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      1 /* $NetBSD: syscallemu.c,v 1.1 2012/01/05 13:26:51 jmcneill Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2012 Jared D. McNeill <jmcneill (at) invisible.ca>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: syscallemu.c,v 1.1 2012/01/05 13:26:51 jmcneill Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/proc.h>
     34 #include <sys/systm.h>
     35 #include <sys/module.h>
     36 #include <sys/atomic.h>
     37 #include <sys/syscallvar.h>
     38 
     39 #include "syscallemu.h"
     40 
     41 #if !defined(__HAVE_SYSCALL_INTERN)
     42 #error syscallemu requires __HAVE_SYSCALL_INTERN
     43 #endif
     44 
     45 static specificdata_key_t syscallemu_data_key;
     46 static unsigned int syscallemu_refcnt;
     47 
     48 static const struct syscall_package syscallemu_syscalls[] = {
     49 	{ SYS_syscallemu,	0, (sy_call_t *)sys_syscallemu	},
     50 	{ 0, 0, NULL },
     51 };
     52 
     53 struct syscallemu_data *
     54 syscallemu_getsce(struct proc *p)
     55 {
     56 	return proc_getspecific(p, syscallemu_data_key);
     57 }
     58 
     59 void
     60 syscallemu_setsce(struct proc *p, struct syscallemu_data *sce)
     61 {
     62 	proc_setspecific(p, syscallemu_data_key, sce);
     63 }
     64 
     65 /*
     66  * specificdata destructor
     67  */
     68 static void
     69 syscallemu_dtor(void *priv)
     70 {
     71 	struct syscallemu_data *sce = priv;
     72 
     73 	kmem_free(sce, sizeof(*sce));
     74 	atomic_dec_uint(&syscallemu_refcnt);
     75 }
     76 
     77 /*
     78  * Allocate private storage for the syscallemu parameters and stash it
     79  * in process specificdata. This can only be called once per process.
     80  *
     81  * Returns EINVAL if the specified start address falls after the end.
     82  * Returns EACCESS if syscallemu has already been configured for this process.
     83  */
     84 int
     85 sys_syscallemu(lwp_t *l, const struct sys_syscallemu_args *uap,
     86     register_t *retval)
     87 {
     88 	/* {
     89 		syscallarg(uintptr_t) user_start;
     90 		syscallarg(uintptr_t) user_end;
     91 	} */
     92 	vaddr_t user_start = (vaddr_t)SCARG(uap, user_start);
     93 	vaddr_t user_end = (vaddr_t)SCARG(uap, user_end);
     94 	struct syscallemu_data *sce;
     95 	struct proc *p = l->l_proc;
     96 
     97 	if (syscallemu_getsce(p) != NULL)
     98 		return EACCES;
     99 	if (user_start >= user_end)
    100 		return EINVAL;
    101 
    102 	sce = kmem_alloc(sizeof(*sce), KM_SLEEP);
    103 	sce->sce_user_start = user_start;
    104 	sce->sce_user_end = user_end;
    105 	sce->sce_md_syscall = md_syscallemu(p);
    106 	KASSERT(sce->sce_md_syscall != NULL);
    107 
    108 	atomic_inc_uint(&syscallemu_refcnt);
    109 	syscallemu_setsce(p, sce);
    110 
    111 #ifdef DEBUG
    112 	printf("syscallemu: enabled for pid %d\n", p->p_pid);
    113 #endif
    114 
    115 	return 0;
    116 }
    117 
    118 /*
    119  * Initialize the syscallemu module
    120  */
    121 static int
    122 syscallemu_init(void)
    123 {
    124 	int error;
    125 
    126 	syscallemu_refcnt = 0;
    127 
    128 	/* XXX workaround for kern/45781 */
    129 	if (emul_netbsd.e_sysent[SYS_syscallemu].sy_call == sys_nosys) {
    130 		printf("syscallemu: applying workaround for kern/45781\n");
    131 		emul_netbsd.e_sysent[SYS_syscallemu].sy_call = sys_nomodule;
    132 	}
    133 	emul_netbsd.e_sysent[SYS_syscallemu].sy_narg =
    134 	    sizeof(struct sys_syscallemu_args) / sizeof(register_t);
    135 	emul_netbsd.e_sysent[SYS_syscallemu].sy_argsize =
    136 	    sizeof(struct sys_syscallemu_args);
    137 
    138 	error = proc_specific_key_create(&syscallemu_data_key, syscallemu_dtor);
    139 	if (error) {
    140 		printf("syscallemu: couldn't create proc specific key (%d)\n",
    141 		    error);
    142 		return error;
    143 	}
    144 
    145 	error = syscall_establish(NULL, syscallemu_syscalls);
    146 	if (error) {
    147 		printf("syscallemu: couldn't establish syscalls\n");
    148 		proc_specific_key_delete(syscallemu_data_key);
    149 		return ENXIO;
    150 	}
    151 
    152 	return 0;
    153 }
    154 
    155 /*
    156  * Finalize the syscallemu module
    157  */
    158 static int
    159 syscallemu_fini(void)
    160 {
    161 	if (syscallemu_refcnt > 0)
    162 		return EBUSY;
    163 
    164 	syscall_disestablish(NULL, syscallemu_syscalls);
    165 	proc_specific_key_delete(syscallemu_data_key);
    166 	return 0;
    167 }
    168 
    169 /*
    170  * Module glue
    171  */
    172 MODULE(MODULE_CLASS_MISC, syscallemu, NULL);
    173 
    174 static int
    175 syscallemu_modcmd(modcmd_t cmd, void *arg)
    176 {
    177 	switch (cmd) {
    178 	case MODULE_CMD_INIT:
    179 		return syscallemu_init();
    180 	case MODULE_CMD_FINI:
    181 		return syscallemu_fini();
    182 	case MODULE_CMD_AUTOUNLOAD:
    183 		return EBUSY;
    184 	default:
    185 		return ENOTTY;
    186 	}
    187 }
    188