From: Arnd Bergmann <arnd@xxxxxxxx> commit ad312f95d41c9de19313c51e388c4984451c010f upstream. 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. Link: http://lkml.kernel.org/r/20190307090146.1874906-1-arnd@xxxxxxxx Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Eric Dumazet <edumazet@xxxxxxxxxx> Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/poll.h | 4 ++++ 1 file changed, 4 insertions(+) --- 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 768 +#else #define MAX_STACK_ALLOC 832 +#endif #define FRONTEND_STACK_ALLOC 256 #define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC #define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
