X-Git-Url: http://plrg.eecs.uci.edu/git/?p=model-checker.git;a=blobdiff_plain;f=snapshot.cc;h=1e7d80b4b5d836d1c4a1cdb653824a626afb82c8;hp=4d71babeb967f9b8daba74542b6fa8044f120380;hb=2cb7ca6d0aa997474b63f240c165e1a941cf6124;hpb=7962faac2edf30977bf5c837e0452c2accb23789 diff --git a/snapshot.cc b/snapshot.cc index 4d71bab..1e7d80b 100644 --- a/snapshot.cc +++ b/snapshot.cc @@ -17,34 +17,58 @@ #include #include -//extern declaration definition -#define FAILURE(mesg) { printf("failed in the API: %s with errno relative message: %s\n", mesg, strerror( errno ) ); exit( -1 ); } +#define FAILURE(mesg) { printf("failed in the API: %s with errno relative message: %s\n", mesg, strerror( errno ) ); exit(EXIT_FAILURE); } + +#ifdef CONFIG_SSDEBUG +#define SSDEBUG printf +#else +#define SSDEBUG(...) do { } while (0) +#endif + +/* extern declaration definition */ #if USE_MPROTECT_SNAPSHOT struct SnapShot * snapshotrecord = NULL; -struct Snapshot_t * sTheRecord = NULL; #else -struct Snapshot_t * sTheRecord = NULL; +struct Snapshot * sTheRecord = NULL; #endif -void DumpIntoLog( const char * filename, const char * message ){ -#if SSDEBUG - static pid_t thePID = getpid(); - char newFn[ 1024 ] ={ 0 }; - sprintf( newFn,"%s-%d.txt", filename, thePID ); - FILE * myFile = fopen( newFn, "w+" ); - fprintf( myFile, "the message %s: the process id %d\n", message, thePID ); - fflush( myFile ); - fclose( myFile ); - myFile = NULL; -#endif -} + #if !USE_MPROTECT_SNAPSHOT +/** @statics +* These variables are necessary because the stack is shared region and +* there exists a race between all processes executing the same function. +* To avoid the problem above, we require variables allocated in 'safe' regions. +* The bug was actually observed with the forkID, these variables below are +* used to indicate the various contexts to which to switch to. +* +* @savedSnapshotContext: contains the point to which takesnapshot() call should switch to. +* @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to +* @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record +*/ static ucontext_t savedSnapshotContext; static ucontext_t savedUserSnapshotContext; static snapshot_id snapshotid = 0; #endif -/* Initialize snapshot data structure */ + +/** PageAlignedAdressUpdate return a page aligned address for the + * address being added as a side effect the numBytes are also changed. + */ +static void * PageAlignAddressUpward(void * addr) { + return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1)); +} + #if USE_MPROTECT_SNAPSHOT -void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions) { + +/** ReturnPageAlignedAddress returns a page aligned address for the + * address being added as a side effect the numBytes are also changed. + */ +static void * ReturnPageAlignedAddress(void * addr) { + return (void *)(((uintptr_t)addr)&~(PAGESIZE-1)); +} + +/** The initSnapShotRecord method initialized the snapshotting data + * structures for the mprotect based snapshot. + */ +static void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions) { snapshotrecord=( struct SnapShot * )MYMALLOC(sizeof(struct SnapShot)); snapshotrecord->regionsToSnapShot=( struct MemoryRegion * )MYMALLOC(sizeof(struct MemoryRegion)*nummemoryregions); snapshotrecord->backingStoreBasePtr= ( struct SnapShotPage * )MYMALLOC( sizeof( struct SnapShotPage ) * (numbackingpages + 1) ); @@ -59,15 +83,17 @@ void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, snapshotrecord->maxBackingPages=numbackingpages; snapshotrecord->maxSnapShots=numsnapshots; } -#endif //nothing to initialize for the fork based snapshotting. -void HandlePF( int sig, siginfo_t *si, void * unused){ -#if USE_MPROTECT_SNAPSHOT +/** HandlePF is the page fault handler for mprotect based snapshotting + * algorithm. + */ +static void HandlePF( int sig, siginfo_t *si, void * unused){ if( si->si_code == SEGV_MAPERR ){ printf("Real Fault at %p\n", si->si_addr); exit( EXIT_FAILURE ); } void* addr = ReturnPageAlignedAddress(si->si_addr); + unsigned int backingpage=snapshotrecord->lastBackingPage++; //Could run out of pages... if (backingpage==snapshotrecord->maxBackingPages) { printf("Out of backing pages at %p\n", si->si_addr); @@ -83,43 +109,34 @@ void HandlePF( int sig, siginfo_t *si, void * unused){ perror("mprotect"); // Handle error by quitting? } -#endif //nothing to handle for non snapshotting case. -} - -//Return a page aligned address for the address being added -//as a side effect the numBytes are also changed. -void * ReturnPageAlignedAddress(void * addr) { - return (void *)(((uintptr_t)addr)&~(PAGESIZE-1)); } +#endif //nothing to handle for non snapshotting case. -//Return a page aligned address for the address being added -//as a side effect the numBytes are also changed. -void * PageAlignAddressUpward(void * addr) { - return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1)); -} -#ifdef __cplusplus -extern "C" { -#endif - void createSharedLibrary(){ +void createSharedLibrary(){ #if !USE_MPROTECT_SNAPSHOT - //step 1. create shared memory. - if( sTheRecord ) return; - int fd = shm_open( "/ModelChecker-Snapshotter", O_RDWR | O_CREAT, 0777 ); //universal permissions. - if( -1 == fd ) FAILURE("shm_open"); - if( -1 == ftruncate( fd, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT ) ) FAILURE( "ftruncate" ); - char * memMapBase = ( char * ) mmap( 0, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 ); - if( MAP_FAILED == memMapBase ) FAILURE("mmap"); - sTheRecord = ( struct Snapshot_t * )memMapBase; - sTheRecord->mSharedMemoryBase = memMapBase + sizeof( struct Snapshot_t ); - sTheRecord->mStackBase = ( char * )memMapBase + ( size_t )SHARED_MEMORY_DEFAULT; - sTheRecord->mStackSize = STACK_SIZE_DEFAULT; - sTheRecord->mIDToRollback = -1; - sTheRecord->currSnapShotID = 0; + //step 1. create shared memory. + if ( sTheRecord ) + return; + int fd = shm_open( "/ModelChecker-Snapshotter", O_RDWR | O_CREAT, 0777 ); //universal permissions. + if ( -1 == fd ) + FAILURE("shm_open"); + if ( -1 == ftruncate( fd, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT ) ) + FAILURE( "ftruncate" ); + void * memMapBase = mmap( 0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 ); + if( MAP_FAILED == memMapBase ) + FAILURE("mmap"); + sTheRecord = ( struct Snapshot * )memMapBase; + sTheRecord->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct Snapshot)); + sTheRecord->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT); + sTheRecord->mStackSize = STACK_SIZE_DEFAULT; + sTheRecord->mIDToRollback = -1; + sTheRecord->currSnapShotID = 0; #endif - } -#ifdef __cplusplus } -#endif + +/** The initSnapShotLibrary function initializes the Snapshot library. + * @param entryPoint the function that should run the program. + */ void initSnapShotLibrary(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions, unsigned int numheappages, VoidFuncPtr entryPoint) { @@ -135,10 +152,17 @@ void initSnapShotLibrary(unsigned int numbackingpages, sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK; sigemptyset( &sa.sa_mask ); sa.sa_sigaction = HandlePF; +#ifdef MAC + if( sigaction( SIGBUS, &sa, NULL ) == -1 ){ + printf("SIGACTION CANNOT BE INSTALLED\n"); + exit(EXIT_FAILURE); + } +#endif if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){ printf("SIGACTION CANNOT BE INSTALLED\n"); - exit(-1); + exit(EXIT_FAILURE); } + initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions); // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links @@ -146,6 +170,7 @@ void initSnapShotLibrary(unsigned int numbackingpages, // Solution is to call our signal handler before we start protecting stuff... siginfo_t si; + memset(&si, 0, sizeof(si)); si.si_addr=ss.ss_sp; HandlePF(SIGSEGV, &si, NULL); snapshotrecord->lastBackingPage--; //remove the fake page we copied @@ -156,70 +181,52 @@ void initSnapShotLibrary(unsigned int numbackingpages, addMemoryRegionToSnapShot(pagealignedbase, numheappages); entryPoint(); #else - //SUBRAMANIAN: WHY IS THIS SIGNAL HANDLER HERE FOR THE FORK BASED APPROACH???? - //IT LOOKS LIKE SOME CODE WAS REMOVED FROM SIGNAL HANDLER... - //IN ANY CASE, DO NOT REUSE THE HANDLEPF CALL!!!! - //add a signal to indicate that the process is going to terminate. - struct sigaction sa; - sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART; - sigemptyset( &sa.sa_mask ); - sa.sa_sigaction = HandlePF; - if( sigaction( SIGUSR1, &sa, NULL ) == -1 ){ - printf("SIGACTION CANNOT BE INSTALLED\n"); - exit(-1); - } + basemySpace=system_malloc((numheappages+1)*PAGESIZE); + void * pagealignedbase=PageAlignAddressUpward(basemySpace); + mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 ); createSharedLibrary(); //step 2 setup the stack context. + ucontext_t newContext; + getcontext( &newContext ); + newContext.uc_stack.ss_sp = sTheRecord->mStackBase; + newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT; + makecontext( &newContext, entryPoint, 0 ); + /* switch to a new entryPoint context, on a new stack */ + swapcontext(&savedSnapshotContext, &newContext); - int alreadySwapped = 0; - getcontext( &savedSnapshotContext ); - if( !alreadySwapped ){ - alreadySwapped = 1; - ucontext_t