From: bdemsky <bdemsky@uci.edu>
Date: Fri, 6 Dec 2019 00:09:43 +0000 (-0800)
Subject: Remove mprotect snapshots
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;ds=sidebyside;h=654801e1e81273424eaafce605bdeb882f3933d9;p=c11tester.git

Remove mprotect snapshots
---

diff --git a/config.h b/config.h
index c276bd03..7ed00f09 100644
--- a/config.h
+++ b/config.h
@@ -31,12 +31,6 @@
 
 /** Snapshotting configurables */
 
-/**
- * If USE_MPROTECT_SNAPSHOT=2, then snapshot by tuned mmap() algorithm
- * If USE_MPROTECT_SNAPSHOT=1, then snapshot by using mmap() and mprotect()
- * If USE_MPROTECT_SNAPSHOT=0, then snapshot by using fork() */
-#define USE_MPROTECT_SNAPSHOT 0
-
 /** Size of signal stack */
 #define SIGSTACKSIZE 65536
 
diff --git a/mymemory.cc b/mymemory.cc
index f78e82d5..efc36e98 100644
--- a/mymemory.cc
+++ b/mymemory.cc
@@ -18,83 +18,30 @@
 size_t allocatedReqs[REQUESTS_BEFORE_ALLOC] = { 0 };
 int nextRequest = 0;
 int howManyFreed = 0;
-#if !USE_MPROTECT_SNAPSHOT
 static mspace sStaticSpace = NULL;
-#endif
 
 /** Non-snapshotting calloc for our use. */
 void *model_calloc(size_t count, size_t size)
 {
-#if USE_MPROTECT_SNAPSHOT
-	static void *(*callocp)(size_t count, size_t size) = NULL;
-	char *error;
-	void *ptr;
-
-	/* get address of libc malloc */
-	if (!callocp) {
-		callocp = (void * (*)(size_t, size_t))dlsym(RTLD_NEXT, "calloc");
-		if ((error = dlerror()) != NULL) {
-			fputs(error, stderr);
-			exit(EXIT_FAILURE);
-		}
-	}
-	ptr = callocp(count, size);
-	return ptr;
-#else
 	if (!sStaticSpace)
 		sStaticSpace = create_shared_mspace();
 	return mspace_calloc(sStaticSpace, count, size);
-#endif
 }
 
 /** Non-snapshotting malloc for our use. */
 void *model_malloc(size_t size)
 {
-#if USE_MPROTECT_SNAPSHOT
-	static void *(*mallocp)(size_t size) = NULL;
-	char *error;
-	void *ptr;
-
-	/* get address of libc malloc */
-	if (!mallocp) {
-		mallocp = (void * (*)(size_t))dlsym(RTLD_NEXT, "malloc");
-		if ((error = dlerror()) != NULL) {
-			fputs(error, stderr);
-			exit(EXIT_FAILURE);
-		}
-	}
-	ptr = mallocp(size);
-	return ptr;
-#else
 	if (!sStaticSpace)
 		sStaticSpace = create_shared_mspace();
 	return mspace_malloc(sStaticSpace, size);
-#endif
 }
 
 /** Non-snapshotting malloc for our use. */
 void *model_realloc(void *ptr, size_t size)
 {
-#if USE_MPROTECT_SNAPSHOT
-	static void *(*reallocp)(void *ptr, size_t size) = NULL;
-	char *error;
-	void *newptr;
-
-	/* get address of libc malloc */
-	if (!reallocp) {
-		reallocp = (void * (*)(size_t))dlsym(RTLD_NEXT, "realloc");
-		if ((error = dlerror()) != NULL) {
-			fputs(error, stderr);
-			exit(EXIT_FAILURE);
-		}
-	}
-	newptr = reallocp(ptr, size);
-	return newptr;
-#else
 	if (!sStaticSpace)
 		sStaticSpace = create_shared_mspace();
 	return mspace_realloc(sStaticSpace, ptr, size);
-#endif
 }
 
 /** @brief Snapshotting malloc, for use by model-checker (not user progs) */
@@ -130,22 +77,7 @@ void snapshot_free(void *ptr)
 /** Non-snapshotting free for our use. */
 void model_free(void *ptr)
 {
-#if USE_MPROTECT_SNAPSHOT
-	static void (*freep)(void *);
-	char *error;
-
-	/* get address of libc free */
-	if (!freep) {
-		freep = (void (*)(void *))dlsym(RTLD_NEXT, "free");
-		if ((error = dlerror()) != NULL) {
-			fputs(error, stderr);
-			exit(EXIT_FAILURE);
-		}
-	}
-	freep(ptr);
-#else
 	mspace_free(sStaticSpace, ptr);
-#endif
 }
 
