/*      $NetBSD: compat_16_machdep.c,v 1.34 2022/08/20 23:49:31 riastradh Exp $ */

/*-
 * Copyright (c) 1996, 1997, 1998, 2000 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Charles M. Hannum.
 *
 * 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>
__KERNEL_RCSID(0, "$NetBSD: compat_16_machdep.c,v 1.34 2022/08/20 23:49:31 riastradh Exp $");

#ifdef _KERNEL_OPT
#include "opt_compat_netbsd.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/signal.h>
#include <sys/signalvar.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>

#include <uvm/uvm_extern.h>

#include <machine/pmap.h>
#include <machine/pmap_private.h>
#include <machine/vmparam.h>
#include <x86/fpu.h>

#if defined(COMPAT_16)

#include <compat/sys/signal.h>
#include <compat/sys/signalvar.h>
/*
 * System call to cleanup state after a signal
 * has been taken.  Reset signal mask and
 * stack state from context left by sendsig (above).
 * Return to previous pc and psl as specified by
 * context left by sendsig. Check carefully to
 * make sure that the user has not modified the
 * psl to gain improper privileges or to cause
 * a machine fault.
 */
int compat_16_sys___sigreturn14(struct lwp *, const struct compat_16_sys___sigreturn14_args *, register_t *);

int
compat_16_sys___sigreturn14(struct lwp *l, const struct compat_16_sys___sigreturn14_args *uap, register_t *retval)
{
        /* {
                syscallarg(struct sigcontext *) sigcntxp;
        } */
        struct proc *p = l->l_proc;
        struct sigcontext *scp, context;
        struct trapframe *tf;

        /*
         * The trampoline code hands us the context.
         * It is unsafe to keep track of it ourselves, in the event that a
         * program jumps out of a signal handler.
         */
        scp = SCARG(uap, sigcntxp);
        if (copyin((void *)scp, &context, sizeof(*scp)) != 0)
                return (EFAULT);

        /* Restore register context. */
        tf = l->l_md.md_regs;

        /*
         * Check for security violations.  If we're returning to
         * protected mode, the CPU will validate the segment registers
         * automatically and generate a trap on violations.  We handle
         * the trap, rather than doing all of the checking here.
         */
        if (((context.sc_eflags ^ tf->tf_eflags) & PSL_USERSTATIC) != 0 ||
            !USERMODE(context.sc_cs))
                return (EINVAL);

        tf->tf_gs = context.sc_gs;
        tf->tf_fs = context.sc_fs;
        tf->tf_es = context.sc_es;
        tf->tf_ds = context.sc_ds;
        tf->tf_eflags &= ~PSL_USER;
        tf->tf_eflags |= context.sc_eflags & PSL_USER;

        tf->tf_edi = context.sc_edi;
        tf->tf_esi = context.sc_esi;
        tf->tf_ebp = context.sc_ebp;
        tf->tf_ebx = context.sc_ebx;
        tf->tf_edx = context.sc_edx;
        tf->tf_ecx = context.sc_ecx;
        tf->tf_eax = context.sc_eax;
        tf->tf_eip = context.sc_eip;
        tf->tf_cs = context.sc_cs;
        tf->tf_esp = context.sc_esp;
        tf->tf_ss = context.sc_ss;

        /* Restore signal stack. */
        mutex_enter(p->p_lock);
        if (context.sc_onstack & SS_ONSTACK)
                l->l_sigstk.ss_flags |= SS_ONSTACK;
        else
                l->l_sigstk.ss_flags &= ~SS_ONSTACK;
        /* Restore signal mask. */
        (void) sigprocmask1(l, SIG_SETMASK, &context.sc_mask, 0);
        mutex_exit(p->p_lock);

