linux-kernel - RE: [PATCH v2 bpf 07/11] samples/bpf: fix uin64

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Date:   Thu, 21 Apr 2022 07:46:05 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Alexander Lobakin' <alobakin@...me>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
CC:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Song Liu <songliubraving@...com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 bpf 07/11] samples/bpf: fix uin64_t format literals

From: Alexander Lobakin
> Sent: 21 April 2022 01:40
> 
> There's a couple places where uin64_t is being passed as an %lu
> format argument. That type is defined as unsigned long on 64-bit
> systems and as unsigned long long on 32-bit, so neither %lu nor
> %llu are not universal.
> One of the options is %PRIu64, but since it's always 8-byte long,
> just cast it to the _proper_ __u64 and print as %llu.

Is __u64 guaranteed to be 'unsigned long long' ? No reason why it should be.
I think you need to cast to (unsigned long long).

	David

> Fixes: 51570a5ab2b7 ("A Sample of using socket cookie and uid for traffic monitoring")
> Fixes: 00f660eaf378 ("Sample program using SO_COOKIE")
> Signed-off-by: Alexander Lobakin <alobakin@...me>
> ---
>  samples/bpf/cookie_uid_helper_example.c | 12 ++++++------
>  samples/bpf/lwt_len_hist_user.c         |  7 ++++---
>  2 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/samples/bpf/cookie_uid_helper_example.c b/samples/bpf/cookie_uid_helper_example.c
> index f0df3dda4b1f..269fac58fd5c 100644
> --- a/samples/bpf/cookie_uid_helper_example.c
> +++ b/samples/bpf/cookie_uid_helper_example.c
> @@ -207,9 +207,9 @@ static void print_table(void)
>  			error(1, errno, "fail to get entry value of Key: %u\n",
>  				curN);
>  		} else {
> -			printf("cookie: %u, uid: 0x%x, Packet Count: %lu,"
> -				" Bytes Count: %lu\n", curN, curEntry.uid,
> -				curEntry.packets, curEntry.bytes);
> +			printf("cookie: %u, uid: 0x%x, Packet Count: %llu, Bytes Count: %llu\n",
> +			       curN, curEntry.uid, (__u64)curEntry.packets,
> +			       (__u64)curEntry.bytes);
>  		}
>  	}
>  }
> @@ -265,9 +265,9 @@ static void udp_client(void)
>  		if (res < 0)
>  			error(1, errno, "lookup sk stat failed, cookie: %lu\n",
>  			      cookie);
> -		printf("cookie: %lu, uid: 0x%x, Packet Count: %lu,"
> -			" Bytes Count: %lu\n\n", cookie, dataEntry.uid,
> -			dataEntry.packets, dataEntry.bytes);
> +		printf("cookie: %llu, uid: 0x%x, Packet Count: %llu, Bytes Count: %llu\n\n",
> +		       (__u64)cookie, dataEntry.uid, (__u64)dataEntry.packets,
> +		       (__u64)dataEntry.bytes);
>  	}
>  	close(s_send);
>  	close(s_rcv);
> diff --git a/samples/bpf/lwt_len_hist_user.c b/samples/bpf/lwt_len_hist_user.c
> index 430a4b7e353e..c682faa75a2b 100644
> --- a/samples/bpf/lwt_len_hist_user.c
> +++ b/samples/bpf/lwt_len_hist_user.c
> @@ -44,7 +44,8 @@ int main(int argc, char **argv)
> 
>  	while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0) {
>  		if (next_key >= MAX_INDEX) {
> -			fprintf(stderr, "Key %lu out of bounds\n", next_key);
> +			fprintf(stderr, "Key %llu out of bounds\n",
> +				(__u64)next_key);
>  			continue;
>  		}
> 
> @@ -66,8 +67,8 @@ int main(int argc, char **argv)
> 
>  	for (i = 1; i <= max_key + 1; i++) {
>  		stars(starstr, data[i - 1], max_value, MAX_STARS);
> -		printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
> -		       (1l << i) >> 1, (1l << i) - 1, data[i - 1],
> +		printf("%8ld -> %-8ld : %-8lld |%-*s|\n",
> +		       (1l << i) >> 1, (1l << i) - 1, (__u64)data[i - 1],
>  		       MAX_STARS, starstr);
>  	}
> 
> --
> 2.36.0
> 

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