Diehard allocator - custom allocators, Operating System

Allocators can also be used to avoid problems with unsafe languages. C and C++ are pervasive, with huge amounts of existing code. They are also memory-unsafe languages, in that they allow many errors and security vulnerabilities. Some examples include double free(), invalid free(), uninitialized reads, dangling pointers, and buffer over?ows in both stack and heap buffers.

DieHard is an allocator developed at UMass which provides (or at least improves) soundness for erroneous programs. There are several hardware trends which are occurring: multicore processors are becoming the norm, physical memory is relatively inexpensive, and 64-bit architectures are increasingly common, with huge virtual address spaces. Meanwhile, most programs have trouble making full use of multiple processors. The net result is that there may soon be unused processing power and enormous virtual address spaces.

If you had an in?nite address space, you wouldn't have to worry about freeing objects. That would mostly eliminate the double free(), invalid free(), and dangling pointer bugs. And if your heap objects were in?nitely far apart in memory, you wouldn't need to worry about buffer over?ows in heap objects.

DieHard tries to provide something along these lines, within the constraints of ?nite physical memory. It uses randomized heap allocation, so objects are not necessarily contiguous in virtual memory. Since the address space is actually ?nite, objects won't actually be in?nitely far apart, and buffer overruns might actually cause collisions between heap objects. But this is where the multicore processors come in: With the unused processor cores, run multiple copies of the application, say three copies, each allocating into their own randomized heap. So the heap errors are independent among the three copies of the application. All copies get the same input, and the output is the result of voting among the three copies of the program. If one instance of the application disagrees with the other two, it is killed, since there was likely a collision between heap objects in that one. Similarly, if one instance dies with a segfault or other error, the others remain running.

Surviving copies can be forked to replace copies which were killed off, though this reduces the independence among copies.

Posted Date: 3/13/2013 2:49:51 AM | Location : United States







Related Discussions:- Diehard allocator - custom allocators, Assignment Help, Ask Question on Diehard allocator - custom allocators, Get Answer, Expert's Help, Diehard allocator - custom allocators Discussions

Write discussion on Diehard allocator - custom allocators
Your posts are moderated
Related Questions
Define logical address and physical address. An address formed by the CPU is referred as logical address. An address seen by the memory unit that is the single loaded into the

Concept of Reentrancy   It is a useful, memory-saving method for multiprogrammed timesharing machines. A Reentrant method is one in which multiple clients can share a singl

Define deadlock prevention. Deadlock prevention is a set of process for ensuring that at least one of the four essential conditions like mutual exclusion, hold and wait, no pr

What are the different accessing methods of a file? The different types of accessing a file are: Sequential access: Information in the file is accessed sequentially

what is secondary storage management

Define busy waiting and spinlock. When a process is in its significant section, any other process that tries to enter its critical section must loop continuously in the entry c

Process termination A process terminates when it finishes implementing its final statement and asks the operating system to delete it by using the exit system call. At that tim

As a group, you may need to make some enhancements to your development server (NOT your stable server!)  It needs to be able to run the makepasswd program, which may require instal


Explain system-wide open-file and per-process open-file The system-wide open-file table have a copy of the FCB of each open file, as well as other information. The per-pr