[Lguest] lguest: mapping switcher would thwack fixmap

[Paul Bolle]

On Wed, 2013-04-17 at 19:22 +0930, Rusty Russell wrote:
> Paul Bolle <pebolle at tiscali.nl> writes:
> > 3) I'll search the mailing list archive for the "unhandled trap" error.
> > That looks familiar. I'm guessing it's not introduced by this patch.
> 
> OK, that's happening really early on.  Strange that it's mapping at
> 0x400000, vs 0x100000 for me...

bzImage versus vmlinux?
$ objdump -j .text -h vmlinux 

vmlinux:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00527545  c0400000  00400000  00001000  2**6
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE

> Can you send me your vmlinux and .config (offlist)?

It's related to CONFIG_OLPC:

$ objdump -j .text -d vmlinux | grep c0400062
c0400054:	74 0c                	je     c0400062 <_text+0x62>
c0400062:	0f 20 d8             	mov    %cr3,%eax

And "mov %cr3,%eax" at offset 0x62 apparently is found in
arch/x86/kernel/head_32.S:

#ifdef CONFIG_OLPC
        /* save OFW's pgdir table for later use when calling into OFW */
        movl %cr3, %eax
        movl %eax, pa(olpc_ofw_pgd)
#endif

I'm currently rebuilding with CONFIG_OLPC disabled. I hope to report
back shortly.


Paul Bolle