From 118a914b24362a958656f3c23016266b4bf20bf0 Mon Sep 17 00:00:00 2001 From: Brian Norris Date: Wed, 2 Jan 2013 18:14:17 -0800 Subject: [PATCH] snapshot: split up fork-based and mprotect-based snapshotting The code is kind of cluttered with #if's and intermixed implementations. Now, snapshot.cc is split into two halves, where the first half implements mprotect-based snapshotting and the latter half implements fork-based snapshotting. --- snapshot.cc | 288 ++++++++++++++++++++++++++-------------------------- 1 file changed, 143 insertions(+), 145 deletions(-) diff --git a/snapshot.cc b/snapshot.cc index a562b91..ccb9ea6 100644 --- a/snapshot.cc +++ b/snapshot.cc @@ -15,7 +15,16 @@ #define FAILURE(mesg) { model_print("failed in the API: %s with errno relative message: %s\n", mesg, strerror(errno)); exit(EXIT_FAILURE); } +/** 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)); +} + #if USE_MPROTECT_SNAPSHOT + /* Each snapshotrecord lists the firstbackingpage that must be written to * revert to that snapshot */ struct SnapShotRecord { @@ -54,51 +63,8 @@ struct SnapShot { unsigned int maxSnapShots; //Stores the total number of snapshots we allow }; -#else - -#include - -#define SHARED_MEMORY_DEFAULT (100 * ((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 - -struct SnapShot { - void *mSharedMemoryBase; - void *mStackBase; - size_t mStackSize; - volatile snapshot_id mIDToRollback; - ucontext_t mContextToRollback; - snapshot_id currSnapShotID; -}; -#endif - static struct SnapShot *snapshotrecord = NULL; -/** 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)); -} - -#if !USE_MPROTECT_SNAPSHOT -/** @statics -* These variables are necessary because the stack is shared region and -* there exists a race between all processes executing the same function. -* To avoid the problem above, we require variables allocated in 'safe' regions. -* The bug was actually observed with the forkID, these variables below are -* used to indicate the various contexts to which to switch to. -* -* @savedSnapshotContext: contains the point to which takesnapshot() call should switch to. -* @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to -* @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record -*/ -static ucontext_t savedSnapshotContext; -static ucontext_t savedUserSnapshotContext; -static snapshot_id snapshotid = 0; - -#else /* USE_MPROTECT_SNAPSHOT */ - /** ReturnPageAlignedAddress returns a page aligned address for the * address being added as a side effect the numBytes are also changed. */ @@ -157,45 +123,10 @@ static void HandlePF(int sig, siginfo_t *si, void *unused) // Handle error by quitting? } } -#endif /* USE_MPROTECT_SNAPSHOT */ - -#if !USE_MPROTECT_SNAPSHOT -static void createSharedMemory() -{ - //step 1. create shared memory. - void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0); - if (MAP_FAILED == memMapBase) - FAILURE("mmap"); - - //Setup snapshot record at top of free region - snapshotrecord = (struct SnapShot *)memMapBase; - snapshotrecord->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct SnapShot)); - snapshotrecord->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT); - snapshotrecord->mStackSize = STACK_SIZE_DEFAULT; - snapshotrecord->mIDToRollback = -1; - snapshotrecord->currSnapShotID = 0; -} - -/** - * Create a new mspace pointer for the non-snapshotting (i.e., inter-process - * shared) memory region. Only for fork-based snapshotting. - * - * @return The shared memory mspace - */ -mspace create_shared_mspace() -{ - if (!snapshotrecord) - createSharedMemory(); - return create_mspace_with_base((void *)(snapshotrecord->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(struct SnapShot), 1); -} -#endif - /** The initSnapshotLibrary function initializes the snapshot library. * @param entryPoint the function that should run the program. */ -#if USE_MPROTECT_SNAPSHOT - void initSnapshotLibrary(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions, unsigned int numheappages, VoidFuncPtr entryPoint) @@ -246,7 +177,137 @@ void initSnapshotLibrary(unsigned int numbackingpages, entryPoint(); } -#else + +/** The addMemoryRegionToSnapShot function assumes that addr is page aligned. */ +void addMemoryRegionToSnapShot(void *addr, unsigned int numPages) +{ + unsigned int memoryregion = snapshotrecord->lastRegion++; + if (memoryregion == snapshotrecord->maxRegions) { + model_print("Exceeded supported number of memory regions!\n"); + exit(EXIT_FAILURE); + } + + snapshotrecord->regionsToSnapShot[memoryregion].basePtr = addr; + snapshotrecord->regionsToSnapShot[memoryregion].sizeInPages = numPages; +} + +/** The takeSnapshot function takes a snapshot. + * @return The snapshot identifier. + */ +snapshot_id takeSnapshot() +{ + for (unsigned int region = 0; region < snapshotrecord->lastRegion; region++) { + if (mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->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 = snapshotrecord->lastSnapShot++; + if (snapshot == snapshotrecord->maxSnapShots) { + model_print("Out of snapshots\n"); + exit(EXIT_FAILURE); + } + snapshotrecord->snapShots[snapshot].firstBackingPage = snapshotrecord->lastBackingPage; + + return snapshot; +} + +/** The rollBack function rollback to the given snapshot identifier. + * @param theID is the snapshot identifier to rollback to. + */ +void rollBack(snapshot_id theID) +{ +#if USE_MPROTECT_SNAPSHOT == 2 + if (snapshotrecord->lastSnapShot == (theID + 1)) { + for (unsigned int page = snapshotrecord->snapShots[theID].firstBackingPage; page < snapshotrecord->lastBackingPage; page++) { + memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->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 < snapshotrecord->lastRegion; region++) { + if (mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->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 = snapshotrecord->snapShots[theID].firstBackingPage; page < snapshotrecord->lastBackingPage; page++) { + if (!duplicateMap.contains(snapshotrecord->backingRecords[page].basePtrOfPage)) { + duplicateMap.put(snapshotrecord->backingRecords[page].basePtrOfPage, true); + memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(snapshot_page_t)); + } + } + snapshotrecord->lastSnapShot = theID; + snapshotrecord->lastBackingPage = snapshotrecord->snapShots[theID].firstBackingPage; + takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared +} + +#else /* !USE_MPROTECT_SNAPSHOT */ + +#include + +#define SHARED_MEMORY_DEFAULT (100 * ((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 + +struct SnapShot { + void *mSharedMemoryBase; + void *mStackBase; + size_t mStackSize; + volatile snapshot_id mIDToRollback; + ucontext_t mContextToRollback; + snapshot_id currSnapShotID; +}; + +static struct SnapShot *snapshotrecord = NULL; + +/** @statics +* These variables are necessary because the stack is shared region and +* there exists a race between all processes executing the same function. +* To avoid the problem above, we require variables allocated in 'safe' regions. +* The bug was actually observed with the forkID, these variables below are +* used to indicate the various contexts to which to switch to. +* +* @savedSnapshotContext: contains the point to which takesnapshot() call should switch to. +* @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to +* @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record +*/ +static ucontext_t savedSnapshotContext; +static ucontext_t savedUserSnapshotContext; +static snapshot_id snapshotid = 0; + +static void createSharedMemory() +{ + //step 1. create shared memory. + void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0); + if (MAP_FAILED == memMapBase) + FAILURE("mmap"); + + //Setup snapshot record at top of free region + snapshotrecord = (struct SnapShot *)memMapBase; + snapshotrecord->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct SnapShot)); + snapshotrecord->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT); + snapshotrecord->mStackSize = STACK_SIZE_DEFAULT; + snapshotrecord->mIDToRollback = -1; + snapshotrecord->currSnapShotID = 0; +} + +/** + * Create a new mspace pointer for the non-snapshotting (i.e., inter-process + * shared) memory region. Only for fork-based snapshotting. + * + * @return The shared memory mspace + */ +mspace create_shared_mspace() +{ + if (!snapshotrecord) + createSharedMemory(); + return create_mspace_with_base((void *)(snapshotrecord->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(struct SnapShot), 1); +} + void initSnapshotLibrary(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions, unsigned int numheappages, VoidFuncPtr entryPoint) @@ -306,85 +367,21 @@ void initSnapshotLibrary(unsigned int numbackingpages, } } } -#endif -/** The addMemoryRegionToSnapShot function assumes that addr is page aligned. - */ void addMemoryRegionToSnapShot(void *addr, unsigned int numPages) { -#if USE_MPROTECT_SNAPSHOT - unsigned int memoryregion = snapshotrecord->lastRegion++; - if (memoryregion == snapshotrecord->maxRegions) { - model_print("Exceeded supported number of memory regions!\n"); - exit(EXIT_FAILURE); - } - - snapshotrecord->regionsToSnapShot[memoryregion].basePtr = addr; - snapshotrecord->regionsToSnapShot[memoryregion].sizeInPages = numPages; -#endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS. + /* not needed for fork-based snapshotting */ } -/** The takeSnapshot function takes a snapshot. - * @return The snapshot identifier. - */ snapshot_id takeSnapshot() { -#if USE_MPROTECT_SNAPSHOT - for (unsigned int region = 0; region < snapshotrecord->lastRegion; region++) { - if (mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->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 = snapshotrecord->lastSnapShot++; - if (snapshot == snapshotrecord->maxSnapShots) { - model_print("Out of snapshots\n"); - exit(EXIT_FAILURE); - } - snapshotrecord->snapShots[snapshot].firstBackingPage = snapshotrecord->lastBackingPage; - - return snapshot; -#else swapcontext(&savedUserSnapshotContext, &savedSnapshotContext); DEBUG("TAKESNAPSHOT RETURN\n"); return snapshotid; -#endif } -/** The rollBack function rollback to the given snapshot identifier. - * @param theID is the snapshot identifier to rollback to. - */ void rollBack(snapshot_id theID) { -#if USE_MPROTECT_SNAPSHOT == 2 - if (snapshotrecord->lastSnapShot == (theID + 1)) { - for (unsigned int page = snapshotrecord->snapShots[theID].firstBackingPage; page < snapshotrecord->lastBackingPage; page++) { - memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(snapshot_page_t)); - } - return; - } -#endif - -#if USE_MPROTECT_SNAPSHOT - HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap; - for (unsigned int region = 0; region < snapshotrecord->lastRegion; region++) { - if (mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->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 = snapshotrecord->snapShots[theID].firstBackingPage; page < snapshotrecord->lastBackingPage; page++) { - if (!duplicateMap.contains(snapshotrecord->backingRecords[page].basePtrOfPage)) { - duplicateMap.put(snapshotrecord->backingRecords[page].basePtrOfPage, true); - memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(snapshot_page_t)); - } - } - snapshotrecord->lastSnapShot = theID; - snapshotrecord->lastBackingPage = snapshotrecord->snapShots[theID].firstBackingPage; - takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared -#else snapshotrecord->mIDToRollback = theID; volatile int sTemp = 0; getcontext(&snapshotrecord->mContextToRollback); @@ -403,5 +400,6 @@ void rollBack(snapshot_id theID) * This fix obviates the need for a finalize call. hence less dependences for model-checker.... */ snapshotrecord->mIDToRollback = -1; -#endif } + +#endif /* !USE_MPROTECT_SNAPSHOT */ -- 2.34.1