On Tue, 11 Mar 2025 at 11:24, Borislav Petkov <bp@xxxxxxxxx> wrote: > > On Mon, Mar 10, 2025 at 11:19:03PM +0100, Ard Biesheuvel wrote: > > and no error. > > Oh fun. > > > Could you capture the output of > > > > objdump -dr .tmp_vmlinux2 --section .head.text > > > > and share it somewhere please? > > See attached. > > Now lemme try to bisect it, see what this machine says since it is magically > toolchain or whatnot-specific. :-\ > There are many occurrences of ffffffff8373cb87: 49 c7 c6 20 c0 55 86 mov $0xffffffff8655c020,%r14 ffffffff8373cb8a: R_X86_64_32S __ref_stack_chk_guard whereas the ordinary Clang uses R_X86_64_REX_GOTPCRELX here, which are relaxed by the linker. I suspect that Ubuntu's Clang 15 has some additional patches that trigger this behavior. We could add __no_stack_protector to __head to work around this.
