Hi I have a question I could not find the answer (a clear answer, atleast) to online or in books. Before the questions, here is my understanding of process/thread address spaces and the stack pointers, please tell me if I am wrong somewhere. 1) A process has it's own address space and a fork() provides a new address space to the child (maybe COW). Since a process binary has a text, data, bss and stack space, the child get's a copy of only the text portion of the parent. Am I right in assuming this? 2) A thread (inside a process) has it's own stack but it shares the rest of the segments (text, bss and data) with the parent, is this right? 3) A thread stack is created INSIDE the address space of the parents stack. For example, if a parent's break_value is at 0x60000000 and it's stack pointer is at 0x80000000, then if we create another thread, it's stack will be somewhere between the break_value and stack pointer (i.e., end of parent's stack space) of the parent? 4) During a context/process switch, the stack pointer is popped from the registers. Where does it go (stored on the hard disk?), and which registers are popped from the stack? What about all the OTHER values in the address space? For example, I am executing process-A and it has a timeslice on the CPU. After it's expired, process-B takes over. Process A must be having a lot of variables the values of which must be stored in the address space of process-A. Now, if we store only the stack pointers and a few other register values, where do we get the whole lot of variable values from when we reinstate process-A into the CPU? For example, how does the CPU know about the "text" segment or let's say the data segment? If the text and data segments are also stored as a "snapshot" into some place, how does the CPU know which process's snapshot is stored where? 5) In linux VM, all processes think they have the whole range of physical memory at their disposal. Can two processes (A and B) have a mapping to the "same" physical address? They are not sharing memory, btw. Or is it that if a process is not sharing memory, every one of it's pages will have to have a different address in the physical space (different from all the page frames of ALL other processes).? Thank you for your time, -- - TD -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
