1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
/*-
* Copyright (c) 1999, 2003 Marcel Moolenaar
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer
* in this position and unchanged.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _MACHINE_UCONTEXT_H_
#define _MACHINE_UCONTEXT_H_
#include <machine/_regset.h>
/*
* The mc_flags field provides the necessary clues when dealing with the gory
* details of ia64 specific contexts. A comprehensive explanation is added for
* everybody's sanity, including the author's.
*
* The first and foremost variation in the context is synchronous contexts
* (= synctx) versus asynchronous contexts (= asynctx). A synctx is created
* synchronously WRT program execution and has the advantage that none of the
* scratch registers have to be saved. They are assumed to be clobbered by the
* call to the function that creates the context. An asynctx needs to have the
* scratch registers preserved because it can describe any point in a thread's
* (or process') execution.
* The second variation is for synchronous contexts. When the kernel creates
* a synchronous context if needs to preserve the scratch registers, because
* the syscall argument and return values are stored there in the trapframe
* and they need to be preserved in order to restart a syscall or return the
* proper return values. Also, the IIP and CFM fields need to be preserved
* as they point to the syscall stub, which the kernel saves as a favor to
* userland (it keeps the stubs small and simple).
*
* Below a description of the flags and their meaning:
*
* _MC_FLAGS_ASYNC_CONTEXT
* If set, indicates that mc_scratch and mc_scratch_fp are both
* valid. IFF not set, _MC_FLAGS_SYSCALL_CONTEXT indicates if the
* synchronous context is one corresponding to a syscall or not.
* Only the kernel is expected to create such a context and it's
* probably wise to let the kernel restore it.
* _MC_FLAGS_HIGHFP_VALID
* If set, indicates that the high FP registers (f32-f127) are
* valid. This flag is very likely not going to be set for any
* sensible synctx, but is not explicitly disallowed. Any synctx
* that has this flag may or may not have the high FP registers
* restored. In short: don't do it.
* _MC_FLAGS_SYSCALL_CONTEXT
* If set (hence _MC_FLAGS_ASYNC_CONTEXT is not set) indicates
* that the scratch registers contain syscall arguments and
* return values and that additionally IIP and CFM are valid.
* Only the kernel is expected to create such a context. It's
* probably wise to let the kernel restore it.
*/
typedef struct __mcontext {
unsigned long mc_flags;
#define _MC_FLAGS_ASYNC_CONTEXT 0x0001
#define _MC_FLAGS_HIGHFP_VALID 0x0002
#define _MC_FLAGS_SYSCALL_CONTEXT 0x0008
unsigned long _reserved_;
struct _special mc_special;
struct _callee_saved mc_preserved;
struct _callee_saved_fp mc_preserved_fp;
struct _caller_saved mc_scratch;
struct _caller_saved_fp mc_scratch_fp;
struct _high_fp mc_high_fp;
} mcontext_t;
#endif /* !_MACHINE_UCONTEXT_H_ */
|
