[PATCH] fix libbpf hashmap with size_t shorter than long long

[Jakub Bogusz <qboosh@pld-linux.org>]

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Hello,

I noticed that _bpftool crashes when building kernel tools (5.7.x) for
32-bit targets because in libbpf hashmap implementation hash_bits()
function returning numbers exceeding hashmap buckets capacity.

Attached patch fixes this problem.


Regards,

-- 
Jakub Bogusz    http://qboosh.pl/

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Ensure that hash_bits returns value fits in given bits (for bits > 0):
multiplier is long long (which is the same or wider than size_t), so shift bits
must be based on long long size, not __WORDSIZE.

Signed-off-by: Jakub Bogusz <qboosh@pld-linux.org>

--- linux-5.7/tools/lib/bpf/hashmap.h.orig	2020-06-01 01:49:15.000000000 +0200
+++ linux-5.7/tools/lib/bpf/hashmap.h	2020-06-21 15:22:07.298466419 +0200
@@ -10,17 +10,12 @@
 
 #include <stdbool.h>
 #include <stddef.h>
-#ifdef __GLIBC__
-#include <bits/wordsize.h>
-#else
-#include <bits/reg.h>
-#endif
 #include "libbpf_internal.h"
 
 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);
+	return (h * 11400714819323198485llu) >> (__SIZEOF_LONG_LONG__ * 8 - bits);
 }
 
 typedef size_t (*hashmap_hash_fn)(const void *key, void *ctx);