/*      $NetBSD: execregs.c,v 1.2 2025/02/28 16:08:19 riastradh Exp $   */

/*-
 * Copyright (c) 2025 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * 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>
__RCSID("$NetBSD: execregs.c,v 1.2 2025/02/28 16:08:19 riastradh Exp $");

#include "execregs.h"

#include <errno.h>
#include <spawn.h>
#include <stddef.h>
#include <stdint.h>
#include <unistd.h>

extern char **environ;

static unsigned long
nonnull(unsigned long x)
{

        x |= x << 8;
        x |= x << 16;
        return x;
}

/*
 * setfpregs()
 *
 *      Set up all the floating-point registers with something nonzero
 *      in each one.  We initialize the floating-point status register
 *      to set various bits so it's not all zero, but nothing that
 *      would trigger traps.
 */
static void
setfpregs(void)
{
        static const uint64_t fpe[] = {
                (__BITS(63,59)          /* all exception flags (VZOUI) set */
                    | __BIT(58)         /* C bit (comparison) set */
                    | __BITS(54,43)     /* CQ (comparison queue) all set */
                    | __SHIFTIN(1, __BITS(42,41))       /* round toward zero */
                    | __SHIFTIN(0, __BIT(38))   /* no delayed trap */
                    | __SHIFTIN(1, __BIT(37))   /* Denormalized As Zero */
                    | __SHIFTIN(0, __BITS(36,32))       /* exceptions masked */
                    | 0x10101010),
                0x9191919111111111,
                0x9292929212121212,
                0x9393939313131313,
        };
        const uint64_t *fpep = fpe;

        static const double fr[28] = {
                0x1.04p0, 0x1.05p0, 0x1.06p0, 0x1.07p0,
                0x1.08p0, 0x1.09p0, 0x1.0ap0, 0x1.0bp0,
                0x1.0cp0, 0x1.0dp0, 0x1.0ep0, 0x1.0fp0,
                0x1.10p0, 0x1.11p0, 0x1.12p0, 0x1.13p0,
                0x1.14p0, 0x1.15p0, 0x1.16p0, 0x1.17p0,
                0x1.18p0, 0x1.19p0, 0x1.1ap0, 0x1.1bp0,
                0x1.1cp0, 0x1.1dp0, 0x1.1ep0, 0x1.1fp0,
        };
        const double *frp = fr;

        __asm volatile(
                "fldds,ma       8(%0), %%fr0\n\t"
                "fldds,ma       8(%0), %%fr1\n\t"
                "fldds,ma       8(%0), %%fr2\n\t"
                "fldds          0(%0), %%fr3"
            : "+r"(fpep)
            : "m"(fpe));

        __asm volatile(
                "fldds,ma       8(%0), %%fr4\n\t"
                "fldds,ma       8(%0), %%fr5\n\t"
                "fldds,ma       8(%0), %%fr6\n\t"
                "fldds,ma       8(%0), %%fr7\n\t"
                "fldds,ma       8(%0), %%fr8\n\t"
                "fldds,ma       8(%0), %%fr9\n\t"
                "fldds,ma       8(%0), %%fr10\n\t"
                "fldds,ma       8(%0), %%fr11\n\t"
                "fldds,ma       8(%0), %%fr12\n\t"
                "fldds,ma       8(%0), %%fr13\n\t"
                "fldds,ma       8(%0), %%fr14\n\t"
                "fldds,ma       8(%0), %%fr15\n\t"
                "fldds,ma       8(%0), %%fr16\n\t"
                "fldds,ma       8(%0), %%fr17\n\t"
                "fldds,ma       8(%0), %%fr18\n\t"
                "fldds,ma       8(%0), %%fr19\n\t"
                "fldds,ma       8(%0), %%fr20\n\t"
                "fldds,ma       8(%0), %%fr21\n\t"
                "fldds,ma       8(%0), %%fr22\n\t"
                "fldds,ma       8(%0), %%fr23\n\t"
                "fldds,ma       8(%0), %%fr24\n\t"
                "fldds,ma       8(%0), %%fr25\n\t"
                "fldds,ma       8(%0), %%fr26\n\t"
                "fldds,ma       8(%0), %%fr27\n\t"
                "fldds,ma       8(%0), %%fr28\n\t"
                "fldds,ma       8(%0), %%fr29\n\t"
                "fldds,ma       8(%0), %%fr30\n\t"
                "fldds          0(%0), %%fr31"
            : "+r"(frp)
            : "m"(fr));
}

/*
 * setpsw()
 *
 *      Set some bits in PSW, the processor status word.
 */
static void
setpsw(void)
{
        uint32_t x = 0xe0000000, y = 0xffffffff, sum;

