dwarves/libbpf-Fix-libbpf-hashmap-on-I-LP32-architectures.patch

From: Jakub Bogusz <qboosh@pld-linux.org>
Date: Thu, 9 Jul 2020 15:57:23 -0700
Subject: libbpf: Fix libbpf hashmap on (I)LP32 architectures
Git-commit: b2f9f1535bb93ee5fa2ea30ac1c26fa0d676154c
Patch-mainline: 5.8-rc5
References: x86_32 crashes fix

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
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 lib/bpf/src/hashmap.h |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/lib/bpf/src/hashmap.h
+++ b/lib/bpf/src/hashmap.h
@@ -16,11 +16,19 @@
 #include <bits/reg.h>
 #endif
 #include "libbpf_internal.h"
+#include <limits.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);
+#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);