xref: /illumos-gate/usr/src/lib/libc/amd64/gen/makectxt.c (revision ed093b41)
17c478bd9Sstevel@tonic-gate /*
27c478bd9Sstevel@tonic-gate  * CDDL HEADER START
37c478bd9Sstevel@tonic-gate  *
47c478bd9Sstevel@tonic-gate  * The contents of this file are subject to the terms of the
57257d1b4Sraf  * Common Development and Distribution License (the "License").
67257d1b4Sraf  * You may not use this file except in compliance with the License.
77c478bd9Sstevel@tonic-gate  *
87c478bd9Sstevel@tonic-gate  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
97c478bd9Sstevel@tonic-gate  * or http://www.opensolaris.org/os/licensing.
107c478bd9Sstevel@tonic-gate  * See the License for the specific language governing permissions
117c478bd9Sstevel@tonic-gate  * and limitations under the License.
127c478bd9Sstevel@tonic-gate  *
137c478bd9Sstevel@tonic-gate  * When distributing Covered Code, include this CDDL HEADER in each
147c478bd9Sstevel@tonic-gate  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
157c478bd9Sstevel@tonic-gate  * If applicable, add the following below this CDDL HEADER, with the
167c478bd9Sstevel@tonic-gate  * fields enclosed by brackets "[]" replaced with your own identifying
177c478bd9Sstevel@tonic-gate  * information: Portions Copyright [yyyy] [name of copyright owner]
187c478bd9Sstevel@tonic-gate  *
197c478bd9Sstevel@tonic-gate  * CDDL HEADER END
207c478bd9Sstevel@tonic-gate  */
217257d1b4Sraf 
227c478bd9Sstevel@tonic-gate /*
237257d1b4Sraf  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
247c478bd9Sstevel@tonic-gate  * Use is subject to license terms.
257c478bd9Sstevel@tonic-gate  */
267c478bd9Sstevel@tonic-gate 
277c478bd9Sstevel@tonic-gate /*	Copyright (c) 1988 AT&T	*/
28*ed093b41SRobert Mustacchi /*	  All Rights Reserved	*/
29*ed093b41SRobert Mustacchi 
30*ed093b41SRobert Mustacchi /*
31*ed093b41SRobert Mustacchi  * Copyright 2023 Oxide Computer Company
32*ed093b41SRobert Mustacchi  */
337c478bd9Sstevel@tonic-gate 
347257d1b4Sraf #pragma weak _makecontext = makecontext
357c478bd9Sstevel@tonic-gate 
367257d1b4Sraf #include "lint.h"
377c478bd9Sstevel@tonic-gate #include <stdarg.h>
387c478bd9Sstevel@tonic-gate #include <ucontext.h>
397c478bd9Sstevel@tonic-gate #include <sys/stack.h>
40*ed093b41SRobert Mustacchi #include <sys/auxv.h>
41*ed093b41SRobert Mustacchi #include <errno.h>
42*ed093b41SRobert Mustacchi #include "libc.h"
437c478bd9Sstevel@tonic-gate 
447c478bd9Sstevel@tonic-gate /*
457c478bd9Sstevel@tonic-gate  * The ucontext_t that the user passes in must have been primed with a
467c478bd9Sstevel@tonic-gate  * call to getcontext(2), have the uc_stack member set to reflect the
477c478bd9Sstevel@tonic-gate  * stack which this context will use, and have the uc_link member set
487c478bd9Sstevel@tonic-gate  * to the context which should be resumed when this context returns.
497c478bd9Sstevel@tonic-gate  * When makecontext() returns, the ucontext_t will be set to run the
507c478bd9Sstevel@tonic-gate  * given function with the given parameters on the stack specified by
517c478bd9Sstevel@tonic-gate  * uc_stack, and which will return to the ucontext_t specified by uc_link.
527c478bd9Sstevel@tonic-gate  */
537c478bd9Sstevel@tonic-gate 
547c478bd9Sstevel@tonic-gate static void resumecontext(void);
557c478bd9Sstevel@tonic-gate 
567c478bd9Sstevel@tonic-gate void
makecontext(ucontext_t * ucp,void (* func)(),int argc,...)577c478bd9Sstevel@tonic-gate makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
587c478bd9Sstevel@tonic-gate {
597c478bd9Sstevel@tonic-gate 	long *sp;
607c478bd9Sstevel@tonic-gate 	long *tsp;
617c478bd9Sstevel@tonic-gate 	va_list ap;
627c478bd9Sstevel@tonic-gate 	size_t size;
637c478bd9Sstevel@tonic-gate 	int pusharg = (argc > 6 ? argc - 6 : 0);
647c478bd9Sstevel@tonic-gate 	greg_t tmp;
657c478bd9Sstevel@tonic-gate 	int i;
667c478bd9Sstevel@tonic-gate 
677c478bd9Sstevel@tonic-gate 	ucp->uc_mcontext.gregs[REG_PC] = (greg_t)func;
687c478bd9Sstevel@tonic-gate 
697c478bd9Sstevel@tonic-gate 	size = sizeof (long) * (pusharg + 1);
707c478bd9Sstevel@tonic-gate 
717c478bd9Sstevel@tonic-gate 	/*
727c478bd9Sstevel@tonic-gate 	 * Calculate new value for %rsp. On entry to a function,
737c478bd9Sstevel@tonic-gate 	 * %rsp must be STACK_ENTRY_ALIGNed but not STACK_ALIGNed.
