#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
-#include <map>
+#include "hashtable.h"
#include <cstring>
#include <cstdio>
#include "snapshot.h"
#include <sys/wait.h>
#include <ucontext.h>
+#include "common.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
#endif
/* extern declaration definition */
-#if USE_MPROTECT_SNAPSHOT
struct SnapShot * snapshotrecord = NULL;
-#else
-struct Snapshot * sTheRecord = NULL;
-#endif
-
-#if !USE_MPROTECT_SNAPSHOT
-static ucontext_t savedSnapshotContext;
-static ucontext_t savedUserSnapshotContext;
-static snapshot_id snapshotid = 0;
-#endif
/** PageAlignedAdressUpdate return a page aligned address for the
* address being added as a side effect the numBytes are also changed.
return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1));
}
-#if USE_MPROTECT_SNAPSHOT
+#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;
+
+#else /* USE_MPROTECT_SNAPSHOT */
/** ReturnPageAlignedAddress returns a page aligned address for the
* address being added as a side effect the numBytes are also changed.
}
/** The initSnapShotRecord method initialized the snapshotting data
- * structures for the mprotect based snapshot.
+ * 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) );
+ 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) );
//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->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->maxBackingPages=numbackingpages;
snapshotrecord->maxSnapShots=numsnapshots;
}
-#endif //nothing to initialize for the fork based snapshotting.
/** HandlePF is the page fault handler for mprotect based snapshotting
* algorithm.
*/
static 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);
+ print_trace();
exit( EXIT_FAILURE );
}
void* addr = ReturnPageAlignedAddress(si->si_addr);
perror("mprotect");
// Handle error by quitting?
}
-#endif //nothing to handle for non snapshotting case.
}
+#endif /* USE_MPROTECT_SNAPSHOT */
-void createSharedLibrary(){
#if !USE_MPROTECT_SNAPSHOT
+void createSharedMemory(){
//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 * )memMapBase;
- sTheRecord->mSharedMemoryBase = memMapBase + sizeof( struct Snapshot );
- sTheRecord->mStackBase = ( char * )memMapBase + ( size_t )SHARED_MEMORY_DEFAULT;
- sTheRecord->mStackSize = STACK_SIZE_DEFAULT;
- sTheRecord->mIDToRollback = -1;
- sTheRecord->currSnapShotID = 0;
- sTheRecord->mbFinalize = false;
-#endif
+ 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.
+/** The initSnapshotLibrary function initializes the snapshot library.
* @param entryPoint the function that should run the program.
*/
-void initSnapShotLibrary(unsigned int numbackingpages,
+#if USE_MPROTECT_SNAPSHOT
+
+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_sp = PageAlignAddressUpward(model_malloc(SIGSTACKSIZE+PAGESIZE-1));
ss.ss_size = SIGSTACKSIZE;
ss.ss_flags = 0;
sigaltstack(&ss, NULL);
HandlePF(SIGSEGV, &si, NULL);
snapshotrecord->lastBackingPage--; //remove the fake page we copied
- basemySpace=MYMALLOC((numheappages+1)*PAGESIZE);
+ void *basemySpace = model_malloc((numheappages+1)*PAGESIZE);
void * pagealignedbase=PageAlignAddressUpward(basemySpace);
- mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 );
+ 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();
+}
#else
+void initSnapshotLibrary(unsigned int numbackingpages,
+ unsigned int numsnapshots, unsigned int nummemoryregions,
+ unsigned int numheappages, VoidFuncPtr entryPoint) {
+ if (!snapshotrecord)
+ createSharedMemory();
- basemySpace=system_malloc((numheappages+1)*PAGESIZE);
- void * pagealignedbase=PageAlignAddressUpward(basemySpace);
- mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 );
- createSharedLibrary();
+ 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.
-
- 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 );
- }
-
- //add the code to take a snapshot here...
- //to return to user process, do a second swapcontext...
+ 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);
+
+ /* 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 = 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();
+
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 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;
- SSDEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d",
+ 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 );
do {
retVal=waitpid( forkedID, &status, 0 );
} while( -1 == retVal && errno == EINTR );
- if( sTheRecord->mIDToRollback != snapshotid )
+ if( snapshotrecord->mIDToRollback != snapshotid ) {
exit(EXIT_SUCCESS);
- else{
- swapContext = true;
}
+ rollback = true;
}
}
-
-#endif
}
+#endif
-/** The addMemoryRegionToSnapShot function assumes that addr is page aligned.
+/** The addMemoryRegionToSnapShot function assumes that addr is page aligned.
*/
void addMemoryRegionToSnapShot( void * addr, unsigned int numPages) {
#if USE_MPROTECT_SNAPSHOT
/** The takeSnapshot function takes a snapshot.
* @return The snapshot identifier.
*/
-
snapshot_id takeSnapshot( ){
#if USE_MPROTECT_SNAPSHOT
for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
return snapshot;
#else
swapcontext( &savedUserSnapshotContext, &savedSnapshotContext );
+ SSDEBUG("TAKESNAPSHOT RETURN\n");
return snapshotid;
#endif
}
/** The rollBack function rollback to the given snapshot identifier.
* @param theID is the snapshot identifier to rollback to.
*/
-
void rollBack( snapshot_id theID ){
+#if USE_MPROTECT_SNAPSHOT==2
+ if (snapshotrecord->lastSnapShot==(theID+1)) {
+ for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; page<snapshotrecord->lastBackingPage; page++) {
+ memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
+ }
+ return;
+ }
+#endif
+
#if USE_MPROTECT_SNAPSHOT
- std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap;
+ HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> 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");
}
}
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 ){
+ 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->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 );
+ 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");
+ SSDEBUG("Invoked rollback\n");
exit(EXIT_SUCCESS);
}
-#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;
+ /*
+ * This fix obviates the need for a finalize call. hence less dependences for model-checker....
+ *
+ */
+ snapshotrecord->mIDToRollback = -1;
#endif
}
projects / model-checker.git / blobdiff