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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Wed, 18 Jul 2018 08:08:02 +0200
Subject: [PATCH] blscfg: Expand the BLS options field instead of showing its
 variables

The values of the BLS fragment fields can either be string literals or
grub2 environment variables, the latter will be expanded by grub2 when
the boot entry is selected.

But from a usability point of view, is much more convenient if the BLS
parse code expand any variables that are present in the options field.

That will allow users to select an entry in the menu by pressing the e
key and edit the kernel command line parameters. So for example instead
of showing the following:

kernel /boot/vmlinuz-4.17.0 $kernelopts

It would show something like the following:

kernel /boot/vmlinuz-4.17.0 root=UUID=cec677c9-c890-4103-b94a-bcc191642935

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
 grub-core/commands/blscfg.c | 69 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 68 insertions(+), 1 deletion(-)

diff --git a/grub-core/commands/blscfg.c b/grub-core/commands/blscfg.c
index c6addc4dc12..80d8814fc3f 100644
--- a/grub-core/commands/blscfg.c
+++ b/grub-core/commands/blscfg.c
@@ -32,6 +32,8 @@
 #include <grub/normal.h>
 #include <grub/lib/envblk.h>
 
+#include <stdbool.h>
+
 GRUB_MOD_LICENSE ("GPLv3+");
 
 #include "loadenv.h"
@@ -506,6 +508,70 @@ static char **bls_make_list (struct bls_entry *entry, const char *key, int *num)
   return list;
 }
 
+static char *field_append(bool is_var, char *buffer, char *start, char *end)
+{
+  char *temp = grub_strndup(start, end - start + 1);
+  const char *field = temp;
+
+  if (is_var) {
+    field = grub_env_get (temp);
+    if (!field)
+      return buffer;
+  }
+
+  if (!buffer) {
+    buffer = grub_strdup(field);
+    if (!buffer)
+      return NULL;
+  } else {
+    buffer = grub_realloc (buffer, grub_strlen(buffer) + grub_strlen(field));
+    if (!buffer)
+      return NULL;
+
+    grub_stpcpy (buffer + grub_strlen(buffer), field);
+  }
+
+  return buffer;
+}
+
+static char *expand_val(char *value)
+{
+  char *buffer = NULL;
+  char *start = value;
+  char *end = value;
+  bool is_var = false;
+
+  while (*value) {
+    if (*value == '$') {
+      if (start != end) {
+	buffer = field_append(is_var, buffer, start, end);
+	if (!buffer)
+	  return NULL;
+      }
+
+      is_var = true;
+      start = value + 1;
+    } else if (is_var) {
+      if (!grub_isalnum(*value) && *value != '_') {
+	buffer = field_append(is_var, buffer, start, end);
+	is_var = false;
+	start = value;
+      }
+    }
+
+    end = value;
+    value++;
+  }
+
+  if (start != end) {
+    buffer = field_append(is_var, buffer, start, end);
+    if (!buffer)
+      return NULL;
+  }
+
+  return buffer;
+}
+
 static void create_entry (struct bls_entry *entry)
 {
   int argc = 0;
@@ -536,7 +602,7 @@ static void create_entry (struct bls_entry *entry)
     }
 
   title = bls_get_val (entry, "title", NULL);
-  options = bls_get_val (entry, "options", NULL);
+  options = expand_val (bls_get_val (entry, "options", NULL));
   initrds = bls_make_list (entry, "initrd", NULL);
 
   hotkey = bls_get_val (entry, "grub_hotkey", NULL);
@@ -594,6 +660,7 @@ static void create_entry (struct bls_entry *entry)
 finish:
   grub_free (initrd);
   grub_free (initrds);
+  grub_free (options);
   grub_free (classes);
   grub_free (args);
   grub_free (argv);