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         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);
  74                 exit( EXIT_FAILURE );
  75         }
  76
  77         //copy page
  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 )) {
  83                 perror("mprotect");
  84                 // Handle error by quitting?
  85         }
  86 #endif //nothing to handle for non snapshotting case.
  87 }
  88
  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));
  93 }
  94
  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));
  99 }
 100 #ifdef __cplusplus
 101 extern "C" {
 102 #endif
 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;
 118                 sTheRecord->mbFinalize = false;
 119 #endif
 120         }
 121 #ifdef __cplusplus
 122 }
 123 #endif
 124 void initSnapShotLibrary(unsigned int numbackingpages,
 125                 unsigned int numsnapshots, unsigned int nummemoryregions,
 126                 unsigned int numheappages, VoidFuncPtr entryPoint) {
 127 #if USE_MPROTECT_SNAPSHOT
 128         /* Setup a stack for our signal handler....  */
 129         stack_t ss;
 130         ss.ss_sp = MYMALLOC(SIGSTACKSIZE);
 131         ss.ss_size = SIGSTACKSIZE;
 132         ss.ss_flags = 0;
 133         sigaltstack(&ss, NULL);
 134
 135         struct sigaction sa;
 136         sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
 137         sigemptyset( &sa.sa_mask );
 138         sa.sa_sigaction = HandlePF;
 139         if( sigaction( SIGSEGV, &sa, NULL ) == -1 ){
 140                 printf("SIGACTION CANNOT BE INSTALLED\n");
 141                 exit(EXIT_FAILURE);
 142         }
 143         initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions);
 144
 145         // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links
 146         // The problem is that we end up protecting state in the dynamic linker...
 147         // Solution is to call our signal handler before we start protecting stuff...
 148
 149         siginfo_t si;
 150         si.si_addr=ss.ss_sp;
 151         HandlePF(SIGSEGV, &si, NULL);
 152         snapshotrecord->lastBackingPage--; //remove the fake page we copied
 153
 154         basemySpace=MYMALLOC((numheappages+1)*PAGESIZE);
 155         void * pagealignedbase=PageAlignAddressUpward(basemySpace);
 156         mySpace = create_mspace_with_base(pagealignedbase,  numheappages*PAGESIZE, 1 );
 157         addMemoryRegionToSnapShot(pagealignedbase, numheappages);
 158         entryPoint();
 159 #else
 160
 161         basemySpace=system_malloc((numheappages+1)*PAGESIZE);
 162         void * pagealignedbase=PageAlignAddressUpward(basemySpace);
 163         mySpace = create_mspace_with_base(pagealignedbase,  numheappages*PAGESIZE, 1 );
 164         createSharedLibrary();
 165
 166         //step 2 setup the stack context.
 167
 168         int alreadySwapped = 0;
 169         getcontext( &savedSnapshotContext );
 170         if( !alreadySwapped ){
 171                 alreadySwapped = 1;
 172                 ucontext_t currentContext, swappedContext, newContext;
 173                 getcontext( &newContext );
 174                 newContext.uc_stack.ss_sp = sTheRecord->mStackBase;
 175                 newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
 176                 newContext.uc_link = &currentContext;
 177                 makecontext( &newContext, entryPoint, 0 );
 178                 swapcontext( &swappedContext, &newContext );
 179         }
 180
 181         //add the code to take a snapshot here...
 182         //to return to user process, do a second swapcontext...
