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);
62 struct MemoryRegion *regionsToSnapShot; //This pointer references an array of memory regions to snapshot
63 snapshot_page_t *backingStore; //This pointer references an array of snapshotpage's that form the backing store
64 void *backingStoreBasePtr; //This pointer references an array of snapshotpage's that form the backing store
65 struct BackingPageRecord *backingRecords; //This pointer references an array of backingpagerecord's (same number of elements as backingstore
66 struct SnapShotRecord *snapShots; //This pointer references the snapshot array
68 unsigned int lastSnapShot; //Stores the next snapshot record we should use
69 unsigned int lastBackingPage; //Stores the next backingpage we should use
70 unsigned int lastRegion; //Stores the next memory region to be used
72 unsigned int maxRegions; //Stores the max number of memory regions we support
73 unsigned int maxBackingPages; //Stores the total number of backing pages
74 unsigned int maxSnapShots; //Stores the total number of snapshots we allow
79 static struct mprot_snapshotter *mprot_snap = NULL;
81 mprot_snapshotter::mprot_snapshotter(unsigned int backing_pages, unsigned int snapshots, unsigned int regions) :
86 maxBackingPages(backing_pages),
87 maxSnapShots(snapshots)
89 regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * regions);
90 backingStoreBasePtr = (void *)model_malloc(sizeof(snapshot_page_t) * (backing_pages + 1));
91 //Page align the backingstorepages
92 backingStore = (snapshot_page_t *)PageAlignAddressUpward(backingStoreBasePtr);
93 backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * backing_pages);
94 snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * snapshots);
97 mprot_snapshotter::~mprot_snapshotter()
99 model_free(regionsToSnapShot);
100 model_free(backingStoreBasePtr);
101 model_free(backingRecords);
102 model_free(snapShots);
105 /** mprot_handle_pf is the page fault handler for mprotect based snapshotting
108 static void mprot_handle_pf(int sig, siginfo_t *si, void *unused)
110 if (si->si_code == SEGV_MAPERR) {
111 model_print("Real Fault at %p\n", si->si_addr);
113 model_print("For debugging, place breakpoint at: %s:%d\n",
117 void* addr = ReturnPageAlignedAddress(si->si_addr);
119 unsigned int backingpage = mprot_snap->lastBackingPage++; //Could run out of pages...
120 if (backingpage == mprot_snap->maxBackingPages) {
121 model_print("Out of backing pages at %p\n", si->si_addr);
126 memcpy(&(mprot_snap->backingStore[backingpage]), addr, sizeof(snapshot_page_t));
127 //remember where to copy page back to
128 mprot_snap->backingRecords[backingpage].basePtrOfPage = addr;
129 //set protection to read/write
130 if (mprotect(addr, sizeof(snapshot_page_t), PROT_READ | PROT_WRITE)) {
132 // Handle error by quitting?
136 static void mprot_snapshot_init(unsigned int numbackingpages,
137 unsigned int numsnapshots, unsigned int nummemoryregions,
138 unsigned int numheappages, VoidFuncPtr entryPoint)
140 /* Setup a stack for our signal handler.... */
142 ss.ss_sp = PageAlignAddressUpward(model_malloc(SIGSTACKSIZE + PAGESIZE - 1));
143 ss.ss_size = SIGSTACKSIZE;
145 sigaltstack(&ss, NULL);
148 sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
149 sigemptyset(&sa.sa_mask);
150 sa.sa_sigaction = mprot_handle_pf;
152 if (sigaction(SIGBUS, &sa, NULL) == -1) {
153 model_print("SIGACTION CANNOT BE INSTALLED\n");
157 if (sigaction(SIGSEGV, &sa, NULL) == -1) {
158 model_print("SIGACTION CANNOT BE INSTALLED\n");
162 mprot_snap = new mprot_snapshotter(numbackingpages, numsnapshots, nummemoryregions);
164 // EVIL HACK: We need to make sure that calls into the mprot_handle_pf method don't cause dynamic links
165 // The problem is that we end up protecting state in the dynamic linker...
