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Re: [PATCH v2 02/13] arm64: introduce KIMAGE_VADDR as the virtual base of the kernel region

Started byChristoffer Dall <christoffer.dall@linaro.org>
First post2016-01-05 15:40 +0100
Last post2016-01-05 16:00 +0100
Articles 3 — 2 participants

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  Re: [PATCH v2 02/13] arm64: introduce KIMAGE_VADDR as the virtual  base of the kernel region Christoffer Dall <christoffer.dall@linaro.org> - 2016-01-05 15:40 +0100
    Re: [PATCH v2 02/13] arm64: introduce KIMAGE_VADDR as the virtual  base of the kernel region Mark Rutland <mark.rutland@arm.com> - 2016-01-05 15:50 +0100
      Re: [PATCH v2 02/13] arm64: introduce KIMAGE_VADDR as the virtual  base of the kernel region Christoffer Dall <christoffer.dall@linaro.org> - 2016-01-05 16:00 +0100

#1301576 — Re: [PATCH v2 02/13] arm64: introduce KIMAGE_VADDR as the virtual base of the kernel region

FromChristoffer Dall <christoffer.dall@linaro.org>
Date2016-01-05 15:40 +0100
SubjectRe: [PATCH v2 02/13] arm64: introduce KIMAGE_VADDR as the virtual base of the kernel region
Message-ID<qNAWf-43s-41@gated-at.bofh.it>
On Wed, Dec 30, 2015 at 04:26:01PM +0100, Ard Biesheuvel wrote:
> This introduces the preprocessor symbol KIMAGE_VADDR which will serve as
> the symbolic virtual base of the kernel region, i.e., the kernel's virtual
> offset will be KIMAGE_VADDR + TEXT_OFFSET. For now, we define it as being
> equal to PAGE_OFFSET, but in the future, it will be moved below it once
> we move the kernel virtual mapping out of the linear mapping.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/arm64/include/asm/memory.h | 10 ++++++++--
>  arch/arm64/kernel/head.S        |  2 +-
>  arch/arm64/kernel/vmlinux.lds.S |  4 ++--
>  3 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index 853953cd1f08..bea9631b34a8 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -51,7 +51,8 @@
>  #define VA_BITS			(CONFIG_ARM64_VA_BITS)
>  #define VA_START		(UL(0xffffffffffffffff) << VA_BITS)
>  #define PAGE_OFFSET		(UL(0xffffffffffffffff) << (VA_BITS - 1))
> -#define MODULES_END		(PAGE_OFFSET)
> +#define KIMAGE_VADDR		(PAGE_OFFSET)
> +#define MODULES_END		(KIMAGE_VADDR)
>  #define MODULES_VADDR		(MODULES_END - SZ_64M)
>  #define PCI_IO_END		(MODULES_VADDR - SZ_2M)
>  #define PCI_IO_START		(PCI_IO_END - PCI_IO_SIZE)
> @@ -75,8 +76,13 @@
>   * private definitions which should NOT be used outside memory.h
>   * files.  Use virt_to_phys/phys_to_virt/__pa/__va instead.
>   */
> -#define __virt_to_phys(x)	(((phys_addr_t)(x) - PAGE_OFFSET + PHYS_OFFSET))
> +#define __virt_to_phys(x) ({						\
> +	phys_addr_t __x = (phys_addr_t)(x);				\
> +	__x >= PAGE_OFFSET ? (__x - PAGE_OFFSET + PHYS_OFFSET) :	\
> +			     (__x - KIMAGE_VADDR + PHYS_OFFSET); })

so __virt_to_phys will now work with a subset of the non-linear namely
all except vmalloced and ioremapped ones?

