X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=snapshot.cc;h=c049167e52bb753e35dcb4dca11c45da821bc5cb;hb=b492e4a6a9bfbd3138878846ab0d9810d8814071;hp=fe5110a03fe5a7b0e45e3b62471788eb396a9aed;hpb=2ada1a461101f16a0be8ba75200c8ae4f9ff9d84;p=c11tester.git diff --git a/snapshot.cc b/snapshot.cc index fe5110a0..c049167e 100644 --- a/snapshot.cc +++ b/snapshot.cc @@ -6,279 +6,103 @@ #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) { 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)); -} +#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 -#if USE_MPROTECT_SNAPSHOT +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; -/* Each SnapShotRecord lists the firstbackingpage that must be written to - * revert to that snapshot */ -struct SnapShotRecord { - unsigned int firstBackingPage; -}; + /** @brief Pointer to the shared (non-snapshot) stack region */ + void *mStackBase; -/** @brief Backing store page */ -typedef unsigned char snapshot_page_t[PAGESIZE]; + /** @brief Size of the shared stack */ + size_t mStackSize; -/* List the base address of the corresponding page in the backing store so we - * know where to copy it to */ -struct BackingPageRecord { - void *basePtrOfPage; -}; + /** + * @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; -/* Struct for each memory region */ -struct MemoryRegion { - void *basePtr; // base of memory region - int sizeInPages; // size of memory region in pages -}; -/* Primary struct for snapshotting system */ -struct 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 -}; -static struct mprot_snapshotter *mprot_snap = NULL; + /** @brief Inter-process tracking of the next snapshot ID */ + snapshot_id currSnapShotID; +}; -/** 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 struct fork_snapshotter *fork_snap = NULL; +ucontext_t shared_ctxt; -/** The initSnapShotRecord method initialized the snapshotting data - * structures for the mprotect based 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. + * + * @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 */ -static void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions) -{ - mprot_snap = (struct mprot_snapshotter *)model_malloc(sizeof(struct mprot_snapshotter)); - mprot_snap->regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * nummemoryregions); - mprot_snap->backingStoreBasePtr = (void *)model_malloc(sizeof(snapshot_page_t) * (numbackingpages + 1)); - //Page align the backingstorepages - mprot_snap->backingStore = (snapshot_page_t *)PageAlignAddressUpward(mprot_snap->backingStoreBasePtr); - mprot_snap->backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * numbackingpages); - mprot_snap->snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * numsnapshots); - mprot_snap->lastSnapShot = 0; - mprot_snap->lastBackingPage = 0; - mprot_snap->lastRegion = 0; - mprot_snap->maxRegions = nummemoryregions; - mprot_snap->maxBackingPages = numbackingpages; - mprot_snap->maxSnapShots = numsnapshots; -} +static ucontext_t private_ctxt; +static ucontext_t exit_ctxt; +static snapshot_id snapshotid = 0; -/** HandlePF is the page fault handler for mprotect based snapshotting - * algorithm. +/** + * @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 HandlePF(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 = 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(&(mprot_snap->backingStore[backingpage]), addr, sizeof(snapshot_page_t)); - //remember where to copy page back to - mprot_snap->backingRecords[backingpage].basePtrOfPage = addr; - //set protection to read/write - if (mprotect(addr, sizeof(snapshot_page_t), PROT_READ | PROT_WRITE)) { - perror("mprotect"); - // Handle error by quitting? - } -} - -static void mprot_snapshot_init(unsigned int numbackingpages, - unsigned int numsnapshots, unsigned int nummemoryregions, - unsigned int numheappages, VoidFuncPtr entryPoint) -{ - /* Setup a stack for our signal handler.... */ - stack_t ss; - 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; -#ifdef MAC - if (sigaction(SIGBUS, &sa, NULL) == -1) { - model_print("SIGACTION CANNOT BE INSTALLED\n"); - exit(EXIT_FAILURE); - } -#endif - if (sigaction(SIGSEGV, &sa, NULL) == -1) { - model_print("SIGACTION CANNOT BE INSTALLED\n"); - 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 - // 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); - 