Re: [PATCH] xen/arm: vgic: Add missing 'U' in VGIC_ICFG_MASK for shifted constant

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 30 Jun 2023, Henry Wang wrote:
> With UBSAN on some arm64 platforms, e.g. FVP_Base_RevC-2xAEMvA, the
> following splat will be printed while Dom0 is booting:
> ```
> (XEN) ==================================================================
> (XEN) UBSAN: Undefined behaviour in arch/arm/vgic.c:372:15
> (XEN) left shift of 1 by 31 places cannot be represented in type 'int'
> (XEN) Xen WARN at common/ubsan/ubsan.c:172
> (XEN) ----[ Xen-4.18-unstable  arm64  debug=y ubsan=y  Not tainted ]----
> ```
> 
> This is because there is a device node in the device tree with 0xf
> as the interrupts property. Example of the device tree node is shown
> below:
> ```
> ethernet@202000000 {
>     compatible = "smsc,lan91c111";
>     reg = <0x2 0x2000000 0x10000>;
>     interrupts = <0xf>;
> };
> ```
> and this value is passed to vgic_get_virq_type() as "index" then "intr"
> in VGIC_ICFG_MASK.
> 
> Add the missing 'U' in VGIC_ICFG_MASK as a fix, and this should also
> addressing MISRA Rule 7.2:
> 
>     A "u" or "U" suffix shall be applied to all integer constants that
>     are represented in an unsigned type
> 
> Signed-off-by: Henry Wang <Henry.Wang@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> This patch should be based on top of Julien's series
> "xen/arm: Enable UBSAN support" to test.
> ---
>  xen/arch/arm/vgic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
> index c61c68870c..97d6f61066 100644
> --- a/xen/arch/arm/vgic.c
> +++ b/xen/arch/arm/vgic.c
> @@ -358,7 +358,7 @@ void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
>      }
>  }
>  
> -#define VGIC_ICFG_MASK(intr) (1 << ((2 * ((intr) % 16)) + 1))
> +#define VGIC_ICFG_MASK(intr) (1U << ((2 * ((intr) % 16)) + 1))
>  
>  /* The function should be called with the rank lock taken */
>  static inline unsigned int vgic_get_virq_type(struct vcpu *v, int n, int 
> index)
> -- 
> 2.25.1
>