ARC: ABI Implementation

This code deals with the ARC ABI.

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

sysdeps/arc/dl-runtime.h

@@ -0,0 +1,42 @@
+/* Helpers for On-demand PLT fixup for shared objects.  ARC version.
+   Copyright (C) 2020 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/>.  */
+
+/* PLT jump into resolver passes PC of PLTn, while _dl_fixup expects the
+   address of corresponding .rela.plt entry.
+
+    - @plt0: runtime pc of first plt entry (DT_PLTGOT)
+    - @pltn: runtime pc of plt entry being resolved
+    - @size: size of .plt.rela entry (unused).  */
+static inline uintptr_t
+reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
+{
+  unsigned long int idx = pltn - plt0;
+
+  /* PLT trampoline is 16 bytes.  */
+  idx /= 16;
+
+  /* Exclude PLT0 and PLT1.  */
+  return idx - 2;
+}
+
+static inline uintptr_t
+reloc_offset (uintptr_t plt0, uintptr_t pltn)
+{
+  size_t sz = sizeof (ElfW(Rela));
+  return reloc_index (plt0, pltn, sz) * sz;
+}