2 * Copyright (c) 1999, 2003 Marcel Moolenaar
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31 #ifndef _MACHINE_UCONTEXT_H_
32 #define _MACHINE_UCONTEXT_H_
34 #include <machine/_regset.h>
37 * The mc_flags field provides the necessary clues when dealing with the gory
38 * details of ia64 specific contexts. A comprehensive explanation is added for
39 * everybody's sanity, including the author's.
41 * The first and foremost variation in the context is synchronous contexts
42 * (= synctx) versus asynchronous contexts (= asynctx). A synctx is created
43 * synchronously WRT program execution and has the advantage that none of the
44 * scratch registers have to be saved. They are assumed to be clobbered by the
45 * call to the function that creates the context. An asynctx needs to have the
46 * scratch registers preserved because it can describe any point in a thread's
47 * (or process') execution.
48 * The second variation is for synchronous contexts. When the kernel creates
49 * a synchronous context if needs to preserve the scratch registers, because
50 * the syscall argument and return values are stored there in the trapframe
51 * and they need to be preserved in order to restart a syscall or return the
52 * proper return values. Also, the IIP and CFM fields need to be preserved
53 * as they point to the syscall stub, which the kernel saves as a favor to
54 * userland (it keeps the stubs small and simple).
56 * Below a description of the flags and their meaning:
58 * _MC_FLAGS_ASYNC_CONTEXT
59 * If set, indicates that mc_scratch and mc_scratch_fp are both
60 * valid. IFF not set, _MC_FLAGS_SYSCALL_CONTEXT indicates if the
61 * synchronous context is one corresponding to a syscall or not.
62 * Only the kernel is expected to create such a context and it's
63 * probably wise to let the kernel restore it.
64 * _MC_FLAGS_HIGHFP_VALID
65 * If set, indicates that the high FP registers (f32-f127) are
66 * valid. This flag is very likely not going to be set for any
67 * sensible synctx, but is not explicitly disallowed. Any synctx
68 * that has this flag may or may not have the high FP registers
69 * restored. In short: don't do it.
70 * _MC_FLAGS_SYSCALL_CONTEXT
71 * If set (hence _MC_FLAGS_ASYNC_CONTEXT is not set) indicates
72 * that the scratch registers contain syscall arguments and
73 * return values and that additionally IIP and CFM are valid.
74 * Only the kernel is expected to create such a context. It's
75 * probably wise to let the kernel restore it.
78 typedef struct __mcontext {
79 unsigned long mc_flags;
80 #define _MC_FLAGS_ASYNC_CONTEXT 0x0001
81 #define _MC_FLAGS_HIGHFP_VALID 0x0002
82 #define _MC_FLAGS_KSE_SET_MBOX 0x0004 /* Undocumented. Has to go. */
83 #define _MC_FLAGS_SYSCALL_CONTEXT 0x0008
84 unsigned long _reserved_;
85 struct _special mc_special;
86 struct _callee_saved mc_preserved;
87 struct _callee_saved_fp mc_preserved_fp;
88 struct _caller_saved mc_scratch;
89 struct _caller_saved_fp mc_scratch_fp;
90 struct _high_fp mc_high_fp;
93 #endif /* !_MACHINE_UCONTEXT_H_ */