Re: [PATCH net-next v4 3/3] eventpoll: Add epoll ioctl for epoll_params

From: Jiri Slaby
Date: Wed Jan 31 2024 - 01:04:17 EST


On 31. 01. 24, 3:27, Joe Damato wrote:
On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote:
On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote:
+struct epoll_params {
+ __aligned_u64 busy_poll_usecs;
+ __u16 busy_poll_budget;
+
+ /* pad the struct to a multiple of 64bits for alignment on all arches */
+ __u8 __pad[6];

You HAVE to check this padding to be sure it is all 0, otherwise it can
never be used in the future for anything.

Is there some preferred mechanism for this in the kernel that I should be
using or is this as simple as adding a for loop to check each u8 == 0 ?

You are likely looking for memchr_inv().

--
js
suse labs