linux 2.6.27 kernel panic on x86 - please revert commit3a85e770aa77e4f1a4096275c97b64c10cd7323e

[Jeff Chua]

Commit 3a85e770aa77e4f1a4096275c97b64c10cd7323e broke linux boot on x86 
resulting in kernel panic. Here's the console output ...

Net: Registered protocol family 17
Using IPI No-Shortcut mode
RAMDISK: Compressed image found at block 0
VFS: Mounted root (ext2 filesystem (readonly).
Freeing unsued kernel memory: 312k freed
init[1]: segfault at ffffe01c up b7f0dc28 sp bfc26628 error 5 in ld-2.7.90.so[b7f0b000+1c000]
Kernel panic - not syncing: Attempted to kill init!


Thanks,
Jeff.


Please revert this ...

commit 3a85e770aa77e4f1a4096275c97b64c10cd7323e
Author: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Date:   Tue Sep 23 14:00:37 2008 -0700

    x86, cpa: remove USER permission from the very early identity mapping attribute

    remove USER from the PTE/PDE attributes for the very early identity
    mapping. We overwrite these mappings with KERNEL attribute later
    in the boot. Just being paranoid here as there is no need for USER bit
    to be set.

    If this breaks something(don't know the history), then we can simply drop
    this change.

    Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
    Cc: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
    Cc: arjan@xxxxxxxxxxxxxxx
    Cc: venkatesh.pallipadi@xxxxxxxxx
    Cc: jeremy@xxxxxxxx
    Signed-off-by: Ingo Molnar <mingo@xxxxxxx>

diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index 0ff73e7..bbf0f59 100644
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -138,8 +138,8 @@
 #ifdef CONFIG_X86_64
 #define __PAGE_KERNEL_IDENT_LARGE_EXEC	__PAGE_KERNEL_LARGE_EXEC
 #else
-#define PTE_IDENT_ATTR	 0x007		/* PRESENT+RW+USER */
-#define PDE_IDENT_ATTR	 0x067		/* PRESENT+RW+USER+DIRTY+ACCESSED */
+#define PTE_IDENT_ATTR	 0x003		/* PRESENT+RW */
+#define PDE_IDENT_ATTR	 0x063		/* PRESENT+RW+DIRTY+ACCESSED */
 #define PGD_IDENT_ATTR	 0x001		/* PRESENT (no other attributes) */
 #endif

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