add header glue
[dragonfly.git] / lib / libc / amd64 / gen / makecontext.c
CommitLineData
17030342
MD
1/*
2 * Copyright (c) 2003 Marcel Moolenaar
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: src/lib/libc/amd64/gen/makecontext.c,v 1.2 2003/12/05 01:36:44 peter Exp $
27 * $DragonFly: src/lib/libc/amd64/gen/Attic/makecontext.c,v 1.1 2004/02/02 05:43:14 dillon Exp $
28 */
29
30
31#include <sys/types.h>
32#include <sys/ucontext.h>
33#include <stdarg.h>
34#include <stdlib.h>
35
36typedef void (*func_t)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
37 uint64_t);
38
39/* Prototypes */
40static void ctx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args);
41
42__weak_reference(__makecontext, makecontext);
43
44void
45__makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...)
46{
47 uint64_t *args;
48 uint64_t *sp;
49 va_list ap;
50 int i;
51
52 /* A valid context is required. */
53 if ((ucp == NULL) || (ucp->uc_mcontext.mc_len != sizeof(mcontext_t)))
54 return;
55 else if ((argc < 0) || (argc > 6) || (ucp->uc_stack.ss_sp == NULL) ||
56 (ucp->uc_stack.ss_size < MINSIGSTKSZ)) {
57 /*
58 * This should really return -1 with errno set to ENOMEM
59 * or something, but the spec says that makecontext is
60 * a void function. At least make sure that the context
61 * isn't valid so it can't be used without an error.
62 */
63 ucp->uc_mcontext.mc_len = 0;
64 return;
65 }
66
67 /* Align the stack to 16 bytes. */
68 sp = (uint64_t *)(ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
69 sp = (uint64_t *)((uint64_t)sp & -15UL);
70
71 /* Allocate space for a maximum of 6 arguments on the stack. */
72 args = sp - 6;
73
74 /*
75 * Account for arguments on stack and do the funky C entry alignment.
76 * This means that we need an 8-byte-odd alignment since the ABI expects
77 * the return address to be pushed, thus breaking the 16 byte alignment.
78 */
79 sp -= 7;
80
81 /* Add the arguments: */
82 va_start(ap, argc);
83 for (i = 0; i < argc; i++)
84 args[i] = va_arg(ap, uint64_t);
85 va_end(ap);
86 for (i = argc; i < 6; i++)
87 args[i] = 0;
88
89 ucp->uc_mcontext.mc_rdi = (register_t)ucp;
90 ucp->uc_mcontext.mc_rsi = (register_t)start;
91 ucp->uc_mcontext.mc_rdx = (register_t)args;
92 ucp->uc_mcontext.mc_rbp = (register_t)sp;
93 ucp->uc_mcontext.mc_rbx = (register_t)sp;
94 ucp->uc_mcontext.mc_rsp = (register_t)sp;
95 ucp->uc_mcontext.mc_rip = (register_t)ctx_wrapper;
96}
97
98static void
99ctx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args)
100{
101 (*func)(args[0], args[1], args[2], args[3], args[4], args[5]);
102 if (ucp->uc_link == NULL)
103 exit(0);
104 setcontext((const ucontext_t *)ucp->uc_link);
105 /* should never get here */
106 abort();
107 /* NOTREACHED */
108}