X-Git-Url: http://plrg.eecs.uci.edu/git/?p=c11tester.git;a=blobdiff_plain;f=snapshot.cc;h=24e8d073ca1330eb778b897955e500dab30f9c5e;hp=642885b038df274b68eb028e7a25d5563b9f2ec6;hb=cd6a138fadb0cf3e886fa1407a3d571578b60cbe;hpb=f01c21655bce58ff70b0e8936f2579a7beeafad4 diff --git a/snapshot.cc b/snapshot.cc index 642885b0..24e8d073 100644 --- a/snapshot.cc +++ b/snapshot.cc @@ -3,324 +3,492 @@ #include #include #include -#include "hashtable.h" -#include -#include -#include "snapshot.h" -#include "snapshotimp.h" -#include "mymemory.h" -#include -#include -#include -#include +#include #include #include -#include +#include "hashtable.h" +#include "snapshot.h" +#include "mymemory.h" #include "common.h" +#include "context.h" +#include "model.h" -#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 */ -struct SnapShot * snapshotrecord = NULL; -#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 +#if USE_MPROTECT_SNAPSHOT /** 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 * )model_malloc(sizeof(struct SnapShot)); - snapshotrecord->regionsToSnapShot=( struct MemoryRegion * )model_malloc(sizeof(struct MemoryRegion)*nummemoryregions); - snapshotrecord->backingStoreBasePtr= ( struct SnapShotPage * )model_malloc( 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 * )model_malloc(sizeof(struct BackingPageRecord)*numbackingpages); - snapshotrecord->snapShots= ( struct SnapShotRecord * )model_malloc(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); } -/** HandlePF is the page fault handler for mprotect based snapshotting +mprot_snapshotter::~mprot_snapshotter() +{ + model_free(regionsToSnapShot); + model_free(backingStoreBasePtr); + model_free(backingRecords); + model_free(snapShots); +} + +/** 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); - print_trace(); - exit( EXIT_FAILURE ); +static void mprot_handle_pf(int sig, siginfo_t *si, void *unused) +{ + if (si->si_code == SEGV_MAPERR) { + model_print("Segmentation fault at %p\n", si->si_addr); + model_print("For debugging, place breakpoint at: %s:%d\n", + __FILE__, __LINE__); + // print_trace(); // Trace printing may cause dynamic memory allocation + 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. - -#if !USE_MPROTECT_SNAPSHOT -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 - snapshotrecord = ( struct SnapShot * )memMapBase; - snapshotrecord->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct SnapShot)); - snapshotrecord->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT); - snapshotrecord->mStackSize = STACK_SIZE_DEFAULT; - snapshotrecord->mIDToRollback = -1; - snapshotrecord->currSnapShotID = 0; -} -#endif - -/** The initSnapShotLibrary function initializes the Snapshot library. - * @param entryPoint the function that should run the program. - */ -#if USE_MPROTECT_SNAPSHOT - -void initSnapShotLibrary(unsigned int numbackingpages, - unsigned int numsnapshots, unsigned int nummemoryregions, - unsigned int numheappages, VoidFuncPtr entryPoint) { +static void mprot_snapshot_init(unsigned int numbackingpages, + unsigned int numsnapshots, unsigned int nummemoryregions, + unsigned int numheappages) +{ /* Setup a stack for our signal handler.... */ stack_t ss; - ss.ss_sp = model_malloc(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) { + perror("sigaction(SIGBUS)"); exit(EXIT_FAILURE); } #endif - if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){ - printf("SIGACTION CANNOT BE INSTALLED\n"); + if (sigaction(SIGSEGV, &sa, NULL) == -1) { + perror("sigaction(SIGSEGV)"); 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=model_malloc((numheappages+1)*PAGESIZE); - void * pagealignedbase=PageAlignAddressUpward(basemySpace); - mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 ); - addMemoryRegionToSnapShot(pagealignedbase, numheappages); - entryPoint(); + 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); } -#else -void initSnapShotLibrary(unsigned int numbackingpages, - unsigned int numsnapshots, unsigned int nummemoryregions, - unsigned int numheappages, VoidFuncPtr entryPoint) { - basemySpace=system_malloc((numheappages+1)*PAGESIZE); - void * pagealignedbase=PageAlignAddressUpward(basemySpace); - mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 ); - if (!snapshotrecord) - createSharedMemory(); - //step 2 setup the stack context. - ucontext_t newContext; - getcontext( &newContext ); - newContext.uc_stack.ss_sp = snapshotrecord->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); +static void mprot_startExecution(ucontext_t * context, VoidFuncPtr entryPoint) { + /* setup the