Hi, On Wed, Sep 22, 2010 at 2:04 PM, Loïc Minier <loic.min...@linaro.org> wrote: > On Wed, Sep 22, 2010, Dave Martin wrote: >> I'm not a toolchain expert, so I'm happy to be overridden... but my >> _guess_ is: >> >> I think that in practice (at least on arm) cc -fPIC = cc -fPIE, and ld >> -pie just forces ld to generate PIC veneers (as for -shared). Beyond >> this, I think ld -shared / -pie / (nothing) probably just changes >> which linker script is used by default. U-Boot overrides the default >> with its own linker script anyway, so it may make no difference. > > Catching up on email, I just came across: > http://article.gmane.org/gmane.comp.boot-loaders.u-boot/84789 > so it seems to be different, but not significantly
Hmmm, interesting discussion: looks like my guess was naive ;) It looks like -fPIE provides some savings after all, since it enables the compiler to make some additional assumptions. > I don't care too strongly, but it might make sense to try to use the > flag which means exactly what we want to allow for future > optimizations? Since U-Boot is now trying to build PIC anyway, I suggest that for things to work robustly one of the following is needed anyway: * -fPIE + -pie * -fPIC + -shared (less optimal?) Logically, pie seems to be the closest match to what is actually happening in U-Boot. Then we can optionally add: * --use-blx (to get rid of ARM<->Thumb interworking veneers) --pic-veneers could be used as a temporary fix, but this feels fragile to me: it only controls a speicific aspect of linker behaviour, so we could hit other problems in the future. We could do this as a short-term workaround to allow the linaro toolchain to be used in the meantime, though. Cheers ---Dave _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-toolchain
