[PATCH 4/7] Use envblk file and fs functions to implement reading the grubenv file from special FS regions

[Paul Dagnelie]

This patch modifies the loadenv command to take advantage of the new envblock
functions provided by a previous patch. These functions will be used instead
of the normal file-based functions if the boot filesystem is detected to
support them. There is also a config variable, grubenv_src, that can be used
to force the file or envblock logic to be used.

Signed-off-by: Paul Dagnelie <address@hidden>
---
 grub-core/commands/loadenv.c | 122 ++++++++++++++++++++++++++++++-----
 include/grub/lib/envblk.h    |   2 +
 2 files changed, 109 insertions(+), 15 deletions(-)

diff --git a/grub-core/commands/loadenv.c b/grub-core/commands/loadenv.c
index 3fd664aac..66f5345ec 100644
--- a/grub-core/commands/loadenv.c
+++ b/grub-core/commands/loadenv.c
@@ -79,6 +79,94 @@ open_envblk_file (char *filename,
   return file;
 }
 
+static grub_file_t
+open_envblk_block (grub_fs_t fs, grub_device_t dev, enum grub_file_type type)
+{
+  if (fs->fs_envblk_open)
+    return grub_file_envblk_open(fs, dev, type);
+  return NULL;
+}
+
+static grub_file_t
+open_envblk (grub_extcmd_context_t ctxt, enum grub_file_type type)
+{
+  struct grub_arg_list *state = ctxt->state;
+  grub_file_t file = NULL;
+  grub_device_t device = NULL;
+  const char *source;
+  grub_fs_t fs = NULL;
+  char *filename = state[0].set ? state[0].arg : NULL;
+
+  source = grub_env_get ("grubenv_src");
+  if (! source || ! grub_strcmp (source, GRUB_ENVBLK_SRC_BLK))
+    {
+      char *device_name;
+      const char *prefix;
+      grub_dprintf ("loadenv", "checking for envblk\n");
+
+      prefix = grub_env_get ("prefix");
+      if (! prefix)
+        {
+          grub_error (GRUB_ERR_FILE_NOT_FOUND, N_("variable `%s' isn't set"), 
"prefix");
+          return NULL;
+        }
+
+      device_name = grub_file_get_device_name (prefix);
+      if (grub_errno)
+       return NULL;
+
+      device = grub_device_open (device_name);
+      if (! device)
+       return NULL;
+
+      fs = grub_fs_probe (device);
+      if (! fs) {
+        grub_device_close (device);
+       return NULL;
+      }
+
+      /* We have to reopen the device here because it was closed in 
grub_fs_probe. */
+      device = grub_device_open (device_name);
+      grub_free (device_name);
+      if (! device)
+       return NULL;
+
+    }
+  if (! source)
+    {
+      if (fs->fs_envblk_open)
+       {
+         source = GRUB_ENVBLK_SRC_BLK;
+         grub_dprintf ("loadenv", "envblk support detected\n");
+       }
+      else
+       {
+         source = GRUB_ENVBLK_SRC_FILE;
+         grub_dprintf ("loadenv", "envblk support not detected\n");
+       }
+    }
+
+  if (! grub_strcmp (source, GRUB_ENVBLK_SRC_FILE))
+    {
+      if (device)
+        grub_device_close (device);
+      file = open_envblk_file (filename, type);
+
+      if (! file)
+       return NULL;
+    }
+  else if (! grub_strcmp (source, GRUB_ENVBLK_SRC_BLK))
+    {
+      file = open_envblk_block (fs, device, type);
+      if (! file)
+       {
+         grub_device_close (device);
+         return NULL;
+       }
+    }
+  return file;
+}
+
 static grub_envblk_t
 read_envblk_file (grub_file_t file)
 {
@@ -165,11 +253,10 @@ grub_cmd_load_env (grub_extcmd_context_t ctxt, int argc, 
char **args)
   whitelist.len = argc;
   whitelist.list = args;
 
