/*      $NetBSD: makecontext.c,v 1.8 2025/04/25 01:18:51 riastradh Exp $        */

/*-
 * Copyright (c) 2001 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Klaus Klein.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: makecontext.c,v 1.8 2025/04/25 01:18:51 riastradh Exp $");
#endif

#include <sys/param.h>
#include <sys/types.h>

#include <machine/frame.h>

#include <inttypes.h>
#include <stdarg.h>
#include <stddef.h>
#include <ucontext.h>

#include "extern.h"

void __resumecontext(void) __dead;

void
makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
{
        __greg_t *gr = ucp->uc_mcontext.__gregs;
        __greg_t *gp, rp, fp;
        register __greg_t dp __asm("r27");
        uintptr_t *sp;
        int i;
        va_list ap;

        /* LINTED uintptr_t is safe */
        sp  = (uintptr_t *)ucp->uc_stack.ss_sp;
        /* LINTED uintptr_t is safe */
        sp += 16;                       /* standard frame */
        sp += (argc >= 4 ? argc : 4);   /* Make room for >=4 arguments. */
        sp  = (uintptr_t *)             /* Align on 64-byte boundary. */
            (((uintptr_t)sp + STACK_ALIGNBYTES) & ~STACK_ALIGNBYTES);

        /* Save away the registers that we'll need. */
        gr[_REG_SP] = (__greg_t)sp;
        rp = (__greg_t)__resumecontext;
        if (rp & 2) {
                gp = (__greg_t *)(rp & ~3);
                rp = gp[0];
                sp[-8] = gp[1];
        }
        gr[_REG_RP] = rp;
        fp = (__greg_t)func;
        if (fp & 2) {
                gp = (__greg_t *)(fp & ~3);
                fp = gp[0];
                gr[_REG_R19] = gp[1];
        }
        gr[_REG_PCOQH] = fp | HPPA_PC_PRIV_USER;
        gr[_REG_PCOQT] = (fp + 4) | HPPA_PC_PRIV_USER;
        /* LINTED dp is reg27, ref. above, so initialized */
        gr[_REG_DP] = dp;

        /* Construct argument list. */
        va_start(ap, argc);
        /* Up to the first four arguments are passed in %arg0-3. */
        for (i = 0; i < argc && i < 4; i++) {
                /* LINTED uintptr_t is safe */
                gr[_REG_ARG0 - i] = va_arg(ap, uintptr_t);
        }
        /* Pass remaining arguments on the stack below the %arg0-3 gap. */
        for (; i < argc; i++) {
                /* LINTED uintptr_t is safe */
                sp[-9 - i] = va_arg(ap, uintptr_t);
        }
        va_end(ap);
}