[PATCH v4 08/15] gdb: If enabled, print line used to load EFI kernel symbols when using gdb_grub script

[Glenn Washburn]

If the macro PRINT_GDB_SYM_LOAD_CMD is non-zero, compile code which will
print the command needed to load symbols for the GRUB EFI kernel. This is
needed because EFI firmware determines where to load the GRUB EFI at
runtime, and so the relevant addresses are not known ahead of time.

The command is a custom command defined in the gdb_grub GDB script. So
GDB should be started with the script as an argument to the -x option or
sourced into an active GDB session before running the outputted command.

Co-developed-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 config.h.in               |  3 +++
 grub-core/kern/efi/efi.c  |  4 ++--
 grub-core/kern/efi/init.c | 19 ++++++++++++++++++-
 include/grub/efi/efi.h    |  2 +-
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/config.h.in b/config.h.in
index 4d1e50eba7..c31eee1bca 100644
--- a/config.h.in
+++ b/config.h.in
@@ -13,6 +13,9 @@
 #define MM_DEBUG @MM_DEBUG@
 #endif
 
+/* Define to 1 to enable printing of gdb command to load module symbols.  */
+#define PRINT_GDB_SYM_LOAD_CMD 0
+
 /* Define to 1 to enable disk cache statistics.  */
 #define DISK_CACHE_STATS @DISK_CACHE_STATS@
 #define BOOT_TIME_STATS @BOOT_TIME_STATS@
diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
index cf49d6357e..17bd06f7e6 100644
--- a/grub-core/kern/efi/efi.c
+++ b/grub-core/kern/efi/efi.c
@@ -299,7 +299,7 @@ grub_efi_get_variable (const char *var, const 
grub_efi_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;
@@ -328,7 +328,7 @@ 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 b67bc73a1b..ed3d463c8f 100644
--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -101,10 +101,24 @@ stack_protector_init (void)
 
 grub_addr_t grub_modbase;
 
+#if PRINT_GDB_SYM_LOAD_CMD
+static 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
+
 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 +141,9 @@ grub_efi_init (void)
   efi_call_4 (grub_efi_system_table->boot_services->set_watchdog_timer,
              0, 0, 0, NULL);
 
+#if PRINT_GDB_SYM_LOAD_CMD
+  grub_efi_print_gdb_info ();
+#endif
   grub_efidisk_init ();
 }
 
diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
index e61272de53..586ac856b5 100644
--- a/include/grub/efi/efi.h
+++ b/include/grub/efi/efi.h
@@ -109,7 +109,7 @@ grub_err_t grub_arch_efi_linux_boot_image(grub_addr_t addr, 
grub_size_t size,
                                            char *args);
 #endif
 
-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);
-- 
2.34.1