shared-stack context */ + create_context(context, fork_snap->mStackBase, model_calloc(STACK_SIZE_DEFAULT, 1), STACK_SIZE_DEFAULT, entryPoint); +} - /* switch back here when takesnapshot is called */ - pid_t forkedID = 0; - snapshotid = snapshotrecord->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 ){ - snapshotrecord->currSnapShotID=snapshotid+1; - forkedID = fork(); +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); + } - if( 0 == forkedID ){ - /* If the rollback bool is set, switch to the context we need to - return to during a rollback. */ - if( rollback) { - setcontext( &( snapshotrecord->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; + DEBUG("snapshot region %p-%p (%u page%s)\n", + addr, (char *)addr + numPages * PAGESIZE, numPages, + numPages > 1 ? "s" : ""); + mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr; + mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages; +} - SSDEBUG("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 ); +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; - do { - retVal=waitpid( forkedID, &status, 0 ); - } while( -1 == retVal && errno == EINTR ); + return snapshot; +} - if( snapshotrecord->mIDToRollback != snapshotid ) { - exit(EXIT_SUCCESS); - } - rollback = true; +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 -/** The addMemoryRegionToSnapShot function assumes that addr is page aligned. + 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 +} + +#else /* !USE_MPROTECT_SNAPSHOT */ + +#define SHARED_MEMORY_DEFAULT (200 * ((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 { + /** @brief Pointer to the shared (non-snapshot) memory heap base + * (NOTE: this has size SHARED_MEMORY_DEFAULT - sizeof(*fork_snap)) */ + void *mSharedMemoryBase; + + /** @brief Pointer to the shared (non-snapshot) stack region */ + void *mStackBase; + + /** @brief Size of the shared stack */ + size_t mStackSize; + + /** + * @brief Stores the ID that we are attempting to roll back to + * + * Used in inter-process communication so that each process can + * determine whether or not to take over execution (w/ matching ID) or + * exit (we're rolling back even further). Dubiously marked 'volatile' + * to prevent compiler optimizations from messing with the + * inter-process behavior. + */ + volatile snapshot_id mIDToRollback; + + + + /** @brief Inter-process tracking of the next snapshot ID */ + snapshot_id currSnapShotID; +}; + +static struct fork_snapshotter *fork_snap = NULL; +ucontext_t shared_ctxt; + +/** @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. + * + * @private_ctxt: the context which is internal to the current process. Used + * for running the internal snapshot/rollback loop. + * @exit_ctxt: a special context used just for exiting from a process (so we + * can use swapcontext() instead of setcontext() + hacks) + * @snapshotid: it is a running counter for the various forked processes + * snapshotid. it is incremented and set in a persistently shared record */ -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"); +static ucontext_t private_ctxt; +static ucontext_t exit_ctxt; +static snapshot_id snapshotid = 0; + +/** + * @brief Create a new context, with a given stack and entry function + * @param ctxt The context structure to fill + * @param stack The stack to run the new context in + * @param stacksize The size of the stack + * @param func The entry point function for the context + */ +static void create_context(ucontext_t *ctxt, void *stack, size_t stacksize, + void (*func)(void)) +{ + getcontext(ctxt); + ctxt->uc_stack.ss_sp = stack; + ctxt->uc_stack.ss_size = stacksize; + ctxt->uc_link = NULL; + makecontext(ctxt, func, 0); +} + +/** @brief An empty function, used for an "empty" context which just exits a + * process */ +static void fork_exit() +{ + _Exit(EXIT_SUCCESS); +} + +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 (memMapBase == MAP_FAILED) { + perror("mmap"); exit(EXIT_FAILURE); } - snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr; - snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages; -#endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS. + //Setup snapshot record at top of free region + fork_snap = (struct fork_snapshotter *)memMapBase; + fork_snap->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(*fork_snap)); + fork_snap->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT); + fork_snap->mStackSize = STACK_SIZE_DEFAULT; + fork_snap->mIDToRollback = -1; + fork_snap->currSnapShotID = 0; } -/** The takeSnapshot function takes a snapshot. - * @return