10 #include "snapshotimp.h"
15 #include <semaphore.h>
20 //extern declaration definition
21 #define FAILURE(mesg) { printf("failed in the API: %s with errno relative message: %s\n", mesg, strerror( errno ) ); exit( -1 ); }
22 #if USE_MPROTECT_SNAPSHOT
23 struct SnapShot * snapshotrecord = NULL;
24 struct Snapshot_t * sTheRecord = NULL;
26 struct Snapshot_t * sTheRecord = NULL;
28 void DumpIntoLog( const char * filename, const char * message ){
30 static pid_t thePID = getpid();
31 char newFn[ 1024 ] ={ 0 };
32 sprintf( newFn,"%s-%d.txt", filename, thePID );
33 FILE * myFile = fopen( newFn, "w+" );
34 fprintf( myFile, "the message %s: the process id %d\n", message, thePID );
40 #if !USE_MPROTECT_SNAPSHOT
41 static ucontext_t savedSnapshotContext;
42 static ucontext_t savedUserSnapshotContext;
43 static snapshot_id snapshotid = 0;
45 /* Initialize snapshot data structure */
46 #if USE_MPROTECT_SNAPSHOT
47 void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions) {
48 snapshotrecord=( struct SnapShot * )MYMALLOC(sizeof(struct SnapShot));
49 snapshotrecord->regionsToSnapShot=( struct MemoryRegion * )MYMALLOC(sizeof(struct MemoryRegion)*nummemoryregions);
50 snapshotrecord->backingStoreBasePtr= ( struct SnapShotPage * )MYMALLOC( sizeof( struct SnapShotPage ) * (numbackingpages + 1) );
51 //Page align the backingstorepages
52 snapshotrecord->backingStore=( struct SnapShotPage * )PageAlignAddressUpward(snapshotrecord->backingStoreBasePtr);
53 snapshotrecord->backingRecords=( struct BackingPageRecord * )MYMALLOC(sizeof(struct BackingPageRecord)*numbackingpages);
54 snapshotrecord->snapShots= ( struct SnapShotRecord * )MYMALLOC(sizeof(struct SnapShotRecord)*numsnapshots);
55 snapshotrecord->lastSnapShot=0;
56 snapshotrecord->lastBackingPage=0;
57 snapshotrecord->lastRegion=0;
58 snapshotrecord->maxRegions=nummemoryregions;
59 snapshotrecord->maxBackingPages=numbackingpages;
60 snapshotrecord->maxSnapShots=numsnapshots;
62 #endif //nothing to initialize for the fork based snapshotting.
64 void HandlePF( int sig, siginfo_t *si, void * unused){
65 #if USE_MPROTECT_SNAPSHOT
66 if( si->si_code == SEGV_MAPERR ){
67 printf("Real Fault at %p\n", si->si_addr);
70 void* addr = ReturnPageAlignedAddress(si->si_addr);
71 unsigned int backingpage=snapshotrecord->lastBackingPage++; //Could run out of pages...
72 if (backingpage==snapshotrecord->maxBackingPages) {
73 printf("Out of backing pages at %p\n", si->si_addr);
78 memcpy(&(snapshotrecord->backingStore[backingpage]), addr, sizeof(struct SnapShotPage));
79 //remember where to copy page back to
80 snapshotrecord->backingRecords[backingpage].basePtrOfPage=addr;
81 //set protection to read/write
82 if (mprotect( addr, sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE )) {
84 // Handle error by quitting?
86 #endif //nothing to handle for non snapshotting case.
89 //Return a page aligned address for the address being added
90 //as a side effect the numBytes are also changed.
91 void * ReturnPageAlignedAddress(void * addr) {
92 return (void *)(((uintptr_t)addr)&~(PAGESIZE-1));
95 //Return a page aligned address for the address being added
96 //as a side effect the numBytes are also changed.
97 void * PageAlignAddressUpward(void * addr) {
98 return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1));
103 void createSharedLibrary(){
104 #if !USE_MPROTECT_SNAPSHOT
105 //step 1. create shared memory.
106 if( sTheRecord ) return;
107 int fd = shm_open( "/ModelChecker-Snapshotter", O_RDWR | O_CREAT, 0777 ); //universal permissions.
108 if( -1 == fd ) FAILURE("shm_open");
109 if( -1 == ftruncate( fd, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT ) ) FAILURE( "ftruncate" );
110 char * memMapBase = ( char * ) mmap( 0, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 );
111 if( MAP_FAILED == memMapBase ) FAILURE("mmap");
112 sTheRecord = ( struct Snapshot_t * )memMapBase;
113 sTheRecord->mSharedMemoryBase = memMapBase + sizeof( struct Snapshot_t );
114 sTheRecord->mStackBase = ( char * )memMapBase + ( size_t )SHARED_MEMORY_DEFAULT;
115 sTheRecord->mStackSize = STACK_SIZE_DEFAULT;
116 sTheRecord->mIDToRollback = -1;
117 sTheRecord->currSnapShotID = 0;
123 void initSnapShotLibrary(unsigned int numbackingpages,
124 unsigned int numsnapshots, unsigned int nummemoryregions,
125 unsigned int numheappages, VoidFuncPtr entryPoint) {
126 #if USE_MPROTECT_SNAPSHOT
127 /* Setup a stack for our signal handler.... */
129 ss.ss_sp = MYMALLOC(SIGSTACKSIZE);
130 ss.ss_size = SIGSTACKSIZE;
132 sigaltstack(&ss, NULL);
135 sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
136 sigemptyset( &sa.sa_mask );
137 sa.sa_sigaction = HandlePF;
138 if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){
139 printf("SIGACTION CANNOT BE INSTALLED\n");
142 initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions);
144 // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links
145 // The problem is that we end up protecting state in the dynamic linker...
