linux-kernel - Re: [RFC/RFT PATCH 15/19] x64/acpi: Use PIC-compatible references in wakeup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMzpN2h_iEPXFqFtSatjZJZgKOa-r8JfG+4iGQFioOvT-Dms=Q@mail.gmail.com>
Date: Fri, 9 Jan 2026 07:51:09 -0500
From: Brian Gerst <brgerst@...il.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Kees Cook <kees@...nel.org>, 
	Uros Bizjak <ubizjak@...il.com>, linux-hardening@...r.kernel.org
Subject: Re: [RFC/RFT PATCH 15/19] x64/acpi: Use PIC-compatible references in wakeup_64.S

On Fri, Jan 9, 2026 at 7:10 AM Ard Biesheuvel <ardb@...nel.org> wrote:
>
> On Fri, 9 Jan 2026 at 13:09, Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Fri, 9 Jan 2026 at 12:46, Brian Gerst <brgerst@...il.com> wrote:
> > >
> > > On Fri, Jan 9, 2026 at 2:59 AM Ard Biesheuvel <ardb@...nel.org> wrote:
> > > >
> > > > On Fri, 9 Jan 2026 at 06:01, Brian Gerst <brgerst@...il.com> wrote:
> > > > >
> > > > > On Thu, Jan 8, 2026 at 4:28 AM Ard Biesheuvel <ardb@...nel.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@...nel.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?
> >
> > arch/x86/kernel/acpi/wakeup_64.o: warning: objtool: wakeup_long64()
> > falls through to next function do_suspend_lowlevel()
>
> Note that this is x86_64_defconfig with CONFIG_X86_KERNEL_IBT disabled.

I do see the error now.  I had missed it when building the .o file and
thought it would show when linking vmlinux.

I was able to make objtool happy by embedding wakeup_long64() into
do_suspend_lowlevel() and using SYM_INNER_LABEL_ALIGN().