]>
git.ipfire.org Git - thirdparty/glibc.git/blob - sysdeps/unix/sysv/linux/x86_64/makecontext.c
01c2340672d5a63f1b4ee598c1c506ef2d26bc37
2 Copyright (C) 2002-2014 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Andreas Jaeger <aj@suse.de>, 2002.
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.
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.
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/>. */
25 #include "ucontext_i.h"
27 /* This implementation can handle any ARGC value but only
28 normal integer parameters.
29 makecontext sets up a stack and the registers for the
30 user context. The stack looks like this:
31 +-----------------------+
33 +-----------------------+
35 +-----------------------+
36 | trampoline address |
37 %rsp -> +-----------------------+
39 The registers are set up like this:
40 %rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6
41 %rbx : address of next context
45 /* XXX: This implementation currently only handles integer arguments.
46 To handle long int and pointer arguments the va_arg arguments needs
47 to be changed to long and also the stdlib/tst-setcontext.c file needs
48 to be changed to pass long arguments to makecontext. */
52 __makecontext (ucontext_t
*ucp
, void (*func
) (void), int argc
, ...)
54 extern void __start_context (void);
56 unsigned int idx_uc_link
;
60 /* Generate room on stack for parameter if needed and uc_link. */
61 sp
= (greg_t
*) ((uintptr_t) ucp
->uc_stack
.ss_sp
62 + ucp
->uc_stack
.ss_size
);
63 sp
-= (argc
> 6 ? argc
- 6 : 0) + 1;
64 /* Align stack and make space for trampoline address. */
65 sp
= (greg_t
*) ((((uintptr_t) sp
) & -16L) - 8);
67 idx_uc_link
= (argc
> 6 ? argc
- 6 : 0) + 1;
69 /* Setup context ucp. */
70 /* Address to jump to. */
71 ucp
->uc_mcontext
.gregs
[REG_RIP
] = (uintptr_t) func
;
73 ucp
->uc_mcontext
.gregs
[REG_RBX
] = (uintptr_t) &sp
[idx_uc_link
];
74 ucp
->uc_mcontext
.gregs
[REG_RSP
] = (uintptr_t) sp
;
77 sp
[0] = (uintptr_t) &__start_context
;
78 sp
[idx_uc_link
] = (uintptr_t) ucp
->uc_link
;
83 The standard says the parameters must all be int values. This is
84 an historic accident and would be done differently today. For
85 x86-64 all integer values are passed as 64-bit values and
86 therefore extending the API to copy 64-bit values instead of
87 32-bit ints makes sense. It does not break existing
88 functionality and it does not violate the standard which says
89 that passing non-int values means undefined behavior. */
90 for (i
= 0; i
< argc
; ++i
)
94 ucp
->uc_mcontext
.gregs
[REG_RDI
] = va_arg (ap
, greg_t
);
97 ucp
->uc_mcontext
.gregs
[REG_RSI
] = va_arg (ap
, greg_t
);
100 ucp
->uc_mcontext
.gregs
[REG_RDX
] = va_arg (ap
, greg_t
);
103 ucp
->uc_mcontext
.gregs
[REG_RCX
] = va_arg (ap
, greg_t
);
106 ucp
->uc_mcontext
.gregs
[REG_R8
] = va_arg (ap
, greg_t
);
109 ucp
->uc_mcontext
.gregs
[REG_R9
] = va_arg (ap
, greg_t
);
112 /* Put value on stack. */
113 sp
[i
- 5] = va_arg (ap
, greg_t
);
121 weak_alias (__makecontext
, makecontext
)