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 #pragma ident "%Z%%M% %I% %E% SMI"
31
32 #pragma weak _makecontext = makecontext
33
34 #include "lint.h"
35 #include <stdarg.h>
36 #include <ucontext.h>
37 #include <sys/stack.h>
38
39 /*
40 * The ucontext_t that the user passes in must have been primed with a
41 * call to getcontext(2), have the uc_stack member set to reflect the
42 * stack which this context will use, and have the uc_link member set
43 * to the context which should be resumed when this context returns.
44 * When makecontext() returns, the ucontext_t will be set to run the
45 * given function with the given parameters on the stack specified by
46 * uc_stack, and which will return to the ucontext_t specified by uc_link.
47 */
48
49 static void resumecontext(void);
50
51 void
52 makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
53 {
54 long *sp;
55 long *tsp;
56 va_list ap;
57 size_t size;
58
59 ucp->uc_mcontext.gregs[EIP] = (greg_t)func;
60
61 size = sizeof (long) * (argc + 1);
62
63 sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
64 ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1));
65
66 tsp = sp + 1;
67
68 va_start(ap, argc);
69
70 while (argc-- > 0) {
71 *tsp++ = va_arg(ap, long);
72 }
73
74 va_end(ap);
75
76 *sp = (long)resumecontext; /* return address */
77
78 ucp->uc_mcontext.gregs[UESP] = (greg_t)sp;
79 }
80
81
82 static void
83 resumecontext(void)
84 {
85 ucontext_t uc;
86
87 (void) getcontext(&uc);
88 (void) setcontext(uc.uc_link);
89 }
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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 #pragma weak _makecontext = makecontext
31
32 #include "lint.h"
33 #include <stdarg.h>
34 #include <ucontext.h>
35 #include <sys/stack.h>
36
37 /*
38 * The ucontext_t that the user passes in must have been primed with a
39 * call to getcontext(2), have the uc_stack member set to reflect the
40 * stack which this context will use, and have the uc_link member set
41 * to the context which should be resumed when this context returns.
42 * When makecontext() returns, the ucontext_t will be set to run the
43 * given function with the given parameters on the stack specified by
44 * uc_stack, and which will return to the ucontext_t specified by uc_link.
45 */
46
47 /*
48 * The original i386 ABI said that the stack pointer need be only 4-byte
49 * aligned before a function call (STACK_ALIGN == 4). The ABI supplement
50 * version 1.0 changed the required alignment to 16-byte for the benefit of
51 * floating point code compiled using sse2. The compiler assumes this
52 * alignment and maintains it for calls it generates. If the stack is
53 * initially properly aligned, it will continue to be so aligned. If it is
54 * not initially so aligned, it will never become so aligned.
55 *
56 * One slightly confusing detail to keep in mind is that the 16-byte
57 * alignment (%esp & 0xf == 0) is true just *before* the call instruction.
58 * The call instruction will then push a return value, decrementing %esp by
59 * 4. Therefore, if one dumps %esp at the at the very first instruction in
60 * a function, it will end with a 0xc. The compiler expects this and
61 * compensates for it properly.
62 *
63 * Note: If you change this value, you need to change it in the following
64 * files as well:
65 *
66 * - lib/libc/i386/threads/machdep.c
67 * - lib/common/i386/crti.s
68 * - lib/common/i386/crt1.s
69 */
70 #undef STACK_ALIGN
71 #define STACK_ALIGN 16
72
73 static void resumecontext(void);
74
75 void
76 makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
77 {
78 long *sp;
79 long *tsp;
80 va_list ap;
81 size_t size;
82
83 ucp->uc_mcontext.gregs[EIP] = (greg_t)func;
84
85 size = sizeof (long) * (argc + 1);
86
87 tsp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
88 ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1));
89
90 /*
91 * Since we're emulating the call instruction, we must push the
92 * return address (which involves adjusting the stack pointer to
93 * have the proper 4-byte bias).
94 */
95 sp = tsp - 1;
96
97 *sp = (long)resumecontext; /* return address */
98
99 ucp->uc_mcontext.gregs[UESP] = (greg_t)sp;
100
101 /*
102 * "push" all the arguments
103 */
104 va_start(ap, argc);
105 while (argc-- > 0)
106 *tsp++ = va_arg(ap, long);
107 va_end(ap);
108 }
109
110
111 static void
112 resumecontext(void)
113 {
114 ucontext_t uc;
115
116 (void) getcontext(&uc);
117 (void) setcontext(uc.uc_link);
118 }
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