747c478bd9Sstevel@tonic-gate 	 * This is because the pushq %rbp will correct the alignment.
757c478bd9Sstevel@tonic-gate 	 */
767c478bd9Sstevel@tonic-gate 
777c478bd9Sstevel@tonic-gate 	sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
787c478bd9Sstevel@tonic-gate 	    ucp->uc_stack.ss_size - size) & ~(STACK_ENTRY_ALIGN - 1));
797c478bd9Sstevel@tonic-gate 
807c478bd9Sstevel@tonic-gate 	if (((uintptr_t)sp & (STACK_ALIGN - 1ul)) == 0)
817c478bd9Sstevel@tonic-gate 		sp -= STACK_ENTRY_ALIGN / sizeof (*sp);
827c478bd9Sstevel@tonic-gate 
837c478bd9Sstevel@tonic-gate 	tsp = sp + 1;
847c478bd9Sstevel@tonic-gate 
857c478bd9Sstevel@tonic-gate 	va_start(ap, argc);
867c478bd9Sstevel@tonic-gate 
877c478bd9Sstevel@tonic-gate 	for (i = 0; i < argc; i++) {
887c478bd9Sstevel@tonic-gate 		tmp = va_arg(ap, long);
897c478bd9Sstevel@tonic-gate 		switch (i) {
907c478bd9Sstevel@tonic-gate 		case 0:
917c478bd9Sstevel@tonic-gate 			ucp->uc_mcontext.gregs[REG_RDI] = tmp;
927c478bd9Sstevel@tonic-gate 			break;
937c478bd9Sstevel@tonic-gate 		case 1:
947c478bd9Sstevel@tonic-gate 			ucp->uc_mcontext.gregs[REG_RSI] = tmp;
957c478bd9Sstevel@tonic-gate 			break;
967c478bd9Sstevel@tonic-gate 		case 2:
977c478bd9Sstevel@tonic-gate 			ucp->uc_mcontext.gregs[REG_RDX] = tmp;
987c478bd9Sstevel@tonic-gate 			break;
997c478bd9Sstevel@tonic-gate 		case 3:
1007c478bd9Sstevel@tonic-gate 			ucp->uc_mcontext.gregs[REG_RCX] = tmp;
1017c478bd9Sstevel@tonic-gate 			break;
1027c478bd9Sstevel@tonic-gate 		case 4:
1037c478bd9Sstevel@tonic-gate 			ucp->uc_mcontext.gregs[REG_R8] = tmp;
1047c478bd9Sstevel@tonic-gate 			break;
1057c478bd9Sstevel@tonic-gate 		case 5:
1067c478bd9Sstevel@tonic-gate 			ucp->uc_mcontext.gregs[REG_R9] = tmp;
1077c478bd9Sstevel@tonic-gate 			break;
1087c478bd9Sstevel@tonic-gate 		default:
1097c478bd9Sstevel@tonic-gate 			*tsp++ = tmp;
1107c478bd9Sstevel@tonic-gate 			break;
1117c478bd9Sstevel@tonic-gate 		}
1127c478bd9Sstevel@tonic-gate 	}
1137c478bd9Sstevel@tonic-gate 
1147c478bd9Sstevel@tonic-gate 	va_end(ap);
1157c478bd9Sstevel@tonic-gate 
1167c478bd9Sstevel@tonic-gate 	*sp = (long)resumecontext;		/* return address */
1177c478bd9Sstevel@tonic-gate 
1187c478bd9Sstevel@tonic-gate 	ucp->uc_mcontext.gregs[REG_SP] = (greg_t)sp;
1197c478bd9Sstevel@tonic-gate }
1207c478bd9Sstevel@tonic-gate 
1217c478bd9Sstevel@tonic-gate 
1227c478bd9Sstevel@tonic-gate static void
resumecontext(void)1237c478bd9Sstevel@tonic-gate resumecontext(void)
1247c478bd9Sstevel@tonic-gate {
1257c478bd9Sstevel@tonic-gate 	ucontext_t uc;
1267c478bd9Sstevel@tonic-gate 
1277257d1b4Sraf 	(void) getcontext(&uc);
1287257d1b4Sraf 	(void) setcontext(uc.uc_link);
1297c478bd9Sstevel@tonic-gate }
130*ed093b41SRobert Mustacchi 
131*ed093b41SRobert Mustacchi /*
132*ed093b41SRobert Mustacchi  * This is the ISA-specific allocation logic for allocating and setting up an
133*ed093b41SRobert Mustacchi  * extended ucontext_t. In particular, we need to allocate and add space for the
134*ed093b41SRobert Mustacchi  * UC_XSAVE member if we have the appropriate hardware support.  The i386 /
135*ed093b41SRobert Mustacchi  * amd64 versions could be consolidated in a single x86 impl, but we don't have
136*ed093b41SRobert Mustacchi  * that yet.
