(+ Arnd) On Wed, 5 Dec 2018 at 09:06, Nathan Chancellor <natechancel...@gmail.com> wrote: > > On Wed, Dec 05, 2018 at 08:37:05AM +0100, Ard Biesheuvel wrote: > > On Wed, 5 Dec 2018 at 02:42, Nathan Chancellor <natechancel...@gmail.com> > > wrote: > > > > > > This flag is not supported by lld: > > > > > > ld.lld: error: unknown argument: --pic-veneer > > > > > > Signed-off-by: Nathan Chancellor <natechancel...@gmail.com> > > > > Hi Nate, > > > > Does this mean ld.lld is guaranteed to produce position independent > > veneers if you build kernels that are bigger than the typical range of > > a relative branch? > > > > Hi Ard, > > Honestly, I'm not quite sure. I saw your commit that introduced this > flag and I wasn't quite sure what to make of it for lld. What > configuration would I use to verify and what would I check for? >
Try building allyesconfig, and check the resulting binary for veneers (which have 'veneer' in the symbol name, at least when ld.bfd emits them). These veneers should not take the [virtual] address of the branch target directly, but take a PC relative offset (as in the example in the commit log of that patch you are referring to) > Additionally, I have filed an LLVM bug for the lld developers to > check and see if this is a flag they should support: > > https://bugs.llvm.org/show_bug.cgi?id=39886 > > Thanks for the quick reply, > Nathan > > > > --- > > > arch/arm/Makefile | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > > > index e2a0baf36766..4fab2aa29570 100644 > > > --- a/arch/arm/Makefile > > > +++ b/arch/arm/Makefile > > > @@ -10,7 +10,7 @@ > > > # > > > # Copyright (C) 1995-2001 by Russell King > > > > > > -LDFLAGS_vmlinux := --no-undefined -X --pic-veneer > > > +LDFLAGS_vmlinux := --no-undefined -X $(call > > > ld-option,--pic-veneer) > > > ifeq ($(CONFIG_CPU_ENDIAN_BE8),y) > > > LDFLAGS_vmlinux += --be8 > > > KBUILD_LDFLAGS_MODULE += --be8 > > > -- > > > 2.20.0.rc1 > > >