selftests: vDSO: fix ELF hash table entry size for s390x

The vDSO self tests fail on s390x for a vDSO linked with the GNU linker
ld as follows:

  # ./vdso_test_gettimeofday
  Floating point exception (core dumped)

On s390x the ELF hash table entries are 64 bits instead of 32 bits in
size (see Glibc sysdeps/unix/sysv/linux/s390/bits/elfclass.h).

Fixes: 40723419 ("kselftest: Enable vDSO test on non x86 platforms")
Reported-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

tools/testing/selftests/vDSO/parse_vdso.c

@@ -36,6 +36,12 @@
 #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
 #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
 
+#ifdef __s390x__
+#define ELF_HASH_ENTRY ELF(Xword)
+#else
+#define ELF_HASH_ENTRY ELF(Word)
+#endif
+
 static struct vdso_info
 {
 	bool valid;
@@ -47,8 +53,8 @@ static struct vdso_info
 	/* Symbol table */
 	ELF(Sym) *symtab;
 	const char *symstrings;
-	ELF(Word) *bucket, *chain;
-	ELF(Word) nbucket, nchain;
+	ELF_HASH_ENTRY *bucket, *chain;
+	ELF_HASH_ENTRY nbucket, nchain;
 
 	/* Version table */
 	ELF(Versym) *versym;
@@ -115,7 +121,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
 	/*
 	 * Fish out the useful bits of the dynamic table.
 	 */
-	ELF(Word) *hash = 0;
+	ELF_HASH_ENTRY *hash = 0;
 	vdso_info.symstrings = 0;
 	vdso_info.symtab = 0;
 	vdso_info.versym = 0;
@@ -133,7 +139,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
 				 + vdso_info.load_offset);
 			break;
 		case DT_HASH:
-			hash = (ELF(Word) *)
+			hash = (ELF_HASH_ENTRY *)
 				((uintptr_t)dyn[i].d_un.d_ptr
 				 + vdso_info.load_offset);
 			break;