>>> Andy Lutomirski <l...@amacapital.net> 11/04/14 8:33 PM >>> >On 11/04/2014 12:49 AM, Jan Beulich wrote: >> Observing that per-CPU data (in the SMP case) is reachable by >> exploiting 64-bit address wraparound, these two patches >> arrange for using the one byte shorter RIP-relative addressing >> forms for the majority of per-CPU accesses. >> >> 1: handle PC-relative relocations on per-CPU data >> 2: use RIP-relative addressing for most per-CPU accesses >> >> Signed-off-by: Jan Beulich <jbeul...@suse.com> >> > >I'm lost here. Can you give an example of a physical and virtual >address of an instruction, the address within the gs segment, and why >the relocations are backwards?
When an instruction using RIP relative addressing gets moved up in address space, the distance to the target address decreases. I.e. it's the opposite of a normal, non-PC-relative base relocation (where the target address increases together with the instruction getting moved up). Jan -- 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/