 183         pid_t forkedID = 0;
 184         snapshotid = sTheRecord->currSnapShotID;
 185         bool swapContext = false;
 186         while( !sTheRecord->mbFinalize ){
 187                 sTheRecord->currSnapShotID=snapshotid+1;
 188                 forkedID = fork();
 189                 if( 0 == forkedID ){
 190                         ucontext_t currentContext;
 191 #if 0
 192                         int dbg = 0;
 193                         while( !dbg );
 194 #endif
 195                         if( swapContext )
 196                                 swapcontext( &currentContext, &( sTheRecord->mContextToRollback ) );
 197                         else{
 198                                 swapcontext( &currentContext, &savedUserSnapshotContext );
 199                         }
 200                 } else {
 201                         int status;
 202                         int retVal;
 203 #if SSDEBUG
 204                         char mesg[ 1024 ] = { 0 };
 205                         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 );
 206                         DumpIntoLog( "ModelSnapshot", mesg );
 207 #endif
 208                         do {
 209                                 retVal=waitpid( forkedID, &status, 0 );
 210                         } while( -1 == retVal && errno == EINTR );
 211
 212                         if( sTheRecord->mIDToRollback != snapshotid )
 213                                 exit(EXIT_SUCCESS);
 214                         else{
 215                                 swapContext = true;
 216                         }
 217                 }
 218         }
 219
 220 #endif
 221 }
 222 /* This function assumes that addr is page aligned */
 223 void addMemoryRegionToSnapShot( void * addr, unsigned int numPages) {
 224 #if USE_MPROTECT_SNAPSHOT
 225         unsigned int memoryregion=snapshotrecord->lastRegion++;
 226         if (memoryregion==snapshotrecord->maxRegions) {
 227                 printf("Exceeded supported number of memory regions!\n");
 228                 exit(EXIT_FAILURE);
 229         }
 230
 231         snapshotrecord->regionsToSnapShot[ memoryregion ].basePtr=addr;
 232         snapshotrecord->regionsToSnapShot[ memoryregion ].sizeInPages=numPages;
 233 #endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
 234 }
 235 //take snapshot
 236 snapshot_id takeSnapshot( ){
 237 #if USE_MPROTECT_SNAPSHOT
 238         for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
 239                 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ ) == -1 ){
 240                         perror("mprotect");
 241                         printf("Failed to mprotect inside of takeSnapShot\n");
 242                         exit(EXIT_FAILURE);
 243                 }
 244         }
 245         unsigned int snapshot=snapshotrecord->lastSnapShot++;
 246         if (snapshot==snapshotrecord->maxSnapShots) {
 247                 printf("Out of snapshots\n");
 248                 exit(EXIT_FAILURE);
 249         }
 250         snapshotrecord->snapShots[snapshot].firstBackingPage=snapshotrecord->lastBackingPage;
 251
 252         return snapshot;
 253 #else
 254         swapcontext( &savedUserSnapshotContext, &savedSnapshotContext );
 255         return snapshotid;
 256 #endif
 257 }
 258 void rollBack( snapshot_id theID ){
 259 #if USE_MPROTECT_SNAPSHOT
 260         std::map< void *, bool, std::less< void * >, MyAlloc< std::pair< const void *, bool > > > duplicateMap;
 261         for(unsigned int region=0; region<snapshotrecord->lastRegion;region++) {
 262                 if( mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages*sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE ) == -1 ){
 263                         perror("mprotect");
 264                         printf("Failed to mprotect inside of takeSnapShot\n");
 265                         exit(EXIT_FAILURE);
 266                 }
 267         }
 268         for(unsigned int page=snapshotrecord->snapShots[theID].firstBackingPage; page<snapshotrecord->lastBackingPage; page++) {
 269                 bool oldVal = false;
 270                 if( duplicateMap.find( snapshotrecord->backingRecords[page].basePtrOfPage ) != duplicateMap.end() ){
 271                         oldVal = true;
 272                 }
 273                 else{
 274                         duplicateMap[ snapshotrecord->backingRecords[page].basePtrOfPage ] = true;
 275                 }
 276                 if(  !oldVal ){
 277                         memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
 278                 }
 279         }
 280         snapshotrecord->lastSnapShot=theID;
 281         snapshotrecord->lastBackingPage=snapshotrecord->snapShots[theID].firstBackingPage;
 282         takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared
 283 #else
 284         sTheRecord->mIDToRollback = theID;
 285         int sTemp = 0;
 286         getcontext( &sTheRecord->mContextToRollback );
 287         if( !sTemp ){
 288                 sTemp = 1;
 289 #if SSDEBUG
 290                 DumpIntoLog( "ModelSnapshot", "Invoked rollback" );
 291 #endif
 292                 exit(EXIT_SUCCESS);
 293         }
 294 #endif
 295 }
 296
 297 void finalize(){
 298 #if !USE_MPROTECT_SNAPSHOT
 299         sTheRecord->mbFinalize = true;
 300 #endif
 301 }
 302