snapshot.cc

   1 #include <inttypes.h>
   2 #include <sys/mman.h>
   3 #include <unistd.h>
   4 #include <signal.h>
   5 #include <stdlib.h>
   6 #include <map>
   7 #include <cstring>
   8 #include <cstdio>
   9 #include "snapshot.h"
  10 #include "snapshotimp.h"
  11 #include "mymemory.h"
  12 #include <fcntl.h>
  13 #include <assert.h>
  14 #include <pthread.h>
  15 #include <semaphore.h>
  16 #include <errno.h>
  17 #include <sys/wait.h>
  18 #include <ucontext.h>
  19
  20 //extern declaration definition
  21 #define FAILURE(mesg) { printf("failed in the API: %s with errno relative message: %s\n", mesg, strerror( errno ) ); exit(EXIT_FAILURE); }
  22 #if USE_MPROTECT_SNAPSHOT
  23 struct SnapShot * snapshotrecord = NULL;
  24 struct Snapshot_t * sTheRecord = NULL;
  25 #else
  26 struct Snapshot_t * sTheRecord = NULL;
  27 #endif
  28 void DumpIntoLog( const char * filename, const char * message ){
  29 #if SSDEBUG
  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 );
  35         fflush( myFile );
  36         fclose( myFile );
  37         myFile = NULL;
  38 #endif
  39 }
  40 #if !USE_MPROTECT_SNAPSHOT
  41 static ucontext_t savedSnapshotContext;
  42 static ucontext_t savedUserSnapshotContext;
  43 static snapshot_id snapshotid = 0;
  44 #endif
  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;
  61 }
  62 #endif //nothing to initialize for the fork based snapshotting.
  63
  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);
  68                 exit( EXIT_FAILURE );
  69         }
  70         void* addr = ReturnPageAlignedAddress(si->si_addr);
  71
  72         unsigned int backingpage=snapshotrecord->lastBackingPage++; //Could run out of pages...
  73         if (backingpage==snapshotrecord->maxBackingPages) {
  74                 printf("Out of backing pages at %p\n", si->si_addr);
  75                 exit( EXIT_FAILURE );
  76         }
  77
  78         //copy page
  79         memcpy(&(snapshotrecord->backingStore[backingpage]), addr, sizeof(struct SnapShotPage));
  80         //remember where to copy page back to
  81         snapshotrecord->backingRecords[backingpage].basePtrOfPage=addr;
  82         //set protection to read/write
  83         if (mprotect( addr, sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE )) {
  84                 perror("mprotect");
  85                 // Handle error by quitting?
  86         }
  87 #endif //nothing to handle for non snapshotting case.
  88 }
  89
  90 //Return a page aligned address for the address being added
  91 //as a side effect the numBytes are also changed.
  92 void * ReturnPageAlignedAddress(void * addr) {
  93         return (void *)(((uintptr_t)addr)&~(PAGESIZE-1));
  94 }
  95
  96 //Return a page aligned address for the address being added
  97 //as a side effect the numBytes are also changed.
  98 void * PageAlignAddressUpward(void * addr) {
  99         return (void *)((((uintptr_t)addr)+PAGESIZE-1)&~(PAGESIZE-1));
 100 }
 101 #ifdef __cplusplus
 102 extern "C" {
 103 #endif
 104         void createSharedLibrary(){
 105 #if !USE_MPROTECT_SNAPSHOT
 106                 //step 1. create shared memory.
 107                 if( sTheRecord ) return;
 108                 int fd = shm_open( "/ModelChecker-Snapshotter", O_RDWR | O_CREAT, 0777 ); //universal permissions.
