10 #include "snapshotimp.h"
15 #include <semaphore.h>
20 #define FAILURE(mesg) { printf("failed in the API: %s with errno relative message: %s\n", mesg, strerror( errno ) ); exit(EXIT_FAILURE); }
23 #define SSDEBUG printf
25 #define SSDEBUG(...) do { } while (0)
28 /* extern declaration definition */
29 #if USE_MPROTECT_SNAPSHOT
30 struct SnapShot * snapshotrecord = NULL;
32 struct Snapshot_t * sTheRecord = NULL;
35 #if !USE_MPROTECT_SNAPSHOT
36 static ucontext_t savedSnapshotContext;
37 static ucontext_t savedUserSnapshotContext;
38 static snapshot_id snapshotid = 0;
41 #if USE_MPROTECT_SNAPSHOT
43 /** The initSnapShotRecord method initialized the snapshotting data
44 * structures for the mprotect based snapshot.
46 void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions) {
47 snapshotrecord=( struct SnapShot * )MYMALLOC(sizeof(struct SnapShot));
48 snapshotrecord->regionsToSnapShot=( struct MemoryRegion * )MYMALLOC(sizeof(struct MemoryRegion)*nummemoryregions);
49 snapshotrecord->backingStoreBasePtr= ( struct SnapShotPage * )MYMALLOC( sizeof( struct SnapShotPage ) * (numbackingpages + 1) );
50 //Page align the backingstorepages
51 snapshotrecord->backingStore=( struct SnapShotPage * )PageAlignAddressUpward(snapshotrecord->backingStoreBasePtr);
52 snapshotrecord->backingRecords=( struct BackingPageRecord * )MYMALLOC(sizeof(struct BackingPageRecord)*numbackingpages);
53 snapshotrecord->snapShots= ( struct SnapShotRecord * )MYMALLOC(sizeof(struct SnapShotRecord)*numsnapshots);
54 snapshotrecord->lastSnapShot=0;
55 snapshotrecord->lastBackingPage=0;
56 snapshotrecord->lastRegion=0;
57 snapshotrecord->maxRegions=nummemoryregions;
58 snapshotrecord->maxBackingPages=numbackingpages;
59 snapshotrecord->maxSnapShots=numsnapshots;
61 #endif //nothing to initialize for the fork based snapshotting.
63 /** HandlePF is the page fault handler for mprotect based snapshotting
67 void HandlePF( int sig, siginfo_t *si, void * unused){
68 #if USE_MPROTECT_SNAPSHOT
69 if( si->si_code == SEGV_MAPERR ){
70 printf("Real Fault at %p\n", si->si_addr);
73 void* addr = ReturnPageAlignedAddress(si->si_addr);
75 unsigned int backingpage=snapshotrecord->lastBackingPage++; //Could run out of pages...
76 if (backingpage==snapshotrecord->maxBackingPages) {
77 printf("Out of backing pages at %p\n", si->si_addr);
82 memcpy(&(snapshotrecord->backingStore[backingpage]), addr, sizeof(struct SnapShotPage));
83 //remember where to copy page back to
84 snapshotrecord->backingRecords[backingpage].basePtrOfPage=addr;
85 //set protection to read/write
86 if (mprotect( addr, sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE )) {
88 // Handle error by quitting?
90 #endif //nothing to handle for non snapshotting case.
93 /** ReturnPageAlignedAddress returns a page aligned address for the
94 * address being added as a side effect the numBytes are also changed.
97 void * ReturnPageAlignedAddress(void * addr) {
98 return (void *)(((uintptr_t)addr)&~(PAGESIZE-1));
101 /** PageAlignedAdressUpdate return a page aligned address for the
102 * address being added as a side effect the numBytes are also changed.
105 void * PageAlignAddressUpward(void * addr) {
106 return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1));
108 void createSharedLibrary(){
109 #if !USE_MPROTECT_SNAPSHOT
110 //step 1. create shared memory.
111 if( sTheRecord ) return;
112 int fd = shm_open( "/ModelChecker-Snapshotter", O_RDWR | O_CREAT, 0777 ); //universal permissions.
113 if( -1 == fd ) FAILURE("shm_open");
114 if( -1 == ftruncate( fd, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT ) ) FAILURE( "ftruncate" );
115 char * memMapBase = ( char * ) mmap( 0, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 );
116 if( MAP_FAILED == memMapBase ) FAILURE("mmap");
117 sTheRecord = ( struct Snapshot_t * )memMapBase;
118 sTheRecord->mSharedMemoryBase = memMapBase + sizeof( struct Snapshot_t );
119 sTheRecord->mStackBase = ( char * )memMapBase + ( size_t )SHARED_MEMORY_DEFAULT;
120 sTheRecord->mStackSize = STACK_SIZE_DEFAULT;
121 sTheRecord->mIDToRollback = -1;
122 sTheRecord->currSnapShotID = 0;
123 sTheRecord->mbFinalize = false;
127 /** The initSnapShotLibrary function initializes the Snapshot library.
128 * @param entryPoint the function that should run the program.
