Create dwarf2/section.[ch]

This moves some section-handling code from dwarf2read.c into new
files, dwarf2/section.[ch].

gdb/ChangeLog
2020-02-08  Tom Tromey  <tom@tromey.com>

	* dwarf2read.h (struct dwarf2_section_info, dwarf2_read_section):
	Move to dwarf2/section.h.
	* dwarf2read.c (get_containing_section, get_section_bfd_owner)
	(get_section_bfd_section, get_section_name)
	(get_section_file_name, get_section_id, get_section_flags)
	(dwarf2_section_empty_p, dwarf2_read_section): Moe to
	dwarf2/section.c.
	* dwarf2/section.h: New file.
	* dwarf2/section.c: New file, from dwarf2read.c.
	* Makefile.in (COMMON_SFILES): Add dwarf2/section.c.

Change-Id: I9f8498094cf99d9521e9481622ce8adbd453daf4

2 files changed, 300 insertions, 0 deletions

diff --git a/gdb/dwarf2/section.c b/gdb/dwarf2/section.c
new file mode 100644
index 0000000..618ab9a
--- /dev/null
+++ b/gdb/dwarf2/section.c
@@ -0,0 +1,179 @@
+/* DWARF 2 low-level section code
+
+   Copyright (C) 1994-2020 Free Software Foundation, Inc.
+
+   Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology,
+   Inc.  with support from Florida State University (under contract
+   with the Ada Joint Program Office), and Silicon Graphics, Inc.
+   Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
+   based on Fred Fish's (Cygnus Support) implementation of DWARF 1
+   support.
+
+   This file is part of GDB.
+
+   This program 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; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "dwarf2/section.h"
+#include "gdb_bfd.h"
+#include "objfiles.h"
+
+struct dwarf2_section_info *
+get_containing_section (const struct dwarf2_section_info *section)
+{
+  gdb_assert (section->is_virtual);
+  return section->s.containing_section;
+}
+
+struct bfd *
+get_section_bfd_owner (const struct dwarf2_section_info *section)
+{
+  if (section->is_virtual)
+    {
+      section = get_containing_section (section);
+      gdb_assert (!section->is_virtual);
+    }
+  return section->s.section->owner;
+}
+
+asection *
+get_section_bfd_section (const struct dwarf2_section_info *section)
+{
+  if (section->is_virtual)
+    {
+      section = get_containing_section (section);
+      gdb_assert (!section->is_virtual);
+    }
+  return section->s.section;
+}
+
+const char *
+get_section_name (const struct dwarf2_section_info *section)
+{
+  asection *sectp = get_section_bfd_section (section);
+
+  gdb_assert (sectp != NULL);
+  return bfd_section_name (sectp);
+}
+
+const char *
+get_section_file_name (const struct dwarf2_section_info *section)
+{
+  bfd *abfd = get_section_bfd_owner (section);
+
+  return bfd_get_filename (abfd);
+}
+
+int
+get_section_id (const struct dwarf2_section_info *section)
+{
+  asection *sectp = get_section_bfd_section (section);
+
+  if (sectp == NULL)
+    return 0;
+  return sectp->id;
+}
+
+int
+get_section_flags (const struct dwarf2_section_info *section)
+{
+  asection *sectp = get_section_bfd_section (section);
+
+  gdb_assert (sectp != NULL);
+  return bfd_section_flags (sectp);
+}
+
+int
+dwarf2_section_empty_p (const struct dwarf2_section_info *section)
+{
+  if (section->is_virtual)
+    return section->size == 0;
+  return section->s.section == NULL || section->size == 0;
+}
+
+void
+dwarf2_read_section (struct objfile *objfile, dwarf2_section_info *info)
+{
+  asection *sectp;
+  bfd *abfd;
+  gdb_byte *buf, *retbuf;
+
+  if (info->readin)
+    return;
+  info->buffer = NULL;
+  info->readin = true;
+
+  if (dwarf2_section_empty_p (info))
+    return;
+
+  sectp = get_section_bfd_section (info);
+
+  /* If this is a virtual section we need to read in the real one first.  */
+  if (info->is_virtual)
+    {
+      struct dwarf2_section_info *containing_section =
+	get_containing_section (info);
+
+      gdb_assert (sectp != NULL);
+      if ((sectp->flags & SEC_RELOC) != 0)
+	{
+	  error (_("Dwarf Error: DWP format V2 with relocations is not"
+		   " supported in section %s [in module %s]"),
+		 get_section_name (info), get_section_file_name (info));
+	}
+      dwarf2_read_section (objfile, containing_section);
+      /* Other code should have already caught virtual sections that don't
+	 fit.  */
+      gdb_assert (info->virtual_offset + info->size
+		  <= containing_section->size);
+      /* If the real section is empty or there was a problem reading the
+	 section we shouldn't get here.  */
+      gdb_assert (containing_section->buffer != NULL);
+      info->buffer = containing_section->buffer + info->virtual_offset;
+      return;
+    }
+
+  /* If the section has relocations, we must read it ourselves.
+     Otherwise we attach it to the BFD.  */
+  if ((sectp->flags & SEC_RELOC) == 0)
+    {
+      info->buffer = gdb_bfd_map_section (sectp, &info->size);
+      return;
+    }
+
+  buf = (gdb_byte *) obstack_alloc (&objfile->objfile_obstack, info->size);
+  info->buffer = buf;
+
+  /* When debugging .o files, we may need to apply relocations; see
