[MIPS] Raise highest supported EI_ABIVERSION value [BZ #24916]

This bumps the highest valid EI_ABIVERSION value to ABSOLUTE ABI.

New testcase loads the symbol from the GOT with the "lb" instruction
so that the EI_ABIVERSION header field of the shared object is set
to ABSOLUTE (it doesn't actually check the value of the symbol), and
makes sure that the main executable is executed without "ABI version
invalid" error.

Tested for all three ABIs (o32, n32, n64) using both static linker which
handles undefined weak symbols correctly [1] (and sets the EI_ABIVERSION
of the test module) and the one that doesn't (EI_ABIVERSION left as 0).

[1] https://sourceware.org/ml/binutils/2018-07/msg00268.html

	[BZ #24916]
	* sysdeps/mips/Makefile [$(subdir) = elf] (tests): Add
	tst-undefined-weak.
	[$(subdir) = elf] (modules-names): Add tst-undefined-weak-lib.
	[$(subdir) = elf] ($(objpfx)tst-undefined-weak): Add dependency.
	* sysdeps/mips/tst-undefined-weak-lib.S: New file.
	* sysdeps/mips/tst-undefined-weak.c: Likewise.
	* sysdeps/unix/sysv/linux/mips/ldsodefs.h (VALID_ELF_ABIVERSION):
	Increment highest valid ABIVERSION value.

1 files changed, 28 insertions, 0 deletions

diff --git a/sysdeps/mips/tst-undefined-weak.c b/sysdeps/mips/tst-undefined-weak.c
new file mode 100644
index 0000000..1231da6
--- /dev/null
+++ b/sysdeps/mips/tst-undefined-weak.c
@@ -0,0 +1,28 @@
+/* Undefined weak symbol loading main executable.
+   Copyright (C) 2019 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
+   <http://www.gnu.org/licenses/>.  */
+
+int *x (void);
+
+int
+do_test (void)
+{
+  x ();
+  return 0;
+}
+
+#include <support/test-driver.c>