Search results
Results from the WOW.Com Content Network
The Global Offset Table, or GOT, is a section of a computer program's (executables and shared libraries) memory used to enable computer program code compiled as an ELF file to run correctly, independent of the memory address where the program's code or data is loaded at runtime. [1]
A memory-mapped file is a segment of virtual memory [1] that has been assigned a direct byte-for-byte correlation with some portion of a file or file-like resource. This resource is typically a file that is physically present on disk, but can also be a device, shared memory object, or other resource that an operating system can reference through a file descriptor.
A shared library or shared object is a computer file that contains executable code designed to be used by multiple computer programs or other libraries at runtime.. When running a program that is configured to use a shared library, the operating system loads the shared library from a file (other than the program's executable file) into memory at load time or runtime.
When a linker links modules to create a shared library, it merges the GOTs and sets the final offsets in code. It is not necessary to adjust the offsets when loading the shared library later. [7] Position-independent functions accessing global data start by determining the absolute address of the GOT given their own current program counter value.
Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
To save space, only one copy of the shared library is loaded into physical memory. Programs which use the same library have virtual addresses that map to the same pages (which contain the library's code and data). When programs want to modify the library's code, they use copy-on-write, so memory is only allocated when needed. Shared memory is ...
An ELF file has two views: the program header shows the segments used at run time, whereas the section header lists the set of sections.. In computing, the Executable and Linkable Format [2] (ELF, formerly named Extensible Linking Format) is a common standard file format for executable files, object code, shared libraries, and core dumps.
In the case of operating systems that support virtual memory, the loader may not actually copy the contents of executable files into memory, but rather may simply declare to the virtual memory subsystem that there is a mapping between a region of memory allocated to contain the running program's code and the contents of the associated ...