X-Git-Url: http://plrg.eecs.uci.edu/git/?p=c11tester.git;a=blobdiff_plain;f=snapshot.cc;h=ba1c09034d6980bdfc1c841664c780668eee33b3;hp=af4284361d61f076c16c12675945ec5d364b968c;hb=2b004336a919f74a5ca8f6d87ad5414360a949c7;hpb=06d9618fd028c3d5a60c65ad6508cfae24741688 diff --git a/snapshot.cc b/snapshot.cc index af428436..ba1c0903 100644 --- a/snapshot.cc +++ b/snapshot.cc @@ -3,318 +3,444 @@ #include #include #include -#include -#include -#include -#include "snapshot.h" -#include "snapshotimp.h" -#include "mymemory.h" -#include -#include -#include -#include +#include #include #include -#include - -#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; -#else -struct Snapshot * sTheRecord = NULL; -#endif +#include "hashtable.h" +#include "snapshot.h" +#include "mymemory.h" +#include "common.h" +#include "context.h" -#if !USE_MPROTECT_SNAPSHOT -static ucontext_t savedSnapshotContext; -static ucontext_t savedUserSnapshotContext; -static snapshot_id snapshotid = 0; -#endif +#define FAILURE(mesg) { model_print("failed in the API: %s with errno relative message: %s\n", mesg, strerror(errno)); exit(EXIT_FAILURE); } /** 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)); +static void * PageAlignAddressUpward(void *addr) +{ + return (void *)((((uintptr_t)addr) + PAGESIZE - 1) & ~(PAGESIZE - 1)); } #if USE_MPROTECT_SNAPSHOT +/* Each SnapShotRecord lists the firstbackingpage that must be written to + * revert to that snapshot */ +struct SnapShotRecord { + unsigned int firstBackingPage; +}; + +/** @brief Backing store page */ +typedef unsigned char snapshot_page_t[PAGESIZE]; + +/* List the base address of the corresponding page in the backing store so we + * know where to copy it to */ +struct BackingPageRecord { + void *basePtrOfPage; +}; + +/* Struct for each memory region */ +struct MemoryRegion { + void *basePtr; // base of memory region + int sizeInPages; // size of memory region in pages +}; + /** 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)); +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) ); +/* Primary struct for snapshotting system */ +struct mprot_snapshotter { + mprot_snapshotter(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions); + ~mprot_snapshotter(); + + struct MemoryRegion *regionsToSnapShot; //This pointer references an array of memory regions to snapshot + snapshot_page_t *backingStore; //This pointer references an array of snapshotpage's that form the backing store + void *backingStoreBasePtr; //This pointer references an array of snapshotpage's that form the backing store + struct BackingPageRecord *backingRecords; //This pointer references an array of backingpagerecord's (same number of elements as backingstore + struct SnapShotRecord *snapShots; //This pointer references the snapshot array + + unsigned int lastSnapShot; //Stores the next snapshot record we should use + unsigned int lastBackingPage; //Stores the next backingpage we should use + unsigned int lastRegion; //Stores the next memory region to be used + + unsigned int maxRegions; //Stores the max number of memory regions we support + unsigned int maxBackingPages; //Stores the total number of backing pages + unsigned int maxSnapShots; //Stores the total number of snapshots we allow + + MEMALLOC +}; + +static struct mprot_snapshotter *mprot_snap = NULL; + +mprot_snapshotter::mprot_snapshotter(unsigned int backing_pages, unsigned int snapshots, unsigned int regions) : + lastSnapShot(0), + lastBackingPage(0), + lastRegion(0), + maxRegions(regions), + maxBackingPages(backing_pages), + maxSnapShots(snapshots) +{ + regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * regions); + backingStoreBasePtr = (void *)model_malloc(sizeof(snapshot_page_t) * (backing_pages + 1)); //Page align the backingstorepages - snapshotrecord->backingStore=( struct SnapShotPage * )PageAlignAddressUpward(snapshotrecord->backingStoreBasePtr); - snapshotrecord->backingRecords=( struct BackingPageRecord * )MYMALLOC(sizeof(struct BackingPageRecord)*numbackingpages); - snapshotrecord->snapShots= ( struct SnapShotRecord * )MYMALLOC(sizeof(struct SnapShotRecord)*numsnapshots); - snapshotrecord->lastSnapShot=0; - snapshotrecord->lastBackingPage=0; - snapshotrecord->lastRegion=0; - snapshotrecord->maxRegions=nummemoryregions; - snapshotrecord->maxBackingPages=numbackingpages; - snapshotrecord->maxSnapShots=numsnapshots; + backingStore = (snapshot_page_t *)PageAlignAddressUpward(backingStoreBasePtr); + backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * backing_pages); + snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * snapshots); +} + +mprot_snapshotter::~mprot_snapshotter() +{ + model_free(regionsToSnapShot); + model_free(backingStoreBasePtr); + model_free(backingRecords); + model_free(snapShots); } -/** HandlePF is the page fault handler for mprotect based snapshotting +/** mprot_handle_pf 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 ); +static void mprot_handle_pf(int sig, siginfo_t *si, void *unused) +{ + if (si->si_code == SEGV_MAPERR) { + model_print("Real Fault at %p\n", si->si_addr); + print_trace(); + model_print("For debugging, place breakpoint at: %s:%d\n", + __FILE__, __LINE__); + 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); - exit( EXIT_FAILURE ); + unsigned int backingpage = mprot_snap->lastBackingPage++; //Could run out of pages... + if (backingpage == mprot_snap->maxBackingPages) { + model_print("Out of backing pages at %p\n", si->si_addr); + exit(EXIT_FAILURE); } //copy page - memcpy(&(snapshotrecord->backingStore[backingpage]), addr, sizeof(struct SnapShotPage)); + memcpy(&(mprot_snap->backingStore[backingpage]), addr, sizeof(snapshot_page_t)); //remember where to copy page back to - snapshotrecord->backingRecords[backingpage].basePtrOfPage=addr; + mprot_snap->backingRecords[backingpage].basePtrOfPage = addr; //set protection to read/write - if (mprotect( addr, sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE )) { + if (mprotect(addr, sizeof(snapshot_page_t), PROT_READ | PROT_WRITE)) { perror("mprotect"); // Handle error by quitting? } } -#endif //nothing to handle for non snapshotting case. -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" ); - void * memMapBase = 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 * )memMapBase; - sTheRecord->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct Snapshot)); - sTheRecord->mStackBase = (void *)((uintptr_t)memMapBase + (size_t)SHARED_MEMORY_DEFAULT); - sTheRecord->mStackSize = STACK_SIZE_DEFAULT; - sTheRecord->mIDToRollback = -1; - sTheRecord->currSnapShotID = 0; - sTheRecord->mbFinalize = false; -#endif -} - -/** The initSnapShotLibrary function initializes the Snapshot library. - * @param entryPoint the function that should run the program. - */ -void initSnapShotLibrary(unsigned int numbackingpages, +static void mprot_snapshot_init(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions, - unsigned int numheappages, VoidFuncPtr entryPoint) { -#if USE_MPROTECT_SNAPSHOT + unsigned int numheappages, VoidFuncPtr entryPoint) +{ /* Setup a stack for our signal handler.... */ stack_t ss; - ss.ss_sp = MYMALLOC(SIGSTACKSIZE); + ss.ss_sp = PageAlignAddressUpward(model_malloc(SIGSTACKSIZE + PAGESIZE - 1)); ss.ss_size = SIGSTACKSIZE; ss.ss_flags = 0; sigaltstack(&ss, NULL); struct sigaction sa; sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK; - sigemptyset( &sa.sa_mask ); - sa.sa_sigaction = HandlePF; + sigemptyset(&sa.sa_mask); + sa.sa_sigaction = mprot_handle_pf; #ifdef MAC - if( sigaction( SIGBUS, &sa, NULL ) == -1 ){ - printf("SIGACTION CANNOT BE INSTALLED\n"); + if (sigaction(SIGBUS, &sa, NULL) == -1) { + model_print("SIGACTION CANNOT BE INSTALLED\n"); exit(EXIT_FAILURE); } #endif - if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){ - printf("SIGACTION CANNOT BE INSTALLED\n"); + if (sigaction(SIGSEGV, &sa, NULL) == -1) { + model_print("SIGACTION