sys/arch/ia64/include/mcontext.h

   1 /*      $NetBSD: mcontext.h,v 1.1 2006/04/07 14:21:18 cherry Exp $      */
   2
   3 /*-
   4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Klaus Klein.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #ifndef _IA64_MCONTEXT_H_
  33 #define _IA64_MCONTEXT_H_
  34
  35 #include <machine/_regset.h>
  36
  37 /*
  38  * The mc_flags field provides the necessary clues when dealing with the gory
  39  * details of ia64 specific contexts. A comprehensive explanation is added for
  40  * everybody's sanity, including the author's.
  41  *
  42  * The first and foremost variation in the context is synchronous contexts
  43  * (= synctx) versus asynchronous contexts (= asynctx). A synctx is created
  44  * synchronously WRT program execution and has the advantage that none of the
  45  * scratch registers have to be saved. They are assumed to be clobbered by the
  46  * call to the function that creates the context. An asynctx needs to have the
  47  * scratch registers preserved because it can describe any point in a thread's
  48  * (or process') execution.
  49  * The second variation is for synchronous contexts. When the kernel creates
  50  * a synchronous context if needs to preserve the scratch registers, because
  51  * the syscall argument and return values are stored there in the trapframe
  52  * and they need to be preserved in order to restart a syscall or return the
  53  * proper return values. Also, the IIP and CFM fields need to be preserved
  54  * as they point to the syscall stub, which the kernel saves as a favor to
  55  * userland (it keeps the stubs small and simple).
  56  *
  57  * Below a description of the flags and their meaning:
  58  *
  59  *      _MC_FLAGS_ASYNC_CONTEXT
  60  *              If set, indicates that mc_scratch and mc_scratch_fp are both
  61  *              valid. IFF not set, _MC_FLAGS_SYSCALL_CONTEXT indicates if the
  62  *              synchronous context is one corresponding to a syscall or not.
  63  *              Only the kernel is expected to create such a context and it's
  64  *              probably wise to let the kernel restore it.
  65  *      _MC_FLAGS_HIGHFP_VALID
  66  *              If set, indicates that the high FP registers (f32-f127) are
  67  *              valid. This flag is very likely not going to be set for any
  68  *              sensible synctx, but is not explicitly disallowed. Any synctx
  69  *              that has this flag may or may not have the high FP registers
  70  *              restored. In short: don't do it.
  71  *      _MC_FLAGS_SYSCALL_CONTEXT
  72  *              If set (hence _MC_FLAGS_ASYNC_CONTEXT is not set) indicates
  73  *              that the scratch registers contain syscall arguments and
  74  *              return values and that additionally IIP and CFM are valid.
  75  *              Only the kernel is expected to create such a context. It's
  76  *              probably wise to let the kernel restore it.
  77  */
  78
  79 typedef struct __mcontext {
  80         unsigned long           mc_flags;
  81 #define _MC_FLAGS_ASYNC_CONTEXT         0x0001
  82 #define _MC_FLAGS_HIGHFP_VALID          0x0002
  83 #define _MC_FLAGS_KSE_SET_MBOX          0x0004  /* Undocumented. Has to go. */
  84 #define _MC_FLAGS_SYSCALL_CONTEXT       0x0008
  85         unsigned long           _reserved_;
  86         struct _special         mc_special;
  87         struct _callee_saved    mc_preserved;
  88         struct _callee_saved_fp mc_preserved_fp;
  89         struct _caller_saved    mc_scratch;
  90         struct _caller_saved_fp mc_scratch_fp;
  91         struct _high_fp         mc_high_fp;
  92 } mcontext_t;
  93
  94 #ifndef _UC_MACHINE_SP
  95 #define _UC_MACHINE_SP(uc)      ((uc)->uc_mcontext.mc_special.sp)
  96 #endif
  97
  98 #endif  /* !_IA64_MCONTEXT_H_ */