From: Ian Rogers <irogers@google.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Yuze Chi <chiyuze@google.com>, Ian Rogers <irogers@google.com>
Subject: [PATCH] libbpf: Fix is_pow_of_2
Date: Thu, 2 Jun 2022 21:17:01 -0700 [thread overview]
Message-ID: <20220603041701.2799595-1-irogers@google.com> (raw)
From: Yuze Chi <chiyuze@google.com>
There is a missing not. Consider a power of 2 number like 4096:
x && (x & (x - 1))
4096 && (4096 & (4096 - 1))
4096 && (4096 & 4095)
4096 && 0
0
with the not this is:
x && !(x & (x - 1))
4096 && !(4096 & (4096 - 1))
4096 && !(4096 & 4095)
4096 && !0
4096 && 1
1
Reported-by: Yuze Chi <chiyuze@google.com>
Signed-off-by: Yuze Chi <chiyuze@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/lib/bpf/libbpf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3f4f18684bd3..fd0414ea00df 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4956,7 +4956,7 @@ static void bpf_map__destroy(struct bpf_map *map);
static bool is_pow_of_2(size_t x)
{
- return x && (x & (x - 1));
+ return x && !(x & (x - 1));
}
static size_t adjust_ringbuf_sz(size_t sz)
--
2.36.1.255.ge46751e96f-goog
next reply other threads:[~2022-06-03 4:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-03 4:17 Ian Rogers [this message]
2022-06-03 4:31 ` [PATCH] libbpf: Fix is_pow_of_2 Zvi Effron
2022-06-03 5:33 ` Andrii Nakryiko
2022-06-03 5:35 ` Andrii Nakryiko
2022-06-19 17:12 ` Pavel Machek
2022-06-21 23:03 ` Zvi Effron
2022-06-22 0:20 ` Tiezhu Yang
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