Support for multiple versions in versioned_symbol, compat_symbol

This essentially folds compat_symbol_unique functionality into
compat_symbol.

This change eliminates the need for intermediate aliases for defining
multiple symbol versions, for both compat_symbol and versioned_symbol.
Some binutils versions do not suport multiple versions per symbol on
some targets, so aliases are automatically introduced, similar to what
compat_symbol_unique did.  To reduce symbol table sizes, a configure
check is added to avoid these aliases if they are not needed.

The new mechanism works with data symbols as well as function symbols,
due to the way an assembler-level redirect is used.  It is not
compatible with weak symbols for old binutils versions, which is why
the definition of __malloc_initialize_hook had to be changed.  This
is not a loss of functionality because weak symbols do not matter
to dynamic linking.

The placeholder symbol needs repeating in nptl/libpthread-compat.c
now that compat_symbol is used, but that seems more obvious than
introducing yet another macro.

A subtle difference was that compat_symbol_unique made the symbol
global automatically.  compat_symbol does not do this, so static
had to be removed from the definition of
__libpthread_version_placeholder.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/sysdeps/ia64/libc-symver.h b/sysdeps/ia64/libc-symver.h
new file mode 100644
index 0000000000..63a3e58dde
--- /dev/null
+++ b/sysdeps/ia64/libc-symver.h
@@ -0,0 +1,33 @@
+/* Symbol version management.  ia64 version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC_SYMVER_H
+
+#include <sysdeps/generic/libc-symver.h>
+
+/* ia64 recognizes loc1 as a register name.  Add the # suffix to all
+   symbol references.  */
+#if !defined (__ASSEMBLER__) && SYMVER_NEEDS_ALIAS
+#undef _set_symbol_version_2
+# define _set_symbol_version_2(real, alias, name_version) \
+  __asm__ (".globl " #alias "#\n\t"                         \
+           ".equiv " #alias ", " #real "#\n\t"              \
+           ".symver " #alias "#," name_version)
+#endif
+
+#endif /* _LIBC_SYMVER_H */