Re: [PATCH v1 1/8] xen/riscv: make sure that identity mapping isn't bigger then page size

[Alistair Francis <alistair23@xxxxxxxxx>]

On Wed, Jun 7, 2023 at 5:55 AM Oleksii Kurochko
<oleksii.kurochko@xxxxxxxxx> wrote:
>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Acked-by: Alistair Francis <alistair.francis@xxxxxxx>

Alistair

> ---
>  xen/arch/riscv/xen.lds.S | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/xen/arch/riscv/xen.lds.S b/xen/arch/riscv/xen.lds.S
> index 878130f313..74afbaab9b 100644
> --- a/xen/arch/riscv/xen.lds.S
> +++ b/xen/arch/riscv/xen.lds.S
> @@ -20,6 +20,7 @@ SECTIONS
>      . = XEN_VIRT_START;
>      _start = .;
>      .text : {
> +        _idmap_start = .;
>          _stext = .;            /* Text section */
>          *(.text.header)
>
> @@ -35,6 +36,7 @@ SECTIONS
>          *(.gnu.warning)
>          . = ALIGN(POINTER_ALIGN);
>          _etext = .;             /* End of text section */
> +        _idmap_end = .;
>      } :text
>
>      . = ALIGN(PAGE_SIZE);
> @@ -174,3 +176,10 @@ ASSERT(!SIZEOF(.got),      ".got non-empty")
>  ASSERT(!SIZEOF(.got.plt),  ".got.plt non-empty")
>
>  ASSERT(_end - _start <= MB(2), "Xen too large for early-boot assumptions")
> +
> +/*
> + * We require that Xen is loaded at a page boundary, so this ensures that any
> + * code running on the identity map cannot cross a page boundary.
> + */
> +ASSERT(IS_ALIGNED(_idmap_start, PAGE_SIZE), "_idmap_start should be 
> page-aligned")
> +ASSERT(_idmap_end - _idmap_start <= PAGE_SIZE, "Identity mapped code is 
> larger than a page size")
> --
> 2.40.1
>
>