The snapshot identifier. +/** + * 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 */ -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(EXIT_FAILURE); - } +mspace create_shared_mspace() +{ + if (!fork_snap) + createSharedMemory(); + return create_mspace_with_base((void *)(fork_snap->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(*fork_snap), 1); +} + +static void fork_snapshot_init(unsigned int numbackingpages, + unsigned int numsnapshots, unsigned int nummemoryregions, + unsigned int numheappages) +{ + if (!fork_snap) + createSharedMemory(); + + model_snapshot_space = create_mspace(numheappages * PAGESIZE, 1); +} + +volatile int modellock = 0; + +static void fork_loop() { + /* switch back here when takesnapshot is called */ + snapshotid = fork_snap->currSnapShotID; + if (model->params.nofork) { + setcontext(&shared_ctxt); + _Exit(EXIT_SUCCESS); } - unsigned int snapshot=snapshotrecord->lastSnapShot++; - if (snapshot==snapshotrecord->maxSnapShots) { - printf("Out of snapshots\n"); - exit(EXIT_FAILURE); + + while (true) { + pid_t forkedID; + fork_snap->currSnapShotID = snapshotid + 1; + + modellock = 1; + forkedID = fork(); + modellock = 0; + + if (0 == forkedID) { + setcontext(&shared_ctxt); + } else { + DEBUG("parent PID: %d, child PID: %d, snapshot ID: %d\n", + getpid(), forkedID, snapshotid); + + while (waitpid(forkedID, NULL, 0) < 0) { + /* waitpid() may be interrupted */ + if (errno != EINTR) { + perror("waitpid"); + exit(EXIT_FAILURE); + } + } + + if (fork_snap->mIDToRollback != snapshotid) + _Exit(EXIT_SUCCESS); + } } - snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage; +} - return snapshot; -#else - swapcontext( &savedUserSnapshotContext, &savedSnapshotContext ); - SSDEBUG("TAKESNAPSHOT RETURN\n"); +static void fork_startExecution(ucontext_t *context, VoidFuncPtr entryPoint) { + /* setup an "exiting" context */ + int exit_stack_size = 256; + create_context(&exit_ctxt, snapshot_calloc(exit_stack_size, 1), exit_stack_size, fork_exit); + + /* setup the system context */ + create_context(context, fork_snap->mStackBase, STACK_SIZE_DEFAULT, entryPoint); + /* switch to a new entryPoint context, on a new stack */ + create_context(&private_ctxt, snapshot_calloc(STACK_SIZE_DEFAULT, 1), STACK_SIZE_DEFAULT, fork_loop); +} + +static snapshot_id fork_take_snapshot() { + model_swapcontext(&shared_ctxt, &private_ctxt); + DEBUG("TAKESNAPSHOT RETURN\n"); return snapshotid; +} + +static void fork_roll_back(snapshot_id theID) +{ + DEBUG("Rollback\n"); + fork_snap->mIDToRollback = theID; + model_swapcontext(model->get_system_context(), &exit_ctxt); + fork_snap->mIDToRollback = -1; +} + +#endif /* !USE_MPROTECT_SNAPSHOT */ + +/** + * @brief Initializes the snapshot system + * @param entryPoint the function that should run the program. + */ +void snapshot_system_init(unsigned int numbackingpages, + unsigned int numsnapshots, unsigned int nummemoryregions, + unsigned int numheappages) +{ +#if USE_MPROTECT_SNAPSHOT + mprot_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages); +#else + fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages); #endif } -/** The rollBack function rollback to the given snapshot identifier. - * @param theID is the snapshot identifier to rollback to. +void startExecution(ucontext_t *context, VoidFuncPtr entryPoint) +{ +#if USE_MPROTECT_SNAPSHOT + mprot_startExecution(context, entryPoint); +#else + fork_startExecution(context, entryPoint); +#endif +} + +/** 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 + /* not needed for fork-based snapshotting */ +#endif +} + +/** Takes a snapshot of memory. + * @return The snapshot identifier. */ -void rollBack( snapshot_id theID ){ +snapshot_id take_snapshot() +{ #if USE_MPROTECT_SNAPSHOT - HashTable< void *, bool, uintptr_t, 4, model_malloc, MYCALLOC, MYFREE> 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++) { - if( !duplicateMap.contains(snapshotrecord->backingRecords[page].basePtrOfPage )) { - duplicateMap.put(snapshotrecord->backingRecords[page].basePtrOfPage, true); - 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 - snapshotrecord->mIDToRollback = theID; - volatile int sTemp = 0; - getcontext( &snapshotrecord->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; - SSDEBUG("Invoked rollback\n"); - exit(EXIT_SUCCESS); - } - /* - * This fix obviates the need for a finalize call. hence less dependences for model-checker.... - * - */ - snapshotrecord->mIDToRollback = -1; + return fork_take_snapshot(); #endif } +/** 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 +}