On Jan 1, 2016 4:30 AM, "Tony Luck" <tony.l...@gmail.com> wrote: > > On Wed, Dec 30, 2015 at 3:32 PM, Tony Luck <tony.l...@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.
That all sounds correct. You could also just to s/UACCESS/INDIRECT/ or whatever and leave using the next bit for whoever does the uaccess part, too. After all, introducing the "uaccess" class without actually implementing it isn't very useful. > > -Tony -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