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); - addMemoryRegionToSnapShot(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); - addMemoryRegionToSnapShot(pagealignedbase, numheappages); - - entryPoint(); -} - -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); - } - - mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr; - mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages; -} - -static snapshot_id mprot_take_snapshot() +static void create_context(ucontext_t *ctxt, void *stack, size_t stacksize, + void (*func)(void)) { - 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; + getcontext(ctxt); + ctxt->uc_stack.ss_sp = stack; + ctxt->uc_stack.ss_size = stacksize; + ctxt->uc_link = NULL; + makecontext(ctxt, func, 0); } -static void mprot_roll_back(snapshot_id theID) +/** @brief An empty function, used for an "empty" context which just exits a + * process */ +static void fork_exit() { -#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 + _Exit(EXIT_SUCCESS); } -#else /* !USE_MPROTECT_SNAPSHOT */ - -#include - -#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"); + if (memMapBase == MAP_FAILED) { + perror("mmap"); + exit(EXIT_FAILURE); + } //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->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; @@ -295,144 +119,110 @@ 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); + 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, VoidFuncPtr entryPoint) + unsigned int numsnapshots, unsigned int nummemoryregions, + unsigned int numheappages) { 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); + model_snapshot_space = create_mspace(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 */ - swapcontext(&savedSnapshotContext, &newContext); +volatile int modellock = 0; +static void fork_loop() { /* switch back here when takesnapshot is called */ - pid_t forkedID = 0; 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 */ + if (model->params.nofork) { + setcontext(&shared_ctxt); + _Exit(EXIT_SUCCESS); + } - bool rollback = false; while (true) { + pid_t forkedID; fork_snap->currSnapShotID = snapshotid + 1; + + modellock = 1; forkedID = fork(); + modellock = 0; 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); - } + setcontext(&shared_ctxt); } else { - int status; - int retVal; - - 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); - - if (fork_snap->mIDToRollback != snapshotid) { - exit(EXIT_SUCCESS); + 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); + } } - rollback = true; + + if (fork_snap->mIDToRollback != snapshotid) + _Exit(EXIT_SUCCESS); } } } -static snapshot_id fork_take_snapshot() -{ - swapcontext(&savedUserSnapshotContext, &savedSnapshotContext); +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; - 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); - } - /* - * This fix obviates the need for a finalize call. hence less dependences for model-checker.... - */ + model_swapcontext(model->get_system_context(), &exit_ctxt); fork_snap->mIDToRollback = -1; } -#endif /* !USE_MPROTECT_SNAPSHOT */ - -/** The initSnapshotLibrary function initializes the snapshot library. - * @param entryPoint the function that should run the program. +/** + * @brief Initializes the snapshot system + * @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) +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, entryPoint); -#else - fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint); -#endif + fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages); } -/** The addMemoryRegionToSnapShot function assumes that addr is page aligned. */ -void addMemoryRegionToSnapShot(void *addr, unsigned int numPages) +void startExecution(ucontext_t *context, VoidFuncPtr entryPoint) { -#if USE_MPROTECT_SNAPSHOT - mprot_add_to_snapshot(addr, numPages); -#else - /* not needed for fork-based snapshotting */ -#endif + fork_startExecution(context, entryPoint); } -/** The takeSnapshot function takes a snapshot. +/** Takes a snapshot of memory. * @return The snapshot identifier. */ -snapshot_id takeSnapshot() +snapshot_id take_snapshot() { -#if USE_MPROTECT_SNAPSHOT - return mprot_take_snapshot(); -#else return fork_take_snapshot(); -#endif } -/** The rollBack function rollback to the given snapshot identifier. +/** Rolls the memory state back to the given snapshot identifier. * @param theID is the snapshot identifier to rollback to. */ -void rollBack(snapshot_id theID) +void snapshot_roll_back(snapshot_id theID) { -#if USE_MPROTECT_SNAPSHOT - mprot_roll_back(theID); -#else fork_roll_back(theID); -#endif }