CFI support: lookup by PC and translate into DWARF location per register

1 files changed, 144 insertions, 0 deletions

diff --git a/libdw/dwarf_frame_register.c b/libdw/dwarf_frame_register.c
new file mode 100644
index 00000000..231459a6
--- /dev/null
+++ b/libdw/dwarf_frame_register.c
@@ -0,0 +1,144 @@
+/* Get register location expression for frame.
+   Copyright (C) 2009 Red Hat, Inc.
+   This file is part of Red Hat elfutils.
+
+   Red Hat elfutils is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by the
+   Free Software Foundation; version 2 of the License.
+
+   Red Hat elfutils 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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along
+   with Red Hat elfutils; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
+
+   In addition, as a special exception, Red Hat, Inc. gives You the
+   additional right to link the code of Red Hat elfutils with code licensed
+   under any Open Source Initiative certified open source license
+   (http://www.opensource.org/licenses/index.php) which requires the
+   distribution of source code with any binary distribution and to
+   distribute linked combinations of the two.  Non-GPL Code permitted under
+   this exception must only link to the code of Red Hat elfutils through
+   those well defined interfaces identified in the file named EXCEPTION
+   found in the source code files (the "Approved Interfaces").  The files
+   of Non-GPL Code may instantiate templates or use macros or inline
+   functions from the Approved Interfaces without causing the resulting
+   work to be covered by the GNU General Public License.  Only Red Hat,
+   Inc. may make changes or additions to the list of Approved Interfaces.
+   Red Hat's grant of this exception is conditioned upon your not adding
+   any new exceptions.  If you wish to add a new Approved Interface or
+   exception, please contact Red Hat.  You must obey the GNU General Public
+   License in all respects for all of the Red Hat elfutils code and other
+   code used in conjunction with Red Hat elfutils except the Non-GPL Code
+   covered by this exception.  If you modify this file, you may extend this
+   exception to your version of the file, but you are not obligated to do
+   so.  If you do not wish to provide this exception without modification,
+   you must delete this exception statement from your version and license
+   this file solely under the GPL without exception.
+
+   Red Hat elfutils is an included package of the Open Invention Network.
+   An included package of the Open Invention Network is a package for which
+   Open Invention Network licensees cross-license their patents.  No patent
+   license is granted, either expressly or impliedly, by designation as an
+   included package.  Should you wish to participate in the Open Invention
+   Network licensing program, please visit www.openinventionnetwork.com
+   <http://www.openinventionnetwork.com>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "cfi.h"
+#include <dwarf.h>
+
+int
+dwarf_frame_register (fs, regno, ops_mem, ops, nops)
+     Dwarf_Frame *fs;
+     int regno;
+     Dwarf_Op ops_mem[2];
+     Dwarf_Op **ops;
+     size_t *nops;
+{
+  /* Maybe there was a previous error.  */
+  if (fs == NULL)
+    return -1;
+
+  if (unlikely (regno < 0))
+    {
+      __libdw_seterrno (DWARF_E_INVALID_ACCESS);
+      return -1;
+    }
+
+  int result = 0;		/* A location, not a value.  */
+
+  if (unlikely ((size_t) regno >= fs->nregs))
+    goto default_rule;
+
+  const struct dwarf_frame_register *reg = &fs->regs[regno];
+
+  switch (reg->rule)
+    {
+    case reg_unspecified:
+    default_rule:
+      /* Use the default rule for registers not yet mentioned in CFI.  */
+      if (fs->cache->default_same_value)
+	goto same_value;
+      /*FALLTHROUGH*/
+    case reg_undefined:
+      /* The value is known to be unavailable.  */
+      result = 1;
+      /*FALLTHROUGH*/
+    case reg_same_value:
+    same_value:
+      /* The location is not known here, but the caller might know it.  */
+      *ops = NULL;
+      *nops = 0;
+      break;
+
+    case reg_val_offset:
+      result = 1;		/* A value, not a location.  */
+      /*FALLTHROUGH*/
+    case reg_offset:
+      ops_mem[0] = (Dwarf_Op) { .atom = DW_OP_call_frame_cfa };
+      ops_mem[1] = (Dwarf_Op) { .atom = DW_OP_plus_uconst,
+				.number = reg->value };
+      *ops = ops_mem;
+      *nops = reg->value == 0 ? 1 : 2;
+      break;
+
+    case reg_register:
+      ops_mem[0] = (Dwarf_Op) { .atom = DW_OP_regx, .number = reg->value };
+      *ops = ops_mem;
+      *nops = 1;
+      break;
+
+    case reg_val_expression:
+      result = 1;		/* A value, not a location.  */
+      /*FALLTHROUGH*/
+    case reg_expression:
+      {
+	unsigned int address_size = (fs->cache->e_ident[EI_CLASS] == ELFCLASS32
+				     ? 4 : 8);
+
+	Dwarf_Block block;
+	const uint8_t *p = fs->cache->data->d.d_buf + reg->value;
+	get_uleb128 (block.length, p);
+	block.data = (void *) p;
+
+	/* Parse the expression into internal form.  */
+	if (__libdw_intern_expression (NULL,
+				       fs->cache->other_byte_order,
+				       address_size,
+				       &fs->cache->expr_tree,
+				       &block, ops, nops,
+				       IDX_debug_frame) < 0)
+	  result = -1;
+	break;
+      }
+    }
+
+  return result;
+}