-  /* state[0] is the -f flag; state[1] is the --skip-sig flag */
-  file = open_envblk_file ((state[0].set) ? state[0].arg : 0,
-                          GRUB_FILE_TYPE_LOADENV
-                          | (state[1].set
-                             ? GRUB_FILE_TYPE_SKIP_SIGNATURE : 
GRUB_FILE_TYPE_NONE));
+  file = open_envblk (ctxt, GRUB_FILE_TYPE_LOADENV
+                            | (state[1].set
+                              ? GRUB_FILE_TYPE_SKIP_SIGNATURE :
+                              GRUB_FILE_TYPE_NONE));
   if (! file)
     return grub_errno;
 
@@ -204,10 +291,9 @@ grub_cmd_list_env (grub_extcmd_context_t ctxt,
   grub_file_t file;
   grub_envblk_t envblk;
 
-  file = open_envblk_file ((state[0].set) ? state[0].arg : 0,
-                          GRUB_FILE_TYPE_LOADENV
-                          | (state[1].set
-                             ? GRUB_FILE_TYPE_SKIP_SIGNATURE : 
GRUB_FILE_TYPE_NONE));
+  file = open_envblk (ctxt, GRUB_FILE_TYPE_LOADENV
+                           | (state[1].set
+                              ? GRUB_FILE_TYPE_SKIP_SIGNATURE : 
GRUB_FILE_TYPE_NONE));
   if (! file)
     return grub_errno;
 
@@ -379,7 +465,6 @@ save_env_read_hook (grub_disk_addr_t sector, unsigned 
offset, unsigned length,
 static grub_err_t
 grub_cmd_save_env (grub_extcmd_context_t ctxt, int argc, char **args)
 {
-  struct grub_arg_list *state = ctxt->state;
   grub_file_t file;
   grub_envblk_t envblk;
   struct grub_cmd_save_env_ctx ctx = {
@@ -390,9 +475,8 @@ grub_cmd_save_env (grub_extcmd_context_t ctxt, int argc, 
char **args)
   if (! argc)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, "no variable is specified");
 
-  file = open_envblk_file ((state[0].set) ? state[0].arg : 0,
-                          GRUB_FILE_TYPE_SAVEENV
-                          | GRUB_FILE_TYPE_SKIP_SIGNATURE);
+  file = open_envblk (ctxt, GRUB_FILE_TYPE_SAVEENV
+                           | GRUB_FILE_TYPE_SKIP_SIGNATURE);
   if (! file)
     return grub_errno;
 
@@ -409,7 +493,7 @@ grub_cmd_save_env (grub_extcmd_context_t ctxt, int argc, 
char **args)
   if (! envblk)
     goto fail;
 
-  if (check_blocklists (envblk, ctx.head, file))
+  if (! grub_file_envblk (file) && check_blocklists (envblk, ctx.head, file))
     goto fail;
 
   while (argc)
@@ -432,7 +516,15 @@ grub_cmd_save_env (grub_extcmd_context_t ctxt, int argc, 
char **args)
       args++;
     }
 
-  write_blocklists (envblk, ctx.head, file);
+  if (grub_file_envblk (file))
+    {
+      grub_file_seek (file, 0);
+      file->fs->fs_envblk_write (file, grub_envblk_buffer (envblk), 
grub_envblk_size (envblk));
+    }
+  else
+    {
+      write_blocklists (envblk, ctx.head, file);
+    }
 
  fail:
   if (envblk)
diff --git a/include/grub/lib/envblk.h b/include/grub/lib/envblk.h
index c3e655921..287c87105 100644
--- a/include/grub/lib/envblk.h
+++ b/include/grub/lib/envblk.h
@@ -21,6 +21,8 @@
 
 #define GRUB_ENVBLK_SIGNATURE  "# GRUB Environment Block\n"
 #define GRUB_ENVBLK_DEFCFG     "grubenv"
+#define GRUB_ENVBLK_SRC_BLK    "block"
+#define GRUB_ENVBLK_SRC_FILE   "file"
 
 #ifndef ASM_FILE
 
-- 
2.19.0