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 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /* Copyright (c) 1988 AT&T */
28 /* All Rights Reserved */
29
30 /*
31 * Copyright 2023 Oxide Computer Company
32 */
33
34 #pragma weak _makecontext = makecontext
35
36 #include "lint.h"
37 #include <stdarg.h>
38 #include <ucontext.h>
39 #include <sys/stack.h>
40 #include <sys/auxv.h>
41 #include <errno.h>
42 #include "libc.h"
43
44 /*
45 * The ucontext_t that the user passes in must have been primed with a
46 * call to getcontext(2), have the uc_stack member set to reflect the
47 * stack which this context will use, and have the uc_link member set
48 * to the context which should be resumed when this context returns.
49 * When makecontext() returns, the ucontext_t will be set to run the
50 * given function with the given parameters on the stack specified by
51 * uc_stack, and which will return to the ucontext_t specified by uc_link.
52 */
53
54 static void resumecontext(void);
55
56 void
makecontext(ucontext_t * ucp,void (* func)(),int argc,...)57 makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
58 {
59 long *sp;
60 long *tsp;
61 va_list ap;
62 size_t size;
63 int pusharg = (argc > 6 ? argc - 6 : 0);
64 greg_t tmp;
65 int i;
66
67 ucp->uc_mcontext.gregs[REG_PC] = (greg_t)func;
68
69 size = sizeof (long) * (pusharg + 1);
70
71 /*
72 * Calculate new value for %rsp. On entry to a function,
73 * %rsp must be STACK_ENTRY_ALIGNed but not STACK_ALIGNed.
74 * This is because the pushq %rbp will correct the alignment.
75 */
76
77 sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
78 ucp->uc_stack.ss_size - size) & ~(STACK_ENTRY_ALIGN - 1));
79
80 if (((uintptr_t)sp & (STACK_ALIGN - 1ul)) == 0)
81 sp -= STACK_ENTRY_ALIGN / sizeof (*sp);
82
83 tsp = sp + 1;
84
85 va_start(ap, argc);
86
87 for (i = 0; i < argc; i++) {
88 tmp = va_arg(ap, long);
89 switch (i) {
90 case 0:
91 ucp->uc_mcontext.gregs[REG_RDI] = tmp;
92 break;
93 case 1:
94 ucp->uc_mcontext.gregs[REG_RSI] = tmp;
95 break;
96 case 2:
97 ucp->uc_mcontext.gregs[REG_RDX] = tmp;
98 break;
99 case 3:
100 ucp->uc_mcontext.gregs[REG_RCX] = tmp;
101 break;
102 case 4:
103 ucp->uc_mcontext.gregs[REG_R8] = tmp;
104 break;
105 case 5:
106 ucp->uc_mcontext.gregs[REG_R9] = tmp;
107 break;
108 default:
109 *tsp++ = tmp;
110 break;
111 }
112 }
113
114 va_end(ap);
115
116 *sp = (long)resumecontext; /* return address */
117
118 ucp->uc_mcontext.gregs[REG_SP] = (greg_t)sp;
119 }
120
121
122 static void
resumecontext(void)123 resumecontext(void)
124 {
125 ucontext_t uc;
126
127 (void) getcontext(&uc);
128 (void) setcontext(uc.uc_link);
129 }
130
131 /*
132 * This is the ISA-specific allocation logic for allocating and setting up an
133 * extended ucontext_t. In particular, we need to allocate and add space for the
134 * UC_XSAVE member if we have the appropriate hardware support. The i386 /
135 * amd64 versions could be consolidated in a single x86 impl, but we don't have
136 * that yet.
137 */
138 ucontext_t *
ucontext_alloc(uint32_t flags)139 ucontext_alloc(uint32_t flags)
140 {
141 boolean_t do_xsave = B_FALSE;
142 size_t to_alloc = sizeof (ucontext_t);
143 ucontext_t *ucp;
144
145 if (flags != 0) {
146 errno = EINVAL;
147 return (NULL);
148 }
149
150 /*
151 * The AT_SUN_FPTYPE value is used as an approximation for the size of
152 * the uc_xsave structure that we need additional space for. Ideally we
153 * should ask the kernel how much space we actually need and only
154 * allocate that much. Because the uc_xsave member does not need to
155 * include the 512-byte XMM structure or the full xsave header, this
156 * will work in the interim.
157 *
158 * Currently the system doesn't support dynamically enabling FPU
159 * features with the Intel xfd (extended feature disable) MSR. When we
160 * have support for that we'll need to redo this and ask the kernel for
161 * the right size. We will probably want to cache the size for rtld as
162 * well. For more information see uts/intel/os/fpu.c's big theory
163 * statement.
164 */
165 switch (___getauxval(AT_SUN_FPTYPE)) {
166 case AT_386_FPINFO_XSAVE:
167 case AT_386_FPINFO_XSAVE_AMD:
168 do_xsave = B_TRUE;
169 to_alloc += ___getauxval(AT_SUN_FPSIZE);
170 break;
171 default:
172 break;
173 }
174
175 ucp = calloc(1, to_alloc);
176 if (ucp == NULL) {
177 return (NULL);
178 }
179
180 if (do_xsave) {
181 /*
182 * Right now we're not really concerned with alignment of the
183 * uc_xsave member. This structure it points to is no defined
184 * for application access and the kernel doesn't care. This will
185 * give us something that is fairly reasonable though.
186 */
187 uintptr_t addr = (uintptr_t)ucp;
188 ucp->uc_xsave = addr + sizeof (ucontext_t);
189 }
190
191 return (ucp);
192 }
193
194 void
ucontext_free(ucontext_t * ucp)195 ucontext_free(ucontext_t *ucp)
196 {
197 free(ucp);
198 }
199