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libbpf: Fix libbpf hashmap on (I)LP32 architectures

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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
This commit is contained in:
Jakub Bogusz 2020-07-09 15:57:23 -07:00 committed by Alexei Starovoitov
parent f43cb0d672
commit b2f9f1535b
1 changed files with 8 additions and 4 deletions
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12
tools/lib/bpf/hashmap.h
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@ -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);