Re: [RFC/RFT PATCH 15/19] x64/acpi: Use PIC-compatible references in wakeup_64.S

Brian Gerst
2026-01-09T11:46:19Z

On Fri, Jan 9, 2026 at 2:59 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Fri, 9 Jan 2026 at 06:01, Brian Gerst <brgerst@gmail.com> wrote:
> >
> > On Thu, Jan 8, 2026 at 4:28 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> > >
> > > Use ordinary RIP-relative references to make the code compatible with
> > > running the linker in PIE mode.
> > >
> > > Note that wakeup_long64() runs in the kernel's ordinary virtual mapping
> > > so there is no need to record the address of .Lresume_point in a global
> > > variable. And fix the comment while at it.
> > >
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > > arch/x86/kernel/acpi/wakeup_64.S | 11 ++++-------
> > > 1 file changed, 4 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> > > index 04f561f75e99..15233a4e1c95 100644
> > > --- a/arch/x86/kernel/acpi/wakeup_64.S
> > > +++ b/arch/x86/kernel/acpi/wakeup_64.S
> > > @@ -14,7 +14,7 @@
> > >
> > > .code64
> > > /*
> > > - * Hooray, we are in Long 64-bit mode (but still running in low memory)
> > > + * Hooray, we are in Long 64-bit mode
> > > */
> > > SYM_FUNC_START(wakeup_long64)
> > > ANNOTATE_NOENDBR
> > > @@ -41,7 +41,7 @@ SYM_FUNC_START(wakeup_long64)
> > > movq saved_rsi(%rip), %rsi
> > > movq saved_rbp(%rip), %rbp
> > >
> > > - movq saved_rip(%rip), %rax
> > > + leaq .Lresume_point(%rip), %rax
> > > ANNOTATE_RETPOLINE_SAFE
> > > jmp *%rax
> >
> > If this is already running on the virtual mapping, this can simply be
> > changed to a direct jump.
> >
>
> Indeed, but I couldn't figure out how to do so without making objtool unhappy.

I replaced it with a simple "jmp .Lresume_point" and objtool seemed
fine with it on a defconfig build. What error did you see?