[binutils-gdb] Make index reading functions more modular

[Simon Marchi <simark at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4485a1c1d8d2b4a20fca2e2b7d1aabcff383b222

commit 4485a1c1d8d2b4a20fca2e2b7d1aabcff383b222
Author: Simon Marchi <simon.marchi@ericsson.com>
Date:   Tue Aug 7 18:08:57 2018 -0400

    Make index reading functions more modular
    
    New in v3:
    
    - Remove changed to dwarf-5 functions.
    
    The read_gdb_index_from_section and read_debug_names_from_section
    functions read the index content, as their names state, from sections of
    object files.  A following patch will make it possible to read index
    content from standalone files.
    
    This patch therefore decouples the code that reads the index content
    from the code that processes that content.  Functions
    dwarf2_read_gdb_index and dwarf2_read_debug_names receive callbacks that
    are responsible for providing the index contents (for both the main file
    and the potential dwz file).
    
    gdb/ChangeLog:
    
    	* dwarf2read.c (read_gdb_index_from_section): Rename to...
    	(read_gdb_index_from_buffer): ... this.  Remove section
    	parameter, add buffer parameter.
    	(get_gdb_index_contents_ftype,
    	get_gdb_index_contents_dwz_ftype): New typedefs.
    	(dwarf2_read_gdb_index): Add callback parameters to get the
    	index contents.
    	(get_gdb_index_contents_from_section): New.
    	(dwarf2_initialize_objfile): Update call to
    	dwarf2_read_gdb_index.

Diff:
---
 gdb/ChangeLog    |  13 ++++++
 gdb/dwarf2read.c | 122 +++++++++++++++++++++++++++++++++++--------------------
 2 files changed, 91 insertions(+), 44 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4766666..52e2dcb 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,18 @@
 2018-08-07  Simon Marchi  <simon.marchi@ericsson.com>
 
+	* dwarf2read.c (read_gdb_index_from_section): Rename to...
+	(read_gdb_index_from_buffer): ... this.  Remove section
+	parameter, add buffer parameter.
+	(get_gdb_index_contents_ftype,
+	get_gdb_index_contents_dwz_ftype): New typedefs.
+	(dwarf2_read_gdb_index): Add callback parameters to get the
+	index contents.
+	(get_gdb_index_contents_from_section): New.
+	(dwarf2_initialize_objfile): Update call to
+	dwarf2_read_gdb_index.
+
+2018-08-07  Simon Marchi  <simon.marchi@ericsson.com>
+
 	* common/filestuff.h (gdb_fopen_cloexec): New overload.
 	(gdb_open_cloexec): Likewise.
 	* nat/linux-osdata.c (command_from_pid): Use string_printf.
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index e4b621d..296b50b 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -3410,8 +3410,8 @@ find_slot_in_mapped_hash (struct mapped_index *index, const char *name,
     }
 }
 
-/* A helper function that reads the .gdb_index from SECTION and fills
-   in MAP.  FILENAME is the name of the file containing the section;
+/* A helper function that reads the .gdb_index from BUFFER and fills
+   in MAP.  FILENAME is the name of the file containing the data;
    it is used for error reporting.  DEPRECATED_OK is true if it is
    ok to use deprecated sections.
 
@@ -3419,37 +3419,23 @@ find_slot_in_mapped_hash (struct mapped_index *index, const char *name,
    out parameters that are filled in with information about the CU and
    TU lists in the section.
 
-   Returns 1 if all went well, 0 otherwise.  */
+   Returns true if all went well, false otherwise.  */
 
 static bool
-read_gdb_index_from_section (struct objfile *objfile,
-			     const char *filename,
-			     bool deprecated_ok,
-			     struct dwarf2_section_info *section,
-			     struct mapped_index *map,
-			     const gdb_byte **cu_list,
-			     offset_type *cu_list_elements,
-			     const gdb_byte **types_list,
-			     offset_type *types_list_elements)
-{
-  const gdb_byte *addr;
-  offset_type version;
-  offset_type *metadata;
-  int i;
-
-  if (dwarf2_section_empty_p (section))
-    return 0;
+read_gdb_index_from_buffer (struct objfile *objfile,
+			    const char *filename,
+			    bool deprecated_ok,
+			    gdb::array_view<const gdb_byte> buffer,
+			    struct mapped_index *map,
+			    const gdb_byte **cu_list,
+			    offset_type *cu_list_elements,
+			    const gdb_byte **types_list,
+			    offset_type *types_list_elements)
+{
+  const gdb_byte *addr = &buffer[0];
 
-  /* Older elfutils strip versions could keep the section in the main
-     executable while splitting it for the separate debug info file.  */
-  if ((get_section_flags (section) & SEC_HAS_CONTENTS) == 0)
-    return 0;
-
-  dwarf2_read_section (objfile, section);
-
-  addr = section->buffer;
   /* Version check.  */
-  version = MAYBE_SWAP (*(offset_type *) addr);
+  offset_type version = MAYBE_SWAP (*(offset_type *) addr);
   /* Versions earlier than 3 emitted every copy of a psymbol.  This
      causes the index to behave very poorly for certain requests.  Version 3
      contained incomplete addrmap.  So, it seems better to just ignore such
@@ -3502,9 +3488,9 @@ to use the section anyway."),
 
   map->version = version;
 
