fs/select: avoid clang stack usage warning
authorArnd Bergmann <arnd@arndb.de>
Tue, 14 May 2019 22:41:42 +0000 (15:41 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 15 May 2019 02:52:48 +0000 (19:52 -0700)
commitad312f95d41c9de19313c51e388c4984451c010f
tree970e3683c194486c4497dbe3ae1118b16aac53d8
parent134fca9063ad4851de767d1768180e5dede9a881
fs/select: avoid clang stack usage warning

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@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/poll.h