[PATCH RESEND v2 08/10] gdb: add objfile -> solib backlink

[Simon Marchi <simon.marchi@efficios.com>]

From: Simon Marchi <simon.marchi@polymtl.ca>

The following "multiple solib_ops" patch will require accessing the
solib(s) related to an objfile fairly often.  To make that easier, add
an objfile to solib backlink.

However, I learned that there may be more than one solib linked to one
objfile.  The only case I am aware of is the dynamic linker itself
(ld-linux.so), where the same instance (same load address) appears in
all namespaces.  We get one solib per "view" of that library, but they
all point to the same objfile.  So this backlink is actually a vector.

Rename find_solib_for_objfile to find_one_solib_for_objfile to reflect
that this function returns just one of possible multiple solibs for the
given objfile (if that ever matters).  To be clear, this doesn't change
its behavior, this is what it was doing before this patch.

Change-Id: I427d19407fdbc274b1790e0cae3004ee5fdbea72
---
 gdb/objfiles.h   | 23 +++++++++++++++++++++++
 gdb/solib-svr4.c | 16 ++++++++--------
 gdb/solib.c      | 13 +++++++++----
 3 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/gdb/objfiles.h b/gdb/objfiles.h
index c8b989911e5f..9bd676f27237 100644
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -450,6 +450,25 @@ struct objfile : intrusive_list_node<objfile>
   /* Return the program space associated with this objfile.  */
   program_space *pspace () { return m_pspace; }
 
+  /* Return the list of struct solib associated to this objfile.  */
+  std::vector<solib *> &solibs () { return m_solibs; }
+
+  /* Add SOLIB to the list of solibs associated to this objfile.  */
+  void add_solib (solib &solib)
+  {
+    gdb_assert (std::find (m_solibs.begin (), m_solibs.end (), &solib)
+		== m_solibs.end ());
+    m_solibs.emplace_back (&solib);
+  }
+
+  /* Remove SOLIB from the list of solibs associated to this objfile.  */
+  void remove_solib (solib &solib)
+  {
+    auto it = std::find (m_solibs.begin (), m_solibs.end (), &solib);
+    gdb_assert (it != m_solibs.end ());
+    m_solibs.erase (it);
+  }
+
   using compunit_symtab_iterator
     = owning_intrusive_list<compunit_symtab>::iterator;
   using compunit_symtab_range = iterator_range<compunit_symtab_iterator>;
@@ -702,6 +721,10 @@ struct objfile : intrusive_list_node<objfile>
 
   program_space *m_pspace;
 
+  /* The solibs associated to this objfile.  This is a 1 objfile to N solibs
+     relationship (see solib.c for details).  */
+  std::vector<solib *> m_solibs;
+
 public:
   /* The object file's BFD.  Can be null if the objfile contains only
      minimal symbols (e.g. the run time common symbols for SunOS4) or
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index 35c81000b10a..33fb6e3cd970 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -3592,10 +3592,10 @@ lp64_svr4_solib_ops::fetch_link_map_offsets () const
 }
 \f
 
-/* Return the DSO matching OBJFILE or nullptr if none can be found.  */
+/* Return one solib matching OBJFILE or nullptr if none can be found.  */
 
-static const solib *
-find_solib_for_objfile (struct objfile *objfile)
+static solib *
+find_one_solib_for_objfile (struct objfile *objfile)
 {
   if (objfile == nullptr)
     return nullptr;
@@ -3605,9 +3605,9 @@ find_solib_for_objfile (struct objfile *objfile)
   if (objfile->separate_debug_objfile_backlink != nullptr)
     objfile = objfile->separate_debug_objfile_backlink;
 
-  for (const solib &so : current_program_space->solibs ())
-    if (so.objfile == objfile)
-      return &so;
+  if (const auto &solibs = objfile->solibs ();
+      !solibs.empty ())
+    return solibs.front ();
 
   return nullptr;
 }
@@ -3676,7 +3676,7 @@ svr4_solib_ops::iterate_over_objfiles_in_search_order
      r_debug object, defaulting to the initial namespace.  */
   svr4_info *info = get_svr4_info (current_program_space);
   CORE_ADDR default_debug_base = this->default_debug_base (info);
-  const solib *curr_solib = find_solib_for_objfile (current_objfile);
+  const solib *curr_solib = find_one_solib_for_objfile (current_objfile);
   CORE_ADDR debug_base = find_debug_base_for_solib (curr_solib);
   if (debug_base == 0)
     debug_base = default_debug_base;
@@ -3691,7 +3691,7 @@ svr4_solib_ops::iterate_over_objfiles_in_search_order
 	 If we fail, e.g. for manually added symbol files or for the main
 	 executable, we assume that they were added to the initial
 	 namespace.  */
-      const solib *solib = find_solib_for_objfile (&objfile);
+      const solib *solib = find_one_solib_for_objfile (&objfile);
       CORE_ADDR solib_base = find_debug_base_for_solib (solib);
       if (solib_base == 0)
 	solib_base = default_debug_base;
diff --git a/gdb/solib.c b/gdb/solib.c
index 1211874d22be..b2cb3870c6e0 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -633,6 +633,7 @@ solib_read_symbols (solib &so, symfile_add_flags flags)
 	  so.objfile->addr_low = so.addr_low;
 	}
 
+      so.objfile->add_solib (so);
       so.symbols_loaded = true;
     }
   catch (const gdb_exception_error &e)
@@ -703,10 +704,14 @@ remove_solib (program_space *pspace,
   notify_solib_unloaded (pspace, *solib_it, still_in_use, false);
 
   /* Unless the user loaded it explicitly, free SO's objfile.  */
-  if (solib_it->objfile != nullptr
-      && !(solib_it->objfile->flags & OBJF_USERLOADED)
-      && !still_in_use)
-    solib_it->objfile->unlink ();
+  if (solib_it->objfile != nullptr)
+    {
+      /* Remove the objfile -> solib backlink.  */
+      solib_it->objfile->remove_solib (*solib_it);
+
+      if (!(solib_it->objfile->flags & OBJF_USERLOADED) && !still_in_use)
+	solib_it->objfile->unlink ();
+    }
 
   pspace->deleted_solibs.push_back (solib_it->name);
 
-- 
2.54.0