+     http://sourceware.org/ml/gdb-patches/2002-04/msg00136.html .
+     We never compress sections in .o files, so we only need to
+     try this when the section is not compressed.  */
+  retbuf = symfile_relocate_debug_section (objfile, sectp, buf);
+  if (retbuf != NULL)
+    {
+      info->buffer = retbuf;
+      return;
+    }
+
+  abfd = get_section_bfd_owner (info);
+  gdb_assert (abfd != NULL);
+
+  if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
+      || bfd_bread (buf, info->size, abfd) != info->size)
+    {
+      error (_("Dwarf Error: Can't read DWARF data"
+	       " in section %s [in module %s]"),
+	     bfd_section_name (sectp), bfd_get_filename (abfd));
+    }
+}
diff --git a/gdb/dwarf2/section.h b/gdb/dwarf2/section.h
new file mode 100644
index 0000000..a1acc5f
--- /dev/null
+++ b/gdb/dwarf2/section.h
@@ -0,0 +1,121 @@
+/* DWARF 2 low-level section code
+
+   Copyright (C) 1994-2020 Free Software Foundation, Inc.
+
+   Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology,
+   Inc.  with support from Florida State University (under contract
+   with the Ada Joint Program Office), and Silicon Graphics, Inc.
+   Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
+   based on Fred Fish's (Cygnus Support) implementation of DWARF 1
+   support.
+
+   This file is part of GDB.
+
+   This program 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; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDB_DWARF2_SECTION_H
+#define GDB_DWARF2_SECTION_H
+
+/* A descriptor for dwarf sections.
+
+   S.ASECTION, SIZE are typically initialized when the objfile is first
+   scanned.  BUFFER, READIN are filled in later when the section is read.
+   If the section contained compressed data then SIZE is updated to record
+   the uncompressed size of the section.
+
+   DWP file format V2 introduces a wrinkle that is easiest to handle by
+   creating the concept of virtual sections contained within a real section.
+   In DWP V2 the sections of the input DWO files are concatenated together
+   into one section, but section offsets are kept relative to the original
+   input section.
+   If this is a virtual dwp-v2 section, S.CONTAINING_SECTION is a backlink to
+   the real section this "virtual" section is contained in, and BUFFER,SIZE
+   describe the virtual section.  */
+
+struct dwarf2_section_info
+{
+  union
+  {
+    /* If this is a real section, the bfd section.  */
+    asection *section;
+    /* If this is a virtual section, pointer to the containing ("real")
+       section.  */
+    struct dwarf2_section_info *containing_section;
+  } s;
+  /* Pointer to section data, only valid if readin.  */
+  const gdb_byte *buffer;
+  /* The size of the section, real or virtual.  */
+  bfd_size_type size;
+  /* If this is a virtual section, the offset in the real section.
+     Only valid if is_virtual.  */
+  bfd_size_type virtual_offset;
+  /* True if we have tried to read this section.  */
+  bool readin;
+  /* True if this is a virtual section, False otherwise.
+     This specifies which of s.section and s.containing_section to use.  */
+  bool is_virtual;
+};
+
+/* Read the contents of the section INFO.
+   OBJFILE is the main object file, but not necessarily the file where
+   the section comes from.  E.g., for DWO files the bfd of INFO is the bfd
+   of the DWO file.
+   If the section is compressed, uncompress it before returning.  */
+
+extern void dwarf2_read_section (struct objfile *objfile,
+				 dwarf2_section_info *info);
+
+extern const char *get_section_name (const struct dwarf2_section_info *);
+
+extern const char *get_section_file_name (const struct dwarf2_section_info *);
+
+/* Return the containing section of virtual section SECTION.  */
+
+extern struct dwarf2_section_info *get_containing_section
+  (const struct dwarf2_section_info *section);
+
+/* Return the bfd owner of SECTION.  */
+
+extern struct bfd *get_section_bfd_owner
+  (const struct dwarf2_section_info *section);
+
+/* Return the bfd section of SECTION.
+   Returns NULL if the section is not present.  */
+
+extern asection *get_section_bfd_section
+  (const struct dwarf2_section_info *section);
+
+/* Return the name of SECTION.  */
+
+extern const char *get_section_name
+  (const struct dwarf2_section_info *section);
+
+/* Return the name of the file SECTION is in.  */
+
+extern const char *get_section_file_name
+  (const struct dwarf2_section_info *section);
+
+/* Return the id of SECTION.
+   Returns 0 if SECTION doesn't exist.  */
+
+extern int get_section_id (const struct dwarf2_section_info *section);
+
+/* Return the flags of SECTION.
+   SECTION (or containing section if this is a virtual section) must exist.  */
+
+extern int get_section_flags (const struct dwarf2_section_info *section);
+
+extern int dwarf2_section_empty_p (const struct dwarf2_section_info *section);
+
+#endif /* GDB_DWARF2_SECTION_H */