> +
>  #define __phys_to_virt(x)	((unsigned long)((x) - PHYS_OFFSET + PAGE_OFFSET))
> +#define __phys_to_kimg(x)	((unsigned long)((x) - PHYS_OFFSET + KIMAGE_VADDR))
>  
>  /*
>   * Convert a page to/from a physical address
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 23cfc08fc8ba..6434c844a0e4 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -389,7 +389,7 @@ __create_page_tables:
>  	 * Map the kernel image (starting with PHYS_OFFSET).
>  	 */
>  	mov	x0, x26				// swapper_pg_dir
> -	mov	x5, #PAGE_OFFSET
> +	ldr	x5, =KIMAGE_VADDR
>  	create_pgd_entry x0, x5, x3, x6
>  	ldr	x6, =KERNEL_END			// __va(KERNEL_END)
>  	mov	x3, x24				// phys offset
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 7de6c39858a5..ced0dedcabcc 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -88,7 +88,7 @@ SECTIONS
>  		*(.discard.*)
>  	}
>  
> -	. = PAGE_OFFSET + TEXT_OFFSET;
> +	. = KIMAGE_VADDR + TEXT_OFFSET;
>  
>  	.head.text : {
>  		_text = .;
> @@ -185,4 +185,4 @@ ASSERT(__idmap_text_end - (__idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,
>  /*
>   * If padding is applied before .head.text, virt<->phys conversions will fail.
>   */
> -ASSERT(_text == (PAGE_OFFSET + TEXT_OFFSET), "HEAD is misaligned")
> +ASSERT(_text == (KIMAGE_VADDR + TEXT_OFFSET), "HEAD is misaligned")
> -- 
> 2.5.0
> 
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#1301580

FromMark Rutland <mark.rutland@arm.com>
Date2016-01-05 15:50 +0100
Message-ID<qNB5T-480-15@gated-at.bofh.it>
In reply to#1301576
On Tue, Jan 05, 2016 at 03:36:34PM +0100, Christoffer Dall wrote:
> On Wed, Dec 30, 2015 at 04:26:01PM +0100, Ard Biesheuvel wrote:
> > This introduces the preprocessor symbol KIMAGE_VADDR which will serve as
> > the symbolic virtual base of the kernel region, i.e., the kernel's virtual
> > offset will be KIMAGE_VADDR + TEXT_OFFSET. For now, we define it as being
> > equal to PAGE_OFFSET, but in the future, it will be moved below it once
> > we move the kernel virtual mapping out of the linear mapping.
> > 
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > ---
> >  arch/arm64/include/asm/memory.h | 10 ++++++++--
> >  arch/arm64/kernel/head.S        |  2 +-
> >  arch/arm64/kernel/vmlinux.lds.S |  4 ++--
> >  3 files changed, 11 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> > index 853953cd1f08..bea9631b34a8 100644
> > --- a/arch/arm64/include/asm/memory.h
> > +++ b/arch/arm64/include/asm/memory.h
> > @@ -51,7 +51,8 @@
> >  #define VA_BITS			(CONFIG_ARM64_VA_BITS)
> >  #define VA_START		(UL(0xffffffffffffffff) << VA_BITS)
> >  #define PAGE_OFFSET		(UL(0xffffffffffffffff) << (VA_BITS - 1))
> > -#define MODULES_END		(PAGE_OFFSET)
> > +#define KIMAGE_VADDR		(PAGE_OFFSET)
> > +#define MODULES_END		(KIMAGE_VADDR)
> >  #define MODULES_VADDR		(MODULES_END - SZ_64M)
> >  #define PCI_IO_END		(MODULES_VADDR - SZ_2M)
> >  #define PCI_IO_START		(PCI_IO_END - PCI_IO_SIZE)
> > @@ -75,8 +76,13 @@
> >   * private definitions which should NOT be used outside memory.h
> >   * files.  Use virt_to_phys/phys_to_virt/__pa/__va instead.
> >   */
> > -#define __virt_to_phys(x)	(((phys_addr_t)(x) - PAGE_OFFSET + PHYS_OFFSET))
> > +#define __virt_to_phys(x) ({						\
> > +	phys_addr_t __x = (phys_addr_t)(x);				\
> > +	__x >= PAGE_OFFSET ? (__x - PAGE_OFFSET + PHYS_OFFSET) :	\
> > +			     (__x - KIMAGE_VADDR + PHYS_OFFSET); })
> 
> so __virt_to_phys will now work with a subset of the non-linear namely
> all except vmalloced and ioremapped ones?

It will work for linear mapped memory and for the kernel image, which is
what it used to do. It's just that the relationship between the image
and the linear map is broken.

