Re: [PATCH V8 10/20] riscv: compat: Re-implement TASK_SIZE for COMPAT_32BIT

Guo Ren
2022-03-21T00:22:24Z

For this patch, we need to add below to fixup the rv32 call rv64 elf
segment fault.

diff --git a/arch/riscv/include/asm/processor.h
b/arch/riscv/include/asm/processor.h
index 0749924d9e55..21c8072dce17 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -19,7 +19,11 @@
#define TASK_UNMAPPED_BASE PAGE_ALIGN(TASK_SIZE / 3)

#define STACK_TOP TASK_SIZE
-#define STACK_TOP_MAX STACK_TOP
+#ifdef CONFIG_64BIT
+#define STACK_TOP_MAX TASK_SIZE_64
+#else
+#define STACK_TOP_MAX TASK_SIZE
+#endif
#define STACK_ALIGN 16

#ifndef __ASSEMBLY__

On Wed, Mar 16, 2022 at 3:04 PM <guoren@kernel.org> wrote:
>
> From: Guo Ren <guoren@linux.alibaba.com>
>
> Make TASK_SIZE from const to dynamic detect TIF_32BIT flag
> function. Refer to arm64 to implement DEFAULT_MAP_WINDOW_64 for
> efi-stub.
>
> Limit 32-bit compatible process in 0-2GB virtual address range
> (which is enough for real scenarios), because it could avoid
> address sign extend problem when 32-bit enter 64-bit and ease
> software design.
>
> The standard 32-bit TASK_SIZE is 0x9dc00000:FIXADDR_START, and
> compared to a compatible 32-bit, it increases 476MB for the
> application's virtual address.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Tested-by: Heiko Stuebner <heiko@sntech.de>
> ---
> arch/riscv/include/asm/pgtable.h | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index e3549e50de95..afdc9ece2ba4 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -705,8 +705,17 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> * 63–48 all equal to bit 47, or else a page-fault exception will occur."
> */
> #ifdef CONFIG_64BIT
> -#define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
> -#define TASK_SIZE_MIN (PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
> +#define TASK_SIZE_64 (PGDIR_SIZE * PTRS_PER_PGD / 2)
> +#define TASK_SIZE_MIN (PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
> +
> +#ifdef CONFIG_COMPAT
> +#define TASK_SIZE_32 (_AC(0x80000000, UL) - PAGE_SIZE)
> +#define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
> + TASK_SIZE_32 : TASK_SIZE_64)
> +#else
> +#define TASK_SIZE TASK_SIZE_64
> +#endif
> +
> #else
> #define TASK_SIZE FIXADDR_START
> #define TASK_SIZE_MIN TASK_SIZE
> --
> 2.25.1
>

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/