On Wed, Oct 17, 2018 at 05:34:57PM +0100, Steve Capper wrote:
> We wish to introduce a 52-bit virtual address space for userspace but
> maintain compatibility with software that assumes the maximum VA space
> size is 48 bit.
>
> In order to achieve this, on 52-bit VA systems, we make mmap behave as
> if it were running on a 48-bit VA system (unless userspace explicitly
> requests a VA where addr[51:48] != 0).
>
> On a system running a 52-bit userspace we need TASK_SIZE to represent
> the 52-bit limit as it is used in various places to distinguish between
> kernelspace and userspace addresses.
>
> Thus we need a new limit for mmap, stack, ELF loader and EFI (which uses
> TTBR0) to represent the non-extended VA space.
>
> This patch introduces DEFAULT_MAP_WINDOW and DEFAULT_MAP_WINDOW_64 and
> switches the appropriate logic to use that instead of TASK_SIZE.
>
> Signed-off-by: Steve Capper <steve.capper@xxxxxxx>
Whilst testing this series I inadvertantly dropped CONFIG_COMPAT which
has led to some kbuild errors with defconfig.
I will make the following changes to this patch.
[...]
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 79657ad91397..46c9d9ff028c 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -26,6 +26,8 @@
>
> #ifndef __ASSEMBLY__
>
> +#define DEFAULT_MAP_WINDOW_64 (UL(1) << VA_BITS)
> +
> /*
> * Default implementation of macro that returns current
> * instruction pointer ("program counter").
> @@ -58,13 +60,16 @@
> TASK_SIZE_32 : TASK_SIZE_64)
> #define TASK_SIZE_OF(tsk) (test_tsk_thread_flag(tsk, TIF_32BIT) ? \
> TASK_SIZE_32 : TASK_SIZE_64)
> +#define DEFAULT_MAP_WINDOW (test_tsk_thread_flag(tsk, TIF_32BIT) ? \
> + TASK_SIZE_32 : DEFAULT_MAP_WINDOW_64)
Instead of test_tsk_thread_flag I will use test_thread_flag for
DEFAULT_MAP_WINDOW.
> #else
> #define TASK_SIZE TASK_SIZE_64
> +#define DEFAULT_MAP_WINDOW DEFAULT_MAP_WINDOW_64
> #endif /* CONFIG_COMPAT */
>
> -#define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 4))
> +#define TASK_UNMAPPED_BASE (PAGE_ALIGN(DEFAULT_MAP_WINDOW / 4))
> +#define STACK_TOP_MAX DEFAULT_MAP_WINDOW_64
>
> -#define STACK_TOP_MAX TASK_SIZE_64
> #ifdef CONFIG_COMPAT
> #define AARCH32_VECTORS_BASE 0xffff0000
> #define STACK_TOP (test_thread_flag(TIF_32BIT) ? \
> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> index 922cfb813109..952cec5b611a 100644
> --- a/drivers/firmware/efi/arm-runtime.c
> +++ b/drivers/firmware/efi/arm-runtime.c
> @@ -38,7 +38,7 @@ static struct ptdump_info efi_ptdump_info = {
> .mm = &efi_mm,
> .markers = (struct addr_marker[]){
> { 0, "UEFI runtime start" },
> - { TASK_SIZE_64, "UEFI runtime end" }
> + { DEFAULT_MAP_WINDOW_64, "UEFI runtime end" }
> },
> .base_addr = 0,
> };
[...]
Also I will modify arch/arm64/mm/init.c:615 to be:
BUILD_BUG_ON(TASK_SIZE_32 > DEFAULT_MAP_WINDOW_64);
The above give me a working kernel with defconig. I will perform more tests
on COMPAT before sending a revised series out.
Cheers,
--
Steve
