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callcontext.c revision 1.6 
      1 /*	$NetBSD: callcontext.c,v 1.6 2007/05/15 13:44:46 pooka Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2006 Antti Kantee.  All Rights Reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  * 3. The name of the company nor the name of the author may be used to
     15  *    endorse or promote products derived from this software without specific
     16  *    prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
     19  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     21  * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  * SUCH DAMAGE.
     29  */
     30 
     31 #include <sys/cdefs.h>
     32 #if !defined(lint)
     33 __RCSID("$NetBSD: callcontext.c,v 1.6 2007/05/15 13:44:46 pooka Exp $");
     34 #endif /* !lint */
     35 
     36 #include <sys/types.h>
     37 
     38 #include <assert.h>
     39 #include <puffs.h>
     40 #include <stdio.h>
     41 #include <stdlib.h>
     42 #include <string.h>
     43 #include <ucontext.h>
     44 
     45 #include "puffs_priv.h"
     46 
     47 /*
     48  * user stuff
     49  */
     50 
     51 void
     52 puffs_cc_yield(struct puffs_cc *pcc)
     53 {
     54 
     55 	assert(pcc->pcc_flags & PCC_REALCC);
     56 	pcc->pcc_flags &= ~PCC_BORROWED;
     57 
     58 	/* romanes eunt domus */
     59 	swapcontext(&pcc->pcc_uc, &pcc->pcc_uc_ret);
     60 }
     61 
     62 void
     63 puffs_cc_continue(struct puffs_cc *pcc)
     64 {
     65 
     66 	assert(pcc->pcc_flags & PCC_REALCC);
     67 
     68 	/* ramble on */
     69 	swapcontext(&pcc->pcc_uc_ret, &pcc->pcc_uc);
     70 }
     71 
     72 /*
     73  * "Borrows" pcc, *NOT* called from pcc owner.  Acts like continue.
     74  * So the idea is to use this, give something the context back to
     75  * run to completion and then jump back to where ever this was called
     76  * from after the op dispatching is complete (or if the pcc decides to
     77  * yield again).
     78  */
     79 void
     80 puffs_goto(struct puffs_cc *loanpcc)
     81 {
     82 
     83 	assert(loanpcc->pcc_flags & PCC_REALCC);
     84 	loanpcc->pcc_flags |= PCC_BORROWED;
     85 
     86 	swapcontext(&loanpcc->pcc_uc_ret, &loanpcc->pcc_uc);
     87 }
     88 
     89 struct puffs_usermount *
     90 puffs_cc_getusermount(struct puffs_cc *pcc)
     91 {
     92 
     93 	return pcc->pcc_pu;
     94 }
     95 
     96 void *
     97 puffs_cc_getspecific(struct puffs_cc *pcc)
     98 {
     99 
    100 	return puffs_getspecific(pcc->pcc_pu);
    101 }
    102 
    103 struct puffs_cc *
    104 puffs_cc_create(struct puffs_usermount *pu)
    105 {
    106 	struct puffs_cc *volatile pcc;
    107 	stack_t *st;
    108 
    109 	pcc = malloc(sizeof(struct puffs_cc));
    110 	if (!pcc)
    111 		return NULL;
    112 	memset(pcc, 0, sizeof(struct puffs_cc));
    113 	pcc->pcc_pu = pu;
    114 	pcc->pcc_flags = PCC_REALCC;
    115 
    116 	/* initialize both ucontext's */
    117 	if (getcontext(&pcc->pcc_uc) == -1) {
    118 		free(pcc);
    119 		return NULL;
    120 	}
    121 	if (getcontext(&pcc->pcc_uc_ret) == -1) {
    122 		free(pcc);
    123 		return NULL;
    124 	}
    125 	/* return here.  it won't actually be "here" due to swapcontext() */
    126 	pcc->pcc_uc.uc_link = &pcc->pcc_uc_ret;
    127 
    128 	/* allocate stack for execution */
    129 	st = &pcc->pcc_uc.uc_stack;
    130 	st->ss_sp = pcc->pcc_stack = malloc(pu->pu_cc_stacksize);
    131 	if (st->ss_sp == NULL) {
    132 		free(pcc);
    133 		return NULL;
    134 	}
    135 	st->ss_size = pu->pu_cc_stacksize;
    136 	st->ss_flags = 0;
    137 
    138 	/*
    139 	 * Give us an initial context to jump to.
    140 	 *
    141 	 * XXX: Our manual page says that portable code shouldn't rely on
    142 	 * being able to pass pointers through makecontext().  kjk says
    143 	 * that NetBSD code doesn't need to worry about this.  uwe says
    144 	 * it would be like putting a "keep away from children" sign on a
    145 	 * box of toys.  I didn't ask what simon says; he's probably busy
    146 	 * "fixing" typos in comments.
    147 	 */
    148 	makecontext(&pcc->pcc_uc, (void *)puffs_calldispatcher,
    149 	    1, (uintptr_t)pcc);
    150 
    151 	return pcc;
    152 }
    153 
    154 void
    155 puffs_cc_destroy(struct puffs_cc *pcc)
    156 {
    157 
    158 	if (pcc->pcc_preq)
    159 		free(pcc->pcc_preq);
    160 	free(pcc->pcc_stack);
    161 	free(pcc);
    162 }
    163