If bits is 0, the case when the map is empty, then the >> is the size of
the register which is undefined behavior - on x86 it is the same as a
shift by 0. Fix by handling the 0 case explicitly.
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
tools/lib/bpf/hashmap.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h
index d5ef212a55ba..781db653d16c 100644
--- a/tools/lib/bpf/hashmap.h
+++ b/tools/lib/bpf/hashmap.h
@@ -19,6 +19,8 @@
static inline size_t hash_bits(size_t h, int bits)
{
/* shuffle bits and return requested number of upper bits */
+ if (bits == 0)
+ return 0;
return (h * 11400714819323198485llu) >> (__WORDSIZE - bits);
}
--
2.26.2.645.ge9eca65c58-goog
