On Thu, Apr 14, 2022 at 3:46 PM Alexander Lobakin <alobakin@xxxxx> wrote:
>
> On 32 bit systems, shifting an unsigned long by 32 positions
> yields the following warning:
>
> samples/bpf/tracex2_kern.c:60:23: warning: shift count >= width of type [-Wshift-count-overflow]
> unsigned int hi = v >> 32;
> ^ ~~
>
long is always 64-bit in BPF, but I suspect this is due to
samples/bpf/Makefile still using this clang + llc combo, where clang
is called with native target and llc for -target bpf. Not sure if we
are ready to ditch that complicated combination. Yonghong, do we still
need that or can we just use -target bpf in samples/bpf?
> The usual way to avoid this is to shift by 16 two times (see
> upper_32_bits() macro in the kernel). Use it across the BPF sample
> code as well.
>
> Fixes: d822a1926849 ("samples/bpf: Add counting example for kfree_skb() function calls and the write() syscall")
> Fixes: 0fb1170ee68a ("bpf: BPF based latency tracing")
> Fixes: f74599f7c530 ("bpf: Add tests and samples for LWT-BPF")
> Signed-off-by: Alexander Lobakin <alobakin@xxxxx>
> ---
> samples/bpf/lathist_kern.c | 2 +-
> samples/bpf/lwt_len_hist_kern.c | 2 +-
> samples/bpf/tracex2_kern.c | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
>
[...]
