From: Andy Lutomirski <[email protected]>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit fc0e81b2bea0ebceb71889b61d2240856141c9ee upstream.
On the 80486 DX, it seems that some exceptions may leave garbage in
the high bits of CS. This causes sporadic failures in which
early_fixup_exception() refuses to fix up an exception.
As far as I can tell, this has been buggy for a long time, but the
problem seems to have been exacerbated by commits:
1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")
e1bfc11c5a6f ("x86/init: Fix cr4_init_shadow() on CR4-less machines")
This appears to have broken for as long as we've had early
exception handling.
[ This backport should apply to kernels from 3.4 - 4.5. ]
Fixes: 4c5023a3fa2e ("x86-32: Handle exception table entries during early boot")
Cc: H. Peter Anvin <[email protected]>
Reported-by: Matthew Whitehead <[email protected]>
Signed-off-by: Andy Lutomirski <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
arch/x86/kernel/head_32.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 30a2aa3782fa..879e67acf463 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -564,7 +564,7 @@ early_idt_handler_common:
movl %eax,%ds
movl %eax,%es
- cmpl $(__KERNEL_CS),32(%esp)
+ cmpw $(__KERNEL_CS),32(%esp)
jne 10f
leal 28(%esp),%eax # Pointer to %eip
--
2.11.0
