47eb01b822
flags. We now create asynchronous contexts or syscall contexts only. Syscall contexts differ from the minimal ABI dictated contexts by having the scratch registers saved and restored because that's where we keep the syscall arguments and syscall return values. Since this change affects KSE, have it use kse_switchin(2) for the "new" syscall context.
94 lines
4.3 KiB
C
94 lines
4.3 KiB
C
/*-
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* Copyright (c) 1999, 2003 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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* The second variation is for synchronous contexts. When the kernel creates
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* a synchronous context if needs to preserve the scratch registers, because
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* the syscall argument and return values are stored there in the trapframe
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* and they need to be preserved in order to restart a syscall or return the
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* proper return values. Also, the IIP and CFM fields need to be preserved
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* as they point to the syscall stub, which the kernel saves as a favor to
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* userland (it keeps the stubs small and simple).
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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_SYSCALL_CONTEXT indicates if the
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* synchronous context is one corresponding to a syscall or not.
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* Only the kernel is expected to create such a context and it's
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* probably wise to let the kernel restore it.
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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_SYSCALL_CONTEXT
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* If set (hence _MC_FLAGS_ASYNC_CONTEXT is not set) indicates
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* that the scratch registers contain syscall arguments and
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* return values and that additionally IIP and CFM are valid.
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* Only the kernel is expected to create such a context. It's
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* probably wise to let the kernel restore it.
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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 /* Undocumented. Has to go. */
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#define _MC_FLAGS_SYSCALL_CONTEXT 0x0008
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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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