gdb: Add gdbinfo command for printing the load address of the EFI application

EFI firmware determines where to load the GRUB EFI at runtime, and so the
addresses of debug symbols are not known ahead of time. There is a command
defined in the gdb_grub script which will load the debug symbols at the
appropriate addresses, if given the application load address for GRUB.
So add a command named "gdbinfo" to allow the user to print this GDB command
string with the application load address on-demand. For the outputted GDB
command to have any effect when entered into a GDB session, GDB should have
been started with the script as an argument to the -x option or sourced into
an active GDB session before running the outputted command.

Documentation for the gdbinfo command is also added.

Co-developed-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/docs/grub.texi b/docs/grub.texi
index 058b0eaafb3e0a5cf97552bb798c1ff381b53659..9b58886a9086a902c883ec9b63648119ccd81427 100644 (file)
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -4324,6 +4324,7 @@ you forget a command, you can run the command @command{help}
 * export::                      Export an environment variable
 * false::                       Do nothing, unsuccessfully
 * fwsetup::                     Reboot into the firmware setup menu
+* gdbinfo::                     Provide info for debugging with GDB
 * gettext::                     Translate a string
 * gptsync::                     Fill an MBR based on GPT entries
 * halt::                        Shut down your computer
@@ -4856,6 +4857,18 @@ exit successfully if so.
 @end deffn
 
 
+@node gdbinfo
+@subsection gdbinfo
+
+@deffn Command gdbinfo
+Output text to be used as a GDB command for a GDB session using the gdb_grub
+script and attached to a running GRUB instance. The GDB command that is
+output will tell GDB how to load debugging symbols to their proper runtime
+address. Currently this is only available for EFI platforms. See the Debugging
+in the developer documentation for more information.
+@end deffn
+
+
 @node gettext
 @subsection gettext
 

diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index a8c0c4a528b57f3d8461d9dae369aac5e3e1815c..e458aa665574de30996fbbacf0aecf529e2a553c 100644 (file)
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -211,6 +211,7 @@ kernel = {
 
   efi = disk/efi/efidisk.c;
   efi = kern/efi/efi.c;
+  efi = kern/efi/debug.c;
   efi = kern/efi/init.c;
   efi = kern/efi/mm.c;
   efi = term/efi/console.c;

diff --git a/grub-core/kern/efi/debug.c b/grub-core/kern/efi/debug.c
new file mode 100644 (file)
index 0000000..5d2ab1a
--- /dev/null
+++ b/grub-core/kern/efi/debug.c
@@ -0,0 +1,38 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2022  Free Software Foundation, Inc.
+ *
+ *  GRUB 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.
+ *
+ *  GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/* debug.c - aides for debugging the EFI application */
+
+#include <grub/efi/debug.h>
+#include <grub/command.h>
+#include <grub/i18n.h>
+
+static grub_err_t
+grub_cmd_gdbinfo (struct grub_command *cmd __attribute__ ((unused)),
+                 int argc __attribute__ ((unused)),
+                 char **args __attribute__ ((unused)))
+{
+  grub_efi_print_gdb_info ();
+  return 0;
+}
+
+void
+grub_efi_register_debug_commands (void)
+{
+  grub_register_command ("gdbinfo", grub_cmd_gdbinfo, 0,
+                        N_("Print infomation useful for GDB debugging"));
+}

diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
index f54fdcacd9b0a9c450f9c69f0deba4b7d34d9943..a2afd8de990abd2be96082d8eb51feb2d304ab77 100644 (file)
--- a/grub-core/kern/efi/efi.c
+++ b/grub-core/kern/efi/efi.c
@@ -320,7 +320,7 @@ grub_efi_get_variable (const char *var, const grub_guid_t *guid,
 /* Search the mods section from the PE32/PE32+ image. This code uses
    a PE32 header, but should work with PE32+ as well.  */
 grub_addr_t
-grub_efi_modules_addr (void)
+grub_efi_section_addr (const char *section_name)
 {
   grub_efi_loaded_image_t *image;
   struct grub_msdos_image_header *header;
@@ -349,7 +349,7 @@ grub_efi_modules_addr (void)
        i < coff_header->num_sections;
        i++, section++)
     {
-      if (grub_strcmp (section->name, "mods") == 0)
+      if (grub_strcmp (section->name, section_name) == 0)
        break;
     }
 

diff --git a/grub-core/kern/efi/init.c b/grub-core/kern/efi/init.c
index 8a9c838c00bf387b789857b6ca5b02353caef0e2..6fe1ff8c868e7911146ce85aa32a0d8f61b8212d 100644 (file)
--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -19,6 +19,7 @@
 
 #include <grub/efi/efi.h>
 #include <grub/efi/console.h>
+#include <grub/efi/debug.h>
 #include <grub/efi/disk.h>
 #include <grub/efi/sb.h>
 #include <grub/lockdown.h>
@@ -104,7 +105,7 @@ grub_addr_t grub_modbase;
 void
 grub_efi_init (void)
 {
-  grub_modbase = grub_efi_modules_addr ();
+  grub_modbase = grub_efi_section_addr ("mods");
   /* First of all, initialize the console so that GRUB can display
      messages.  */
   grub_console_init ();
@@ -127,6 +128,8 @@ grub_efi_init (void)
   grub_efi_system_table->boot_services->set_watchdog_timer (0, 0, 0, NULL);
 
   grub_efidisk_init ();
+
+  grub_efi_register_debug_commands ();
 }
 
 void (*grub_efi_net_config) (grub_efi_handle_t hnd,

diff --git a/include/grub/efi/debug.h b/include/grub/efi/debug.h
new file mode 100644 (file)
index 0000000..c2d2a03
--- /dev/null
+++ b/include/grub/efi/debug.h
@@ -0,0 +1,41 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2022  Free Software Foundation, Inc.
+ *
+ *  GRUB 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.
+ *
+ *  GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/* debug.h - declare variables and functions for EFI debugging support */
+
+#ifndef GRUB_EFI_DEBUG_HEADER
+#define GRUB_EFI_DEBUG_HEADER  1
+
+#include <grub/efi/efi.h>
+#include <grub/misc.h>
+
+
+void grub_efi_register_debug_commands (void);
+
+static inline void
+grub_efi_print_gdb_info (void)
+{
+  grub_addr_t text;
+
+  text = grub_efi_section_addr (".text");
+  if (!text)
+    return;
+
+  grub_printf ("dynamic_load_symbols %p\n", (void *)text);
+}
+
+#endif /* ! GRUB_EFI_DEBUG_HEADER */

diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
index cd977cbbcfb08bb4ad8653bd2f1a5c7cdfd7870f..572f7135f1c2775519e96197d31b81785d214c3a 100644 (file)
--- a/include/grub/efi/efi.h
+++ b/include/grub/efi/efi.h
@@ -129,7 +129,7 @@ grub_err_t grub_arch_efi_linux_load_image_header(grub_file_t file,
 grub_err_t grub_arch_efi_linux_boot_image(grub_addr_t addr, grub_size_t size,
                                            char *args);
 
-grub_addr_t grub_efi_modules_addr (void);
+grub_addr_t grub_efi_section_addr (const char *section);
 
 void grub_efi_mm_init (void);
 void grub_efi_mm_fini (void);