From FEDORA_PATCHES Mon Sep 17 00:00:00 2001

From: Keith Seitz <keiths@redhat.com>

Date: Tue, 28 Jul 2020 09:32:50 -0400

Subject: gdb-rhbz1842691-corefile-mem-access-12of15.patch

;; Add new command "maint print core-file-backed-mappings"

;; Kevin Buettner, RH BZ 1842961

   Author: Kevin Buettner <kevinb@redhat.com>

   Date:   Fri Jul 3 21:55:51 2020 -0700

    Add new command "maint print core-file-backed-mappings"

    I wrote a read_core_file_mappings method for FreeBSD and then registered

    this gdbarch method.  I saw some strange behavior while testing it and

    wanted a way to make sure that mappings were being correctly loaded

    into corelow.c, so I wrote the new command which is the topic of this

    commit.  I think it might be occasionally useful for debugging strange

    corefile behavior.

    With regard to FreeBSD, my work isn't ready yet.  Unlike Linux,

    FreeBSD puts all mappings into its core file note.  And, unlike Linux,

    it doesn't dump load segments which occupy no space in the file.  So

    my (perhaps naive) implementation of a FreeBSD read_core_file_mappings

    didn't work all that well:  I saw more failures in the corefile2.exp

    tests than without it.  I think it should be possible to make FreeBSD

    work as well as Linux, but it will require doing something with all of

    the mappings, not just the file based mappings that I was considering.

    In the v4 series, Pedro asked the following:

        I don't understand what this command provides that "info proc

        mappings" doesn't?  Can you give an example of when you'd use this

        command over "info proc mappings" ?

    On Linux, "info proc mappings" and "maint print core-file-backed-mappings"

    will produce similar, possibly identical, output.  This need not be

    the case for other OSes.  E.g. on FreeBSD, had I finished the

    implementation, the output from these commands would have been very

    different.  The FreeBSD "info proc mappings" command would show

    additional (non-file-backed) mappings in addition to at least one

    additional field (memory permissions) for each mapping.

    As noted earlier, I was seeing some unexpected behavior while working

    on the FreeBSD implementation and wanted to be certain that the

    mappings were being correctly loaded by corelow.c.  "info proc

    mappings" prints the core file mappings, but doesn't tell us anything

    about whether they've been loaded by corelow.c This new maintenance

    command directly interrogates the data structures and prints the

    values found there.

    gdb/ChangeLog:

    	* corelow.c (gdbcmd.h): Include.

    	(core_target::info_proc_mappings): New method.

    	(get_current_core_target): New function.

    	(maintenance_print_core_file_backed_mappings): New function.

    	(_initialize_corelow): Add core-file-backed-mappings to

    	"maint print" commands.

diff --git a/gdb/corelow.c b/gdb/corelow.c

--- a/gdb/corelow.c

+++ b/gdb/corelow.c

@@ -51,6 +51,7 @@

 #include "build-id.h"

 #include "gdbsupport/pathstuff.h"

 #include <unordered_map>

+#include "gdbcmd.h"

 #ifndef O_LARGEFILE

 #define O_LARGEFILE 0

@@ -121,6 +122,9 @@ public:

 				  const char *human_name,

 				  bool required);

+  /* See definition.  */

+  void info_proc_mappings (struct gdbarch *gdbarch);

+

 private: /* per-core data */

   /* The core's section table.  Note that these target sections are

@@ -1170,6 +1174,86 @@ core_target::info_proc (const char *args, enum info_proc_what request)

   return true;

 }

+/* Get a pointer to the current core target.  If not connected to a

+   core target, return NULL.  */

+

+static core_target *

+get_current_core_target ()

+{

+  target_ops *proc_target = find_target_at (process_stratum);

+  return dynamic_cast<core_target *> (proc_target);

+}

+

+/* Display file backed mappings from core file.  */

+

+void

+core_target::info_proc_mappings (struct gdbarch *gdbarch)

+{

+  if (m_core_file_mappings.sections != m_core_file_mappings.sections_end)

+    {

+      printf_filtered (_("Mapped address spaces:\n\n"));

+      if (gdbarch_addr_bit (gdbarch) == 32)

+	{

+	  printf_filtered ("\t%10s %10s %10s %10s %s\n",

+			   "Start Addr",

+			   "  End Addr",

+			   "      Size", "    Offset", "objfile");

+	}

+      else

+	{

+	  printf_filtered ("  %18s %18s %10s %10s %s\n",

+			   "Start Addr",

+			   "  End Addr",

+			   "      Size", "    Offset", "objfile");

+	}

+    }

+

+  for (const struct target_section *tsp = m_core_file_mappings.sections;

+       tsp < m_core_file_mappings.sections_end;

+       tsp++)

+    {

+      ULONGEST start = tsp->addr;

+      ULONGEST end = tsp->endaddr;

+      ULONGEST file_ofs = tsp->the_bfd_section->filepos;

+      const char *filename = bfd_get_filename (tsp->the_bfd_section->owner);

+

+      if (gdbarch_addr_bit (gdbarch) == 32)

+	printf_filtered ("\t%10s %10s %10s %10s %s\n",

+			 paddress (gdbarch, start),

+			 paddress (gdbarch, end),

+			 hex_string (end - start),

+			 hex_string (file_ofs),

+			 filename);

+      else

+	printf_filtered ("  %18s %18s %10s %10s %s\n",

+			 paddress (gdbarch, start),

+			 paddress (gdbarch, end),

+			 hex_string (end - start),

+			 hex_string (file_ofs),

+			 filename);

+    }

+}

+

+/* Implement "maintenance print core-file-backed-mappings" command.  

+

+   If mappings are loaded, the results should be similar to the

+   mappings shown by "info proc mappings".  This command is mainly a

+   debugging tool for GDB developers to make sure that the expected

+   mappings are present after loading a core file.  For Linux, the

+   output provided by this command will be very similar (if not

+   identical) to that provided by "info proc mappings".  This is not

+   necessarily the case for other OSes which might provide

+   more/different information in the "info proc mappings" output.  */

+

+static void

+maintenance_print_core_file_backed_mappings (const char *args, int from_tty)

+{

+  core_target *targ = get_current_core_target ();

+  if (targ != nullptr)

+    targ->info_proc_mappings (targ->core_gdbarch ());

+}

+

+void _initialize_corelow ();

 void

 _initialize_corelow (void)

 {

@@ -1181,4 +1265,8 @@ Set whether CORE-FILE loads the build-id associated files automatically."), _("\

 Show whether CORE-FILE loads the build-id associated files automatically."),

 			   NULL, NULL, NULL,

 			   &setlist, &showlist);

+  add_cmd ("core-file-backed-mappings", class_maintenance,

+           maintenance_print_core_file_backed_mappings,

+	   _("Print core file's file-backed mappings"),

+	   &maintenanceprintlist);

 }