grub2/SOURCES/0152-Simplify-BLS-entry-key-val-pairs-lookup.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Fri, 11 May 2018 23:47:31 +0200
Subject: [PATCH] Simplify BLS entry key val pairs lookup

The <key,value> pairs found in the BLS are being sorted but this isn't
really needed and it makes the implementation complex and error prone.

For example, the current implementation has the following issues:

1) Fields not present in the grub2 menu entry

  linux /linuz
  initrd /foo
  initrd /bar

  load_video
  set gfx_payload=keep
  insmod gzio
  linux /boot/linuz
  initrd /boot/bar

2) Fields present but in the wrong order

  title Fedora (4.16.6-300.fc28.x86_64-tuned) 28 (Twenty Eight)
  version 4.16.6-300.fc28.x86_64
  linux /vmlinuz-4.16.6-300.fc28.x86_64
  initrd /foo.img
  initrd /bar.img
  options $kernelopts
  id fedora-20180430150025-4.16.6-300.fc28.x86_64

  load_video
  set gfx_payload=keep
  insmod gzio
  linux /boot/vmlinuz-4.16.6-300.fc28.x86_64 $kernelopts
  initrd /boot/bar.img /boot/foo.img

It's important to preserve the order in which fields have been defined
in the BLS fragment since for some of the fields the order has meaning.
For example, initramfs images have to be passed to the kernel in order
that were defined in the BLS fragment.

This patch simplifies the <key,value> pairs storage and lookup. Rather
than sorting and attempt to later figure out what's the expected order,
just store it in the same order as they were defined in the BLS config
file and return in that same order to callers when these look them up.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
 grub-core/commands/blscfg.c | 88 ++++++++++-----------------------------------
 1 file changed, 18 insertions(+), 70 deletions(-)

diff --git a/grub-core/commands/blscfg.c b/grub-core/commands/blscfg.c
index c52d2b2e0..fb08d8e4c 100644
--- a/grub-core/commands/blscfg.c
+++ b/grub-core/commands/blscfg.c
@@ -169,84 +169,35 @@ static void bls_free_entry(struct bls_entry *entry)
   grub_free (entry);
 }
 
-static int keyval_cmp (const void *p0, const void *p1,
-		       void *state UNUSED)
-{
-  const struct keyval *kv0 = *(struct keyval * const *)p0;
-  const struct keyval *kv1 = *(struct keyval * const *)p1;
-  int rc;
-
-  rc = grub_strcmp(kv0->key, kv1->key);
-
-  return rc;
-}
-
 /* Find they value of the key named by keyname.  If there are allowed to be
  * more than one, pass a pointer to an int set to -1 the first time, and pass
  * the same pointer through each time after, and it'll return them in sorted
- * order. */
+ * order as defined in the BLS fragment file */
 static char *bls_get_val(struct bls_entry *entry, const char *keyname, int *last)
 {
-  char *foo = (char *)"";
-  struct keyval *kv = NULL, **kvp, key = {keyname, foo}, *keyp = &key;
+  int idx, start = 0;
+  struct keyval *kv = NULL;
 
-  /* if we've already found an entry that matches, just iterate */
-  if (last && *last >= 0)
-    {
-      int next = ++last[0];
+  if (last)
+    start = *last + 1;
 
-      if (next == entry->nkeyvals)
-	{
-done:
-	  *last = -1;
-	  return NULL;
-	}
+  for (idx = start; idx < entry->nkeyvals; idx++) {
+    kv = entry->keyvals[idx];
 
-      kv = entry->keyvals[next];
-      if (grub_strcmp (keyname, kv->key))
-	goto done;
+    if (!grub_strcmp (keyname, kv->key))
+      break;
+  }
 
-      return kv->val;
-    }
+  if (idx == entry->nkeyvals) {
+    if (last)
+      *last = -1;
+    return NULL;
+  }
 
-  kvp = grub_bsearch(&keyp, &entry->keyvals[0], entry->nkeyvals,
-		    sizeof (struct keyval *), keyval_cmp, NULL);
-  if (kvp)
-    kv = *kvp;
+  if (last)
+    *last = idx;
 
-  if (kv)
-    {
-      /* if we've got uninitialized but present state, track back until we find
-       * the first match */
-      if (last)
-	{
-	  grub_dprintf("blscfg", "%s trying to find another entry because last was set\n", __func__);
-	  /* figure out the position of this entry in the array */
-	  int idx;
-	  for (idx = 0 ; idx < entry->nkeyvals; idx++)
-	    if (entry->keyvals[idx] == kv)
-	      break;
-	  *last = idx;
-
-	  while (idx > 0)
-	    {
-	      struct keyval *kvtmp = entry->keyvals[idx-1];
-	      if (idx == 0 || grub_strcmp (keyname, kvtmp->key))
-		{
-		  /* if we're at the start, or if the previous entry doesn't
-		   * match, then we're done */
-		  *last = idx;
-		  break;
-		}
-	      else
-		/* but if it does match, keep going backwards */
-		idx--;
-	    }
-	}
-
-      return kv->val;
-    }
-  return NULL;
+  return kv->val;
 }
 
 #define goto_return(x) ({ ret = (x); goto finish; })
@@ -503,9 +454,6 @@ static int read_entry (
 	break;
     }
 
-  grub_qsort(&entry->keyvals[0], entry->nkeyvals, sizeof (struct keyval *),
-	     keyval_cmp, NULL);
-
 finish:
   grub_free (p);