CANNOT BE INSTALLED\n"); exit(EXIT_FAILURE); } - initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions); + mprot_snap = new mprot_snapshotter(numbackingpages, numsnapshots, nummemoryregions); - // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links + // EVIL HACK: We need to make sure that calls into the mprot_handle_pf method don't cause dynamic links // The problem is that we end up protecting state in the dynamic linker... // 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 - - basemySpace=MYMALLOC((numheappages+1)*PAGESIZE); - void * pagealignedbase=PageAlignAddressUpward(basemySpace); - mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 ); - addMemoryRegionToSnapShot(pagealignedbase, numheappages); + si.si_addr = ss.ss_sp; + mprot_handle_pf(SIGSEGV, &si, NULL); + mprot_snap->lastBackingPage--; //remove the fake page we copied + + void *basemySpace = model_malloc((numheappages + 1) * PAGESIZE); + void *pagealignedbase = PageAlignAddressUpward(basemySpace); + user_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1); + snapshot_add_memory_region(pagealignedbase, numheappages); + + void *base_model_snapshot_space = model_malloc((numheappages + 1) * PAGESIZE); + pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space); + model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1); + snapshot_add_memory_region(pagealignedbase, numheappages); + entryPoint(); -#else +} - basemySpace=system_malloc((numheappages+1)*PAGESIZE); - void * pagealignedbase=PageAlignAddressUpward(basemySpace); - mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 ); - createSharedLibrary(); +static void mprot_add_to_snapshot(void *addr, unsigned int numPages) +{ + unsigned int memoryregion = mprot_snap->lastRegion++; + if (memoryregion == mprot_snap->maxRegions) { + model_print("Exceeded supported number of memory regions!\n"); + exit(EXIT_FAILURE); + } - //step 2 setup the stack context. + mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr; + mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages; +} - 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 ); +static snapshot_id mprot_take_snapshot() +{ + for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) { + if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ) == -1) { + perror("mprotect"); + model_print("Failed to mprotect inside of takeSnapShot\n"); + exit(EXIT_FAILURE); + } } + unsigned int snapshot = mprot_snap->lastSnapShot++; + if (snapshot == mprot_snap->maxSnapShots) { + model_print("Out of snapshots\n"); + exit(EXIT_FAILURE); + } + mprot_snap->snapShots[snapshot].firstBackingPage = mprot_snap->lastBackingPage; + + return snapshot; +} + +static void mprot_roll_back(snapshot_id theID) +{ +#if USE_MPROTECT_SNAPSHOT == 2 + if (mprot_snap->lastSnapShot == (theID + 1)) { + for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) { + memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t)); + } + return; + } +#endif + + HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap; + for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) { + if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ | PROT_WRITE) == -1) { + perror("mprotect"); + model_print("Failed to mprotect inside of takeSnapShot\n"); + exit(EXIT_FAILURE); + } + } + for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) { + if (!duplicateMap.contains(mprot_snap->backingRecords[page].basePtrOfPage)) { + duplicateMap.put(mprot_snap->backingRecords[page].basePtrOfPage, true); + memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t)); + } + } + mprot_snap->lastSnapShot = theID; + mprot_snap->lastBackingPage = mprot_snap->snapShots[theID].firstBackingPage; + mprot_take_snapshot(); //Make sure current snapshot is still good...All later ones are cleared +} - //add the code to take a snapshot here... - //to return to user process, do a second swapcontext... +#else /* !USE_MPROTECT_SNAPSHOT */ + +#define