1634f50b1b
when we create contexts. The meaning of the flags are documented in <machine/ucontext.h>. I only list them here to help browsing the commit logs: _MC_FLAGS_ASYNC_CONTEXT _MC_FLAGS_HIGHFP_VALID _MC_FLAGS_KSE_SET_MBOX _MC_FLAGS_RETURN_VALID _MC_FLAGS_SCRATCH_VALID Yes, _MC_FLAGS_KSE_SET_MBOX is a hack and I'm proud of it :-)
100 lines
4.4 KiB
C
100 lines
4.4 KiB
C
/*-
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* Copyright (c) 1999 Marcel Moolenaar
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _MACHINE_UCONTEXT_H_
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#define _MACHINE_UCONTEXT_H_
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#include <machine/_regset.h>
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/*
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* The mc_flags field provides the necessary clues when dealing with the gory
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* details of ia64 specific contexts. A comprehensive explanation is added for
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* everybody's sanity, including the author's.
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*
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* The first and foremost variation in the context is synchronous contexts
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* (= synctx) versus asynchronous contexts (= asynctx). A synctx is created
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* synchronously WRT program execution and has the advantage that none of the
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* scratch registers have to be saved. They are assumed to be clobbered by the
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* call to the function that creates the context. An asynctx needs to have the
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* scratch registers preserved because it can describe any point in a thread's
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* (or process') execution.
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*
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* Below a description of the flags and their meaning:
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*
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* _MC_FLAGS_ASYNC_CONTEXT
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* If set, indicates that mc_scratch and mc_scratch_fp are both
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* valid. IFF not set, _MC_FLAGS_RETURN_VALID indicates if the
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* return registers are valid or not.
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* _MC_FLAGS_HIGHFP_VALID
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* If set, indicates that the high FP registers (f32-f127) are
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* valid. This flag is very likely not going to be set for any
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* sensible synctx, but is not explicitly disallowed. Any synctx
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* that has this flag may or may not have the high FP registers
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* restored. In short: don't do it.
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* _MC_FLAGS_KSE_SET_MBOX
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* This flag is special to setcontext(2) and swapcontext(2). It
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* instructs the kernel to write the value in mc_special.isr to
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* the memory address pointed to by mc_special.ifa. This allows
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* the kernel to switch to a new context in a KSE based threaded
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* program. Note that this is a non-srandard extension to the
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* otherwise standard system calls and use of this flag should be
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* limited to KSE.
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* _MC_FLAGS_RETURN_VALID
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* If set and _MC_FLAGS_ASYNC_CONTEXT is not set indicates that
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* the ABI defined return registers are valid. Both getcontext(2)
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* and swapcontext(2) need to save the system call return values.
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* Any synctx that does not have this flag may still have the
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* return registers restored from the context.
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* _MC_FLAGS_SCRATCH_VALID
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* If set and _MC_FLAGS_ASYNC_CONTEXT is not set indicates that
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* the scratch registers, but not the FP registers are valid.
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* This flag is set in contexts passed to signal handlers. This
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* flag is a superset of _MC_FLAGS_RETURN_VALID. If both flags
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* are set, this flag takes precedence.
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*/
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typedef struct __mcontext {
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unsigned long mc_flags;
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#define _MC_FLAGS_ASYNC_CONTEXT 0x0001
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#define _MC_FLAGS_HIGHFP_VALID 0x0002
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#define _MC_FLAGS_KSE_SET_MBOX 0x0004
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#define _MC_FLAGS_RETURN_VALID 0x0008
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#define _MC_FLAGS_SCRATCH_VALID 0x0010
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unsigned long _reserved_;
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struct _special mc_special;
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struct _callee_saved mc_preserved;
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struct _callee_saved_fp mc_preserved_fp;
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struct _caller_saved mc_scratch;
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struct _caller_saved_fp mc_scratch_fp;
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struct _high_fp mc_high_fp;
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} mcontext_t;
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#endif /* !_MACHINE_UCONTEXT_H_ */
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