xtensa: add FDPIC support

This change implements Xtensa FDPIC ABI as specified in the first
version of the following document:

 https://github.com/jcmvbkbc/xtensa-abi/blob/master/fdpic-xtensa.txt

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 105 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/xtensa/crtreloc.c b/libc/sysdeps/linux/xtensa/crtreloc.c
new file mode 100644
index 000000000..697ef91ab
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/crtreloc.c
@@ -0,0 +1,105 @@
+/* Copyright (C) 2003, 2004 Free Software Foundation, Inc.
+   written by Alexandre Oliva <aoliva@redhat.com>
+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.
+
+In addition to the permissions in the GNU Lesser General Public
+License, the Free Software Foundation gives you unlimited
+permission to link the compiled version of this file with other
+programs, and to distribute those programs without any restriction
+coming from the use of this file.  (The GNU Lesser General Public
+License restrictions do apply in other respects; for example, they
+cover modification of the file, and distribution when not linked
+into another program.)
+
+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
+Library 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; see the file COPYING.LIB.  If
+not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef __FDPIC__
+
+#include <sys/types.h>
+#include <link.h>
+
+/* This file is to be compiled into crt object files, to enable
+   executables to easily self-relocate.  */
+
+/* Compute the runtime address of pointer in the range [p,e), and then
+   map the pointer pointed by it.  */
+static __always_inline void ***
+reloc_range_indirect (void ***p, void ***e,
+		      const struct elf32_fdpic_loadmap *map)
+{
+  while (p < e)
+    {
+      if (*p != (void **)-1)
+	{
+	  void *ptr = __reloc_pointer (*p, map);
+
+	  if (ptr != (void *)-1)
+	    {
+	      unsigned long off = ((unsigned long)ptr & 3) * 8;
+	      unsigned long *pa = (unsigned long *)((unsigned long)ptr & -4);
+	      unsigned long v2;
+	      void *pt;
+
+	      if (off)
+		{
+		  unsigned long v0, v1;
+#ifdef __XTENSA_EB__
+		  v0 = pa[1]; v1 = pa[0];
+		  v2 = (v1 >> (32 - off)) | (v0 << off);
+#else /* __XTENSA_EL__ */
+		  v0 = pa[0]; v1 = pa[1];
+		  v2 = (v0 << (32 - off)) | (v1 >> off);
+#endif
+		  pt = (void *)((v1 << (32 - off)) | (v0 >> off));
+		}
+	      else
+		pt = *(void**)ptr;
+	      pt = __reloc_pointer (pt, map);
+	      if (off)
+		{
+		  unsigned long v = (unsigned long)pt;
+#ifdef __XTENSA_EB__
+		  pa[0] = (v2 << (32 - off)) | (v >> off);
+		  pa[1] = (v << (32 - off)) | (v2 >> off);
+#else /* __XTENSA_EL__ */
+		  pa[0] = (v2 >> (32 - off)) | (v << off);
+		  pa[1] = (v >> (32 - off)) | (v2 << off);
+#endif
+		}
+	      else
+		*(void**)ptr = pt;
+	    }
+	}
+      p++;
+    }
+  return p;
+}
+
+/* Call __reloc_range_indirect for the given range except for the last
+   entry, whose contents are only relocated.  It's expected to hold
+   the GOT value.  */
+attribute_hidden void*
+__self_reloc (const struct elf32_fdpic_loadmap *map,
+	      void ***p, void ***e)
+{
+  p = reloc_range_indirect (p, e-1, map);
+
+  if (p >= e)
+    return (void*)-1;
+
+  return __reloc_pointer (*p, map);
+}
+
+#endif /* __FDPIC__ */