-  metadata = (offset_type *) (addr + sizeof (offset_type));
+  offset_type *metadata = (offset_type *) (addr + sizeof (offset_type));
 
-  i = 0;
+  int i = 0;
   *cu_list = addr + MAYBE_SWAP (metadata[i]);
   *cu_list_elements = ((MAYBE_SWAP (metadata[i + 1]) - MAYBE_SWAP (metadata[i]))
 		       / 8);
@@ -3535,23 +3521,41 @@ to use the section anyway."),
   return 1;
 }
 
+/* Callback types for dwarf2_read_gdb_index.  */
+
+typedef gdb::function_view
+    <gdb::array_view<const gdb_byte>(objfile *, dwarf2_per_objfile *)>
+    get_gdb_index_contents_ftype;
+typedef gdb::function_view
+    <gdb::array_view<const gdb_byte>(objfile *, dwz_file *)>
+    get_gdb_index_contents_dwz_ftype;
+
 /* Read .gdb_index.  If everything went ok, initialize the "quick"
    elements of all the CUs and return 1.  Otherwise, return 0.  */
 
 static int
-dwarf2_read_gdb_index (struct dwarf2_per_objfile *dwarf2_per_objfile)
+dwarf2_read_gdb_index
+  (struct dwarf2_per_objfile *dwarf2_per_objfile,
+   get_gdb_index_contents_ftype get_gdb_index_contents,
+   get_gdb_index_contents_dwz_ftype get_gdb_index_contents_dwz)
 {
   const gdb_byte *cu_list, *types_list, *dwz_list = NULL;
   offset_type cu_list_elements, types_list_elements, dwz_list_elements = 0;
   struct dwz_file *dwz;
   struct objfile *objfile = dwarf2_per_objfile->objfile;
 
+  gdb::array_view<const gdb_byte> main_index_contents
+    = get_gdb_index_contents (objfile, dwarf2_per_objfile);
+
+  if (main_index_contents.empty ())
+    return 0;
+
   std::unique_ptr<struct mapped_index> map (new struct mapped_index);
-  if (!read_gdb_index_from_section (objfile, objfile_name (objfile),
-				    use_deprecated_index_sections,
-				    &dwarf2_per_objfile->gdb_index, map.get (),
-				    &cu_list, &cu_list_elements,
-				    &types_list, &types_list_elements))
+  if (!read_gdb_index_from_buffer (objfile, objfile_name (objfile),
+				   use_deprecated_index_sections,
+				   main_index_contents, map.get (), &cu_list,
+				   &cu_list_elements, &types_list,
+				   &types_list_elements))
     return 0;
 
   /* Don't use the index if it's empty.  */
@@ -3567,12 +3571,18 @@ dwarf2_read_gdb_index (struct dwarf2_per_objfile *dwarf2_per_objfile)
       const gdb_byte *dwz_types_ignore;
       offset_type dwz_types_elements_ignore;
 
-      if (!read_gdb_index_from_section (objfile,
-					bfd_get_filename (dwz->dwz_bfd), 1,
-					&dwz->gdb_index, &dwz_map,
-					&dwz_list, &dwz_list_elements,
-					&dwz_types_ignore,
-					&dwz_types_elements_ignore))
+      gdb::array_view<const gdb_byte> dwz_index_content
+	= get_gdb_index_contents_dwz (objfile, dwz);
+
+      if (dwz_index_content.empty ())
+	return 0;
+
+      if (!read_gdb_index_from_buffer (objfile,
+				       bfd_get_filename (dwz->dwz_bfd), 1,
+				       dwz_index_content, &dwz_map,
+				       &dwz_list, &dwz_list_elements,
+				       &dwz_types_ignore,
+				       &dwz_types_elements_ignore))
 	{
 	  warning (_("could not read '.gdb_index' section from %s; skipping"),
 		   bfd_get_filename (dwz->dwz_bfd));
@@ -6154,6 +6164,28 @@ const struct quick_symbol_functions dwarf2_debug_names_functions =
   dw2_map_symbol_filenames
 };
 
+/* Get the content of the .gdb_index section of OBJ.  SECTION_OWNER should point
+   to either a dwarf2_per_objfile or dwz_file object.  */
+
+template <typename T>
+static gdb::array_view<const gdb_byte>
+get_gdb_index_contents_from_section (objfile *obj, T *section_owner)
+{
+  dwarf2_section_info *section = &section_owner->gdb_index;
+
+  if (dwarf2_section_empty_p (section))
+    return {};
+
+  /* Older elfutils strip versions could keep the section in the main
+     executable while splitting it for the separate debug info file.  */
+  if ((get_section_flags (section) & SEC_HAS_CONTENTS) == 0)
+    return {};
+
+  dwarf2_read_section (obj, section);
+
+  return {section->buffer, section->size};
+}
+
 /* See symfile.h.  */
 
 bool
@@ -6197,7 +6229,9 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
       return true;
     }
 
-  if (dwarf2_read_gdb_index (dwarf2_per_objfile))
+  if (dwarf2_read_gdb_index (dwarf2_per_objfile,
+			     get_gdb_index_contents_from_section<struct dwarf2_per_objfile>,
+			     get_gdb_index_contents_from_section<dwz_file>))
     {
       *index_kind = dw_index_kind::GDB_INDEX;
       return true;