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From cd016d93f7bf280fe6f2dfc723257786dd3ffd00 Mon Sep 17 00:00:00 2001
From: Jakub Bogusz <qboosh@pld-linux.org>
Date: Thu, 9 Jul 2020 15:57:23 -0700
Subject: [PATCH] libbpf: Fix libbpf hashmap on (I)LP32 architectures
On ILP32, 64-bit result was shifted by value calculated for 32-bit long type
and returned value was much outside hashmap capacity.
As advised by Andrii Nakryiko, this patch uses different hashing variant for
architectures with size_t shorter than long long.
Fixes: e3b924224028 ("libbpf: add resizable non-thread safe internal hashmap")
Signed-off-by: Jakub Bogusz <qboosh@pld-linux.org>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200709225723.1069937-1-andriin@fb.com
---
hashmap.h | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/hashmap.h b/hashmap.h
index df59fd4..e0af36b 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -11,14 +11,18 @@
#include <stdbool.h>
#include <stddef.h>
#include <limits.h>
-#ifndef __WORDSIZE
-#define __WORDSIZE (__SIZEOF_LONG__ * 8)
-#endif
static inline size_t hash_bits(size_t h, int bits)
{
/* shuffle bits and return requested number of upper bits */
- return (h * 11400714819323198485llu) >> (__WORDSIZE - bits);
+#if (__SIZEOF_SIZE_T__ == __SIZEOF_LONG_LONG__)
+ /* LP64 case */
+ return (h * 11400714819323198485llu) >> (__SIZEOF_LONG_LONG__ * 8 - bits);
+#elif (__SIZEOF_SIZE_T__ <= __SIZEOF_LONG__)
+ return (h * 2654435769lu) >> (__SIZEOF_LONG__ * 8 - bits);
+#else
+# error "Unsupported size_t size"
+#endif
}
typedef size_t (*hashmap_hash_fn)(const void *key, void *ctx);
--
2.26.2
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