1 /* Create new context.
2 Copyright (C) 2008-2016 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by David S. Miller <davem@davemloft.net>, 2008.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20 #include <sysdep.h>
21 #include <stdarg.h>
22 #include <stdint.h>
23 #include <ucontext.h>
24
25 /* Sets up the outgoing arguments and the program counter for a user
26 context for the requested function call.
27
28 Returning to the correct parent context is pretty simple on
29 Sparc. We only need to link up the register windows correctly.
30 Since global registers are clobbered by calls, we need not be
31 concerned about those, and thus is all could be worked out without
32 using a trampoline.
33
34 Except that we must deal with the signal mask, thus a trampoline
35 is unavoidable. 32-bit stackframe layout:
36 +-----------------------------------------+
37 | 7th and further parameters |
38 +-----------------------------------------+
39 | backup storage for initial 6 parameters |
40 +-----------------------------------------+
41 | struct return pointer |
42 +-----------------------------------------+
43 | 8 incoming registers |
44 +-----------------------------------------+
45 | 8 local registers |
46 %sp --> +-----------------------------------------+
47
48 */
49
50 void
__makecontext(ucontext_t * ucp,void (* func)(void),int argc,...)51 __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
52 {
53 extern void __start_context (void);
54 unsigned long int *sp;
55 va_list ap;
56 int i;
57
58 sp = (unsigned long int *) (ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
59 sp -= 16 + 7 + argc;
60 sp = (unsigned long int *) (((uintptr_t) sp) & ~(8 - 1));
61
62 for (i = 0; i < 8; i++)
63 sp[i + 8] = ucp->uc_mcontext.gregs[REG_O0 + i];
64
65 /* The struct return pointer is essentially unused, so we can
66 place the link there. */
67 sp[16] = (unsigned long int) ucp->uc_link;
68
69 va_start (ap, argc);
70
71 /* Fill in outgoing arguments, including those which will
72 end up being passed on the stack. */
73 for (i = 0; i < argc; i++)
74 {
75 unsigned long int arg = va_arg (ap, unsigned long int);
76 if (i < 6)
77 ucp->uc_mcontext.gregs[REG_O0 + i] = arg;
78 else
79 sp[i + 23 - 6] = arg;
80 }
81
82 va_end (ap);
83
84 ucp->uc_mcontext.gregs[REG_O6] = (unsigned long int) sp;
85
86 ucp->uc_mcontext.gregs[REG_O7] = ((unsigned long int) __start_context) - 8;
87
88 ucp->uc_mcontext.gregs[REG_PC] = (unsigned long int) func;
89 ucp->uc_mcontext.gregs[REG_nPC] = ucp->uc_mcontext.gregs[REG_PC] + 4;
90 }
91
92 weak_alias (__makecontext, makecontext)
93