On Thu, Mar 07, 2019 at 10:01:36AM +0100, Arnd Bergmann wrote: > The select() implementation is carefully tuned to put a sensible amount > of data on the stack for holding a copy of the user space fd_set, > but not too large to risk overflowing the kernel stack. > > When building a 32-bit kernel with clang, we need a little more space > than with gcc, which often triggers a warning: > > fs/select.c:619:5: error: stack frame size of 1048 bytes in function 'core_sys_select' [-Werror,-Wframe-larger-than=] > int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, > > I experimentally found that for 32-bit ARM, reducing the maximum > stack usage by 64 bytes keeps us reliably under the warning limit > again. Could just use 768 bytes unconditionally. I doubt a few bytes more or less will make too much difference. Other than that Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> -Andi
