Messages in this thread Patch in this message | | | Date | Thu, 14 Apr 2022 22:46:39 +0000 | From | Alexander Lobakin <> | Subject | [PATCH bpf-next 08/11] samples: bpf: fix shifting unsigned long by 32 positions |
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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; ^ ~~
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@pm.me> --- 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(-)
diff --git a/samples/bpf/lathist_kern.c b/samples/bpf/lathist_kern.c index 4adfcbbe6ef4..9744ed547abe 100644 --- a/samples/bpf/lathist_kern.c +++ b/samples/bpf/lathist_kern.c @@ -53,7 +53,7 @@ static unsigned int log2(unsigned int v)
static unsigned int log2l(unsigned long v) { - unsigned int hi = v >> 32; + unsigned int hi = (v >> 16) >> 16;
if (hi) return log2(hi) + 32; diff --git a/samples/bpf/lwt_len_hist_kern.c b/samples/bpf/lwt_len_hist_kern.c index 1fa14c54963a..bf32fa04c91f 100644 --- a/samples/bpf/lwt_len_hist_kern.c +++ b/samples/bpf/lwt_len_hist_kern.c @@ -49,7 +49,7 @@ static unsigned int log2(unsigned int v)
static unsigned int log2l(unsigned long v) { - unsigned int hi = v >> 32; + unsigned int hi = (v >> 16) >> 16; if (hi) return log2(hi) + 32; else diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c index 5bc696bac27d..6bf22056ff95 100644 --- a/samples/bpf/tracex2_kern.c +++ b/samples/bpf/tracex2_kern.c @@ -57,7 +57,7 @@ static unsigned int log2(unsigned int v)
static unsigned int log2l(unsigned long v) { - unsigned int hi = v >> 32; + unsigned int hi = (v >> 16) >> 16; if (hi) return log2(hi) + 32; else -- 2.35.2
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