[DEBUG 1/2] misc: Allow selective disabling of debug conditionals

[Glenn Washburn]

Sometimes you know only know which debug logging conditionals you want to
turn off, not necessarily all the ones you want enabled. This patch allows
the debug string to contain conditionals in the $debug variable which are
prefixed with a "-" to disable debug log messages for that conditional. This
is only significant when "all" is a word in the comma-separated list of the
$debug variable. Say you want all debug logging on except for btrfs and
scripting, then do "set debug=all,-btrfs,-scripting".

Note, only the first occurance of the conditional is searched for to
determine if the conditional is enabled. So simply appending ",-conditional"
to the $debug variable may not disable that conditional, if, for example,
the conditional is already present. To illustrate, the command
"set debug=all,btrfs,-scripting,-btrfs" will not disable btrfs.

Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 grub-core/kern/misc.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/grub-core/kern/misc.c b/grub-core/kern/misc.c
index 3af336ee2..ecef4839e 100644
--- a/grub-core/kern/misc.c
+++ b/grub-core/kern/misc.c
@@ -162,13 +162,28 @@ __attribute__ ((alias("grub_printf")));
 int
 grub_debug_enabled (const char * condition)
 {
-  const char *debug;
+  const char *debug, *found;
+  char found_end;
 
   debug = grub_env_get ("debug");
   if (!debug)
     return 0;
 
-  if (grub_strword (debug, "all") || grub_strword (debug, condition))
+  if (grub_strword (debug, "all"))
+    {
+      if (debug[3] == '\0')
+       return 1;
+      found = grub_strstr (debug, condition);
+      /* If found conditional is preceeded by a '-' and whole, disable debug */
+      if (found > debug && *(found-1) == '-')
+       {
+         found_end = *(found + grub_strlen (condition));
+         if (found_end == '\0' || grub_iswordseparator (found_end))
+           return 0;
+       }
+      return 1;
+    }
+  else if (grub_strword (debug, condition))
     return 1;
 
   return 0;
-- 
2.27.0