 /** Bootstrap allocation. Problem is that the dynamic linker calls require
@@ -173,120 +105,6 @@ void * HandleEarlyAllocationRequest(size_t sz)
 /** @brief Global mspace reference for the model-checker's snapshotting heap */
 mspace model_snapshot_space = NULL;
 
-#if USE_MPROTECT_SNAPSHOT
-
-/** @brief Global mspace reference for the user's snapshotting heap */
-mspace user_snapshot_space = NULL;
-
-/** Check whether this is bootstrapped memory that we should not free */
-static bool DontFree(void *ptr)
-{
-	return (ptr >= (&bootstrapmemory[0]) && ptr < (&bootstrapmemory[BOOTSTRAPBYTES]));
-}
-
-/**
- * @brief The allocator function for "user" allocation
- *
- * Should only be used for allocations which will not disturb the allocation
- * patterns of a user thread.
- */
-static void * user_malloc(size_t size)
-{
-	void *tmp = mspace_malloc(user_snapshot_space, size);
-	ASSERT(tmp);
-	return tmp;
-}
-
-/**
- * @brief Snapshotting malloc implementation for user programs
- *
- * Do NOT call this function from a model-checker context. Doing so may disrupt
- * the allocation patterns of a user thread.
- */
-void *malloc(size_t size)
-{
-	void *tmp;
-	if (user_snapshot_space) {
-		/* Only perform user allocations from user context */
-		ASSERT(!model || thread_current());
-		tmp = user_malloc(size);
-	} else
-		tmp = HandleEarlyAllocationRequest(size);
-	recordCalloc(tmp, size);
-	return tmp;
-}
-
-/** @brief Snapshotting free implementation for user programs */
-void free(void * ptr)
-{
-	if (!DontFree(ptr)) {
-		mspace_free(user_snapshot_space, ptr);
-	}
-}
-
-/** @brief Snapshotting realloc implementation for user programs */
-void *realloc(void *ptr, size_t size)
-{
-	void *tmp = mspace_realloc(user_snapshot_space, ptr, size);
-	recordCalloc(tmp, size);
-	ASSERT(tmp);
-	return tmp;
-}
-
-/** @brief Snapshotting calloc implementation for user programs */
-void * calloc(size_t num, size_t size)
-{
-	if (user_snapshot_space) {
-		void *tmp = mspace_calloc(user_snapshot_space, num, size);
-		ASSERT(tmp);
-		recordAlloc(tmp, num*size);
-		return tmp;
-	} else {
-		void *tmp = HandleEarlyAllocationRequest(size * num);
-		memset(tmp, 0, size * num);
-		recordAlloc(tmp, num*size);
-		return tmp;
-	}
-}
-
-/** @brief Snapshotting allocation function for use by the Thread class only */
-void * Thread_malloc(size_t size)
-{
-	return user_malloc(size);
-}
-
-/** @brief Snapshotting free function for use by the Thread class only */
-void Thread_free(void *ptr)
-{
-	free(ptr);
-}
-
-/** @brief Snapshotting new operator for user programs */
-void * operator new(size_t size) throw(std::bad_alloc)
-{
-	return malloc(size);
-}
-
-/** @brief Snapshotting delete operator for user programs */
-void operator delete(void *p) throw()
-{
-	free(p);
-}
-
-/** @brief Snapshotting new[] operator for user programs */
-void * operator new[](size_t size) throw(std::bad_alloc)
-{
-	return malloc(size);
-}
-
-/** @brief Snapshotting delete[] operator for user programs */
-void operator delete[](void *p, size_t size)
-{
-	free(p);
-}
-
-#else	/* !USE_MPROTECT_SNAPSHOT */
-
 /** @brief Snapshotting allocation function for use by the Thread class only */
 void * Thread_malloc(size_t size)
 {
@@ -298,5 +116,3 @@ void Thread_free(void *ptr)
 {
 	snapshot_free(ptr);
 }
-
-#endif	/* !USE_MPROTECT_SNAPSHOT */
diff --git a/mymemory.h b/mymemory.h
index 567ff936..bb313928 100644
--- a/mymemory.h
+++ b/mymemory.h
@@ -255,10 +255,6 @@ extern void * mspace_calloc(mspace msp, size_t n_elements, size_t elem_size);
 extern mspace create_mspace_with_base(void* base, size_t capacity, int locked);
 extern mspace create_mspace(size_t capacity, int locked);
 