        /*
         * Trigger some arithmetic that causes the carry/borrow
         * (PSW[C/B]) bits to be set.
         *
         * XXX Also set PSW[V].
         */
        __asm volatile("sh3add %[sum], %[x], %[y]"
            : /* outputs */ [sum] "=r"(sum)
            : /* inputs */ [x] "r"(x), [y] "r"(y));
}

int
execregschild(char *path)
{
        register long t1 __asm("r22") = nonnull(22);
        register long t2 __asm("r21") = nonnull(21);
        /* r30/sp: stack pointer */
        register long t3 __asm("r20") = nonnull(20);
        /* cr17/iisq_head: privileged */
        /* cr17/iisq_tail: privileged */
        /* cr18/iioq_head: privileged */
        /* cr18/iioq_tail: privileged */
        /* cr15/eiem: privileged */
        /* cr22/ipsw: privileged */
        /* sr3: privileged(?) */
        /* cr8/pidr1: privileged */
        /* cr20/isr: privileged */
        /* cr21/ior: privileged */
        /* cr19/iir: privileged */
        /* flags: N/A(?) */
        long sar = nonnull(0x8a);       /* cr11 */
        /* r1: ADDIL (add immediate left) result, nonnull anyway */
        /* r2/rp: return pointer, nonnull anyway */
        /* r3: frame pointer, nonnull anyway */
        register long r4 __asm("r4") = nonnull(4);
        register long r5 __asm("r5") = nonnull(5);
        register long r6 __asm("r6") = nonnull(6);
        register long r7 __asm("r7") = nonnull(7);
        register long r8 __asm("r8") = nonnull(8);
        register long r9 __asm("r9") = nonnull(9);
        register long r10 __asm("r10") = nonnull(10);
        register long r11 __asm("r11") = nonnull(11);
        register long r12 __asm("r12") = nonnull(12);
        register long r13 __asm("r13") = nonnull(13);
        register long r14 __asm("r14") = nonnull(14);
        register long r15 __asm("r15") = nonnull(15);
        register long r16 __asm("r16") = nonnull(16);
        register long r17 __asm("r17") = nonnull(17);
        register long r18 __asm("r18") = nonnull(18);
        register long t4 __asm("r19") = nonnull(19);
        register long arg3 __asm("r23") = nonnull(23);
        /* r24/arg2: envp, nonnull anyway */
        /* r25/arg1: argv, nonnull anyway */
        /* r26/arg0: path, nonnull anyway */
        /* r27/dp: data pointer, nonnull anyway */
        register long ret0 __asm("r28") = nonnull(28);
        register long ret1 __asm("r29") = nonnull(29);
        register long r31 __asm("r31") = nonnull(31);
        /* sr0-sr7: space registers initialized by kernel */
        /* cr9/pidr2: privileged */
        /* cr12/pidr3: privileged */
        /* cr13/pidr4: privileged */
        /* cr0/rctr: privileged */
        /* cr10/ccr: privileged */
        /* cr23/eirr: privileged */
        /* cr24: privileged */
        /* cr25/vtop: privileged */
        /* cr27/tr3: _lwp_private, thread-local storage -- nonnull anyway */
        /* cr28: privileged */
        /* cr30/fpregs: privileged */
        /* cr31: privileged */

        char *argv[] = {path, NULL};
        char **envp = environ;

        setfpregs();
        setpsw();

        /*
         * Not perfect -- compiler might use some registers for
         * stack/argument transfers, but all the arguments are nonnull
         * so this is probably a good test anyway.
         */
        __asm volatile("mtctl %[sar], %%sar"    /* cr11 */
            : /* outputs */
            : [sar] "r"(sar)
            : "memory");
        __asm volatile("" :
            "+r"(t1),
            "+r"(t2),
            "+r"(t3),
            "+r"(r4),
            "+r"(r5),
            "+r"(r6),
            "+r"(r7),
            "+r"(r8),
            "+r"(r9),
            "+r"(r10),
            "+r"(r11),
            "+r"(r12)
            :: "memory");
        /* pacify gcc error: more than 30 operands in 'asm' */
        __asm volatile("" :
            "+r"(r13),
            "+r"(r14),
            "+r"(r15),
            "+r"(r16),
            "+r"(r17),
            "+r"(r18),
            "+r"(t4),
            "+r"(arg3),
            "+r"(ret0),
            "+r"(ret1),
            "+r"(r31)
            :: "memory");

