11 #include "hashtable.h"
16 #define FAILURE(mesg) { model_print("failed in the API: %s with errno relative message: %s\n", mesg, strerror(errno)); exit(EXIT_FAILURE); }
18 /** PageAlignedAdressUpdate return a page aligned address for the
19 * address being added as a side effect the numBytes are also changed.
21 static void * PageAlignAddressUpward(void *addr)
23 return (void *)((((uintptr_t)addr) + PAGESIZE - 1) & ~(PAGESIZE - 1));
26 #if USE_MPROTECT_SNAPSHOT
28 /* Each SnapShotRecord lists the firstbackingpage that must be written to
29 * revert to that snapshot */
30 struct SnapShotRecord {
31 unsigned int firstBackingPage;
34 /** @brief Backing store page */
35 typedef unsigned char snapshot_page_t[PAGESIZE];
37 /* List the base address of the corresponding page in the backing store so we
38 * know where to copy it to */
39 struct BackingPageRecord {
43 /* Struct for each memory region */
45 void *basePtr; // base of memory region
46 int sizeInPages; // size of memory region in pages
49 /** ReturnPageAlignedAddress returns a page aligned address for the
50 * address being added as a side effect the numBytes are also changed.
52 static void * ReturnPageAlignedAddress(void *addr)
54 return (void *)(((uintptr_t)addr) & ~(PAGESIZE - 1));
57 /* Primary struct for snapshotting system */
58 struct mprot_snapshotter {
59 mprot_snapshotter(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions);
61 struct MemoryRegion *regionsToSnapShot; //This pointer references an array of memory regions to snapshot
62 snapshot_page_t *backingStore; //This pointer references an array of snapshotpage's that form the backing store
63 void *backingStoreBasePtr; //This pointer references an array of snapshotpage's that form the backing store
64 struct BackingPageRecord *backingRecords; //This pointer references an array of backingpagerecord's (same number of elements as backingstore
65 struct SnapShotRecord *snapShots; //This pointer references the snapshot array
67 unsigned int lastSnapShot; //Stores the next snapshot record we should use
68 unsigned int lastBackingPage; //Stores the next backingpage we should use
69 unsigned int lastRegion; //Stores the next memory region to be used
71 unsigned int maxRegions; //Stores the max number of memory regions we support
72 unsigned int maxBackingPages; //Stores the total number of backing pages
73 unsigned int maxSnapShots; //Stores the total number of snapshots we allow
78 static struct mprot_snapshotter *mprot_snap = NULL;
80 mprot_snapshotter::mprot_snapshotter(unsigned int backing_pages, unsigned int snapshots, unsigned int regions) :
85 maxBackingPages(backing_pages),
86 maxSnapShots(snapshots)
88 regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * regions);
89 backingStoreBasePtr = (void *)model_malloc(sizeof(snapshot_page_t) * (backing_pages + 1));
90 //Page align the backingstorepages
91 backingStore = (snapshot_page_t *)PageAlignAddressUpward(backingStoreBasePtr);
92 backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * backing_pages);
93 snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * snapshots);
96 /** mprot_handle_pf is the page fault handler for mprotect based snapshotting
99 static void mprot_handle_pf(int sig, siginfo_t *si, void *unused)
101 if (si->si_code == SEGV_MAPERR) {
102 model_print("Real Fault at %p\n", si->si_addr);
104 model_print("For debugging, place breakpoint at: %s:%d\n",
108 void* addr = ReturnPageAlignedAddress(si->si_addr);
110 unsigned int backingpage = mprot_snap->lastBackingPage++; //Could run out of pages...
111 if (backingpage == mprot_snap->maxBackingPages) {
112 model_print("Out of backing pages at %p\n", si->si_addr);
117 memcpy(&(mprot_snap->backingStore[backingpage]), addr, sizeof(snapshot_page_t));
118 //remember where to copy page back to
119 mprot_snap->backingRecords[backingpage].basePtrOfPage = addr;
120 //set protection to read/write
121 if (mprotect(addr, sizeof(snapshot_page_t), PROT_READ | PROT_WRITE)) {
123 // Handle error by quitting?
