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

Christoffer Dall
2016-01-05T14:36:08Z

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
>