137*ed093b41SRobert Mustacchi  */
138*ed093b41SRobert Mustacchi ucontext_t *
ucontext_alloc(uint32_t flags)139*ed093b41SRobert Mustacchi ucontext_alloc(uint32_t flags)
140*ed093b41SRobert Mustacchi {
141*ed093b41SRobert Mustacchi 	boolean_t do_xsave = B_FALSE;
142*ed093b41SRobert Mustacchi 	size_t to_alloc = sizeof (ucontext_t);
143*ed093b41SRobert Mustacchi 	ucontext_t *ucp;
144*ed093b41SRobert Mustacchi 
145*ed093b41SRobert Mustacchi 	if (flags != 0) {
146*ed093b41SRobert Mustacchi 		errno = EINVAL;
147*ed093b41SRobert Mustacchi 		return (NULL);
148*ed093b41SRobert Mustacchi 	}
149*ed093b41SRobert Mustacchi 
150*ed093b41SRobert Mustacchi 	/*
151*ed093b41SRobert Mustacchi 	 * The AT_SUN_FPTYPE value is used as an approximation for the size of
152*ed093b41SRobert Mustacchi 	 * the uc_xsave structure that we need additional space for. Ideally we
153*ed093b41SRobert Mustacchi 	 * should ask the kernel how much space we actually need and only
154*ed093b41SRobert Mustacchi 	 * allocate that much. Because the uc_xsave member does not need to
155*ed093b41SRobert Mustacchi 	 * include the 512-byte XMM structure or the full xsave header, this
156*ed093b41SRobert Mustacchi 	 * will work in the interim.
157*ed093b41SRobert Mustacchi 	 *
158*ed093b41SRobert Mustacchi 	 * Currently the system doesn't support dynamically enabling FPU
159*ed093b41SRobert Mustacchi 	 * features with the Intel xfd (extended feature disable) MSR. When we
160*ed093b41SRobert Mustacchi 	 * have support for that we'll need to redo this and ask the kernel for
161*ed093b41SRobert Mustacchi 	 * the right size. We will probably want to cache the size for rtld as
162*ed093b41SRobert Mustacchi 	 * well. For more information see uts/intel/os/fpu.c's big theory
163*ed093b41SRobert Mustacchi 	 * statement.
164*ed093b41SRobert Mustacchi 	 */
165*ed093b41SRobert Mustacchi 	switch (___getauxval(AT_SUN_FPTYPE)) {
166*ed093b41SRobert Mustacchi 	case AT_386_FPINFO_XSAVE:
167*ed093b41SRobert Mustacchi 	case AT_386_FPINFO_XSAVE_AMD:
168*ed093b41SRobert Mustacchi 		do_xsave = B_TRUE;
169*ed093b41SRobert Mustacchi 		to_alloc += ___getauxval(AT_SUN_FPSIZE);
170*ed093b41SRobert Mustacchi 		break;
171*ed093b41SRobert Mustacchi 	default:
172*ed093b41SRobert Mustacchi 		break;
173*ed093b41SRobert Mustacchi 	}
174*ed093b41SRobert Mustacchi 
175*ed093b41SRobert Mustacchi 	ucp = calloc(1, to_alloc);
176*ed093b41SRobert Mustacchi 	if (ucp == NULL) {
177*ed093b41SRobert Mustacchi 		return (NULL);
178*ed093b41SRobert Mustacchi 	}
179*ed093b41SRobert Mustacchi 
180*ed093b41SRobert Mustacchi 	if (do_xsave) {
181*ed093b41SRobert Mustacchi 		/*
182*ed093b41SRobert Mustacchi 		 * Right now we're not really concerned with alignment of the
183*ed093b41SRobert Mustacchi 		 * uc_xsave member. This structure it points to is no defined
184*ed093b41SRobert Mustacchi 		 * for application access and the kernel doesn't care. This will
185*ed093b41SRobert Mustacchi 		 * give us something that is fairly reasonable though.
186*ed093b41SRobert Mustacchi 		 */
187*ed093b41SRobert Mustacchi 		uintptr_t addr = (uintptr_t)ucp;
188*ed093b41SRobert Mustacchi 		ucp->uc_xsave = addr + sizeof (ucontext_t);
189*ed093b41SRobert Mustacchi 	}
190*ed093b41SRobert Mustacchi 
191*ed093b41SRobert Mustacchi 	return (ucp);
192*ed093b41SRobert Mustacchi }
193*ed093b41SRobert Mustacchi 
194*ed093b41SRobert Mustacchi void
ucontext_free(ucontext_t * ucp)195*ed093b41SRobert Mustacchi ucontext_free(ucontext_t *ucp)
196*ed093b41SRobert Mustacchi {
197*ed093b41SRobert Mustacchi 	free(ucp);
198*ed093b41SRobert Mustacchi }
199