        return execve(path, argv, envp);
}

pid_t
spawnregschild(char *path, int fd)
{
        register long t1 __asm("r22") = nonnull(22);
        register long t2 __asm("r21") = nonnull(21);
        /* r30/sp: stack pointer */
        register long t3 __asm("r20") = nonnull(20);
        /* cr17/iisq_head: privileged */
        /* cr17/iisq_tail: privileged */
        /* cr18/iioq_head: privileged */
        /* cr18/iioq_tail: privileged */
        /* cr15/eiem: privileged */
        /* cr22/ipsw: privileged */
        /* sr3: privileged(?) */
        /* cr8/pidr1: privileged */
        /* cr20/isr: privileged */
        /* cr21/ior: privileged */
        /* cr19/iir: privileged */
        /* flags: N/A(?) */
        long sar = nonnull(0x8a);       /* cr11 */
        /* r1: ADDIL (add immediate left) result, nonnull anyway */
        /* r2/rp: return pointer, nonnull anyway */
        /* r3: frame pointer, nonnull anyway */
        register long r4 __asm("r4") = nonnull(4);
        register long r5 __asm("r5") = nonnull(5);
        register long r6 __asm("r6") = nonnull(6);
        register long r7 __asm("r7") = nonnull(7);
        register long r8 __asm("r8") = nonnull(8);
        register long r9 __asm("r9") = nonnull(9);
        register long r10 __asm("r10") = nonnull(10);
        register long r11 __asm("r11") = nonnull(11);
        register long r12 __asm("r12") = nonnull(12);
        register long r13 __asm("r13") = nonnull(13);
        register long r14 __asm("r14") = nonnull(14);
        register long r15 __asm("r15") = nonnull(15);
        register long r16 __asm("r16") = nonnull(16);
        register long r17 __asm("r17") = nonnull(17);
        register long r18 __asm("r18") = nonnull(18);
        register long t4 __asm("r19") = nonnull(19);
        /* r23/arg3: attrp, nonnull anyway */
        /* r24/arg2: fileactsp, nonnull anyway */
        /* r25/arg1: path, nonnull anyway */
        /* r26/arg0: pidp, nonnull anyway */
        /* r27/dp: data pointer, nonnull anyway */
        register long ret0 __asm("r28") = nonnull(28);
        register long ret1 __asm("r29") = nonnull(29);
        register long r31 __asm("r31") = nonnull(31);
        /* sr0-sr7: space registers initialized by kernel */
        /* cr9/pidr2: privileged */
        /* cr12/pidr3: privileged */
        /* cr13/pidr4: privileged */
        /* cr0/rctr: privileged */
        /* cr10/ccr: privileged */
        /* cr23/eirr: privileged */
        /* cr24: privileged */
        /* cr25/vtop: privileged */
        /* cr27/tr3: _lwp_private, thread-local storage -- nonnull anyway */
        /* cr28: privileged */
        /* cr30/fpregs: privileged */
        /* cr31: privileged */

        char *argv[] = {path, NULL};
        char **envp = environ;
        posix_spawn_file_actions_t fileacts;
        posix_spawnattr_t attr;
        pid_t pid;
        int error;

        error = posix_spawn_file_actions_init(&fileacts);
        if (error)
                goto out;
        error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
        if (error)
                goto out;
        error = posix_spawnattr_init(&attr);
        if (error)
                goto out;

        setfpregs();
        setpsw();

        /*
         * Not perfect -- compiler might use some registers for
         * stack/argument transfers, but all the arguments are nonnull
         * so this is probably a good test anyway.
         */
        __asm volatile("mtctl %[sar], %%sar"    /* cr11 */
            : /* outputs */
            : [sar] "r"(sar)
            : "memory");
        __asm volatile("" :
            "+r"(t1),
            "+r"(t2),
            "+r"(t3),
            "+r"(r4),
            "+r"(r5),
            "+r"(r6),
            "+r"(r7),
            "+r"(r8),
            "+r"(r9),
            "+r"(r10),
            "+r"(r11),
            "+r"(r12)
            :: "memory");
        /* pacify gcc error: more than 30 operands in 'asm' */
        __asm volatile("" :
            "+r"(r13),
            "+r"(r14),
            "+r"(r15),
            "+r"(r16),
            "+r"(r17),
            "+r"(r18),
            "+r"(t4),
            "+r"(ret0),
            "+r"(ret1),
            "+r"(r31)
            :: "memory");

        error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
        if (error)
                goto out;

out:    posix_spawnattr_destroy(&attr);
        posix_spawn_file_actions_destroy(&fileacts);
        if (error) {
                errno = error;
                return -1;
        }
        return 0;
}