 109                 if( -1 == fd ) FAILURE("shm_open");
 110                 if( -1 == ftruncate( fd, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT ) ) FAILURE( "ftruncate" );
 111                 char * memMapBase = ( char * ) mmap( 0, ( size_t )SHARED_MEMORY_DEFAULT + ( size_t )STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 );
 112                 if( MAP_FAILED == memMapBase ) FAILURE("mmap");
 113                 sTheRecord = ( struct Snapshot_t * )memMapBase;
 114                 sTheRecord->mSharedMemoryBase = memMapBase + sizeof( struct Snapshot_t );
 115                 sTheRecord->mStackBase = ( char * )memMapBase + ( size_t )SHARED_MEMORY_DEFAULT;
 116                 sTheRecord->mStackSize = STACK_SIZE_DEFAULT;
 117                 sTheRecord->mIDToRollback = -1;
 118                 sTheRecord->currSnapShotID = 0;
 119                 sTheRecord->mbFinalize = false;
 120 #endif
 121         }
 122 #ifdef __cplusplus
 123 }
 124 #endif
 125 void initSnapShotLibrary(unsigned int numbackingpages,
 126                 unsigned int numsnapshots, unsigned int nummemoryregions,
 127                 unsigned int numheappages, VoidFuncPtr entryPoint) {
 128 #if USE_MPROTECT_SNAPSHOT
 129         /* Setup a stack for our signal handler....  */
 130         stack_t ss;
 131         ss.ss_sp = MYMALLOC(SIGSTACKSIZE);
 132         ss.ss_size = SIGSTACKSIZE;
 133         ss.ss_flags = 0;
 134         sigaltstack(&ss, NULL);
 135
 136         struct sigaction sa;
 137         sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
 138         sigemptyset( &sa.sa_mask );
 139         sa.sa_sigaction = HandlePF;
 140 #ifdef MAC
 141         if( sigaction( SIGBUS, &sa, NULL ) == -1 ){
 142                 printf("SIGACTION CANNOT BE INSTALLED\n");
 143                 exit(EXIT_FAILURE);
 144         }
 145 #endif
 146         if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){
 147                 printf("SIGACTION CANNOT BE INSTALLED\n");
 148                 exit(EXIT_FAILURE);
 149         }
 150
 151         initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions);
 152
 153         // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links
 154         // The problem is that we end up protecting state in the dynamic linker...
 155         // Solution is to call our signal handler before we start protecting stuff...
 156
 157         siginfo_t si;
 158         memset(&si, 0, sizeof(si));
 159         si.si_addr=ss.ss_sp;
 160         HandlePF(SIGSEGV, &si, NULL);
 161         snapshotrecord->lastBackingPage--; //remove the fake page we copied
 162
 163         basemySpace=MYMALLOC((numheappages+1)*PAGESIZE);
 164         void * pagealignedbase=PageAlignAddressUpward(basemySpace);
 165         mySpace = create_mspace_with_base(pagealignedbase,  numheappages*PAGESIZE, 1 );
 166         addMemoryRegionToSnapShot(pagealignedbase, numheappages);
 167         entryPoint();
 168 #else
 169
 170         basemySpace=system_malloc((numheappages+1)*PAGESIZE);
 171         void * pagealignedbase=PageAlignAddressUpward(basemySpace);
 172         mySpace = create_mspace_with_base(pagealignedbase,  numheappages*PAGESIZE, 1 );
 173         createSharedLibrary();
 174
 175         //step 2 setup the stack context.
 176
 177         int alreadySwapped = 0;
 178         getcontext( &savedSnapshotContext );
 179         if( !alreadySwapped ){
 180                 alreadySwapped = 1;
 181                 ucontext_t currentContext, swappedContext, newContext;
 182                 getcontext( &newContext );
 183                 newContext.uc_stack.ss_sp = sTheRecord->mStackBase;
 184                 newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
 185                 newContext.uc_link = &currentContext;
 186                 makecontext( &newContext, entryPoint, 0 );
 187                 swapcontext( &swappedContext, &newContext );
 188         }
 189
 190         //add the code to take a snapshot here...
 191         //to return to user process, do a second swapcontext...
