On Thu, 24 Oct 2024 at 10:07, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> Clang 19 prints a warning when we pass &th->guid to efi_pa_va_lookup():
>
> drivers/acpi/prmt.c:156:29: error: passing 1-byte aligned argument to
> 4-byte aligned parameter 1 of 'efi_pa_va_lookup' may result in an
> unaligned pointer access [-Werror,-Walign-mismatch]
> 156 | (void *)efi_pa_va_lookup(&th->guid, handler_info->handler_address);
> | ^
>
> The problem is that efi_pa_va_lookup() takes a efi_guid_t and &th->guid
> is a regular guid_t. The difference between the two types is the
> alignment. efi_guid_t is a typedef.
>
> typedef guid_t efi_guid_t __aligned(__alignof__(u32));
>
> It's possible that this a bug in Clang 19. Even though the alignment of
> &th->guid is not explicitly specified, it will still end up being aligned
> at 4 or 8 bytes.
>
> Anyway, as Ard points out, it's cleaner to change guid to efi_guid_t type
> and that also makes the warning go away.
>
> Fixes: 088984c8d54c ("ACPI: PRM: Find EFI_MEMORY_RUNTIME block for PRM handler and context")
> Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
In case this wasn't implied already,
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> Sorry for the unfair Fixes tags since you obviously aren't to blame. But it's
> more practical if we avoid breaking the build in backports or etc. Fixes tags
> are quite often unfair in this way...
>
> drivers/acpi/prmt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
> index d59307a76ca3..747f83f7114d 100644
> --- a/drivers/acpi/prmt.c
> +++ b/drivers/acpi/prmt.c
> @@ -52,7 +52,7 @@ struct prm_context_buffer {
> static LIST_HEAD(prm_module_list);
>
> struct prm_handler_info {
> - guid_t guid;
> + efi_guid_t guid;
> efi_status_t (__efiapi *handler_addr)(u64, void *);
> u64 static_data_buffer_addr;
> u64 acpi_param_buffer_addr;
> --
> 2.45.2
>
