Re: [PATCH v1] xen/riscv: make calculation of stack address PC-relative

[Bobby Eshleman <bobbyeshleman@xxxxxxxxx>]

On Tue, Mar 14, 2023 at 06:00:41PM +0200, Oleksii Kurochko wrote:
> The patch is needed to keep all addresses PC-relative.
> 
> Pseudoinstruction 'la' can be transformed to 'auipc/addi' or
> 'auipc/l{w|d}'. It depends on the .option directive: nopic and pic.
> 
> Right now, 'la' transforms to 'auipc/l{w|d}', which in case of
> cpu0_boot_stack[] will lead to the usage of _GLOBAL_OFFSET_TABLE_
> where all addresses will be without counting that it might happen
> that linker address != load address.
> 
> To be sure that SP is loaded always PC-relative address
> 'la' should be changed to 'lla', which always transforms to
> 'auipc/addi'.
> 
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> ---
>  xen/arch/riscv/riscv64/head.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/riscv/riscv64/head.S b/xen/arch/riscv/riscv64/head.S
> index 8887f0cbd4..e12d2a7cf3 100644
> --- a/xen/arch/riscv/riscv64/head.S
> +++ b/xen/arch/riscv/riscv64/head.S
> @@ -27,7 +27,7 @@ ENTRY(start)
>          add     t3, t3, __SIZEOF_POINTER__
>          bltu    t3, t4, .L_clear_bss
>  
> -        la      sp, cpu0_boot_stack
> +        lla     sp, cpu0_boot_stack
>          li      t0, STACK_SIZE
>          add     sp, sp, t0
>  
> -- 
> 2.39.2
> 
> 

Reviewed-by: Bobby Eshleman <bobbyeshleman@xxxxxxxxx>