linux-kernel - Re: [PATCH v3 3/7] x86/boot: Move the early GDT/IDT setup code into startup/

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Message-ID: <Z_ZhglTgGStO8K5O@gmail.com>
Date: Wed, 9 Apr 2025 14:01:06 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Ard Biesheuvel <ardb+git@...gle.com>, linux-efi@...r.kernel.org,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	Tom Lendacky <thomas.lendacky@....com>,
	Dionna Amalie Glaze <dionnaglaze@...gle.com>,
	Kevin Loughlin <kevinloughlin@...gle.com>
Subject: Re: [PATCH v3 3/7] x86/boot: Move the early GDT/IDT setup code into
 startup/


* Ard Biesheuvel <ardb@...nel.org> wrote:

> On Wed, 9 Apr 2025 at 12:07, Ingo Molnar <mingo@...nel.org> wrote:
> >
> >
> > * Ingo Molnar <mingo@...nel.org> wrote:
> >
> > >
> > > * Ard Biesheuvel <ardb+git@...gle.com> wrote:
> > >
> > > > From: Ard Biesheuvel <ardb@...nel.org>
> > > >
> > > > Move the early GDT/IDT setup code that runs long before the kernel
> > > > virtual mapping is up into arch/x86/boot/startup/, and build it in a way
> > > > that ensures that the code tolerates being called from the 1:1 mapping
> > > > of memory. The code itself is left unchanged by this patch.
> > > >
> > > > Also tweak the sed symbol matching pattern in the decompressor to match
> > > > on lower case 't' or 'b', as these will be emitted by Clang for symbols
> > > > with hidden linkage.
> > > >
> > > > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> > > > ---
> > > >  arch/x86/boot/compressed/Makefile |  2 +-
> > > >  arch/x86/boot/startup/Makefile    | 15 ++++
> > > >  arch/x86/boot/startup/gdt_idt.c   | 83 ++++++++++++++++++++
> > > >  arch/x86/kernel/head64.c          | 73 -----------------
> > > >  4 files changed, 99 insertions(+), 74 deletions(-)
> > >
> > > This causes the following build failure on x86-64-defconfig:
> > >
> > >    arch/x86/boot/startup/gdt_idt.c:67:55: error: cast to generic address space pointer from disjoint ‘__seg_gs’ address space pointer [-Werror]
> >
> > Caused by the previous patch:
> >
> >   x86/asm: Make rip_rel_ptr() usable from fPIC code
> >
> 
> Oops, sorry about that. I saw that error and thought I had fixed it
> with the (__force void*) cast.

NP, caught it early enough.

Thanks,

	Ingo