127 static void mprot_snapshot_init(unsigned int numbackingpages,
128 unsigned int numsnapshots, unsigned int nummemoryregions,
129 unsigned int numheappages, VoidFuncPtr entryPoint)
131 /* Setup a stack for our signal handler.... */
133 ss.ss_sp = PageAlignAddressUpward(model_malloc(SIGSTACKSIZE + PAGESIZE - 1));
134 ss.ss_size = SIGSTACKSIZE;
136 sigaltstack(&ss, NULL);
139 sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
140 sigemptyset(&sa.sa_mask);
141 sa.sa_sigaction = mprot_handle_pf;
143 if (sigaction(SIGBUS, &sa, NULL) == -1) {
144 model_print("SIGACTION CANNOT BE INSTALLED\n");
148 if (sigaction(SIGSEGV, &sa, NULL) == -1) {
149 model_print("SIGACTION CANNOT BE INSTALLED\n");
153 mprot_snap = new mprot_snapshotter(numbackingpages, numsnapshots, nummemoryregions);
155 // EVIL HACK: We need to make sure that calls into the mprot_handle_pf method don't cause dynamic links
156 // The problem is that we end up protecting state in the dynamic linker...
157 // Solution is to call our signal handler before we start protecting stuff...
160 memset(&si, 0, sizeof(si));
161 si.si_addr = ss.ss_sp;
162 mprot_handle_pf(SIGSEGV, &si, NULL);
163 mprot_snap->lastBackingPage--; //remove the fake page we copied
165 void *basemySpace = model_malloc((numheappages + 1) * PAGESIZE);
166 void *pagealignedbase = PageAlignAddressUpward(basemySpace);
167 user_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
168 addMemoryRegionToSnapShot(pagealignedbase, numheappages);
170 void *base_model_snapshot_space = model_malloc((numheappages + 1) * PAGESIZE);
171 pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space);
172 model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
173 addMemoryRegionToSnapShot(pagealignedbase, numheappages);
178 static void mprot_add_to_snapshot(void *addr, unsigned int numPages)
180 unsigned int memoryregion = mprot_snap->lastRegion++;
181 if (memoryregion == mprot_snap->maxRegions) {
182 model_print("Exceeded supported number of memory regions!\n");
186 mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr;
187 mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages;
190 static snapshot_id mprot_take_snapshot()
192 for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) {
193 if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ) == -1) {
195 model_print("Failed to mprotect inside of takeSnapShot\n");
199 unsigned int snapshot = mprot_snap->lastSnapShot++;
200 if (snapshot == mprot_snap->maxSnapShots) {
201 model_print("Out of snapshots\n");
204 mprot_snap->snapShots[snapshot].firstBackingPage = mprot_snap->lastBackingPage;
209 static void mprot_roll_back(snapshot_id theID)
211 #if USE_MPROTECT_SNAPSHOT == 2
212 if (mprot_snap->lastSnapShot == (theID + 1)) {
213 for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) {
214 memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
220 HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap;
221 for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) {
222 if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ | PROT_WRITE) == -1) {
224 model_print("Failed to mprotect inside of takeSnapShot\n");
228 for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) {
229 if (!duplicateMap.contains(mprot_snap->backingRecords[page].basePtrOfPage)) {
230 duplicateMap.put(mprot_snap->backingRecords[page].basePtrOfPage, true);
231 memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
234 mprot_snap->lastSnapShot = theID;
235 mprot_snap->lastBackingPage = mprot_snap->snapShots[theID].firstBackingPage;
236 mprot_take_snapshot(); //Make sure current snapshot is still good...All later ones are cleared
239 #else /* !USE_MPROTECT_SNAPSHOT */
241 #include <ucontext.h>
243 #define SHARED_MEMORY_DEFAULT (100 * ((size_t)1 << 20)) // 100mb for the shared memory
244 #define STACK_SIZE_DEFAULT (((size_t)1 << 20) * 20) // 20 mb out of the above 100 mb for my stack
246 struct fork_snapshotter {
247 void *mSharedMemoryBase;
250 volatile snapshot_id mIDToRollback;
251 ucontext_t mContextToRollback;
252 snapshot_id currSnapShotID;
255 static struct fork_snapshotter *fork_snap = NULL;
258 * These variables are necessary because the stack is shared region and
259 * there exists a race between all processes executing the same function.
260 * To avoid the problem above, we require variables allocated in 'safe' regions.
261 * The bug was actually observed with the forkID, these variables below are
262 * used to indicate the various contexts to which to switch to.
264 * @savedSnapshotContext: contains the point to which takesnapshot() call should switch to.
265 * @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to
266 * @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record
268 static ucontext_t savedSnapshotContext;
269 static ucontext_t savedUserSnapshotContext;
270 static snapshot_id snapshotid = 0;
272 static void createSharedMemory()
274 //step 1. create shared memory.