-#if USE_MPROTECT_SNAPSHOT
-extern mspace user_snapshot_space;
-#endif
-
 extern mspace model_snapshot_space;
 
 #ifdef __cplusplus
diff --git a/snapshot.cc b/snapshot.cc
index 24e8d073..1770fd64 100644
--- a/snapshot.cc
+++ b/snapshot.cc
@@ -15,244 +15,6 @@
 #include "model.h"
 
 
-#if USE_MPROTECT_SNAPSHOT
-
-/** PageAlignedAdressUpdate return a page aligned address for the
- * address being added as a side effect the numBytes are also changed.
- */
-static void * PageAlignAddressUpward(void *addr)
-{
-	return (void *)((((uintptr_t)addr) + PAGESIZE - 1) & ~(PAGESIZE - 1));
-}
-
-/* Each SnapShotRecord lists the firstbackingpage that must be written to
- * revert to that snapshot */
-struct SnapShotRecord {
-	unsigned int firstBackingPage;
-};
-
-/** @brief Backing store page */
-typedef unsigned char snapshot_page_t[PAGESIZE];
-
-/* List the base address of the corresponding page in the backing store so we
- * know where to copy it to */
-struct BackingPageRecord {
-	void *basePtrOfPage;
-};
-
-/* Struct for each memory region */
-struct MemoryRegion {
-	void *basePtr;	// base of memory region
-	int sizeInPages;	// size of memory region in pages
-};
-
-/** ReturnPageAlignedAddress returns a page aligned address for the
- * address being added as a side effect the numBytes are also changed.
- */
-static void * ReturnPageAlignedAddress(void *addr)
-{
-	return (void *)(((uintptr_t)addr) & ~(PAGESIZE - 1));
-}
-
-/* Primary struct for snapshotting system */
-struct mprot_snapshotter {
-	mprot_snapshotter(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions);
-	~mprot_snapshotter();
-
-	struct MemoryRegion *regionsToSnapShot;	//This pointer references an array of memory regions to snapshot
-	snapshot_page_t *backingStore;	//This pointer references an array of snapshotpage's that form the backing store
-	void *backingStoreBasePtr;	//This pointer references an array of snapshotpage's that form the backing store
-	struct BackingPageRecord *backingRecords;	//This pointer references an array of backingpagerecord's (same number of elements as backingstore
-	struct SnapShotRecord *snapShots;	//This pointer references the snapshot array
-
-	unsigned int lastSnapShot;	//Stores the next snapshot record we should use
-	unsigned int lastBackingPage;	//Stores the next backingpage we should use
-	unsigned int lastRegion;	//Stores the next memory region to be used
-
-	unsigned int maxRegions;	//Stores the max number of memory regions we support
-	unsigned int maxBackingPages;	//Stores the total number of backing pages
-	unsigned int maxSnapShots;	//Stores the total number of snapshots we allow
-
-	MEMALLOC
-};
-
-static struct mprot_snapshotter *mprot_snap = NULL;
-
-mprot_snapshotter::mprot_snapshotter(unsigned int backing_pages, unsigned int snapshots, unsigned int regions) :
-	lastSnapShot(0),
-	lastBackingPage(0),
-	lastRegion(0),
-	maxRegions(regions),
-	maxBackingPages(backing_pages),
-	maxSnapShots(snapshots)
-{
-	regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * regions);
-	backingStoreBasePtr = (void *)model_malloc(sizeof(snapshot_page_t) * (backing_pages + 1));
-	//Page align the backingstorepages
-	backingStore = (snapshot_page_t *)PageAlignAddressUpward(backingStoreBasePtr);
-	backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * backing_pages);
-	snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * snapshots);
-}
-
-mprot_snapshotter::~mprot_snapshotter()
-{
-	model_free(regionsToSnapShot);
-	model_free(backingStoreBasePtr);
-	model_free(backingRecords);
-	model_free(snapShots);
-}
-
-/** mprot_handle_pf is the page fault handler for mprotect based snapshotting
- * algorithm.
- */
-static void mprot_handle_pf(int sig, siginfo_t *si, void *unused)
-{
-	if (si->si_code == SEGV_MAPERR) {
-		model_print("Segmentation fault at %p\n", si->si_addr);
-		model_print("For debugging, place breakpoint at: %s:%d\n",
-								__FILE__, __LINE__);
-		// print_trace(); // Trace printing may cause dynamic memory allocation
-		exit(EXIT_FAILURE);
-	}
-	void* addr = ReturnPageAlignedAddress(si->si_addr);
-
-	unsigned int backingpage = mprot_snap->lastBackingPage++;	//Could run out of pages...
-	if (backingpage == mprot_snap->maxBackingPages) {
-		model_print("Out of backing pages at %p\n", si->si_addr);
-		exit(EXIT_FAILURE);
-	}
-
-	//copy page
-	memcpy(&(mprot_snap->backingStore[backingpage]), addr, sizeof(snapshot_page_t));
-	//remember where to copy page back to
-	mprot_snap->backingRecords[backingpage].basePtrOfPage = addr;
-	//set protection to read/write
-	if (mprotect(addr, sizeof(snapshot_page_t), PROT_READ | PROT_WRITE)) {
-		perror("mprotect");
-		// Handle error by quitting?
