https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119386
--- Comment #44 from Alexander Monakov <amonakov at gcc dot gnu.org> --- (In reply to Ard Biesheuvel from comment #43) > arch/arm64/Makefile specifies '-shared' for the linker flags, but does not > pass -fpic of -fpie to the compiler. We used to pass '-pie -shared' but that > was changed a while ago to accommodate lld. Oof. And you couldn't drop -shared (leaving -pie) because the linker would then write a useless .interp section? BFD ld now has -static-pie; not sure about LLD. I see that that Makefile passes -z notext, as you're trying to link a PIE from non-PIC objects, and the linker can emit text relocations. Makes sense. > The goal is to build a PIE (or -shared) executable, so that we get the > dynamic relocations needed to randomize the placement of the kernel in the > virtual address space at boot. On arm64, that doesn't currently require > -fpic of -fpie, and adding those options results in worse code due to all > the GOT indirections. (PIE with textrels, crucially, right?) > Non-PIC might be more efficient, but there are cases where we cannot use it. > The early startup code on x86 runs from a different virtual mapping than it > was linked at, and this has been causing lots of issues. Grep for > RIP_REL_REF() in the Linux source tree and weep :-) Is x86 somehow special here, or can arm64 find itself in a similar situation? Thanks for bearing with me!
