From: Arnd Bergmann arnd@arndb.de
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@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 Signed-off-by: Miles Chen miles.chen@mediatek.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- include/linux/poll.h | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/include/linux/poll.h b/include/linux/poll.h index 7e0fdcf..1cdc32b 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 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