From b15ce5b6ceb0ba0cbb91d460c5a745a14c2050df Mon Sep 17 00:00:00 2001 From: David Gibson Date: Tue, 1 Aug 2023 13:36:47 +1000 Subject: [PATCH] Use static assertion to verify that union epoll_ref is the right size union epoll_ref is used to subdivide the 64-bit data field in struct epoll_event. Thus it *must* fit within that field or we're likely to get very subtle and nasty bugs. C11 introduces the notion of static assertions which we can use to verify this is the case at compile time. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- passt.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/passt.h b/passt.h index 8b7235a..edc4841 100644 --- a/passt.h +++ b/passt.h @@ -32,6 +32,8 @@ struct tap_l4_msg { union epoll_ref; #include +#include +#include #include "packet.h" #include "icmp.h" @@ -64,6 +66,8 @@ union epoll_ref { }; uint64_t u64; }; +static_assert(sizeof(union epoll_ref) <= sizeof(union epoll_data), + "epoll_ref must have same size as epoll_data"); #define TAP_BUF_BYTES \ ROUND_DOWN(((ETH_MAX_MTU + sizeof(uint32_t)) * 128), PAGE_SIZE)