gthosani1

 Profile Answers by gthosani1 

• Dec 18th, 2007

 

The u area.

In addition to the text, data, and stack segment, the OS also maintains for each process a region called the u area (User Area). The u area contains information specific to the process (e.g. open files, current directory, signal action, accounting information) and a system stack segment for process use. If the process makes a system call (e.g., the system call to write in the function in main ), the stack frame information for the system is stored in the system stack segment. Again, this information is kept by the OS in an area that the process doesn't normally have access to. Thus, if this information is needed, the process must use special system call to access it. Like the process itself, the contents of the u area for the process are paged in and out bye the OS.

akki1af1

 Profile Answers by akki1af1 

• May 20th, 2009

 

Every process has a private u area, yet the kernel acesses it as if there were only one u area in the system, that of the running process. The kernel changes its virtual address translation map according to the executing process to access the correct u area. When compiling the operating system, the loader assign the variable u, the name of the u area, a fixed virtual address. The value of the u area virtual address is known to other parts of the kernel, in particular, the module that does the context switch.