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/* proto1.c: PROTECTION FOR DIGITAL UNIX
*
* $Id$
* Copyright (c) 2001 Ravenbrook Limited. See end of file for license.
*/
/* open sesame magic, see standards(5) */
#define _POSIX_C_SOURCE 199309L
#define _XOPEN_SOURCE_EXTENDED 1
#include "mpm.h"
#ifndef MPS_OS_O1
#error "proto1.c is OSF/1-specific, but MPS_OS_O1 is not set"
#endif
#ifndef PROTECTION
#error "proto1.c implements protection, but PROTECTION is not set"
#endif
#include <limits.h>
#include <stddef.h>
#include <stdlib.h>
#include <signal.h>
#include <siginfo.h>
#include <sys/mman.h>
/* for getpid() */
#include <unistd.h>
SRCID(proto1, "$Id$");
/* The previously-installed signal action, as returned by */
/* sigaction(3). See ProtSetup. */
static struct sigaction sigNext;
/* == Protection Signal Handler ==
*
* This is the signal handler installed by ProtSetup to deal with
* protection faults. It is installed on the SIGSEGV signal.
* It decodes the protection fault details from the signal context
* and passes them to ArenaAccess, which attempts to handle the
* fault and remove its cause. If the fault is handled, then
* the handler returns and execution resumes. If it isn't handled,
* then sigHandle does its best to pass the signal on to the
* previously installed signal handler (sigNext).
*
* .sigh.addr: We assume that the OS decodes the address to something
* sensible
* .sigh.limit: We throw away the limit information.
*/
static void sigHandle(int sig, siginfo_t *info, void *context)
{
int e;
sigset_t sigset, oldset;
struct sigaction sa;
AVER(sig == SIGSEGV);
AVER(info != NULL);
if(info->si_code == SEGV_ACCERR) {
AccessSet mode;
Addr base, limit;
/* We can't determine the access mode (read, write, etc.) */
/* under Solaris without decoding the faulting instruction. */
/* Don't bother, yet. We can do this if necessary. */
mode = AccessREAD | AccessWRITE;
/* We assume that the access is for one word at the address. */
base = (Addr)info->si_addr;
limit = AddrAdd(base, (Size)sizeof(Addr));
/* Offer each protection structure the opportunity to handle the */
/* exception. If it succeeds, then allow the mutator to continue. */
/* MutatorFaultContext parameter is a dummy parameter in this */
/* implementation */
if(ArenaAccess(base, mode, NULL))
return;
}
/* The exception was not handled by any known protection structure, */
/* so throw it to the previously installed handler. */
/* @@ This is really weak.
* Need to implement rest of the contract of sigaction */
e = sigaction(SIGSEGV, &sigNext, &sa);
AVER(e == 0);
sigemptyset(&sigset);
sigaddset(&sigset, SIGSEGV);
e = sigprocmask(SIG_UNBLOCK, &sigset, &oldset);
AVER(e == 0);
kill(getpid(), SIGSEGV);
e = sigprocmask(SIG_SETMASK, &oldset, NULL);
AVER(e == 0);
e = sigaction(SIGSEGV, &sa, NULL);
AVER(e == 0);
}
/* ProtSetup -- global protection setup
*
* Under DIGITAL UNIX, the global setup involves installing a signal handler
* on SIGSEGV to catch and handle protection faults (see sigHandle).
* The previous handler is recorded so that it can be reached from
* sigHandle if it fails to handle the fault.
*
* NOTE: There are problems with this approach:
* 1. we can't honor the wishes of the sigaction(2) entry for the
* previous handler,
* 2. what if this thread is suspended just after calling signal(3)?
* The sigNext variable will never be initialized!
*/
void ProtSetup(void)
{
struct sigaction sa;
int result;
sa.sa_sigaction = sigHandle;
sa.sa_flags = SA_SIGINFO;
result = sigaction(SIGSEGV, &sa, &sigNext);
AVER(result == 0);
}
/* ProtSet -- set protection
*
* This is just a thin veneer on top of mprotect(2).
*/
void ProtSet(Addr base, Addr limit, AccessSet mode)
{
int flags;
AVER(sizeof(size_t) == sizeof(Addr));
AVER(base < limit);
AVER(base != 0);
AVER(AddrOffset(base, limit) <= INT_MAX); /* should be redundant */
/* convert between MPS AccessSet and UNIX PROT thingies. */
switch(mode) {
case AccessWRITE | AccessREAD:
case AccessREAD: /* forbids writes as well */
flags = PROT_NONE;
break;
case AccessWRITE:
flags = PROT_READ | PROT_EXEC;
break;
case AccessSetEMPTY:
flags = PROT_READ | PROT_WRITE | PROT_EXEC;
break;
default:
NOTREACHED;
flags = PROT_NONE;
}
if(mprotect((void *)base, (size_t)AddrOffset(base, limit), flags) != 0)
NOTREACHED;
}
/* ProtSync -- synchronize protection settings with hardware
*
* This does nothing under Solaris.
*/
void ProtSync(Arena arena)
{
UNUSED(arena);
NOOP;
}
/* ProtTramp -- protection trampoline
*
* The protection trampoline is trivial under DIGITAL UNIX, as there is
* nothing that needs to be done in the dynamic context of the mutator in
* order to catch faults. (Contrast this with Win32 Structured Exception
* Handling.)
*/
void ProtTramp(void **resultReturn, void *(*f)(void *, size_t),
void *p, size_t s)
{
AVER(resultReturn != NULL);
AVER(FUNCHECK(f));
/* Can't check p and s as they are interpreted by the client */
*resultReturn = (*f)(p, s);
}
/* C. COPYRIGHT AND LICENSE
*
* Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
* All rights reserved. This is an open source license. Contact
* Ravenbrook for commercial licensing options.
*
* 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.
*
* 3. Redistributions in any form must be accompanied by information on how
* to obtain complete source code for this software and any accompanying
* software that uses this software. The source code must either be
* included in the distribution or be available for no more than the cost
* of distribution plus a nominal fee, and must be freely redistributable
* under reasonable conditions. For an executable file, complete source
* code means the source code for all modules it contains. It does not
* include source code for modules or files that typically accompany the
* major components of the operating system on which the executable file
* runs.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS AND 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.
*/
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