[PATCH v2 2/2] Make a "gdb" dprintf that tells us load addresses

[Robbie Harwood]

From: Peter Jones <pjones@redhat.com>

Add a grub_dprintf() call during platform init and during module loading
that tells us the virtual addresses of the .text and .data sections of
grub-core/kernel.exec and any modules it loads.

Specifically, it displays them in the gdb "add-symbol-file" syntax, with
the presumption that there's a variable $grubdir that reflects the path
to any such binaries.

Signed-off-by: Peter Jones <pjones@redhat.com>
[rharwood@redhat.com: remove custom function, adjust commit message]
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
---
 grub-core/kern/dl.c       | 50 +++++++++++++++++++++++++++++++++++++++
 grub-core/kern/efi/efi.c  |  4 ++--
 grub-core/kern/efi/init.c | 26 +++++++++++++++++++-
 include/grub/efi/efi.h    |  2 +-
 4 files changed, 78 insertions(+), 4 deletions(-)

diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
index 6a52de168..a5def4ea3 100644
--- a/grub-core/kern/dl.c
+++ b/grub-core/kern/dl.c
@@ -447,6 +447,23 @@ grub_dl_find_section (Elf_Ehdr *e, const char *name)
       return s;
   return NULL;
 }
+static long
+grub_dl_find_section_index (Elf_Ehdr *e, const char *name)
+{
+  Elf_Shdr *s;
+  const char *str;
+  unsigned i;
+
+  s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
+  str = (char *) e + s->sh_offset;
+
+  for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
+       i < e->e_shnum;
+       i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
+    if (grub_strcmp (str + s->sh_name, name) == 0)
+      return (long)i;
+  return -1;
+}
 
 /* Me, Vladimir Serbinenko, hereby I add this module check as per new
    GNU module policy. Note that this license check is informative only.
@@ -607,6 +624,37 @@ grub_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
 
   return GRUB_ERR_NONE;
 }
+static void
+grub_dl_print_gdb_info (grub_dl_t mod, Elf_Ehdr *e)
+{
+  void *text, *data = NULL;
+  long idx;
+
+  idx = grub_dl_find_section_index (e, ".text");
+  if (idx < 0)
+    return;
+
+  text = grub_dl_get_section_addr (mod, idx);
+  if (!text)
+    return;
+
+  idx = grub_dl_find_section_index (e, ".data");
+  if (idx >= 0)
+    data = grub_dl_get_section_addr (mod, idx);
+
+  if (data)
+    grub_dprintf ("gdb", "add-symbol-file \\\n"
+                 "/usr/lib/debug/usr/lib/grub/%s-%s/%s.debug "
+                 "\\\n %p -s .data %p\n",
+                 GRUB_TARGET_CPU, GRUB_PLATFORM,
+                 mod->name, text, data);
+  else
+    grub_dprintf ("gdb", "add-symbol-file \\\n"
+                 "/usr/lib/debug/usr/lib/grub/%s-%s/%s.debug "
+                 "\\\n%p\n",
+                 GRUB_TARGET_CPU, GRUB_PLATFORM,
+                 mod->name, text);
+}
 
 /* Load a module from core memory.  */
 grub_dl_t
@@ -666,6 +714,8 @@ grub_dl_load_core_noinit (void *addr, grub_size_t size)
   grub_dprintf ("modules", "module name: %s\n", mod->name);
   grub_dprintf ("modules", "init function: %p\n", mod->init);
 
+  grub_dl_print_gdb_info (mod, e);
+
   if (grub_dl_add (mod))
     {
       grub_dl_unload (mod);
diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
index 8cff7be02..f12fd5893 100644
--- a/grub-core/kern/efi/efi.c
+++ b/grub-core/kern/efi/efi.c
@@ -291,7 +291,7 @@ 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_pe32_header *header;
@@ -316,7 +316,7 @@ 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 7facacf09..35f787915 100644
--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -82,10 +82,33 @@ stack_protector_init (void)
 
 grub_addr_t grub_modbase;
 
+static void
+grub_efi_print_gdb_info (void)
+{
+  grub_addr_t text;
+  grub_addr_t data;
+
+  text = grub_efi_section_addr (".text");
+  if (!text)
+    return;
+
+  data = grub_efi_section_addr (".data");
+  if (data)
+    grub_dprintf ("gdb",
+                 "add-symbol-file /usr/lib/debug/usr/lib/grub/%s-%s/"
+                 "kernel.exec %p -s .data %p\n",
+                 GRUB_TARGET_CPU, GRUB_PLATFORM, (void *)text, (void *)data);
+  else
+    grub_dprintf ("gdb",
+                 "add-symbol-file /usr/lib/debug/usr/lib/grub/%s-%s/"
+                 "kernel.exec %p\n",
+                 GRUB_TARGET_CPU, GRUB_PLATFORM, (void *)text);
+}
+
 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 ();
@@ -108,6 +131,7 @@ grub_efi_init (void)
   efi_call_4 (grub_efi_system_table->boot_services->set_watchdog_timer,
              0, 0, 0, NULL);
 
+  grub_efi_print_gdb_info ();
   grub_efidisk_init ();
 }
 
diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
index 83d958f99..73b754177 100644
--- a/include/grub/efi/efi.h
+++ b/include/grub/efi/efi.h
@@ -105,7 +105,7 @@ 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);
-- 
2.33.0