[BUG] Argument-alignment build error with clang

[Paul E. McKenney]

Hello!

Running rcutorture on next-20241023 got me lots of these:

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);

This is built with CC=clang.  I don't see this diagnostic with GCC.
But we are supposed to be able to build with clang, so...

The first argument is the address of one of these:

typedef struct {
	__u8 b[UUID_SIZE];
} guid_t;

Where UUID_SIZE is as follows:

#define UUID_SIZE 16

But this guid_t is a member of one of these:

struct prm_handler_info {
	guid_t guid;
	efi_status_t (__efiapi *handler_addr)(u64, void *);
	u64 static_data_buffer_addr;
	u64 acpi_param_buffer_addr;

	struct list_head handler_list;
};

One can argue that this structure must be 16-bit aligned on a
64-bit build.  So maybe this is a bug in clang's diagnostics, hence
linux-toolchains on CC.

Thoughts?

						Thanx, Paul