linux-kernel - [PATCH] selftests/vDSO: fix GNU hash table entry size for s390x

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Message-Id: <20250213-selftests-vdso-s390-gnu-hash-v1-1-ace3bcc940a3@linutronix.de>
Date: Thu, 13 Feb 2025 10:41:21 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Shuah Khan <shuah@...nel.org>, Fangrui Song <i@...kray.me>, 
 Xi Ruoyao <xry111@...111.site>
Cc: Shuah Khan <skhan@...uxfoundation.org>, 
 Heiko Carstens <hca@...ux.ibm.com>, Jens Remus <jremus@...ux.ibm.com>, 
 "Jason A. Donenfeld" <Jason@...c4.com>, linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH] selftests/vDSO: fix GNU hash table entry size for s390x

Commit 14be4e6f3522 ("selftests: vDSO: fix ELF hash table entry size for s390x")
changed the type of the ELF hash table entries to 64bit on s390x.
However the *GNU* hash tables entries are always 32bit.
The "bucket" pointer is shared between both hash algorithms.
On s390x the GNU algorithm assigns and dereferences this 64bit pointer as a
32bit pointer, leading to compiler warnings and runtime crashes.

Introduce a new dedicated "gnu_bucket" pointer which is used by the GNU hash.

Fixes: e0746bde6f82 ("selftests/vDSO: support DT_GNU_HASH")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 tools/testing/selftests/vDSO/parse_vdso.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
index 2fe5e983cb22f1ed066d0310a54f6aef2ed77ed8..f89d052c730eb43eea28d69ca27b56e897503e16 100644
--- a/tools/testing/selftests/vDSO/parse_vdso.c
+++ b/tools/testing/selftests/vDSO/parse_vdso.c
@@ -53,7 +53,7 @@ static struct vdso_info
 	/* Symbol table */
 	ELF(Sym) *symtab;
 	const char *symstrings;
-	ELF(Word) *gnu_hash;
+	ELF(Word) *gnu_hash, *gnu_bucket;
 	ELF_HASH_ENTRY *bucket, *chain;
 	ELF_HASH_ENTRY nbucket, nchain;

@@ -185,8 +185,8 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
 		/* The bucket array is located after the header (4 uint32) and the bloom
 		 * filter (size_t array of gnu_hash[2] elements).
 		 */
-		vdso_info.bucket = vdso_info.gnu_hash + 4 +
-				   sizeof(size_t) / 4 * vdso_info.gnu_hash[2];
+		vdso_info.gnu_bucket = vdso_info.gnu_hash + 4 +
+				       sizeof(size_t) / 4 * vdso_info.gnu_hash[2];
 	} else {
 		vdso_info.nbucket = hash[0];
 		vdso_info.nchain = hash[1];
@@ -268,11 +268,11 @@ void *vdso_sym(const char *version, const char *name)
 	if (vdso_info.gnu_hash) {
 		uint32_t h1 = gnu_hash(name), h2, *hashval;

-		i = vdso_info.bucket[h1 % vdso_info.nbucket];
+		i = vdso_info.gnu_bucket[h1 % vdso_info.nbucket];
 		if (i == 0)
 			return 0;
 		h1 |= 1;
-		hashval = vdso_info.bucket + vdso_info.nbucket +
+		hashval = vdso_info.gnu_bucket + vdso_info.nbucket +
 			  (i - vdso_info.gnu_hash[1]);
 		for (;; i++) {
 			ELF(Sym) *sym = &vdso_info.symtab[i];

---
base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
change-id: 20250213-selftests-vdso-s390-gnu-hash-7206671abc85

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>