lkml.org 
[lkml]   [2015]   [Dec]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks
From
On Wed, Dec 30, 2015 at 3:32 PM, Tony Luck <tony.luck@gmail.com> wrote:
> Fifth is just a hack because I clearly didn't understand what I was
> doing in parts 2&3 because my new class shows up as '3' not '1'!
>
> Andy: Can you explain the assembler/linker arithmetic for the class?

Never mind ... figured it out.

The fixup entry in the extable is:

label - . + 0x2000000 - BIAS

The "label - ." part evaluates to a smallish negative value (because
the .fixup section is bundled in towards the end of .text, and the
ex_table section comes right after.

Then you add 0x20000000 to get a positive number, then *subtract*
the BIAS. I'd picked BIAS = 0x40000000 thinking that would show
up directly in class bits. But 0x1ffff000 - 0x40000000 is 0xdffff000
so bits 31 & 31 are both set, and this is class3

I switched to BIAS 0xC0000000 ... and now I get class 1 entries
(bit31=0, bit30=1).

New patch series coming soon.

-Tony


\
 
 \ /
  Last update: 2015-12-31 22:01    [W:0.079 / U:0.264 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site