Add new gdbarch method, read_core_file_mappings

The new gdbarch method, read_core_file_mappings, will be used for
reading file-backed mappings from a core file.  It'll be used
for two purposes: 1) to construct a table of file-backed mappings
in corelow.c, and 2) for display of core file mappings.

For Linux, I tried a different approach in which knowledge of the note
format was placed directly in corelow.c.  This seemed okay at first;
it was only one note format and the note format was fairly simple.
After looking at FreeBSD's note/mapping reading code, I concluded
that it's best to leave architecture specific details for decoding
the note in (architecture specific) tdep files.

With regard to display of core file mappings, I experimented with
placing the mappings display code in corelow.c.  It has access to the
file-backed mappings which were read in when the core file was loaded.
And, better, still common code could be used for all architectures.
But, again, the FreeBSD mapping code convinced me that this was not
the best approach since it has even more mapping info than Linux.
Display code which would work well for Linux will leave out mappings
as well as protection info for mappings.

So, for these reasons, I'm introducing a new gdbarch method for
reading core file mappings.

gdb/ChangeLog:

	* arch-utils.c (default_read_core_file_mappings): New function.
	* arch-utils.c (default_read_core_file_mappings): Declare.
	* gdbarch.sh (read_core_file_mappings): New gdbarch method.
	* gdbarch.h, gdbarch.c: Regenerate.

6 files changed, 67 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 2c7506e..f5925c6 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 2020-07-22  Kevin Buettner  <kevinb@redhat.com>
 
+	* arch-utils.c (default_read_core_file_mappings): New function.
+	* arch-utils.c (default_read_core_file_mappings): Declare.
+	* gdbarch.sh (read_core_file_mappings): New gdbarch method.
+	* gdbarch.h, gdbarch.c: Regenerate.
+
+2020-07-22  Kevin Buettner  <kevinb@redhat.com>
+
 	PR corefiles/25631
 	* corelow.c (core_target:xfer_partial):  Revise
 	TARGET_OBJECT_MEMORY case to consider non-SEC_HAS_CONTENTS
diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c
index 13ba50a..12e3b8d 100644
--- a/gdb/arch-utils.c
+++ b/gdb/arch-utils.c
@@ -1036,6 +1036,22 @@ default_get_pc_address_flags (frame_info *frame, CORE_ADDR pc)
   return "";
 }
 
+/* See arch-utils.h.  */
+void
+default_read_core_file_mappings (struct gdbarch *gdbarch,
+                                 struct bfd *cbfd,
+				 gdb::function_view<void (ULONGEST count)>
+				   pre_loop_cb,
+				 gdb::function_view<void (int num,
+				                          ULONGEST start,
+							  ULONGEST end,
+							  ULONGEST file_ofs,
+							  const char *filename,
+							  const void *other)>
+				   loop_cb)
+{
+}
+
 void _initialize_gdbarch_utils ();
 void
 _initialize_gdbarch_utils ()
diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h
index 43d64b1..8cb0db0 100644
--- a/gdb/arch-utils.h
+++ b/gdb/arch-utils.h
@@ -280,4 +280,16 @@ extern ULONGEST default_type_align (struct gdbarch *gdbarch,
 extern std::string default_get_pc_address_flags (frame_info *frame,
 						 CORE_ADDR pc);
 
+/* Default implementation of gdbarch read_core_file_mappings method.  */
+extern void default_read_core_file_mappings (struct gdbarch *gdbarch,
+					     struct bfd *cbfd,
+					     gdb::function_view<void (ULONGEST count)>
+					       pre_loop_cb,
+					     gdb::function_view<void (int num,
+								      ULONGEST start,
+								      ULONGEST end,
+								      ULONGEST file_ofs,
+								      const char *filename,
+								      const void *other)>
+					       loop_cb);
 #endif /* ARCH_UTILS_H */
diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index fd5b030..f8fe03c 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -348,6 +348,7 @@ struct gdbarch
   const disasm_options_and_args_t * valid_disassembler_options;
   gdbarch_type_align_ftype *type_align;
   gdbarch_get_pc_address_flags_ftype *get_pc_address_flags;
+  gdbarch_read_core_file_mappings_ftype *read_core_file_mappings;
 };
 