-	}
-}
-
-static void mprot_snapshot_init(unsigned int numbackingpages,
-																unsigned int numsnapshots, unsigned int nummemoryregions,
-																unsigned int numheappages)
-{
-	/* Setup a stack for our signal handler....  */
-	stack_t ss;
-	ss.ss_sp = PageAlignAddressUpward(model_malloc(SIGSTACKSIZE + PAGESIZE - 1));
-	ss.ss_size = SIGSTACKSIZE;
-	ss.ss_flags = 0;
-	sigaltstack(&ss, NULL);
-
-	struct sigaction sa;
-	sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
-	sigemptyset(&sa.sa_mask);
-	sa.sa_sigaction = mprot_handle_pf;
-#ifdef MAC
-	if (sigaction(SIGBUS, &sa, NULL) == -1) {
-		perror("sigaction(SIGBUS)");
-		exit(EXIT_FAILURE);
-	}
-#endif
-	if (sigaction(SIGSEGV, &sa, NULL) == -1) {
-		perror("sigaction(SIGSEGV)");
-		exit(EXIT_FAILURE);
-	}
-
-	mprot_snap = new mprot_snapshotter(numbackingpages, numsnapshots, nummemoryregions);
-
-	// EVIL HACK: We need to make sure that calls into the mprot_handle_pf method don't cause dynamic links
-	// The problem is that we end up protecting state in the dynamic linker...
-	// Solution is to call our signal handler before we start protecting stuff...
-
-	siginfo_t si;
-	memset(&si, 0, sizeof(si));
-	si.si_addr = ss.ss_sp;
-	mprot_handle_pf(SIGSEGV, &si, NULL);
-	mprot_snap->lastBackingPage--;	//remove the fake page we copied
-
-	void *basemySpace = model_malloc((numheappages + 1) * PAGESIZE);
-	void *pagealignedbase = PageAlignAddressUpward(basemySpace);
-	user_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
-	snapshot_add_memory_region(pagealignedbase, numheappages);
-
-	void *base_model_snapshot_space = model_malloc((numheappages + 1) * PAGESIZE);
-	pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space);
-	model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
-	snapshot_add_memory_region(pagealignedbase, numheappages);
-}
-
-static void mprot_startExecution(ucontext_t * context, VoidFuncPtr entryPoint) {
-	/* setup the shared-stack context */
-	create_context(context, fork_snap->mStackBase, model_calloc(STACK_SIZE_DEFAULT, 1), STACK_SIZE_DEFAULT, entryPoint);
-}
-
-static void mprot_add_to_snapshot(void *addr, unsigned int numPages)
-{
-	unsigned int memoryregion = mprot_snap->lastRegion++;
-	if (memoryregion == mprot_snap->maxRegions) {
-		model_print("Exceeded supported number of memory regions!\n");
-		exit(EXIT_FAILURE);
-	}
-
-	DEBUG("snapshot region %p-%p (%u page%s)\n",
-				addr, (char *)addr + numPages * PAGESIZE, numPages,
-				numPages > 1 ? "s" : "");
-	mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr;
-	mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages;
-}
-
-static snapshot_id mprot_take_snapshot()
-{
-	for (unsigned int region = 0;region < mprot_snap->lastRegion;region++) {
-		if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ) == -1) {
-			perror("mprotect");
-			model_print("Failed to mprotect inside of takeSnapShot\n");
-			exit(EXIT_FAILURE);
-		}
-	}
-	unsigned int snapshot = mprot_snap->lastSnapShot++;
-	if (snapshot == mprot_snap->maxSnapShots) {
-		model_print("Out of snapshots\n");
-		exit(EXIT_FAILURE);
-	}
-	mprot_snap->snapShots[snapshot].firstBackingPage = mprot_snap->lastBackingPage;
-
-	return snapshot;
-}
-
-static void mprot_roll_back(snapshot_id theID)
-{
-#if USE_MPROTECT_SNAPSHOT == 2
-	if (mprot_snap->lastSnapShot == (theID + 1)) {
-		for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage;page < mprot_snap->lastBackingPage;page++) {
-			memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
-		}
-		return;
-	}
-#endif
-
-	HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap;
-	for (unsigned int region = 0;region < mprot_snap->lastRegion;region++) {
-		if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ | PROT_WRITE) == -1) {
-			perror("mprotect");
-			model_print("Failed to mprotect inside of takeSnapShot\n");
-			exit(EXIT_FAILURE);
-		}
-	}
-	for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage;page < mprot_snap->lastBackingPage;page++) {
-		if (!duplicateMap.contains(mprot_snap->backingRecords[page].basePtrOfPage)) {
-			duplicateMap.put(mprot_snap->backingRecords[page].basePtrOfPage, true);
-			memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
-		}
-	}
-	mprot_snap->lastSnapShot = theID;
-	mprot_snap->lastBackingPage = mprot_snap->snapShots[theID].firstBackingPage;
-	mprot_take_snapshot();	//Make sure current snapshot is still good...All later ones are cleared
-}
-
-#else	/* !USE_MPROTECT_SNAPSHOT */
-
 #define SHARED_MEMORY_DEFAULT  (200 * ((size_t)1 << 20))	// 100mb for the shared memory
 #define STACK_SIZE_DEFAULT      (((size_t)1 << 20) * 20)	// 20 mb out of the above 100 mb for my stack
 
