the expected error
1187 + * code and fake a GP fault. Note on 64-bit hypervisor we need
1188 + * to undo the XPV_TRAP_POP and push rcx and r11 back on the stack
1189 + * because gptrap will pop them again with its own XPV_TRAP_POP.
1190 + */
1191 + XPV_TRAP_POP
1192 +nopop_int80:
1193 + subq $2, (%rsp) /* int insn 2-bytes */
1194 + pushq $_CONST(_MUL(T_INT80, GATE_DESC_SIZE) + 2)
1195 +#if defined(__xpv)
1196 + push %r11
1197 + push %rcx
1198 +#endif
1199 + jmp gptrap / GP fault
1200 + SET_SIZE(sys_int80)
1201 + SET_SIZE(brand_sys_int80)
1202 +#endif /* __lint */
1203 +
1162 1204
1163 1205 /*
1164 1206 * This is the destination of the "int $T_SYSCALLINT" interrupt gate, used by
1165 1207 * the generic i386 libc to do system calls. We do a small amount of setup
1166 1208 * before jumping into the existing sys_syscall32 path.
1167 1209 */
1168 1210 #if defined(__lint)
1169 1211
1170 1212 /*ARGSUSED*/
1171 1213 void
1172 1214 sys_syscall_int()
1173 1215 {}
1174 1216
1175 1217 #else /* __lint */
1176 1218
1177 1219 ENTRY_NP(brand_sys_syscall_int)
1178 1220 SWAPGS /* kernel gsbase */
1179 1221 XPV_TRAP_POP
1180 1222 BRAND_CALLBACK(BRAND_CB_INT91, BRAND_URET_FROM_INTR_STACK())
1181 1223 jmp nopop_syscall_int
1182 1224
1183 1225 ALTENTRY(sys_syscall_int)
1184 1226 SWAPGS /* kernel gsbase */
1185 1227 XPV_TRAP_POP
1186 1228
1187 1229 nopop_syscall_int:
1188 1230 movq %gs:CPU_THREAD, %r15
1189 1231 movq T_STACK(%r15), %rsp
1190 1232 movl %eax, %eax
1191 1233 /*
1192 1234 * Set t_post_sys on this thread to force ourselves out via the slow
1193 1235 * path. It might be possible at some later date to optimize this out
1194 1236 * and use a faster return mechanism.
1195 1237 */
1196 1238 movb $1, T_POST_SYS(%r15)
1197 1239 CLEAN_CS
1198 1240 jmp _syscall32_save
1199 1241 /*
1200 1242 * There should be no instructions between this label and SWAPGS/IRET
1201 1243 * or we could end up breaking branded zone support. See the usage of
1202 1244 * this label in lx_brand_int80_callback and sn1_brand_int91_callback
1203 1245 * for examples.
1204 1246 */
1205 1247 ALTENTRY(sys_sysint_swapgs_iret)
1206 1248 SWAPGS /* user gsbase */
1207 1249 IRET
1208 1250 /*NOTREACHED*/
1209 1251 SET_SIZE(sys_sysint_swapgs_iret)
1210 1252 SET_SIZE(sys_syscall_int)
1211 1253 SET_SIZE(brand_sys_syscall_int)
1212 1254
1213 1255 #endif /* __lint */
1214 1256
1215 1257 /*
1216 1258 * Legacy 32-bit applications and old libc implementations do lcalls;
1217 1259 * we should never get here because the LDT entry containing the syscall
1218 1260 * segment descriptor has the "segment present" bit cleared, which means
1219 1261 * we end up processing those system calls in trap() via a not-present trap.
1220 1262 *
1221 1263 * We do it this way because a call gate unhelpfully does -nothing- to the
1222 1264 * interrupt flag bit, so an interrupt can run us just after the lcall
1223 1265 * completes, but just before the swapgs takes effect. Thus the INTR_PUSH and
1224 1266 * INTR_POP paths would have to be slightly more complex to dance around
1225 1267 * this problem, and end up depending explicitly on the first
1226 1268 * instruction of this handler being either swapgs or cli.
1227 1269 */
1228 1270
1229 1271 #if defined(__lint)
1230 1272
1231 1273 /*ARGSUSED*/
1232 1274 void
1233 1275 sys_lcall32()
1234 1276 {}
1235 1277
1236 1278 #else /* __lint */
1237 1279
1238 1280 ENTRY_NP(sys_lcall32)
1239 1281 SWAPGS /* kernel gsbase */
1240 1282 pushq $0
1241 1283 pushq %rbp
1242 1284 movq %rsp, %rbp
1243 1285 leaq __lcall_panic_str(%rip), %rdi
1244 1286 xorl %eax, %eax
1245 1287 call panic
1246 1288 SET_SIZE(sys_lcall32)
1247 1289
1248 1290 __lcall_panic_str:
1249 1291 .string "sys_lcall32: shouldn't be here!"
1250 1292
1251 1293 /*
1252 1294 * Declare a uintptr_t which covers the entire pc range of syscall
1253 1295 * handlers for the stack walkers that need this.
1254 1296 */
1255 1297 .align CPTRSIZE
1256 1298 .globl _allsyscalls_size
1257 1299 .type _allsyscalls_size, @object
1258 1300 _allsyscalls_size:
1259 1301 .NWORD . - _allsyscalls
1260 1302 SET_SIZE(_allsyscalls_size)
1261 1303
1262 1304 #endif /* __lint */
1263 1305
1264 1306 /*
1265 1307 * These are the thread context handlers for lwps using sysenter/sysexit.
1266 1308 */
1267 1309
1268 1310 #if defined(__lint)
1269 1311
1270 1312 /*ARGSUSED*/
1271 1313 void
1272 1314 sep_save(void *ksp)
1273 1315 {}
1274 1316
1275 1317 /*ARGSUSED*/
1276 1318 void
1277 1319 sep_restore(void *ksp)
1278 1320 {}
1279 1321
1280 1322 #else /* __lint */
1281 1323
1282 1324 /*
1283 1325 * setting this value to zero as we switch away causes the
1284 1326 * stack-pointer-on-sysenter to be NULL, ensuring that we
1285 1327 * don't silently corrupt another (preempted) thread stack
1286 1328 * when running an lwp that (somehow) didn't get sep_restore'd
1287 1329 */
1288 1330 ENTRY_NP(sep_save)
1289 1331 xorl %edx, %edx
1290 1332 xorl %eax, %eax
1291 1333 movl $MSR_INTC_SEP_ESP, %ecx
1292 1334 wrmsr
1293 1335 ret
1294 1336 SET_SIZE(sep_save)
1295 1337
1296 1338 /*
1297 1339 * Update the kernel stack pointer as we resume onto this cpu.
1298 1340 */
1299 1341 ENTRY_NP(sep_restore)
1300 1342 movq %rdi, %rdx
1301 1343 shrq $32, %rdx
1302 1344 movl %edi, %eax
1303 1345 movl $MSR_INTC_SEP_ESP, %ecx
1304 1346 wrmsr
1305 1347 ret
1306 1348 SET_SIZE(sep_restore)
1307 1349
1308 1350 #endif /* __lint */
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