166 // Solution is to call our signal handler before we start protecting stuff...
169 memset(&si, 0, sizeof(si));
170 si.si_addr = ss.ss_sp;
171 mprot_handle_pf(SIGSEGV, &si, NULL);
172 mprot_snap->lastBackingPage--; //remove the fake page we copied
174 void *basemySpace = model_malloc((numheappages + 1) * PAGESIZE);
175 void *pagealignedbase = PageAlignAddressUpward(basemySpace);
176 user_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
177 snapshot_add_memory_region(pagealignedbase, numheappages);
179 void *base_model_snapshot_space = model_malloc((numheappages + 1) * PAGESIZE);
180 pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space);
181 model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
182 snapshot_add_memory_region(pagealignedbase, numheappages);
187 static void mprot_add_to_snapshot(void *addr, unsigned int numPages)
189 unsigned int memoryregion = mprot_snap->lastRegion++;
190 if (memoryregion == mprot_snap->maxRegions) {
191 model_print("Exceeded supported number of memory regions!\n");
195 mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr;
196 mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages;
199 static snapshot_id mprot_take_snapshot()
201 for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) {
202 if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ) == -1) {
204 model_print("Failed to mprotect inside of takeSnapShot\n");
208 unsigned int snapshot = mprot_snap->lastSnapShot++;
209 if (snapshot == mprot_snap->maxSnapShots) {
210 model_print("Out of snapshots\n");
213 mprot_snap->snapShots[snapshot].firstBackingPage = mprot_snap->lastBackingPage;
218 static void mprot_roll_back(snapshot_id theID)
220 #if USE_MPROTECT_SNAPSHOT == 2
221 if (mprot_snap->lastSnapShot == (theID + 1)) {
222 for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) {
223 memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
229 HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap;
230 for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) {
231 if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ | PROT_WRITE) == -1) {
233 model_print("Failed to mprotect inside of takeSnapShot\n");
237 for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) {
238 if (!duplicateMap.contains(mprot_snap->backingRecords[page].basePtrOfPage)) {
239 duplicateMap.put(mprot_snap->backingRecords[page].basePtrOfPage, true);
240 memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
243 mprot_snap->lastSnapShot = theID;
244 mprot_snap->lastBackingPage = mprot_snap->snapShots[theID].firstBackingPage;
245 mprot_take_snapshot(); //Make sure current snapshot is still good...All later ones are cleared
248 #else /* !USE_MPROTECT_SNAPSHOT */
250 #include <ucontext.h>
252 #define SHARED_MEMORY_DEFAULT (100 * ((size_t)1 << 20)) // 100mb for the shared memory
253 #define STACK_SIZE_DEFAULT (((size_t)1 << 20) * 20) // 20 mb out of the above 100 mb for my stack
255 struct fork_snapshotter {
256 void *mSharedMemoryBase;
259 volatile snapshot_id mIDToRollback;
260 ucontext_t mContextToRollback;
261 snapshot_id currSnapShotID;
264 static struct fork_snapshotter *fork_snap = NULL;
267 * These variables are necessary because the stack is shared region and
268 * there exists a race between all processes executing the same function.
269 * To avoid the problem above, we require variables allocated in 'safe' regions.
270 * The bug was actually observed with the forkID, these variables below are
271 * used to indicate the various contexts to which to switch to.
273 * @savedSnapshotContext: contains the point to which takesnapshot() call should switch to.
274 * @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to
275 * @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record
277 static ucontext_t savedSnapshotContext;
278 static ucontext_t savedUserSnapshotContext;
279 static snapshot_id snapshotid = 0;
281 static void createSharedMemory()
283 //step 1. create shared memory.
284 void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
285 if (MAP_FAILED == memMapBase)
288 //Setup snapshot record at top of free region
289 fork_snap = (struct fork_snapshotter *)memMapBase;
290 fork_snap->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct fork_snapshotter));
291 fork_snap->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT);
292 fork_snap->mStackSize = STACK_SIZE_DEFAULT;
293 fork_snap->mIDToRollback = -1;
294 fork_snap->currSnapShotID = 0;
298 * Create a new mspace pointer for the non-snapshotting (i.e., inter-process
299 * shared) memory region. Only for fork-based snapshotting.
