v2: Add GRUB_FILE_TYPE_CONFIG to grub_file_open, see also upstream commit
ca0a4f689 verifiers: File type for fine-grained signature-verification controlling

--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -28,6 +28,7 @@
 #include <grub/env.h>
 #include <grub/mm.h>
 #include <grub/kernel.h>
+#include <grub/file.h>
 #include <grub/stack_protector.h>
 
 #ifdef GRUB_STACK_PROTECTOR
@@ -135,6 +136,67 @@
 void (*grub_efi_net_config) (grub_efi_handle_t hnd,
 			     char **device,
 			     char **path);
+static char *
+workaround_efi_firmware_path (const char *device, const char *path)
+{
+  char *config = NULL;;
+  char *config_upper = NULL;
+  char *path_upper = NULL;
+  char *ret_path = NULL;
+  grub_file_t config_fd = NULL;
+  char *s;
+
+  if (!device || !path)
+    return NULL;
+
+  /* only workaround if booting off from cd device */
+  if (grub_strncmp (device, "cd", 2) != 0)
+    goto quit;
+
+  config = grub_xasprintf ("(%s)%s/grub.cfg", device, path);
+  config_fd = grub_file_open (config, GRUB_FILE_TYPE_CONFIG);
+
+  /* everything's fine, so quit the workaround */
+  if (config_fd)
+    goto quit;
+
+  /* reset grub error state because noone else does... */
+  grub_errno = GRUB_ERR_NONE;
+
+  /* try again, this time upper case path */
+  path_upper = grub_strdup (path);
+  if (! path_upper)
+    goto quit;
+
+  s = path_upper;
+  for (; *s; s++) *s = grub_toupper(*s);
+
+  config_upper = grub_xasprintf ("(%s)%s/grub.cfg", device, path_upper);
+  if (! config_upper)
+    goto quit;
+
+  config_fd = grub_file_open (config_upper, GRUB_FILE_TYPE_CONFIG);
+
+  /* if config can be found by the upper case path, return it */
+  if (config_fd)
+    ret_path = grub_strdup (path_upper);
+
+quit:
+
+  if (config_fd)
+    grub_file_close (config_fd);
+
+  if (grub_errno)
+    grub_errno = GRUB_ERR_NONE;
+
+  if (config)
+    grub_free (config);
+
+  if (config_upper)
+    grub_free (config_upper);
+
+  return ret_path;
+}
 
 void
 grub_machine_get_bootlocation (char **device, char **path)
@@ -159,6 +221,12 @@
       p = grub_strrchr (*path, '/');
       if (p)
         *p = '\0';
+
+      if ((p = workaround_efi_firmware_path (*device, *path)))
+	{
+	  grub_free (*path);
+	  *path = p;
+	}
     }
 }