On Wed, Jan 27, 2016 at 11:28:09PM +1030, Alan Modra wrote: > On Wed, Jan 27, 2016 at 09:19:27PM +1100, Michael Ellerman wrote: > > > > Can we use r11 instead? eg: > > > > _GLOBAL(_mcount) > > mflr r11 > > mtctr r11 > > mtlr r0 > > bctr > > Depends on what you need to support. As Torsten says, the code to > call _mcount when -mprofile-kernel is emitted before the prologue of a > function (similar to -m32), but after the ELFv2 global entry point > code. If you trash r11 here you're killing the static chain pointer, > used by C nested functions or other languages that use a static chain, > eg. Pascal. r11 has *not* been saved for ELFv2. Even if nested functions aren't supported in the Linux kernel(?), I think it was an earlier version of mcount when r11 usage ruined my day. > r12 might be a better choice for a temp reg. Good idea. r12 holds the function entry point and is used to calculate the new TOC value just _before_ the call. It should be available. I'll try, thanks for the hint. Torsten -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