The same rules apply to x86, where their virt_to_phys eventually boils down to:

static inline unsigned long __phys_addr_nodebug(unsigned long x)
{
        unsigned long y = x - __START_KERNEL_map;

        /* use the carry flag to determine if x was < __START_KERNEL_map */
        x = y + ((x > y) ? phys_base : (__START_KERNEL_map - PAGE_OFFSET));

        return x;
}

Thanks,
Mark.
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#1301587

FromChristoffer Dall <christoffer.dall@linaro.org>
Date2016-01-05 16:00 +0100
Message-ID<qNBfB-4bp-31@gated-at.bofh.it>
In reply to#1301580
On Tue, Jan 05, 2016 at 02:46:50PM +0000, Mark Rutland wrote:
> On Tue, Jan 05, 2016 at 03:36:34PM +0100, Christoffer Dall wrote:
> > On Wed, Dec 30, 2015 at 04:26:01PM +0100, Ard Biesheuvel wrote:
> > > This introduces the preprocessor symbol KIMAGE_VADDR which will serve as
> > > the symbolic virtual base of the kernel region, i.e., the kernel's virtual
> > > offset will be KIMAGE_VADDR + TEXT_OFFSET. For now, we define it as being
> > > equal to PAGE_OFFSET, but in the future, it will be moved below it once
> > > we move the kernel virtual mapping out of the linear mapping.
> > > 
> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > > ---
> > >  arch/arm64/include/asm/memory.h | 10 ++++++++--
> > >  arch/arm64/kernel/head.S        |  2 +-
> > >  arch/arm64/kernel/vmlinux.lds.S |  4 ++--
> > >  3 files changed, 11 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> > > index 853953cd1f08..bea9631b34a8 100644
> > > --- a/arch/arm64/include/asm/memory.h
> > > +++ b/arch/arm64/include/asm/memory.h
> > > @@ -51,7 +51,8 @@
> > >  #define VA_BITS			(CONFIG_ARM64_VA_BITS)
> > >  #define VA_START		(UL(0xffffffffffffffff) << VA_BITS)
> > >  #define PAGE_OFFSET		(UL(0xffffffffffffffff) << (VA_BITS - 1))
> > > -#define MODULES_END		(PAGE_OFFSET)
> > > +#define KIMAGE_VADDR		(PAGE_OFFSET)
> > > +#define MODULES_END		(KIMAGE_VADDR)
> > >  #define MODULES_VADDR		(MODULES_END - SZ_64M)
> > >  #define PCI_IO_END		(MODULES_VADDR - SZ_2M)
> > >  #define PCI_IO_START		(PCI_IO_END - PCI_IO_SIZE)
> > > @@ -75,8 +76,13 @@
> > >   * private definitions which should NOT be used outside memory.h
> > >   * files.  Use virt_to_phys/phys_to_virt/__pa/__va instead.
> > >   */
> > > -#define __virt_to_phys(x)	(((phys_addr_t)(x) - PAGE_OFFSET + PHYS_OFFSET))
> > > +#define __virt_to_phys(x) ({						\
> > > +	phys_addr_t __x = (phys_addr_t)(x);				\
> > > +	__x >= PAGE_OFFSET ? (__x - PAGE_OFFSET + PHYS_OFFSET) :	\
> > > +			     (__x - KIMAGE_VADDR + PHYS_OFFSET); })
> > 
> > so __virt_to_phys will now work with a subset of the non-linear namely
> > all except vmalloced and ioremapped ones?
> 
> It will work for linear mapped memory and for the kernel image, which is
> what it used to do. It's just that the relationship between the image
> and the linear map is broken.
> 
> The same rules apply to x86, where their virt_to_phys eventually boils down to:
> 
> static inline unsigned long __phys_addr_nodebug(unsigned long x)
> {
>         unsigned long y = x - __START_KERNEL_map;
> 
>         /* use the carry flag to determine if x was < __START_KERNEL_map */
>         x = y + ((x > y) ? phys_base : (__START_KERNEL_map - PAGE_OFFSET));
> 
>         return x;
> }
> 
ok, thanks for the snippet :)

-Christoffer
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