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/* protli.c: PROTECTION FOR LINUX (INTEL 386)
*
* $Id$
* Copyright (c) 2001 Ravenbrook Limited. See end of file for license.
*
* SOURCES
*
* .source.i486: Intel486 Microprocessor Family Programmer's
* Reference Manual
*
* .source.linux.kernel: Linux kernel source files.
*/
#include "prmcix.h"
#ifndef MPS_OS_LI
#error "protli.c is Linux-specific, but MPS_OS_LI is not set"
#endif
#ifndef PROTECTION
#error "protli.c implements protection, but PROTECTION is not set"
#endif
#include <limits.h>
#include <stddef.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
SRCID(protli, "$Id$");
/* 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 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.context: We check si_code for being a memory access
* si_addr gives the fault address. See
* .source.linux.kernel (linux/arch/i386/mm/fault.c and
* linux/arch/x86/mm/fault.c).
*
* .sigh.addr: We assume that the OS decodes the address to something
* sensible
*/
/* This is defined here to keep the sources closer to those in protsgix.c
* They can't be merged yet because protsgix doesn't pass the context to
* ArenaAccess */
#define PROT_SIGNAL SIGSEGV
static void sigHandle(int sig, siginfo_t *info, void *context) /* .sigh.args */
{
int e;
/* sigset renamed to asigset due to clash with global on Darwin. */
sigset_t asigset, oldset;
struct sigaction sa;
AVER(sig == PROT_SIGNAL);
if(info->si_code == SEGV_ACCERR) { /* .sigh.context */
AccessSet mode;
Addr base;
ucontext_t *ucontext;
MutatorFaultContextStruct mfContext;
ucontext = (ucontext_t *)context;
mfContext.ucontext = ucontext;
mfContext.info = info;
/* on linux we used to be able to tell whether this was a read or a write */
mode = AccessREAD | AccessWRITE;
/* We assume that the access is for one word at the address. */
base = (Addr)info->si_addr; /* .sigh.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. */
if(ArenaAccess(base, mode, &mfContext))
return;
}
/* The exception was not handled by any known protection structure, */
/* so throw it to the previously installed handler. That handler won't */
/* get an accurate context (the MPS would fail if it were the second in */
/* line) but it's the best we can do. */
e = sigaction(PROT_SIGNAL, &sigNext, &sa);
AVER(e == 0);
sigemptyset(&asigset);
sigaddset(&asigset, PROT_SIGNAL);
e = sigprocmask(SIG_UNBLOCK, &asigset, &oldset);
AVER(e == 0);
kill(getpid(), PROT_SIGNAL);
e = sigprocmask(SIG_SETMASK, &oldset, NULL);
AVER(e == 0);
e = sigaction(PROT_SIGNAL, &sa, NULL);
AVER(e == 0);
}
/* ProtSetup -- global protection setup
*
* Under Linux, the global setup involves installing a signal handler
* on SIGSEGV to catch and handle page 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 sa_flags 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;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_SIGINFO;
result = sigaction(PROT_SIGNAL, &sa, &sigNext);
AVER(result == 0);
}
/* 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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