Re: [PATCH v5 06/10] powerpc/fsl_booke/32: implement KASLR infrastructure

[Jason Yan]

On 2019/8/7 21:04, Michael Ellerman wrote:
> Jason Yan <yanaijie@xxxxxxxxxx> writes:
> > This patch add support to boot kernel from places other than KERNELBASE.
> > Since CONFIG_RELOCATABLE has already supported, what we need to do is
> > map or copy kernel to a proper place and relocate. Freescale Book-E
> > parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
> > entries are not suitable to map the kernel directly in a randomized
> > region, so we chose to copy the kernel to a proper place and restart to
> > relocate.
>
> So to be 100% clear you are randomising the location of the kernel in
> virtual and physical space, by the same amount, and retaining the 1:1
> linear mapping.

100% right :)

> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 77f6ebf97113..755378887912 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -548,6 +548,17 @@ config RELOCATABLE
> >   	  setting can still be useful to bootwrappers that need to know the
> >   	  load address of the kernel (eg. u-boot/mkimage).
> >   
> > +config RANDOMIZE_BASE
> > +	bool "Randomize the address of the kernel image"
> > +	depends on (FSL_BOOKE && FLATMEM && PPC32)
> > +	select RELOCATABLE
>
> I think this should depend on RELOCATABLE, rather than selecting it.
>
> > diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c
> > new file mode 100644
> > index 000000000000..30f84c0321b2
> > --- /dev/null
> > +++ b/arch/powerpc/kernel/kaslr_booke.c
> > @@ -0,0 +1,84 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2019 Jason Yan <yanaijie@xxxxxxxxxx>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
>
> You don't need that paragraph now that you have the SPDX tag.
>
> Rather than using a '//' comment followed by a single line block comment
> you can format it as:
>
> // SPDX-License-Identifier: GPL-2.0-only
> //
> // Copyright (C) 2019 Jason Yan <yanaijie@xxxxxxxxxx>
> >
> > +#include <linux/signal.h>
> > +#include <linux/sched.h>
> > +#include <linux/kernel.h>
> > +#include <linux/errno.h>
> > +#include <linux/string.h>
> > +#include <linux/types.h>
> > +#include <linux/ptrace.h>
> > +#include <linux/mman.h>
> > +#include <linux/mm.h>
> > +#include <linux/swap.h>
> > +#include <linux/stddef.h>
> > +#include <linux/vmalloc.h>
> > +#include <linux/init.h>
> > +#include <linux/delay.h>
> > +#include <linux/highmem.h>
> > +#include <linux/memblock.h>
> > +#include <asm/pgalloc.h>
> > +#include <asm/prom.h>
> > +#include <asm/io.h>
> > +#include <asm/mmu_context.h>
> > +#include <asm/pgtable.h>
> > +#include <asm/mmu.h>
> > +#include <linux/uaccess.h>
> > +#include <asm/smp.h>
> > +#include <asm/machdep.h>
> > +#include <asm/setup.h>
> > +#include <asm/paca.h>
> > +#include <mm/mmu_decl.h>
>
> Do you really need all those headers?

I will remove useless headers.

> > +extern int is_second_reloc;
>
> That should be in a header.
>
> Any reason why it isn't a bool?

Oh yes, it should be in a header. This variable is already defined 
before and also used in assembly code. I think it was not defined as a 
bool just because there is no 'bool' in assembly code.

> cheers
>
>
> .