On Mon, 27 Jan 2025 at 07:46, Michal Orzel <[email protected]> wrote:
> On Arm32, when CONFIG_PHYS_ADDR_T_32 is set, a build failure is observed:
> common/device-tree/bootfdt.c: In function 'build_assertions':
> ./include/xen/macros.h:47:31: error: static assertion failed:
> "!(alignof(struct membanks) != 8)"
> 47 | #define BUILD_BUG_ON(cond) ({ _Static_assert(!(cond), "!(" #cond
> ")"); })
> | ^~~~~~~~~~~~~~
> common/device-tree/bootfdt.c:31:5: note: in expansion of macro
> 'BUILD_BUG_ON'
> 31 | BUILD_BUG_ON(alignof(struct membanks) != 8);
>
> When CONFIG_PHYS_ADDR_T_32 is set, paddr_t is defined as unsigned long,
> therefore the struct membanks alignment is 4B. Fix it.
Usually, we add a BUILD_BUG_ON when other parts of the code rely on a
specific property (in this case alignment). Can you explain in the commit
message why the new check is still ok?
Cheers,
>
> Fixes: 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory
> bank structures")
> Signed-off-by: Michal Orzel <[email protected]>
> ---
> xen/common/device-tree/bootfdt.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/xen/common/device-tree/bootfdt.c
> b/xen/common/device-tree/bootfdt.c
> index 47386d4fffea..511700ccc2ba 100644
> --- a/xen/common/device-tree/bootfdt.c
> +++ b/xen/common/device-tree/bootfdt.c
> @@ -27,8 +27,8 @@ static void __init __maybe_unused build_assertions(void)
> */
> BUILD_BUG_ON((offsetof(struct membanks, bank) !=
> offsetof(struct meminfo, bank)));
> - /* Ensure "struct membanks" is 8-byte aligned */
> - BUILD_BUG_ON(alignof(struct membanks) != 8);
> + /* Ensure "struct membanks" is paddr aligned */
> + BUILD_BUG_ON(alignof(struct membanks) != sizeof(paddr_t));
> }
>
> static bool __init device_tree_node_is_available(const void *fdt, int
> node)
> --
> 2.25.1
>
>
