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authorAndy Lutomirski <luto@kernel.org>2016-11-19 18:42:40 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-12-08 07:15:24 +0100
commit5a5f7030194da0c47201c04b4831f1ca623779a9 (patch)
tree02daa076bd0daaa116b0dc0d1821d88d0dc70262 /arch/x86/kernel/head_32.S
parent995761627d97cc374f14203589b3a6385019bf0b (diff)
x86/traps: Ignore high word of regs->cs in early_fixup_exception()
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 <hpa@zytor.com> Reported-by: Matthew Whitehead <tedheadster@gmail.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kernel/head_32.S')
-rw-r--r--arch/x86/kernel/head_32.S2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 6bc9ae24b6d2..8f1a3f443f7d 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -571,7 +571,7 @@ 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