[PATCH v3 7/8] dl: Add support for persistent modules

[Daniel Kiper <daniel.kiper@oracle.com>]

This type of modules cannot be unloaded. This is useful if a given
functionality, e.g. UEFI secure boot shim signature verification, should
not be disabled if it was enabled at some point in time. Somebody may
say that we can use standalone GRUB2 here. That is true. However, the
code is not so big nor complicated hence it make sense to support
modularized configs too.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/commands/minicmd.c |    3 +++
 include/grub/dl.h            |   13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/grub-core/commands/minicmd.c b/grub-core/commands/minicmd.c
index fc20c65..6bbce31 100644
--- a/grub-core/commands/minicmd.c
+++ b/grub-core/commands/minicmd.c
@@ -137,6 +137,9 @@ grub_mini_cmd_rmmod (struct grub_command *cmd __attribute__ ((unused)),
   if (! mod)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, "no such module");
 
+  if (grub_dl_is_persistent (mod))
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "cannot unload persistent module");
+
   if (grub_dl_unref (mod) <= 0)
     grub_dl_unload (mod);
 
diff --git a/include/grub/dl.h b/include/grub/dl.h
index 2bca56c..fee27a1 100644
--- a/include/grub/dl.h
+++ b/include/grub/dl.h
@@ -175,6 +175,7 @@ struct grub_dl
 {
   char *name;
   int ref_count;
+  int persistent;
   grub_dl_dep_t dep;
   grub_dl_segment_t segment;
   Elf_Sym *symtab;
@@ -240,6 +241,18 @@ grub_dl_get (const char *name)
   return 0;
 }
 
+static inline void
+grub_dl_set_persistent (grub_dl_t mod)
+{
+  mod->persistent = 1;
+}
+
+static inline int
+grub_dl_is_persistent (grub_dl_t mod)
+{
+  return mod->persistent;
+}
+
 #endif
 
 grub_err_t grub_dl_register_symbol (const char *name, void *addr,
-- 
1.7.10.4