Re: [PATCH 1/2] xen/arm: address violations of Rule 11.3

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Nicola,

> On 24 Jun 2025, at 02:20, victorm.lira@xxxxxxx wrote:
> 
> From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> 
> Use {get,put}_unaligned_t to ensure that reads and writes are
> safe to perform even on potentially misaligned pointers.
> 

Make sense as we convert a void* to uint32_t * so might be misaligned.

> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> Signed-off-by: Victor Lira <victorm.lira@xxxxxxx>

Acked-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Cc: Michal Orzel <michal.orzel@xxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Julien Grall <julien@xxxxxxx>
> Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> Cc: Federico Serafini <federico.serafini@xxxxxxxxxxx>
> Cc: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> ---
> xen/arch/arm/efi/efi-boot.h      | 9 +++++----
> xen/common/device-tree/bootfdt.c | 3 ++-
> 2 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index ee80560e13..12dbb6961f 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -9,6 +9,7 @@
> 
> #include <xen/device_tree.h>
> #include <xen/libfdt/libfdt.h>
> +#include <xen/unaligned.h>
> #include <asm/setup.h>
> #include <asm/smp.h>
> 
> @@ -85,7 +86,7 @@ static int __init setup_chosen_node(void *fdt, int 
> *addr_cells, int *size_cells)
>         *addr_cells = 2;
>     }
>     else
> -        *addr_cells = fdt32_to_cpu(*((uint32_t *)prop->data));
> +        *addr_cells = fdt32_to_cpu(get_unaligned_t(uint32_t, prop->data));
> 
>     prop = fdt_get_property(fdt, node, "#size-cells", &len);
>     if ( !prop )
> @@ -96,7 +97,7 @@ static int __init setup_chosen_node(void *fdt, int 
> *addr_cells, int *size_cells)
>         *size_cells = 2;
>     }
>     else
> -        *size_cells = fdt32_to_cpu(*((uint32_t *)prop->data));
> +        *size_cells = fdt32_to_cpu(get_unaligned_t(uint32_t, prop->data));
> 
>     /*
>      * Make sure ranges is empty if it exists, otherwise create empty ranges
> @@ -824,7 +825,7 @@ static int __init handle_dom0less_domain_node(const 
> EFI_LOADED_IMAGE *loaded_ima
>         return ERROR_MISSING_DT_PROPERTY;
>     }
> 
> -    addr_cells = fdt32_to_cpu(*((uint32_t *)prop->data));
> +    addr_cells = fdt32_to_cpu(get_unaligned_t(uint32_t, prop->data));
> 
>     prop = fdt_get_property(fdt_efi, domain_node, "#size-cells", &len);
>     if ( !prop )
> @@ -833,7 +834,7 @@ static int __init handle_dom0less_domain_node(const 
> EFI_LOADED_IMAGE *loaded_ima
>         return ERROR_MISSING_DT_PROPERTY;
>     }
> 
> -    size_cells = fdt32_to_cpu(*((uint32_t *)prop->data));
> +    size_cells = fdt32_to_cpu(get_unaligned_t(uint32_t, prop->data));
> 
>     /* Check for nodes compatible with multiboot,module inside this node */
>     for ( module_node = fdt_first_subnode(fdt_efi, domain_node);
> diff --git a/xen/common/device-tree/bootfdt.c 
> b/xen/common/device-tree/bootfdt.c
> index 529c91e603..9f255027ea 100644
> --- a/xen/common/device-tree/bootfdt.c
> +++ b/xen/common/device-tree/bootfdt.c
> @@ -13,6 +13,7 @@
> #include <xen/lib.h>
> #include <xen/libfdt/libfdt-xen.h>
> #include <xen/sort.h>
> +#include <xen/unaligned.h>
> #include <xsm/xsm.h>
> #include <asm/setup.h>
> #ifdef CONFIG_STATIC_SHM
> @@ -213,7 +214,7 @@ u32 __init device_tree_get_u32(const void *fdt, int node,
>     if ( !prop || prop->len < sizeof(u32) )
>         return dflt;
> 
> -    return fdt32_to_cpu(*(uint32_t*)prop->data);
> +    return fdt32_to_cpu(get_unaligned_t(uint32_t, prop->data));
> }
> 
> /**
> --
> 2.25.1