linux-kernel - Re: [PATCH 1/4] x86/boot/compressed/64: Compile pagetable.c unconditionally

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Message-ID: <20171110092501.uef43yx4m4yq5eeo@node.shutemov.name>
Date:   Fri, 10 Nov 2017 12:25:01 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...capital.net>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Borislav Petkov <bp@...e.de>, Andi Kleen <ak@...ux.intel.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] x86/boot/compressed/64: Compile pagetable.c
 unconditionally

On Fri, Nov 10, 2017 at 10:12:36AM +0100, Ingo Molnar wrote:
> 
> * Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> wrote:
> 
> > We are going to put few helpers into pagetable.c that are not specific
> > to KASLR.
> > 
> > Let's make compilation of the file independent of KASLR and wrap
> > KASLR-depended code into ifdef.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > ---
> >  arch/x86/boot/compressed/Makefile    | 2 +-
> >  arch/x86/boot/compressed/pagetable.c | 5 +++++
> >  2 files changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> > index 65a150a7f15c..f7b64ecd09b3 100644
> > --- a/arch/x86/boot/compressed/Makefile
> > +++ b/arch/x86/boot/compressed/Makefile
> > @@ -77,7 +77,7 @@ vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
> >  vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o
> >  vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o
> >  ifdef CONFIG_X86_64
> > -	vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/pagetable.o
> > +	vmlinux-objs-y += $(obj)/pagetable.o
> >  endif
> >  
> >  $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
> > diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c
> > index f1aa43854bed..a15bbfcb3413 100644
> > --- a/arch/x86/boot/compressed/pagetable.c
> > +++ b/arch/x86/boot/compressed/pagetable.c
> > @@ -27,6 +27,9 @@
> >  /* These actually do the work of building the kernel identity maps. */
> >  #include <asm/init.h>
> >  #include <asm/pgtable.h>
> > +
> > +#ifdef CONFIG_RANDOMIZE_BASE
> > +
> >  /* Use the static base for this part of the boot process */
> >  #undef __PAGE_OFFSET
> >  #define __PAGE_OFFSET __PAGE_OFFSET_BASE
> > @@ -149,3 +152,5 @@ void finalize_identity_maps(void)
> >  {
> >  	write_cr3(top_level_pgt);
> >  }
> > +
> > +#endif /* CONFIG_RANDOMIZE_BASE */
> 
> The #ifdeffery becomes really ugly in this file. I think we should split these 
> into separate .c files:
> 
>   arch/x86/boot/compressed/kaslr.c
>   arch/x86/boot/compressed/5-level-paging.c
> 
> With core data structures and code and a well defined interface:
> 
>   arch/x86/boot/compressed/pagetable.c
>   arch/x86/boot/compressed/pagetable.h
> 
> or so.

Okay, I'll do this.

-- 
 Kirill A. Shutemov