Re: [PATCH 1/3] x86, ras: Add new infrastructure for machine check fixup tables

Andy Lutomirski
2015-11-12T04:15:00Z

On 11/06/2015 12:57 PM, Tony Luck wrote:
> Copy the existing page fault fixup mechanisms to create a new table
> to be used when fixing machine checks. Note:
> 1) At this time we only provide a macro to annotate assembly code
> 2) We assume all fixups will in code builtin to the kernel.

Shouldn't the first step be to fixup failures during user memory access?

>
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
> arch/x86/include/asm/asm.h | 7 +++++++
> arch/x86/include/asm/uaccess.h | 1 +
> arch/x86/mm/extable.c | 16 ++++++++++++++++
> include/asm-generic/vmlinux.lds.h | 6 ++++++
> include/linux/module.h | 1 +
> kernel/extable.c | 14 ++++++++++++++
> 6 files changed, 45 insertions(+)
>
> diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
> index 189679aba703..f2fa7973f18f 100644
> --- a/arch/x86/include/asm/asm.h
> +++ b/arch/x86/include/asm/asm.h
> @@ -58,6 +58,13 @@
> .long (to) - . + 0x7ffffff0 ; \
> .popsection
>
> +# define _ASM_MCEXTABLE(from, to) \
> + .pushsection "__mcex_table", "a" ; \
> + .balign 8 ; \
> + .long (from) - . ; \
> + .long (to) - . ; \
> + .popsection
> +

This does something really weird to rax. (Also, what happens on 32-bit
kernels? There's no bit 63.)

Please at least document it clearly.

--Andy