146 // Solution is to call our signal handler before we start protecting stuff...
150 HandlePF(SIGSEGV, &si, NULL);
151 snapshotrecord->lastBackingPage--; //remove the fake page we copied
153 basemySpace=MYMALLOC((numheappages+1)*PAGESIZE);
154 void * pagealignedbase=PageAlignAddressUpward(basemySpace);
155 mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 );
156 addMemoryRegionToSnapShot(pagealignedbase, numheappages);
159 //add a signal to indicate that the process is going to terminate.
161 sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART;
162 sigemptyset( &sa.sa_mask );
163 sa.sa_sigaction = HandlePF;
164 if( sigaction( SIGUSR1, &sa, NULL ) == -1 ){
165 printf("SIGACTION CANNOT BE INSTALLED\n");
168 createSharedLibrary();
170 //step 2 setup the stack context.
172 int alreadySwapped = 0;
173 getcontext( &savedSnapshotContext );
174 if( !alreadySwapped ){
176 ucontext_t currentContext, swappedContext, newContext;
177 getcontext( &newContext );
178 newContext.uc_stack.ss_sp = sTheRecord->mStackBase;
179 newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
180 newContext.uc_link = ¤tContext;
181 makecontext( &newContext, entryPoint, 0 );
182 swapcontext( &swappedContext, &newContext );
185 //add the code to take a snapshot here...
186 //to return to user process, do a second swapcontext...
188 snapshotid = sTheRecord->currSnapShotID;
189 bool swapContext = false;
190 while( !sTheRecord->mbFinalize ){
191 sTheRecord->currSnapShotID=snapshotid+1;
194 ucontext_t currentContext;
200 swapcontext( ¤tContext, &( sTheRecord->mContextToRollback ) );
202 swapcontext( ¤tContext, &savedUserSnapshotContext );
208 char mesg[ 1024 ] = { 0 };
209 sprintf( mesg, "The process id of child is %d and the process id of this process is %d and snapshot id is %d", forkedID, getpid(), snapshotid );
210 DumpIntoLog( "ModelSnapshot", mesg );
213 retVal=waitpid( forkedID, &status, 0 );
214 } while( -1 == retVal && errno == EINTR );
216 if( sTheRecord->mIDToRollback != snapshotid )
226 /* This function assumes that addr is page aligned */
227 void addMemoryRegionToSnapShot( void * addr, unsigned int numPages) {
228 #if USE_MPROTECT_SNAPSHOT
229 unsigned int memoryregion=snapshotrecord->lastRegion++;
230 if (memoryregion==snapshotrecord->maxRegions) {
231 printf("Exceeded supported number of memory regions!\n");
235 snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr;
236 snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages;
237 #endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
240 snapshot_id takeSnapshot( ){
241 #if USE_MPROTECT_SNAPSHOT
242 for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
243 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ ) == -1 ){
245 printf("Failed to mprotect inside of takeSnapShot\n");
249 unsigned int snapshot=snapshotrecord->lastSnapShot++;
250 if (snapshot==snapshotrecord->maxSnapShots) {
251 printf("Out of snapshots\n");
254 snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage;
258 swapcontext( &savedUserSnapshotContext, &savedSnapshotContext );
262 void rollBack( snapshot_id theID ){
263 #if USE_MPROTECT_SNAPSHOT
264 std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap;
265 for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
266 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE ) == -1 ){
268 printf("Failed to mprotect inside of takeSnapShot\n");
272 for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; page<snapshotrecord->lastBackingPage; page++) {
274 if( duplicateMap.find( snapshotrecord->backingRecords[page].basePtrOfPage ) != duplicateMap.end() ){
278 duplicateMap[ snapshotrecord->backingRecords[page].basePtrOfPage ] = true;
281 memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
284 snapshotrecord->lastSnapShot=theID;
285 snapshotrecord->lastBackingPage=snapshotrecord->snapShots[theID].firstBackingPage;
286 takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared
288 sTheRecord->mIDToRollback = theID;
290 getcontext( &sTheRecord->mContextToRollback );
294 DumpIntoLog( "ModelSnapshot", "Invoked rollback" );
302 #if !USE_MPROTECT_SNAPSHOT
303 sTheRecord->mbFinalize = true;