#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
-#include <map>
-#include <cstring>
-#include <cstdio>
-#include "snapshot.h"
-#include "snapshotimp.h"
-#include "mymemory.h"
-#include <fcntl.h>
-#include <assert.h>
-#include <pthread.h>
-#include <semaphore.h>
+#include <string.h>
#include <errno.h>
#include <sys/wait.h>
-#include <ucontext.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 */
-#if USE_MPROTECT_SNAPSHOT
-struct SnapShot * snapshotrecord = NULL;
-#else
-struct Snapshot_t * sTheRecord = NULL;
-#endif
-
-#if !USE_MPROTECT_SNAPSHOT
-static ucontext_t savedSnapshotContext;
-static ucontext_t savedUserSnapshotContext;
-static snapshot_id snapshotid = 0;
-#endif
-
-#if USE_MPROTECT_SNAPSHOT
-/** The initSnapShotRecord method initialized the snapshotting data
- * structures for the mprotect based snapshot.
+#include "hashtable.h"
+#include "snapshot.h"
+#include "mymemory.h"
+#include "common.h"
+#include "context.h"
+#include "model.h"
+
+
+#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 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) );
- //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;
-}
-#endif //nothing to initialize for the fork based snapshotting.
+static ucontext_t private_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 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);
+}
-void HandlePF( int sig, siginfo_t *si, void * unused){
-#if USE_MPROTECT_SNAPSHOT
- if( si->si_code == SEGV_MAPERR ){
- printf("Real Fault at %p\n", si->si_addr);
- exit( EXIT_FAILURE );
- }
- void* addr = ReturnPageAlignedAddress(si->si_addr);
+/** @brief An empty function, used for an "empty" context which just exits a
+ * process */
+static void fork_exit()
+{
+ _Exit(EXIT_SUCCESS);
+}
- 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 );
+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);
}
- //copy page
- memcpy(&(snapshotrecord->backingStore[backingpage]), addr, sizeof(struct SnapShotPage));
- //remember where to copy page back to
- snapshotrecord->backingRecords[backingpage].basePtrOfPage=addr;
- //set protection to read/write
- if (mprotect( addr, sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE )) {
- perror("mprotect");
- // Handle error by quitting?
- }
-#endif //nothing to handle for non snapshotting case.
+ //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;
}
-/** ReturnPageAlignedAddress returns a page aligned address for the
- * address being added as a side effect the numBytes are also changed.
+/**
+ * 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
*/
-
-void * ReturnPageAlignedAddress(void * addr) {
- return (void *)(((uintptr_t)addr)&~(PAGESIZE-1));
+mspace create_shared_mspace()
+{
+ if (!fork_snap)
+ createSharedMemory();
+ return create_mspace_with_base((void *)(fork_snap->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(*fork_snap), 1);
}
-/** PageAlignedAdressUpdate return a page aligned address for the
- * address being added as a side effect the numBytes are also changed.
- */
+static void fork_snapshot_init(unsigned int numbackingpages,
+ unsigned int numsnapshots, unsigned int nummemoryregions,
+ unsigned int numheappages)
+{
+ if (!fork_snap)
+ createSharedMemory();
-void * PageAlignAddressUpward(void * addr) {
- return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1));
-}
-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;
- sTheRecord->mbFinalize = false;
-#endif
+ model_snapshot_space = create_mspace(numheappages * PAGESIZE, 1);
}
-/** 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) {
-#if USE_MPROTECT_SNAPSHOT
- /* Setup a stack for our signal handler.... */
- stack_t ss;
- ss.ss_sp = MYMALLOC(SIGSTACKSIZE);
- 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 ){
- printf("SIGACTION CANNOT BE INSTALLED\n");
- exit(EXIT_FAILURE);
- }
-#endif
- if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){
- printf("SIGACTION CANNOT BE INSTALLED\n");
- exit(EXIT_FAILURE);
- }
+volatile int modellock = 0;
- 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);
- 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);
- entryPoint();
-#else
-
- 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.
-
- 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 void fork_loop() {
+ /* switch back here when takesnapshot is called */
+ snapshotid = fork_snap->currSnapShotID;
+ if (model->params.nofork) {
+ setcontext(&shared_ctxt);
+ _Exit(EXIT_SUCCESS);
}
- //add the code to take a snapshot here...
- //to return to user process, do a second swapcontext...
- pid_t forkedID = 0;
- snapshotid = sTheRecord->currSnapShotID;
- bool swapContext = false;
- while( !sTheRecord->mbFinalize ){
- sTheRecord->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 );
- }
- } else {
- int status;
- int retVal;
+ while (true) {
+ pid_t forkedID;
+ fork_snap->currSnapShotID = snapshotid + 1;
- 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 );
+ modellock = 1;
+ forkedID = fork();
+ modellock = 0;
- if( sTheRecord->mIDToRollback != snapshotid )
- exit(EXIT_SUCCESS);
- else{
- swapContext = true;
+ 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);
}
}
+}
-#endif
+static void fork_startExecution() {
+ /* 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);
}
-/** 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 snapshot_id fork_take_snapshot() {
+ model_swapcontext(&shared_ctxt, &private_ctxt);
+ DEBUG("TAKESNAPSHOT RETURN\n");
+ fork_snap->mIDToRollback = -1;
+ return snapshotid;
+}
- snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr;
- snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages;
-#endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
+static void fork_roll_back(snapshot_id theID)
+{
+ DEBUG("Rollback\n");
+ fork_snap->mIDToRollback = theID;
+ fork_exit();
}
-/** The takeSnapshot function takes a snapshot.
- * @return The snapshot identifier.
+/**
+ * @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)
+{
+ fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages);
+}
-snapshot_id takeSnapshot( ){
-#if USE_MPROTECT_SNAPSHOT
- for(unsigned int region=0; region<snapshotrecord->lastRegion;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;
-
- return snapshot;
-#else
- swapcontext( &savedUserSnapshotContext, &savedSnapshotContext );
- return snapshotid;
-#endif
+void startExecution() {
+ fork_startExecution();
}
-/** 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 ){
-#if USE_MPROTECT_SNAPSHOT
- std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap;
- for(unsigned int region=0; region<snapshotrecord->lastRegion;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; page<snapshotrecord->lastBackingPage; 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
-#else
- sTheRecord->mIDToRollback = theID;
- int sTemp = 0;
- getcontext( &sTheRecord->mContextToRollback );
- if( !sTemp ){
- sTemp = 1;
- SSDEBUG("Invoked rollback");
- exit(EXIT_SUCCESS);
- }
-#endif
+snapshot_id take_snapshot()
+{
+ return fork_take_snapshot();
}
-/** 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;
-#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)
+{
+ fork_roll_back(theID);
}
-
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