SHARED_MEMORY_DEFAULT (100 * ((size_t)1 << 20)) // 100mb for the shared memory +#define STACK_SIZE_DEFAULT (((size_t)1 << 20) * 20) // 20 mb out of the above 100 mb for my stack + +struct fork_snapshotter { + void *mSharedMemoryBase; + void *mStackBase; + size_t mStackSize; + volatile snapshot_id mIDToRollback; + ucontext_t mContextToRollback; + snapshot_id currSnapShotID; +}; + +static struct fork_snapshotter *fork_snap = NULL; + +/** @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; + +static void createSharedMemory() +{ + //step 1. create shared memory. + void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0); + if (MAP_FAILED == memMapBase) + FAILURE("mmap"); + + //Setup snapshot record at top of free region + fork_snap = (struct fork_snapshotter *)memMapBase; + fork_snap->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct fork_snapshotter)); + fork_snap->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT); + fork_snap->mStackSize = STACK_SIZE_DEFAULT; + fork_snap->mIDToRollback = -1; + fork_snap->currSnapShotID = 0; +} + +/** + * Create a new mspace pointer for the non-snapshotting (i.e., inter-process + * shared) memory region. Only for fork-based snapshotting. + * + * @return The shared memory mspace + */ +mspace create_shared_mspace() +{ + if (!fork_snap) + createSharedMemory(); + return create_mspace_with_base((void *)(fork_snap->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(struct fork_snapshotter), 1); +} + +static void fork_snapshot_init(unsigned int numbackingpages, + unsigned int numsnapshots, unsigned int nummemoryregions, + unsigned int numheappages, VoidFuncPtr entryPoint) +{ + if (!fork_snap) + createSharedMemory(); + + void *base_model_snapshot_space = malloc((numheappages + 1) * PAGESIZE); + void *pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space); + model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1); + + //step 2 setup the stack context. + ucontext_t newContext; + getcontext(&newContext); + newContext.uc_stack.ss_sp = fork_snap->mStackBase; + newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT; + makecontext(&newContext, entryPoint, 0); + /* switch to a new entryPoint context, on a new stack */ + model_swapcontext(&savedSnapshotContext, &newContext); + + /* switch back here when takesnapshot is called */ pid_t forkedID = 0; - snapshotid = sTheRecord->currSnapShotID; - bool swapContext = false; - while( !sTheRecord->mbFinalize ){ - sTheRecord->currSnapShotID=snapshotid+1; + snapshotid = fork_snap->currSnapShotID; + /* This bool indicates that the current process's snapshotid is same + as the id to which the rollback needs to occur */ + + bool rollback = false; + while (true) { + fork_snap->currSnapShotID = snapshotid + 1; forkedID = fork(); - if( 0 == forkedID ){ - ucontext_t currentContext; -#if 0 - int dbg = 0; - while( !dbg ); -#endif - if( swapContext ) - swapcontext( ¤tContext, &( sTheRecord->mContextToRollback ) ); - else{ - swapcontext( ¤tContext, &savedUserSnapshotContext ); + + if (0 == forkedID) { + /* If the rollback bool is set, switch to the context we need to + return to during a rollback. */ + if (rollback) { + setcontext(&(fork_snap->mContextToRollback)); + } else { + /*Child process which is forked as a result of takesnapshot + call should switch back to the takesnapshot context*/ + setcontext(&savedUserSnapshotContext); } } else { int status; int retVal; - 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 ); + DEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d\n", + forkedID, getpid(), snapshotid); do { - retVal=waitpid( forkedID, &status, 0 ); - } while( -1 == retVal && errno == EINTR ); + retVal = waitpid(forkedID, &status, 0); + } while (-1 == retVal && errno == EINTR); - if( sTheRecord->mIDToRollback != snapshotid ) + if (fork_snap->mIDToRollback != snapshotid) { exit(EXIT_SUCCESS); - else{ - swapContext = true; } + rollback = true; } } +} -#endif +static