@@ -433,8 +195,6 @@ static void fork_roll_back(snapshot_id theID)
 	fork_snap->mIDToRollback = -1;
 }
 
-#endif	/* !USE_MPROTECT_SNAPSHOT */
-
 /**
  * @brief Initializes the snapshot system
  * @param entryPoint the function that should run the program.
@@ -443,30 +203,18 @@ void snapshot_system_init(unsigned int numbackingpages,
 													unsigned int numsnapshots, unsigned int nummemoryregions,
 													unsigned int numheappages)
 {
-#if USE_MPROTECT_SNAPSHOT
-	mprot_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages);
-#else
 	fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages);
-#endif
 }
 
 void startExecution(ucontext_t *context, VoidFuncPtr entryPoint)
 {
-#if USE_MPROTECT_SNAPSHOT
-	mprot_startExecution(context, entryPoint);
-#else
 	fork_startExecution(context, entryPoint);
-#endif
 }
 
 /** Assumes that addr is page aligned. */
 void snapshot_add_memory_region(void *addr, unsigned int numPages)
 {
-#if USE_MPROTECT_SNAPSHOT
-	mprot_add_to_snapshot(addr, numPages);
-#else
 	/* not needed for fork-based snapshotting */
-#endif
 }
 
 /** Takes a snapshot of memory.
@@ -474,11 +222,7 @@ void snapshot_add_memory_region(void *addr, unsigned int numPages)
  */
 snapshot_id take_snapshot()
 {
-#if USE_MPROTECT_SNAPSHOT
-	return mprot_take_snapshot();
-#else
 	return fork_take_snapshot();
-#endif
 }
 
 /** Rolls the memory state back to the given snapshot identifier.
@@ -486,9 +230,5 @@ snapshot_id take_snapshot()
  */
 void snapshot_roll_back(snapshot_id theID)
 {
-#if USE_MPROTECT_SNAPSHOT
-	mprot_roll_back(theID);
-#else
 	fork_roll_back(theID);
-#endif
 }
diff --git a/snapshot.h b/snapshot.h
index d3fc7b80..1aa1435f 100644
--- a/snapshot.h
+++ b/snapshot.h
@@ -12,9 +12,6 @@
 void snapshot_add_memory_region(void *ptr, unsigned int numPages);
 snapshot_id take_snapshot();
 void snapshot_roll_back(snapshot_id theSnapShot);
-
-#if !USE_MPROTECT_SNAPSHOT
 mspace create_shared_mspace();
-#endif
 
 #endif