Subject: Re: [PATCH bpf] selftests/bpf: Fix xdp_synproxy compilation failure in 32-bit arch

From: Yonghong Song <[email-masked]>
Date: Tue, 8 Nov 2022 07:59:43 -0800

On 11/8/22 5:12 AM, Yang Jihong wrote:
> xdp_synproxy fails to be compiled in the 32-bit arch, log is as follows:
> 
>    xdp_synproxy.c: In function 'parse_options':
>    xdp_synproxy.c:175:36: error: left shift count >= width of type [-Werror=shift-count-overflow]
>      175 |                 *tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
>          |                                    ^~
>    xdp_synproxy.c: In function 'syncookie_open_bpf_maps':
>    xdp_synproxy.c:289:28: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>      289 |                 .map_ids = (__u64)map_ids,
>          |                            ^
> 
> Fix it.
> 
> Fixes: fb5cd0ce70d4 ("selftests/bpf: Add selftests for raw syncookie helpers")
> Signed-off-by: Yang Jihong <[email-masked]>
> ---
>   tools/testing/selftests/bpf/xdp_synproxy.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/xdp_synproxy.c b/tools/testing/selftests/bpf/xdp_synproxy.c
> index ff35320d2be9..45fef01a87a8 100644
> --- a/tools/testing/selftests/bpf/xdp_synproxy.c
> +++ b/tools/testing/selftests/bpf/xdp_synproxy.c
> @@ -172,7 +172,7 @@ static void parse_options(int argc, char *argv[], unsigned int *ifindex, __u32 *
>   	if (tcpipopts_mask == 0xf) {
>   		if (mss4 == 0 || mss6 == 0 || wscale == 0 || ttl == 0)
>   			usage(argv[0]);
> -		*tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
> +		*tcpipopts = ((unsigned long long)mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;

This looks weird. Maybe we should define mss6 as unsigned long long to 
avoid this casting at all?

>   	} else if (tcpipopts_mask != 0) {
>   		usage(argv[0]);
>   	}
> @@ -286,7 +286,7 @@ static int syncookie_open_bpf_maps(__u32 prog_id, int *values_map_fd, int *ports
>   
>   	prog_info = (struct bpf_prog_info) {
>   		.nr_map_ids = 8,
> -		.map_ids = (__u64)map_ids,
> +		.map_ids = (__u64)(unsigned long)map_ids,
>   	};
>   	info_len = sizeof(prog_info);
>