diff options
| author | Andy Lutomirski <luto@kernel.org> | 2016-11-19 18:42:40 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-12-08 07:15:24 +0100 |
| commit | 5a5f7030194da0c47201c04b4831f1ca623779a9 (patch) | |
| tree | 02daa076bd0daaa116b0dc0d1821d88d0dc70262 /arch/x86/kernel/head_32.S | |
| parent | 995761627d97cc374f14203589b3a6385019bf0b (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.S | 2 |
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 |