        return (EJUSTRETURN);
}
#endif

#ifdef COMPAT_16
/*
 * Send an interrupt to process.
 *
 * Stack is set up to allow sigcode stored
 * in u. to call routine, followed by kcall
 * to sigreturn routine below.  After sigreturn
 * resets the signal mask, the stack, and the
 * frame pointer, it returns to the user
 * specified pc, psl.
 */
void
sendsig_sigcontext(const ksiginfo_t *ksi, const sigset_t *mask)
{
        struct lwp *l = curlwp;
        struct proc *p = l->l_proc;
        struct pmap *pmap = vm_map_pmap(&p->p_vmspace->vm_map);
        int sel = pmap->pm_hiexec > I386_MAX_EXE_ADDR ?
            GUCODEBIG_SEL : GUCODE_SEL;
        struct sigacts *ps = p->p_sigacts;
        struct trapframe *tf = l->l_md.md_regs;
        int onstack, error;
        int sig = ksi->ksi_signo;
        u_long code = KSI_TRAPCODE(ksi);
        struct sigframe_sigcontext *fp = getframe(l, sig, &onstack), frame;
        sig_t catcher = SIGACTION(p, sig).sa_handler;

        fp--;

        /* Build stack frame for signal trampoline. */
        switch (ps->sa_sigdesc[sig].sd_vers) {
        case __SIGTRAMP_SIGCODE_VERSION:        /* legacy on-stack sigtramp */
                frame.sf_ra = (int)p->p_sigctx.ps_sigcode;
                break;

        case __SIGTRAMP_SIGCONTEXT_VERSION:
                frame.sf_ra = (int)ps->sa_sigdesc[sig].sd_tramp;
                break;

        default:
                /* Don't know what trampoline version; kill it. */
                sigexit(l, SIGILL);
        }

        frame.sf_signum = sig;
        frame.sf_code = code;
        frame.sf_scp = &fp->sf_sc;

        /* Save register context. */
        frame.sf_sc.sc_gs = tf->tf_gs;
        frame.sf_sc.sc_fs = tf->tf_fs;
        frame.sf_sc.sc_es = tf->tf_es;
        frame.sf_sc.sc_ds = tf->tf_ds;
        frame.sf_sc.sc_eflags = tf->tf_eflags;

        frame.sf_sc.sc_edi = tf->tf_edi;
        frame.sf_sc.sc_esi = tf->tf_esi;
        frame.sf_sc.sc_ebp = tf->tf_ebp;
        frame.sf_sc.sc_ebx = tf->tf_ebx;
        frame.sf_sc.sc_edx = tf->tf_edx;
        frame.sf_sc.sc_ecx = tf->tf_ecx;
        frame.sf_sc.sc_eax = tf->tf_eax;
        frame.sf_sc.sc_eip = tf->tf_eip;
        frame.sf_sc.sc_cs = tf->tf_cs;
        frame.sf_sc.sc_esp = tf->tf_esp;
        frame.sf_sc.sc_ss = tf->tf_ss;
        frame.sf_sc.sc_trapno = tf->tf_trapno;
        frame.sf_sc.sc_err = tf->tf_err;

        /* Save signal stack. */
        frame.sf_sc.sc_onstack = l->l_sigstk.ss_flags & SS_ONSTACK;

        /* Save signal mask. */
        frame.sf_sc.sc_mask = *mask;

#ifdef COMPAT_13
        /*
         * XXX We always have to save an old style signal mask because
         * XXX we might be delivering a signal to a process which will
         * XXX escape from the signal in a non-standard way and invoke
         * XXX sigreturn() directly.
         */
        native_sigset_to_sigset13(mask, &frame.sf_sc.__sc_mask13);
#endif

        sendsig_reset(l, sig);

        mutex_exit(p->p_lock);
        error = copyout(&frame, fp, sizeof(frame));
        mutex_enter(p->p_lock);

        if (error != 0) {
                /*
                 * Process has trashed its stack; give it an illegal
                 * instruction to halt it in its tracks.
                 */
                sigexit(l, SIGILL);
                /* NOTREACHED */
        }

        buildcontext(l, sel, catcher, fp);

        /* Remember that we're now on the signal stack. */
        if (onstack)
                l->l_sigstk.ss_flags |= SS_ONSTACK;
}
#endif