On Tue, Aug 27, 2013 at 04:07:49PM +1000, Paul Mackerras wrote: > On 64-bit, __pa(&static_var) gets miscompiled by recent versions of > gcc as something like: > > addis 3,2,.LANCHOR1+4611686018427387904@toc@ha > addi 3,3,.LANCHOR1+4611686018427387904@toc@l
I might argue that this isn't a miscompilation, since -mcmodel=medium assumes everything can be accessed within +/-2G of the toc pointer, but it's definitely a problem since gas and/or ld don't give an overflow error. They would except for the fact that our ABI has a hole in it. We have relocs that error on 16-bit overflow, eg. addi 3,2,x@toc will give an error if x is more than +/-32k from the toc pointer, but @ha and _HA/_HI relocs don't error on 32-bit overflow. (They can't, because they were really designed to be used in HIHGESTA, HIGHERA, HA, LO sequences to build up 64-bit values.) The proper fix is to define a whole slew of new relocations and reloc specifiers, and modify everything to use them, but that seems like too much bother. I had ideas once upon a time to implement gas and ld options that makes @ha and _HA report overflows, but haven't found one of those round tuits. -- Alan Modra Australia Development Lab, IBM _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
