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/* protxcpp.c: PROTECTION FOR MAC OS X ON POWERPC
*
* $Id$
* Copyright (c) 2001,2005 Ravenbrook Limited. See end of file for license.
*
* Most of this was copied from protso.c and modified.
*
* REFERENCES
*
* [PEM] "PowerPC Microprocessor Family: The Programming Environments for
* 32-bit Microprocessors", Motorola, 1997-01. MPCFPE32B/AD REV.1
*
* [SIGNALH] /usr/include/sys/signal.h on drj's iBook (Mac OS X 10.3.8)
*
* [PPCUCH] /usr/include/ppc/ucontext.h
*
*/
#include "mpm.h"
#ifndef MPS_OS_XC
#error "protxcpp.c is Mac OS X specific, but MPS_OS_XC is not set"
#endif
#ifndef MPS_ARCH_PP
#error "protxcpp.c is PowerPC specific, but MPS_ARCH_PP is not set"
#endif
#ifndef PROTECTION
#error "protxcpp.c implements protection, but PROTECTION is not set"
#endif
#include <signal.h>
#include <sys/ucontext.h>
SRCID(protxcpp, "$Id$");
/* The previously-installed signal action, as returned by */
/* sigaction(3). See ProtSetup. */
static struct sigaction sigNext;
/* sigHandle -- protection signal handler
*
* This is the signal handler installed by ProtSetup to deal with
* protection faults. It is installed on the SIGBUS 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: si_addr, on Darwin 7.8.0, is the address of the faulting
* instruction (by observation). [SIGNALH] says, in the declaration of
* siginfo_t, that this field should be the faulting instruction, but
* below that says that for SIGBUS it should be the faulting address).
* We grub around in the ucontext to find the PowerPC DAR register (See
* [PEM] 6-25, Table 6-9) which contains the faulting address.
*
* .sigh.limit: We throw away the limit information.
*/
static void sigHandle(int sig, siginfo_t *info, void *contextArg)
{
ucontext_t *ucontext;
AVER(sig == SIGBUS);
AVER(info != NULL);
ucontext = contextArg;
/* On OS X the si_code field does't appear to be useful. Protection
* faults appear as SIGBUS signals, and the only documented code for
* SIGBUS is BUS_ADRALN (invalid address alignment) which is what
* si_code is set to (it has value 1), even though the address is
* in fact aligned.
* On other platforms a test like info->si_code == SEGV_ACCERR appears
* here. */
if(1) {
AccessSet mode;
Addr base, limit;
/* We dont't bother to determine the access mode (read, write, etc.)
* under OS X. It's possible that this information is available in
* the context structures. Needs more investigation.
*/
mode = AccessREAD | AccessWRITE;
/* We assume that the access is for one word at the address. */
/* See [PPCUCH] */
base = (Addr)ucontext->uc_mcontext->es.dar;
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 for 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 */
(*sigNext.sa_sigaction)(sig, info, contextArg);
}
/* ProtSetup -- global protection setup
*
* Under OS X, the global setup involves installing a signal handler
* on SIGBUS 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 sigvec(2) entry for the
* previous handler,
*/
/* This function itself probably isn't architecture specific, but it
* references the sigHandle which is currently static and which is
* architecture specific. */
void ProtSetup(void)
{
struct sigaction sa;
int result;
sa.sa_sigaction = sigHandle;
/* No idea if sigemptyset is necessary, copied from protfri3.c,
* 2005-03-02 DRJ */
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_SIGINFO;
result = sigaction(SIGBUS, &sa, &sigNext);
AVER(result == 0);
}
/* C. COPYRIGHT AND LICENSE
*
* Copyright (C) 2001-2002,2005 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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