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      1 /*	$NetBSD: makecontext.c,v 1.8 2025/04/25 01:18:51 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2001 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 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: makecontext.c,v 1.8 2025/04/25 01:18:51 riastradh Exp $");
     35 #endif
     36 
     37 #include <sys/param.h>
     38 #include <sys/types.h>
     39 
     40 #include <machine/frame.h>
     41 
     42 #include <inttypes.h>
     43 #include <stdarg.h>
     44 #include <stddef.h>
     45 #include <ucontext.h>
     46 
     47 #include "extern.h"
     48 
     49 void __resumecontext(void) __dead;
     50 
     51 void
     52 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     53 {
     54 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     55 	__greg_t *gp, rp, fp;
     56 	register __greg_t dp __asm("r27");
     57 	uintptr_t *sp;
     58 	int i;
     59 	va_list ap;
     60 
     61 	/* LINTED uintptr_t is safe */
     62 	sp  = (uintptr_t *)ucp->uc_stack.ss_sp;
     63 	/* LINTED uintptr_t is safe */
     64 	sp += 16;			/* standard frame */
     65 	sp += (argc >= 4 ? argc : 4);	/* Make room for >=4 arguments. */
     66 	sp  = (uintptr_t *)		/* Align on 64-byte boundary. */
     67 	    (((uintptr_t)sp + STACK_ALIGNBYTES) & ~STACK_ALIGNBYTES);
     68 
     69 	/* Save away the registers that we'll need. */
     70 	gr[_REG_SP] = (__greg_t)sp;
     71 	rp = (__greg_t)__resumecontext;
     72 	if (rp & 2) {
     73 		gp = (__greg_t *)(rp & ~3);
     74 		rp = gp[0];
     75 		sp[-8] = gp[1];
     76 	}
     77 	gr[_REG_RP] = rp;
     78 	fp = (__greg_t)func;
     79 	if (fp & 2) {
     80 		gp = (__greg_t *)(fp & ~3);
     81 		fp = gp[0];
     82 		gr[_REG_R19] = gp[1];
     83 	}
     84 	gr[_REG_PCOQH] = fp | HPPA_PC_PRIV_USER;
     85 	gr[_REG_PCOQT] = (fp + 4) | HPPA_PC_PRIV_USER;
     86 	/* LINTED dp is reg27, ref. above, so initialized */
     87 	gr[_REG_DP] = dp;
     88 
     89 	/* Construct argument list. */
     90 	va_start(ap, argc);
     91 	/* Up to the first four arguments are passed in %arg0-3. */
     92 	for (i = 0; i < argc && i < 4; i++) {
     93 		/* LINTED uintptr_t is safe */
     94 		gr[_REG_ARG0 - i] = va_arg(ap, uintptr_t);
     95 	}
     96 	/* Pass remaining arguments on the stack below the %arg0-3 gap. */
     97 	for (; i < argc; i++) {
     98 		/* LINTED uintptr_t is safe */
     99 		sp[-9 - i] = va_arg(ap, uintptr_t);
    100 	}
    101 	va_end(ap);
    102 }
    103