Re: [Xen-devel] [PATCH v2 23/35] xen/arm32: head: Introduce print_reg

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 22 Jul 2019, Julien Grall wrote:
> At the moment, the user should save r14/lr if it cares about it.
> 
> Follow-up patches will introduce more use of putn in place where lr
> should be preserved.
> 
> Furthermore, any user of putn should also move the value to register r0
> if it was stored in a different register.
> 
> For convenience, a new macro is introduced to print a given register.
> The macro will take care for us to move the value to r0 and also
> preserve lr.
> 
> Lastly the new macro is used to replace all the callsite of putn. This
> will simplify rework/review later on.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>     Changes in v2:
>         - Patch added
> ---
>  xen/arch/arm/arm32/head.S | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 134c3dda92..bbcfdcd351 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -79,8 +79,25 @@
>  98:     .asciz _s          ;\
>          .align 2           ;\
>  99:
> +
> +/*
> + * Macro to print the value of register \rb
> + *
> + * Clobbers r0 - r4
> + */
> +.macro print_reg rb
> +        mov   r0, \rb
> +        mov   r4, lr
> +        bl    putn
> +        mov   lr, r4
> +.endm
> +
>  #else /* CONFIG_EARLY_PRINTK */
>  #define PRINT(s)
> +
> +.macro print_reg rb
> +.endm
> +
>  #endif /* !CONFIG_EARLY_PRINTK */
>  
>          .arm
> @@ -159,8 +176,7 @@ GLOBAL(init_secondary)
>  #ifdef CONFIG_EARLY_PRINTK
>          mov_w r11, EARLY_UART_BASE_ADDRESS   /* r11 := UART base address */
>          PRINT("- CPU ")
> -        mov   r0, r7
> -        bl    putn
> +        print_reg r7
>          PRINT(" booting -\r\n")
>  #endif
>  
> @@ -211,8 +227,7 @@ skip_bss:
>          bne   1f
>          mov   r4, r0
>          PRINT("- Missing processor info: ")
> -        mov   r0, r4
> -        bl    putn
> +        print_reg r4
>          PRINT(" -\r\n")
>          b     fail
>  1:
> -- 
> 2.11.0
> 

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