Dear Raj > My question is regarding this particular scenario. Consider that a > process A has mmap'ed the text region of a library libfoo.so. The > text region will have corresponding VMA in the process which with > read and execute permissions. Now if another process B does a mmap of > the same library file it will have its own VMA for the text region. IMHO that is correct. Different process owns different VMA, but it points to the same pages which map to the same shared lib... > Now how does the process B gets the same pages mapped by process A. > Is it through the address_space structure that the same pages are > shared ? IIRC, page with the help of address_space object is hashed (or inserted into a tree?), so at the first time, the kernel finds if the an inode which relates to certain file (in this case a shared lib) is already mmap-ep or not. In the case of shared lib, Paul Brook from Qemu community privately gave me short explanation (via IRC) that it is also the work of ld.so which load and link the shared libs with any executable which need some functionalities on the shared libs. He said that ld.so maintains a lookup table (?) named GOT/LOT (I don't know what it stands for) that helps ld.so to determine which shared lib held a need function and load it as neccessary > Also which function checks whether is already an existing > address_space structure for a file ? I don't know about it, sorry... I am still a beginner on VFS and Linux MM. Perhaps Mr Al Viro can provide better enlightenment.... regards Mulyadi -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