snapshot_id fork_take_snapshot() +{ + model_swapcontext(&savedUserSnapshotContext, &savedSnapshotContext); + DEBUG("TAKESNAPSHOT RETURN\n"); + return snapshotid; } -/** 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(EXIT_FAILURE); +static void fork_roll_back(snapshot_id theID) +{ + fork_snap->mIDToRollback = theID; + volatile int sTemp = 0; + getcontext(&fork_snap->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; + DEBUG("Invoked rollback\n"); + exit(EXIT_SUCCESS); } - - snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr; - snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages; -#endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS. + /* + * This fix obviates the need for a finalize call. hence less dependences for model-checker.... + */ + fork_snap->mIDToRollback = -1; } -/** The takeSnapshot function takes a snapshot. - * @return The snapshot identifier. +#endif /* !USE_MPROTECT_SNAPSHOT */ + +/** + * @brief Initializes the snapshot system + * @param entryPoint the function that should run the program. */ -snapshot_id takeSnapshot( ){ +void snapshot_system_init(unsigned int numbackingpages, + unsigned int numsnapshots, unsigned int nummemoryregions, + unsigned int numheappages, VoidFuncPtr entryPoint) +{ #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(EXIT_FAILURE); - } - } - unsigned int snapshot=snapshotrecord->lastSnapShot++; - if (snapshot==snapshotrecord->maxSnapShots) { - printf("Out of snapshots\n"); - exit(EXIT_FAILURE); - } - snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage; + mprot_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint); +#else + fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint); +#endif +} - return snapshot; +/** Assumes that addr is page aligned. */ +void snapshot_add_memory_region(void *addr, unsigned int numPages) +{ +#if USE_MPROTECT_SNAPSHOT + mprot_add_to_snapshot(addr, numPages); #else - swapcontext( &savedUserSnapshotContext, &savedSnapshotContext ); - return snapshotid; + /* not needed for fork-based snapshotting */ #endif } -/** The rollBack function rollback to the given snapshot identifier. - * @param theID is the snapshot identifier to rollback to. +/** Takes a snapshot of memory. + * @return The snapshot identifier. */ -void rollBack( snapshot_id theID ){ +snapshot_id take_snapshot() +{ #if USE_MPROTECT_SNAPSHOT - std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap; - for(unsigned int region=0; regionlastRegion;region++) { - 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(EXIT_FAILURE); - } - } - for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; pagelastBackingPage; page++) { - bool oldVal = false; - if( duplicateMap.find( snapshotrecord->backingRecords[page].basePtrOfPage ) != duplicateMap.end() ){ - oldVal = true; - } - else{ - duplicateMap[ snapshotrecord->backingRecords[page].basePtrOfPage ] = true; - } - if( !oldVal ){ - memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage)); - } - } - snapshotrecord->lastSnapShot=theID; - snapshotrecord->lastBackingPage=snapshotrecord->snapShots[theID].firstBackingPage; - takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared + return mprot_take_snapshot(); #else - sTheRecord->mIDToRollback = theID; - int sTemp = 0; - getcontext( &sTheRecord->mContextToRollback ); - if( !sTemp ){ - sTemp = 1; - SSDEBUG("Invoked rollback"); - exit(EXIT_SUCCESS); - } + return fork_take_snapshot(); #endif } -/** The finalize method shuts down the snapshotting system. */ -//Subramanian -- remove this function from the external interface and -//have us call it internally -void finalize(){ -#if !USE_MPROTECT_SNAPSHOT - sTheRecord->mbFinalize = true; +/** Rolls the memory state back to the given snapshot identifier. + * @param theID is the snapshot identifier to rollback to. + */ +void snapshot_roll_back(snapshot_id theID) +{ +#if USE_MPROTECT_SNAPSHOT + mprot_roll_back(theID); +#else + fork_roll_back(theID); #endif }