[PATCH v3] arm: OABI compat: fix build when EPOLL is not enabled

[Nicolas Pitre]

On Sat, 20 Feb 2021, Randy Dunlap wrote:

> When CONFIG_EPOLL is not set/enabled, sys_oabi-compat.c has build
> errors. Fix these by surrounding them with ifdef CONFIG_EPOLL/endif
> and providing stubs for the "EPOLL is not set" case.
> 
> ../arch/arm/kernel/sys_oabi-compat.c: In function 'sys_oabi_epoll_ctl':
> ../arch/arm/kernel/sys_oabi-compat.c:257:6: error: implicit declaration of function 'ep_op_has_event' [-Werror=implicit-function-declaration]
>   257 |  if (ep_op_has_event(op) &&
>       |      ^~~~~~~~~~~~~~~
> ../arch/arm/kernel/sys_oabi-compat.c:264:9: error: implicit declaration of function 'do_epoll_ctl'; did you mean 'sys_epoll_ctl'? [-Werror=implicit-function-declaration]
>   264 |  return do_epoll_ctl(epfd, op, fd, &kernel, false);
>       |         ^~~~~~~~~~~~
> 
> Fixes: c281634c8652 ("ARM: compat: remove KERNEL_DS usage in sys_oabi_epoll_ctl()")
> Signed-off-by: Randy Dunlap <rdunlap at infradead.org>
> Reported-by: kernel test robot <lkp at intel.com> # from an lkp .config file
> Cc: Russell King <linux at armlinux.org.uk>
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: Nicolas Pitre <nico at fluxnic.net>
> Cc: Alexander Viro <viro at zeniv.linux.org.uk>
> Cc: patches at armlinux.org.uk

Acked-by: Nicolas Pitre <nico at fluxnic.net>

> ---
> v2: use correct Fixes: tag (thanks, rmk)
> v3: add patches@ to Cc: list
> 
>  arch/arm/kernel/sys_oabi-compat.c |   15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> --- linux-next-20201214.orig/arch/arm/kernel/sys_oabi-compat.c
> +++ linux-next-20201214/arch/arm/kernel/sys_oabi-compat.c
> @@ -248,6 +248,7 @@ struct oabi_epoll_event {
>  	__u64 data;
>  } __attribute__ ((packed,aligned(4)));
>  
> +#ifdef CONFIG_EPOLL
>  asmlinkage long sys_oabi_epoll_ctl(int epfd, int op, int fd,
>  				   struct oabi_epoll_event __user *event)
>  {
> @@ -298,6 +299,20 @@ asmlinkage long sys_oabi_epoll_wait(int
>  	kfree(kbuf);
>  	return err ? -EFAULT : ret;
>  }
> +#else
> +asmlinkage long sys_oabi_epoll_ctl(int epfd, int op, int fd,
> +				   struct oabi_epoll_event __user *event)
> +{
> +	return -EINVAL;
> +}
> +
> +asmlinkage long sys_oabi_epoll_wait(int epfd,
> +				    struct oabi_epoll_event __user *events,
> +				    int maxevents, int timeout)
> +{
> +	return -EINVAL;
> +}
> +#endif
>  
>  struct oabi_sembuf {
>  	unsigned short	sem_num;
>