On 10/6/2022 3:21 PM, Nick Desaulniers wrote:
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. Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> --- include/linux/poll.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/linux/poll.h b/include/linux/poll.h index 7e0fdcf905d2..1cdc32b1f1b0 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -16,7 +16,11 @@ extern struct ctl_table epoll_table[]; /* for sysctl */ /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating additional memory. */ +#ifdef __clang__ +#define MAX_STACK_ALLOC 768Hi Arnd, Upon a toolchain upgrade for Android, our 32b x86 image used for first-party developer VMs started tripping -Wframe-larger-than= again (thanks -Werror) which is blocking our ability to upgrade our toolchain.
I wonder if there is a way to disable the warning or increase the threshold just for this function. I don't think attribute optimize would work, but perhaps some pragma?
-Andi
