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This was achieved by partially undoing changelist 24817, including an accidental corruption of eventgen.pl. Copied from Perforce Change: 24877 ServerID: perforce.ravenbrook.com
152 lines
4.6 KiB
C
152 lines
4.6 KiB
C
/* impl.c.protlii3: PROTECTION FOR LINUX (INTEL 386)
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*
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* $Id$
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* $HopeName: MMsrc!protlii3.c(trunk.4) $
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* Copyright (c) 2001 Ravenbrook Limited.
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*
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* SOURCES
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*
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* .source.i486: Intel486 Microprocessor Family Programmer's
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* Reference Manual
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*
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* .source.linux.kernel: Linux kernel source files.
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*/
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#include "prmcli.h"
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#ifndef MPS_OS_LI
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#error "protlii3.c is Linux-specific, but MPS_OS_LI is not set"
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#endif
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#if !defined(MPS_ARCH_I3) && !defined(MPS_ARCH_I4)
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#error "protlii3.c is Intel-specific, but MPS_ARCH_I3 or MPS_ARCH_I4 is not set"
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#endif
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#ifndef PROTECTION
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#error "protlii3.c implements protection, but PROTECTION is not set"
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#endif
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#include <limits.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <signal.h>
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SRCID(protlii3, "$Id$");
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/* Useful stuff that doesn't appear to be in any header files. */
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/* Interrupt number 14 is Page Fault. */
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#define TRAPNO_PAGE_FAULT 14
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/* Bits in err field of sigcontext for interrupt 14 (page fault) */
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#define PAGE_FAULT_ERR_PAGEPROT 0x1
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#define PAGE_FAULT_ERR_WRITE 0x2
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#define PAGE_FAULT_ERR_USERMODE 0x4
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/* The previously-installed signal action, as returned by */
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/* sigaction(3). See ProtSetup. */
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static struct sigaction sigNext;
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typedef void (*__real_lii3_sighandler_t)(int, struct sigcontext);
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/* sigHandle -- protection signal handler
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*
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* This is the signal handler installed by ProtSetup to deal with
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* protection faults. It is installed on the SIGSEGV signal.
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* It decodes the protection fault details from the signal context
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* and passes them to ArenaAccess, which attempts to handle the
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* fault and remove its cause. If the fault is handled, then
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* the handler returns and execution resumes. If it isn't handled,
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* then sigHandle does its best to pass the signal on to the
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* previously installed signal handler (sigNext).
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*
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* .sigh.args: There is no officially documented way of getting the
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* sigcontext, but on x86 Linux at least it is passed BY VALUE as a
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* second argument to the signal handler. The prototype doesn't
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* include this arg.
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* See .source.linux.kernel (linux/arch/i386/kernel/signal.c).
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*
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* .sigh.context: We only know how to handle interrupt 14, where
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* context.err gives the page fault error code and context.cr2 gives
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* the fault address. See .source.i486 (9.9.14) and
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* .source.linux.kernel (linux/arch/i386/mm/fault.c).
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*
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* .sigh.addr: We assume that the OS decodes the address to something
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* sensible
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*/
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static void sigHandle(int sig, struct sigcontext context) /* .sigh.args */
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{
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AVER(sig == SIGSEGV);
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if(context.trapno == TRAPNO_PAGE_FAULT) { /* .sigh.context */
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AccessSet mode;
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Addr base, limit;
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MutatorFaultContextStruct mfContext;
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mfContext.scp = &context;
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mode = ((context.err & PAGE_FAULT_ERR_WRITE) != 0) /* .sigh.context */
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? (AccessREAD | AccessWRITE)
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: AccessREAD;
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/* We assume that the access is for one word at the address. */
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base = (Addr)context.cr2; /* .sigh.addr */
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limit = AddrAdd(base, (Size)sizeof(Addr));
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/* Offer each protection structure the opportunity to handle the */
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/* exception. If it succeeds, then allow the mutator to continue. */
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if(ArenaAccess(base, mode, &mfContext))
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return;
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}
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/* The exception was not handled by any known protection structure, */
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/* so throw it to the previously installed handler. */
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/* @@@@ This is really weak. */
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/* Need to implement rest of the contract of sigaction */
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/* We might also want to set SA_RESETHAND in the flags and explicitly */
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/* reinstall the handler from withint itself so the SIG_DFL/SIG_IGN */
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/* case can work properly by just returning. */
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switch ((int)sigNext.sa_handler) {
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case (int)SIG_DFL:
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case (int)SIG_IGN:
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abort();
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NOTREACHED;
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break;
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default:
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(*(__real_lii3_sighandler_t)sigNext.sa_handler)(sig, context);
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break;
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}
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}
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/* ProtSetup -- global protection setup
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*
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* Under Linux, the global setup involves installing a signal handler
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* on SIGSEGV to catch and handle page faults (see sigHandle).
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* The previous handler is recorded so that it can be reached from
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* sigHandle if it fails to handle the fault.
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*
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* NOTE: There are problems with this approach:
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* 1. we can't honor the sa_flags for the previous handler,
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* 2. what if this thread is suspended just after calling signal(3)?
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* The sigNext variable will never be initialized!
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*/
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void ProtSetup(void)
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{
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struct sigaction sa;
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int result;
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sa.sa_handler = (__sighandler_t)sigHandle; /* .sigh.args */
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sigemptyset(&sa.sa_mask);
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sa.sa_flags = 0;
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result = sigaction(SIGSEGV, &sa, &sigNext);
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AVER(result == 0);
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}
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