bring initial context to a known state

When GRUB starts initial_context is in an unknown state. This can lead to GRUB detecting bogus variables from it. Attached patch zeroes that struct during initialisation to avoid that.

Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call, if you are unable to speak?
(as seen on /.)

2007-10-07 Robert Millan <[email protected]>

* kern/env.c (grub_env_init): New function. Set initial_context struct to zero.
* kern/main.c (grub_main): Call grub_env_init() after grub_machine_init().

diff -ur grub2/kern/env.c grub2.env_init/kern/env.c
@@ -47,6 +47,13 @@
 /* The current context.  */
 static struct grub_env_context *current_context = &initial_context;
 
+/* Bring initial context to a known state.  */
+void
+grub_env_init ()
+{
+  grub_memset (&initial_context, 0, sizeof(initial_context));
+}
+
 /* Return the hash representation of the string S.  */
 static unsigned int
 grub_env_hashval (const char *s)

diff -ur grub2/kern/main.c grub2.env_init/kern/main.c
@@ -112,6 +112,9 @@
   /* First of all, initialize the machine.  */
   grub_machine_init ();
 
+  /* Initialize context.  */
+  grub_env_init ();
+
   /* Hello.  */
   grub_setcolorstate (GRUB_TERM_COLOR_HIGHLIGHT);
   grub_printf ("Welcome to GRUB!\n\n");

Hell[o]

This change broken command line argument handling for ieee1275. Arguments are read by grub_machine_init() in this case and zeroing is done just after that.

I guess it should be placed before grub_machine_init() to avoid this problem.

--- Marcin 'Morgoth' Kurek ---

Uhm.. Marco pointed out that it's in the ELF standard that memory is zeroed before load. So there isn't really a problem, and my issue was just found in an inconsistent situation when playing with LB self-boot.

Let's kill this thread.

Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call, if you are unable to speak?
(as seen on /.)