memory-managementlinux-device-driverdma

How to get page size programmatically within Linux kernel module code


I am working on a Linux module for IA64. My current problem is that the driver uses the PAGE_SIZE and PAGE_SHIFT macros for dma page allocation. The problem I am having is that the machine compiling the driver is not the ones that needed to run the driver. So, if the PAGE_SIZE on the compiling machine is 2^14K and the destination machine is 2^16K then the driver fails.

I don't want to turn this question into a 'best practice' issue about compiling modules on machines which are not the ones running the modules. I understand the issues about that. What I found is that people mostly uses getpagesize() or sysconf(_SC_PAGE_SIZE). These two options are out of the ia64 kernel headers so I can't use them. Is there another way that I could get the runtime PAGE_SIZE?

Options I am looking at:

  • Reading some file in /proc?
  • syscall?
  • Other function that let me calculate the PAGE_SIZE by inference (e.g ORDER, getpageshift, etc)?
  • Other?

Solution

  • This is what I finally did:

    • Re-work my current module to take a new module parameter called page_shift and used that to calculate the PAGE_SIZE (PAGE_SIZE = 1 << PAGE_SHIFT)
    • Created a module loader wrapper which gets the current system PAGE_SHIFT using getconf API from libc. This wrapper gets the current system page shift and pass it as a module parameter.

    Right now the module is being loaded on different architectures with different PAGE_SIZE without any problems.