275 void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
276 if (MAP_FAILED == memMapBase)
279 //Setup snapshot record at top of free region
280 fork_snap = (struct fork_snapshotter *)memMapBase;
281 fork_snap->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct fork_snapshotter));
282 fork_snap->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT);
283 fork_snap->mStackSize = STACK_SIZE_DEFAULT;
284 fork_snap->mIDToRollback = -1;
285 fork_snap->currSnapShotID = 0;
289 * Create a new mspace pointer for the non-snapshotting (i.e., inter-process
290 * shared) memory region. Only for fork-based snapshotting.
292 * @return The shared memory mspace
294 mspace create_shared_mspace()
297 createSharedMemory();
298 return create_mspace_with_base((void *)(fork_snap->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(struct fork_snapshotter), 1);
301 static void fork_snapshot_init(unsigned int numbackingpages,
302 unsigned int numsnapshots, unsigned int nummemoryregions,
303 unsigned int numheappages, VoidFuncPtr entryPoint)
306 createSharedMemory();
308 void *base_model_snapshot_space = malloc((numheappages + 1) * PAGESIZE);
309 void *pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space);
310 model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
312 //step 2 setup the stack context.
313 ucontext_t newContext;
314 getcontext(&newContext);
315 newContext.uc_stack.ss_sp = fork_snap->mStackBase;
316 newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
317 makecontext(&newContext, entryPoint, 0);
318 /* switch to a new entryPoint context, on a new stack */
319 swapcontext(&savedSnapshotContext, &newContext);
321 /* switch back here when takesnapshot is called */
323 snapshotid = fork_snap->currSnapShotID;
324 /* This bool indicates that the current process's snapshotid is same
325 as the id to which the rollback needs to occur */
327 bool rollback = false;
329 fork_snap->currSnapShotID = snapshotid + 1;
333 /* If the rollback bool is set, switch to the context we need to
334 return to during a rollback. */
336 setcontext(&(fork_snap->mContextToRollback));
338 /*Child process which is forked as a result of takesnapshot
339 call should switch back to the takesnapshot context*/
340 setcontext(&savedUserSnapshotContext);
346 DEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d\n",
347 forkedID, getpid(), snapshotid);
350 retVal = waitpid(forkedID, &status, 0);
351 } while (-1 == retVal && errno == EINTR);
353 if (fork_snap->mIDToRollback != snapshotid) {
361 static snapshot_id fork_take_snapshot()
363 swapcontext(&savedUserSnapshotContext, &savedSnapshotContext);
364 DEBUG("TAKESNAPSHOT RETURN\n");
368 static void fork_roll_back(snapshot_id theID)
370 fork_snap->mIDToRollback = theID;
371 volatile int sTemp = 0;
372 getcontext(&fork_snap->mContextToRollback);
374 * This is used to quit the process on rollback, so that the process
375 * which needs to rollback can quit allowing the process whose
376 * snapshotid matches the rollbackid to switch to this context and
381 DEBUG("Invoked rollback\n");
385 * This fix obviates the need for a finalize call. hence less dependences for model-checker....
387 fork_snap->mIDToRollback = -1;
390 #endif /* !USE_MPROTECT_SNAPSHOT */
392 /** The initSnapshotLibrary function initializes the snapshot library.
393 * @param entryPoint the function that should run the program.
395 void initSnapshotLibrary(unsigned int numbackingpages,
396 unsigned int numsnapshots, unsigned int nummemoryregions,
397 unsigned int numheappages, VoidFuncPtr entryPoint)
399 #if USE_MPROTECT_SNAPSHOT
400 mprot_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint);
402 fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint);
406 /** The addMemoryRegionToSnapShot function assumes that addr is page aligned. */
407 void addMemoryRegionToSnapShot(void *addr, unsigned int numPages)
409 #if USE_MPROTECT_SNAPSHOT
410 mprot_add_to_snapshot(addr, numPages);
412 /* not needed for fork-based snapshotting */
416 /** The takeSnapshot function takes a snapshot.
417 * @return The snapshot identifier.
419 snapshot_id takeSnapshot()
421 #if USE_MPROTECT_SNAPSHOT
422 return mprot_take_snapshot();
424 return fork_take_snapshot();
428 /** The rollBack function rollback to the given snapshot identifier.
429 * @param theID is the snapshot identifier to rollback to.
431 void rollBack(snapshot_id theID)
433 #if USE_MPROTECT_SNAPSHOT
434 mprot_roll_back(theID);
436 fork_roll_back(theID);