130 void initSnapShotLibrary(unsigned int numbackingpages,
131 unsigned int numsnapshots, unsigned int nummemoryregions,
132 unsigned int numheappages, VoidFuncPtr entryPoint) {
133 #if USE_MPROTECT_SNAPSHOT
134 /* Setup a stack for our signal handler.... */
136 ss.ss_sp = MYMALLOC(SIGSTACKSIZE);
137 ss.ss_size = SIGSTACKSIZE;
139 sigaltstack(&ss, NULL);
142 sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
143 sigemptyset( &sa.sa_mask );
144 sa.sa_sigaction = HandlePF;
146 if( sigaction( SIGBUS, &sa, NULL ) == -1 ){
147 printf("SIGACTION CANNOT BE INSTALLED\n");
151 if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){
152 printf("SIGACTION CANNOT BE INSTALLED\n");
156 initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions);
158 // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links
159 // The problem is that we end up protecting state in the dynamic linker...
160 // Solution is to call our signal handler before we start protecting stuff...
163 memset(&si, 0, sizeof(si));
165 HandlePF(SIGSEGV, &si, NULL);
166 snapshotrecord->lastBackingPage--; //remove the fake page we copied
168 basemySpace=MYMALLOC((numheappages+1)*PAGESIZE);
169 void * pagealignedbase=PageAlignAddressUpward(basemySpace);
170 mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 );
171 addMemoryRegionToSnapShot(pagealignedbase, numheappages);
175 basemySpace=system_malloc((numheappages+1)*PAGESIZE);
176 void * pagealignedbase=PageAlignAddressUpward(basemySpace);
177 mySpace = create_mspace_with_base(pagealignedbase, numheappages*PAGESIZE, 1 );
178 createSharedLibrary();
180 //step 2 setup the stack context.
182 int alreadySwapped = 0;
183 getcontext( &savedSnapshotContext );
184 if( !alreadySwapped ){
186 ucontext_t currentContext, swappedContext, newContext;
187 getcontext( &newContext );
188 newContext.uc_stack.ss_sp = sTheRecord->mStackBase;
189 newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
190 newContext.uc_link = ¤tContext;
191 makecontext( &newContext, entryPoint, 0 );
192 swapcontext( &swappedContext, &newContext );
195 //add the code to take a snapshot here...
196 //to return to user process, do a second swapcontext...
198 snapshotid = sTheRecord->currSnapShotID;
199 bool swapContext = false;
200 while( !sTheRecord->mbFinalize ){
201 sTheRecord->currSnapShotID=snapshotid+1;
204 ucontext_t currentContext;
210 swapcontext( ¤tContext, &( sTheRecord->mContextToRollback ) );
212 swapcontext( ¤tContext, &savedUserSnapshotContext );
218 SSDEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d",
219 forkedID, getpid(), snapshotid );
222 retVal=waitpid( forkedID, &status, 0 );
223 } while( -1 == retVal && errno == EINTR );
225 if( sTheRecord->mIDToRollback != snapshotid )
236 /** The addMemoryRegionToSnapShot function assumes that addr is page aligned.
238 void addMemoryRegionToSnapShot( void * addr, unsigned int numPages) {
239 #if USE_MPROTECT_SNAPSHOT
240 unsigned int memoryregion=snapshotrecord->lastRegion++;
241 if (memoryregion==snapshotrecord->maxRegions) {
242 printf("Exceeded supported number of memory regions!\n");
246 snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr;
247 snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages;
248 #endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
251 /** The takeSnapshot function takes a snapshot.
252 * @return The snapshot identifier.
255 snapshot_id takeSnapshot( ){
256 #if USE_MPROTECT_SNAPSHOT
257 for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
258 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ ) == -1 ){
260 printf("Failed to mprotect inside of takeSnapShot\n");
264 unsigned int snapshot=snapshotrecord->lastSnapShot++;
265 if (snapshot==snapshotrecord->maxSnapShots) {
266 printf("Out of snapshots\n");
269 snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage;
273 swapcontext( &savedUserSnapshotContext, &savedSnapshotContext );
278 /** The rollBack function rollback to the given snapshot identifier.
279 * @param theID is the snapshot identifier to rollback to.
282 void rollBack( snapshot_id theID ){
283 #if USE_MPROTECT_SNAPSHOT
284 std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap;
285 for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
286 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE ) == -1 ){
288 printf("Failed to mprotect inside of takeSnapShot\n");
292 for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; page<snapshotrecord->lastBackingPage; page++) {
294 if( duplicateMap.find( snapshotrecord->backingRecords[page].basePtrOfPage ) != duplicateMap.end() ){
298 duplicateMap[ snapshotrecord->backingRecords[page].basePtrOfPage ] = true;
301 memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
304 snapshotrecord->lastSnapShot=theID;
305 snapshotrecord->lastBackingPage=snapshotrecord->snapShots[theID].firstBackingPage;
306 takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared
308 sTheRecord->mIDToRollback = theID;
310 getcontext( &sTheRecord->mContextToRollback );
313 SSDEBUG("Invoked rollback");
319 /** The finalize method shuts down the snapshotting system. */
320 //Subramanian -- remove this function from the external interface and
321 //have us call it internally
324 #if !USE_MPROTECT_SNAPSHOT
325 sTheRecord->mbFinalize = true;