currentContext, swappedContext, newContext; - getcontext( &newContext ); - newContext.uc_stack.ss_sp = sTheRecord->mStackBase; - newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT; - newContext.uc_link = ¤tContext; - makecontext( &newContext, entryPoint, 0 ); - swapcontext( &swappedContext, &newContext ); - } - - //add the code to take a snapshot here... - //to return to user process, do a second swapcontext... + /* switch back here when takesnapshot is called */ pid_t forkedID = 0; snapshotid = sTheRecord->currSnapShotID; bool swapContext = false; - while( !sTheRecord->mbFinalize ){ + while( true ){ sTheRecord->currSnapShotID=snapshotid+1; forkedID = fork(); if( 0 == forkedID ){ ucontext_t currentContext; -#if 0 - int dbg = 0; - while( !dbg ); -#endif + /*If the rollback bool is set{ see below }, switch to the context we need to return to during a rollback*/ if( swapContext ) swapcontext( ¤tContext, &( sTheRecord->mContextToRollback ) ); else{ + /*Child process which is forked as a result of takesnapshot call should switch back to the takesnapshot context*/ swapcontext( ¤tContext, &savedUserSnapshotContext ); } } else { int status; int retVal; -#if SSDEBUG - char mesg[ 1024 ] = { 0 }; - sprintf( mesg, "The process id of child is %d and the process id of this process is %d and snapshot id is %d", forkedID, getpid(), snapshotid ); - DumpIntoLog( "ModelSnapshot", mesg ); -#endif + + SSDEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d", + forkedID, getpid(), snapshotid ); + do { retVal=waitpid( forkedID, &status, 0 ); } while( -1 == retVal && errno == EINTR ); if( sTheRecord->mIDToRollback != snapshotid ) - exit(0); + exit(EXIT_SUCCESS); else{ + /*This bool indicates that the current process's snapshotid is same as the id to which the rollback needs to occur*/ swapContext = true; } } @@ -227,33 +234,38 @@ void initSnapShotLibrary(unsigned int numbackingpages, #endif } -/* This function assumes that addr is page aligned */ + +/** The addMemoryRegionToSnapShot function assumes that addr is page aligned. + */ void addMemoryRegionToSnapShot( void * addr, unsigned int numPages) { #if USE_MPROTECT_SNAPSHOT unsigned int memoryregion=snapshotrecord->lastRegion++; if (memoryregion==snapshotrecord->maxRegions) { printf("Exceeded supported number of memory regions!\n"); - exit(-1); + exit(EXIT_FAILURE); } snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr; snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages; #endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS. } -//take snapshot + +/** The takeSnapshot function takes a snapshot. + * @return The snapshot identifier. + */ snapshot_id takeSnapshot( ){ #if USE_MPROTECT_SNAPSHOT for(unsigned int region=0; regionlastRegion;region++) { if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ ) == -1 ){ perror("mprotect"); printf("Failed to mprotect inside of takeSnapShot\n"); - exit(-1); + exit(EXIT_FAILURE); } } unsigned int snapshot=snapshotrecord->lastSnapShot++; if (snapshot==snapshotrecord->maxSnapShots) { printf("Out of snapshots\n"); - exit(-1); + exit(EXIT_FAILURE); } snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage; @@ -263,6 +275,10 @@ snapshot_id takeSnapshot( ){ return snapshotid; #endif } + +/** The rollBack function rollback to the given snapshot identifier. + * @param theID is the snapshot identifier to rollback to. + */ void rollBack( snapshot_id theID ){ #if USE_MPROTECT_SNAPSHOT std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap; @@ -270,7 +286,7 @@ void rollBack( snapshot_id theID ){ if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE ) == -1 ){ perror("mprotect"); printf("Failed to mprotect inside of takeSnapShot\n"); - exit(-1); + exit(EXIT_FAILURE); } } for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; pagelastBackingPage; page++) { @@ -292,19 +308,21 @@ void rollBack( snapshot_id theID ){ sTheRecord->mIDToRollback = theID; int sTemp = 0; getcontext( &sTheRecord->mContextToRollback ); + /* + * This is used to quit the process on rollback, so that + * the process which needs to rollback can quit allowing the process whose snapshotid matches the rollbackid to switch to + * this context and continue.... + */ if( !sTemp ){ sTemp = 1; -#if SSDEBUG - DumpIntoLog( "ModelSnapshot", "Invoked rollback" ); -#endif - exit( 0 ); + SSDEBUG("Invoked rollback"); + exit(EXIT_SUCCESS); } -#endif -} - -void finalize(){ -#if !USE_MPROTECT_SNAPSHOT - sTheRecord->mbFinalize = true; + /* + * This fix obviates the need for a finalize call. hence less dependences for model-checker.... + * + */ + sTheRecord->mIDToRollback = -1; #endif }