X-Git-Url: http://plrg.eecs.uci.edu/git/?p=c11tester.git;a=blobdiff_plain;f=snapshot.cc;h=1f0cf352d2e214c0e5218818addb29fab2a37330;hp=1e7d80b4b5d836d1c4a1cdb653824a626afb82c8;hb=7742256df627848c1c375f979f5369a45c92057b;hpb=f48c73aeda479368d4bfaf96fe9fe07f3d3d8bdb

diff --git a/snapshot.cc b/snapshot.cc
index 1e7d80b4..1f0cf352 100644
--- a/snapshot.cc
+++ b/snapshot.cc
@@ -3,326 +3,215 @@
 #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); }
+#include "hashtable.h"
+#include "snapshot.h"
+#include "mymemory.h"
+#include "common.h"
+#include "context.h"
+#include "model.h"
 
-#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
+#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
-/** @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
+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;
 
-/** 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));
-}
+	/** @brief Pointer to the shared (non-snapshot) stack region */
+	void *mStackBase;
 
-#if USE_MPROTECT_SNAPSHOT
+	/** @brief Size of the shared stack */
+	size_t mStackSize;
 
-/** ReturnPageAlignedAddress returns a page aligned address for the
- * address being added as a side effect the numBytes are also changed.
+	/**
+	 * @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
  */
-static void * ReturnPageAlignedAddress(void * addr) {
-	return (void *)(((uintptr_t)addr)&~(PAGESIZE-1));
-}
+static ucontext_t private_ctxt;
+static snapshot_id snapshotid = 0;
 
-/** The initSnapShotRecord method initialized the snapshotting data
- *  structures for the mprotect based snapshot. 
+/**
+ * @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 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;
+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);
 }
 
-/** 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);
+/** @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?
-	}
+	//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;
+	sStaticSpace = create_shared_mspace();
 }
-#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, 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
+/**
+ * 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(*fork_snap), 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);
-	}
+static void fork_snapshot_init(unsigned int numheappages)
+{
+	if (!fork_snap)
+		createSharedMemory();
 
-	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.
-	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);
+	model_snapshot_space = create_mspace(numheappages * PAGESIZE, 1);
+}
+
+volatile int modellock = 0;
 
+static void fork_loop() {
 	/* switch back here when takesnapshot is called */
-	pid_t forkedID = 0;
-	snapshotid = sTheRecord->currSnapShotID;
-	bool swapContext = false;
-	while( true ){
-		sTheRecord->currSnapShotID=snapshotid+1;
-		forkedID = fork();
-		if( 0 == forkedID ){
-			ucontext_t currentContext;
-			/*If the rollback bool is set{ see below }, switch to the context we need to return to during a rollback*/
-			if( swapContext )
-				swapcontext( &currentContext, &( sTheRecord->mContextToRollback ) );
-			else{
-				/*Child process which is forked as a result of takesnapshot call should switch back to the takesnapshot context*/
-				swapcontext( &currentContext, &savedUserSnapshotContext );
-			}
-		} else {
-			int status;
-			int retVal;
+	snapshotid = fork_snap->currSnapShotID;
+	if (model->params.nofork) {
+		setcontext(&shared_ctxt);
+		_Exit(EXIT_SUCCESS);
+	}
 
-			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 );
+	while (true) {
+		pid_t forkedID;
+		fork_snap->currSnapShotID = snapshotid + 1;
 
-			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{
-				/*This bool indicates that the current process's snapshotid is same as the id to which the rollback needs to occur*/
-				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);
+}
+
+static snapshot_id fork_take_snapshot() {
+	model_swapcontext(&shared_ctxt, &private_ctxt);
+	DEBUG("TAKESNAPSHOT RETURN\n");
+	fork_snap->mIDToRollback = -1;
+	return snapshotid;
 }
 
-/** The addMemoryRegionToSnapShot function assumes that addr is page aligned. 
+static void fork_roll_back(snapshot_id theID)
+{
+	DEBUG("Rollback\n");
+	fork_snap->mIDToRollback = theID;
+	fork_exit();
+}
+
+/**
+ * @brief Initializes the snapshot system
+ * @param entryPoint the function that should run the program.
  */
-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);
-	}
+void snapshot_system_init(unsigned int numheappages)
+{
+	fork_snapshot_init(numheappages);
+}
 
-	snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr;
-	snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages;
-#endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
+void startExecution() {
+	fork_startExecution();
 }
 
-/** The takeSnapshot function takes a snapshot.
+/** Takes a snapshot of memory.
  * @return The snapshot identifier.
  */
-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
+snapshot_id take_snapshot()
+{
+	return fork_take_snapshot();
 }
 
-/** 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 ){
-#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 );
-	/*
-	* 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");
-		exit(EXIT_SUCCESS);
-	}
-    /*
-	* This fix obviates the need for a finalize call. hence less dependences for model-checker....
-    *
-    */
-	sTheRecord->mIDToRollback = -1;
-#endif
+void snapshot_roll_back(snapshot_id theID)
+{
+	fork_roll_back(theID);
 }
-