301 * @return The shared memory mspace
303 mspace create_shared_mspace()
306 createSharedMemory();
307 return create_mspace_with_base((void *)(fork_snap->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(struct fork_snapshotter), 1);
310 static void fork_snapshot_init(unsigned int numbackingpages,
311 unsigned int numsnapshots, unsigned int nummemoryregions,
312 unsigned int numheappages, VoidFuncPtr entryPoint)
315 createSharedMemory();
317 void *base_model_snapshot_space = malloc((numheappages + 1) * PAGESIZE);
318 void *pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space);
319 model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
321 //step 2 setup the stack context.
322 ucontext_t newContext;
323 getcontext(&newContext);
324 newContext.uc_stack.ss_sp = fork_snap->mStackBase;
325 newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
326 makecontext(&newContext, entryPoint, 0);
327 /* switch to a new entryPoint context, on a new stack */
328 swapcontext(&savedSnapshotContext, &newContext);
330 /* switch back here when takesnapshot is called */
332 snapshotid = fork_snap->currSnapShotID;
333 /* This bool indicates that the current process's snapshotid is same
334 as the id to which the rollback needs to occur */
336 bool rollback = false;
338 fork_snap->currSnapShotID = snapshotid + 1;
342 /* If the rollback bool is set, switch to the context we need to
343 return to during a rollback. */
345 setcontext(&(fork_snap->mContextToRollback));
347 /*Child process which is forked as a result of takesnapshot
348 call should switch back to the takesnapshot context*/
349 setcontext(&savedUserSnapshotContext);
355 DEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d\n",
356 forkedID, getpid(), snapshotid);
359 retVal = waitpid(forkedID, &status, 0);
360 } while (-1 == retVal && errno == EINTR);
362 if (fork_snap->mIDToRollback != snapshotid) {
370 static snapshot_id fork_take_snapshot()
372 swapcontext(&savedUserSnapshotContext, &savedSnapshotContext);
373 DEBUG("TAKESNAPSHOT RETURN\n");
377 static void fork_roll_back(snapshot_id theID)
379 fork_snap->mIDToRollback = theID;
380 volatile int sTemp = 0;
381 getcontext(&fork_snap->mContextToRollback);
383 * This is used to quit the process on rollback, so that the process
384 * which needs to rollback can quit allowing the process whose
385 * snapshotid matches the rollbackid to switch to this context and
390 DEBUG("Invoked rollback\n");
394 * This fix obviates the need for a finalize call. hence less dependences for model-checker....
396 fork_snap->mIDToRollback = -1;
399 #endif /* !USE_MPROTECT_SNAPSHOT */
402 * @brief Initializes the snapshot system
403 * @param entryPoint the function that should run the program.
405 void snapshot_system_init(unsigned int numbackingpages,
406 unsigned int numsnapshots, unsigned int nummemoryregions,
407 unsigned int numheappages, VoidFuncPtr entryPoint)
409 #if USE_MPROTECT_SNAPSHOT
410 mprot_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint);
412 fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint);
416 /** Assumes that addr is page aligned. */
417 void snapshot_add_memory_region(void *addr, unsigned int numPages)
419 #if USE_MPROTECT_SNAPSHOT
420 mprot_add_to_snapshot(addr, numPages);
422 /* not needed for fork-based snapshotting */
426 /** Takes a snapshot of memory.
427 * @return The snapshot identifier.
429 snapshot_id take_snapshot()
431 #if USE_MPROTECT_SNAPSHOT
432 return mprot_take_snapshot();
434 return fork_take_snapshot();
438 /** Rolls the memory state back to the given snapshot identifier.
439 * @param theID is the snapshot identifier to rollback to.
441 void snapshot_roll_back(snapshot_id theID)
443 #if USE_MPROTECT_SNAPSHOT
444 mprot_roll_back(theID);
446 fork_roll_back(theID);