| Message ID | 20220421003152.339542-9-alobakin@pm.me (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: random unpopular userspace fixes (32 bit et al) | expand |
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
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; ^ ~~ sizeof(long) is always 8 for the BPF architecture, so this is not correct, but the BPF samples Makefile still uses the Clang native + LLC combo which enforces that. Until the samples are switched to `-target bpf`, do it the usual way: shift by 16 two times (see upper_32_bits() macro in the kernel). 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") Acked-by: Song Liu <songliubraving@fb.com> 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(-) -- 2.36.0