On Tue, 11 Mar 2025 at 11:24, Borislav Petkov bp@alien8.de 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.