/* $NetBSD: syscallemu_x86.c,v 1.1 2012/01/06 13:16:20 jmcneill Exp $ */

/*-
* Copyright (c) 2011 Reinoud Zandijk <[email protected]>
* Copyright (c) 2012 Jared D. McNeill <[email protected]>
* 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>
__KERNEL_RCSID(0, "$NetBSD: syscallemu_x86.c,v 1.1 2012/01/06 13:16:20 jmcneill Exp $");

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>

#include <machine/userret.h>

#include "syscallemu.h"

/*
* If syscallemu specific data is present for the process, verify that the
* caller is allowed to execute system calls. If not, deliver a SIGILL to
* the process. When syscallemu specific data is not present, simply defer
* to the original syscall handler.
*/
static void
x86_syscall_emu(struct trapframe *frame)
{
       void (*md_syscall)(struct trapframe *) = NULL;
       struct syscallemu_data *sce;
       register_t rip_call;
       struct proc *p;
       ksiginfo_t ksi;
       lwp_t *l;

       l = curlwp;
       p = l->l_proc;

       rip_call = X86_TF_RIP(frame) - frame->tf_err;

       /* Determine if we need to emulate the system call */
       sce = syscallemu_getsce(p);
       if (sce) {
               if ((rip_call >= sce->sce_user_start &&
                    rip_call < sce->sce_user_end) ||
                   (rip_call + frame->tf_err >= sce->sce_user_start &&
                    rip_call + frame->tf_err < sce->sce_user_end)) {
                       md_syscall = NULL;
               } else {
                       md_syscall = sce->sce_md_syscall;
               }
       } else {
               md_syscall = p->p_md.md_syscall;
       }

       if (md_syscall == NULL) {
               /* If emulating, deliver SIGILL to process */
               X86_TF_RIP(frame) = rip_call;
               KSI_INIT_TRAP(&ksi);
               ksi.ksi_signo = SIGILL;
               ksi.ksi_code = ILL_ILLTRP;
               ksi.ksi_addr = (void *)X86_TF_RIP(frame);
               ksi.ksi_trap = 0;
               trapsignal(l, &ksi);
               userret(l);
       } else {
               /* Not emulating, so treat as a normal syscall */
               KASSERT(md_syscall != NULL);
               md_syscall(frame);
       }
}

/*
* Set p_md.md_syscall to our syscall filter, and return a pointer to the
* original syscall handler.
*/
void *
md_syscallemu(struct proc *p)
{
       void *osyscall;

       osyscall = p->p_md.md_syscall;
       p->p_md.md_syscall = x86_syscall_emu;

       return osyscall;
}