On Wed, 14 Jul 2004, Cristina Rivera wrote: > I'm coding a syscall that requests pages to the operating system, and, > searching for macros to use I've found these two that are very similar. I've > read what is doing each one of the two but I really don't find them very > different. pmd_offset() searches for offset in 2nd level pagetable (and is called by pmd_alloc()), on the other hand pmd_alloc() first allocates space for middle directory and then returns, using pmd_offset(), the offset in the pagetable directory, for the particular address. > Another doubt, I need to find at what vma belongs a given address, having > known the address and the mm descriptor with (current->mm). I've read about > find_vma( ) and that there's a possibility of obtaining a vma that doesn't > include address because this function searches the first vma that has vm_end > field greater than address. How can I be sure that the vma that I'm getting > is really the vma that I'm searching for? You can look at fields vm_start and vm_end of acutal vm_area_struct. However, I can see only two possibilities when you, using find_vma(), find vma which doesn't contain the specified address - the address is not present in any vma (which really is worth checking) - you have overlapping vmas, which is bug -- JiKos. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