 192         pid_t forkedID = 0;
 193         snapshotid = sTheRecord->currSnapShotID;
 194         bool swapContext = false;
 195         while( !sTheRecord->mbFinalize ){
 196                 sTheRecord->currSnapShotID=snapshotid+1;
 197                 forkedID = fork();
 198                 if( 0 == forkedID ){
 199                         ucontext_t currentContext;
 200 #if 0
 201                         int dbg = 0;
 202                         while( !dbg );
 203 #endif
 204                         if( swapContext )
 205                                 swapcontext( &currentContext, &( sTheRecord->mContextToRollback ) );
 206                         else{
 207                                 swapcontext( &currentContext, &savedUserSnapshotContext );
 208                         }
 209                 } else {
 210                         int status;
 211                         int retVal;
 212 #if SSDEBUG
 213                         char mesg[ 1024 ] = { 0 };
 214                         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 );
 215                         DumpIntoLog( "ModelSnapshot", mesg );
 216 #endif
 217                         do {
 218                                 retVal=waitpid( forkedID, &status, 0 );
 219                         } while( -1 == retVal && errno == EINTR );
 220
 221                         if( sTheRecord->mIDToRollback != snapshotid )
 222                                 exit(EXIT_SUCCESS);
 223                         else{
 224                                 swapContext = true;
 225                         }
 226                 }
 227         }
 228
 229 #endif
 230 }
 231 /* This function assumes that addr is page aligned */
 232 void addMemoryRegionToSnapShot( void * addr, unsigned int numPages) {
 233 #if USE_MPROTECT_SNAPSHOT
 234         unsigned int memoryregion=snapshotrecord->lastRegion++;
 235         if (memoryregion==snapshotrecord->maxRegions) {
 236                 printf("Exceeded supported number of memory regions!\n");
 237                 exit(EXIT_FAILURE);
 238         }
 239
 240         snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr;
 241         snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages;
 242 #endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
 243 }
 244 //take snapshot
 245 snapshot_id takeSnapshot( ){
 246 #if USE_MPROTECT_SNAPSHOT
 247         for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
 248                 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ ) == -1 ){
 249                         perror("mprotect");
 250                         printf("Failed to mprotect inside of takeSnapShot\n");
 251                         exit(EXIT_FAILURE);
 252                 }
 253         }
 254         unsigned int snapshot=snapshotrecord->lastSnapShot++;
 255         if (snapshot==snapshotrecord->maxSnapShots) {
 256                 printf("Out of snapshots\n");
 257                 exit(EXIT_FAILURE);
 258         }
 259         snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage;
 260
 261         return snapshot;
 262 #else
 263         swapcontext( &savedUserSnapshotContext, &savedSnapshotContext );
 264         return snapshotid;
 265 #endif
 266 }
 267 void rollBack( snapshot_id theID ){
 268 #if USE_MPROTECT_SNAPSHOT
 269         std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap;
 270         for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
 271                 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE ) == -1 ){
 272                         perror("mprotect");
 273                         printf("Failed to mprotect inside of takeSnapShot\n");
 274                         exit(EXIT_FAILURE);
 275                 }
 276         }
 277         for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; page<snapshotrecord->lastBackingPage; page++) {
 278                 bool oldVal = false;
 279                 if( duplicateMap.find( snapshotrecord->backingRecords[page].basePtrOfPage ) != duplicateMap.end() ){
 280                         oldVal = true;
 281                 }
 282                 else{
 283                         duplicateMap[ snapshotrecord->backingRecords[page].basePtrOfPage ] = true;
 284                 }
 285                 if(  !oldVal ){
 286                         memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
 287                 }
 288         }
 289         snapshotrecord->lastSnapShot=theID;
 290         snapshotrecord->lastBackingPage=snapshotrecord->snapShots[theID].firstBackingPage;
 291         takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared
 292 #else
 293         sTheRecord->mIDToRollback = theID;
 294         int sTemp = 0;
 295         getcontext( &sTheRecord->mContextToRollback );
 296         if( !sTemp ){
 297                 sTemp = 1;
 298 #if SSDEBUG
 299                 DumpIntoLog( "ModelSnapshot", "Invoked rollback" );
 300 #endif
 301                 exit(EXIT_SUCCESS);
 302         }
 303 #endif
 304 }
 305
 306 void finalize(){
 307 #if !USE_MPROTECT_SNAPSHOT
 308         sTheRecord->mbFinalize = true;
 309 #endif
 310 }
 311