 /* Create a new ``struct gdbarch'' based on information provided by
@@ -464,6 +465,7 @@ gdbarch_alloc (const struct gdbarch_info *info,
   gdbarch->addressable_memory_unit_size = default_addressable_memory_unit_size;
   gdbarch->type_align = default_type_align;
   gdbarch->get_pc_address_flags = default_get_pc_address_flags;
+  gdbarch->read_core_file_mappings = default_read_core_file_mappings;
   /* gdbarch_alloc() */
 
   return gdbarch;
@@ -712,6 +714,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
   /* Skip verify of valid_disassembler_options, invalid_p == 0 */
   /* Skip verify of type_align, invalid_p == 0 */
   /* Skip verify of get_pc_address_flags, invalid_p == 0 */
+  /* Skip verify of read_core_file_mappings, invalid_p == 0 */
   if (!log.empty ())
     internal_error (__FILE__, __LINE__,
                     _("verify_gdbarch: the following are invalid ...%s"),
@@ -1276,6 +1279,9 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
                       "gdbarch_dump: ravenscar_ops = %s\n",
                       host_address_to_string (gdbarch->ravenscar_ops));
   fprintf_unfiltered (file,
+                      "gdbarch_dump: read_core_file_mappings = <%s>\n",
+                      host_address_to_string (gdbarch->read_core_file_mappings));
+  fprintf_unfiltered (file,
                       "gdbarch_dump: gdbarch_read_pc_p() = %d\n",
                       gdbarch_read_pc_p (gdbarch));
   fprintf_unfiltered (file,
@@ -5137,6 +5143,23 @@ set_gdbarch_get_pc_address_flags (struct gdbarch *gdbarch,
   gdbarch->get_pc_address_flags = get_pc_address_flags;
 }
 
+void
+gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, struct bfd *cbfd,gdb::function_view<void (ULONGEST count)> pre_loop_cb,gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const void *other)> loop_cb)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->read_core_file_mappings != NULL);
+  if (gdbarch_debug >= 2)
+    fprintf_unfiltered (gdb_stdlog, "gdbarch_read_core_file_mappings called\n");
+  gdbarch->read_core_file_mappings (gdbarch, cbfd, pre_loop_cb, loop_cb);
+}
+
+void
+set_gdbarch_read_core_file_mappings (struct gdbarch *gdbarch,
+                                     gdbarch_read_core_file_mappings_ftype read_core_file_mappings)
+{
+  gdbarch->read_core_file_mappings = read_core_file_mappings;
+}
+
 
 /* Keep a registry of per-architecture data-pointers required by GDB
    modules.  */
diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
index 6c125d1..7a3060e 100644
--- a/gdb/gdbarch.h
+++ b/gdb/gdbarch.h
@@ -1627,6 +1627,12 @@ typedef std::string (gdbarch_get_pc_address_flags_ftype) (frame_info *frame, COR
 extern std::string gdbarch_get_pc_address_flags (struct gdbarch *gdbarch, frame_info *frame, CORE_ADDR pc);
 extern void set_gdbarch_get_pc_address_flags (struct gdbarch *gdbarch, gdbarch_get_pc_address_flags_ftype *get_pc_address_flags);
 
+/* Read core file mappings */
+
+typedef void (gdbarch_read_core_file_mappings_ftype) (struct gdbarch *gdbarch, struct bfd *cbfd,gdb::function_view<void (ULONGEST count)> pre_loop_cb,gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const void *other)> loop_cb);
+extern void gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, struct bfd *cbfd,gdb::function_view<void (ULONGEST count)> pre_loop_cb,gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const void *other)> loop_cb);
+extern void set_gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, gdbarch_read_core_file_mappings_ftype *read_core_file_mappings);
+
 extern struct gdbarch_tdep *gdbarch_tdep (struct gdbarch *gdbarch);
 
 
diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh
index 5adfd29..6d3c5c8 100755
--- a/gdb/gdbarch.sh
+++ b/gdb/gdbarch.sh
@@ -1176,6 +1176,9 @@ m;ULONGEST;type_align;struct type *type;type;;default_type_align;;0
 # Return a string containing any flags for the given PC in the given FRAME.
 f;std::string;get_pc_address_flags;frame_info *frame, CORE_ADDR pc;frame, pc;;default_get_pc_address_flags;;0
 
+# Read core file mappings
+m;void;read_core_file_mappings;struct bfd *cbfd,gdb::function_view<void (ULONGEST count)> pre_loop_cb,gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const void *other)> loop_cb;cbfd, pre_loop_cb, loop_cb;;default_read_core_file_mappings;;0
+
 EOF
 }