modpost: fix acpi MODULE_DEVICE_TABLE built with mismatched endianness

When CONFIG_SATA_AHCI_PLATFORM=m, modpost outputs incorect acpi
MODULE_ALIAS() if the endianness of the target and the build machine
do not match.

When the endianness of the target kernel and the build machine match,
the output is correct:

  $ grep 'MODULE_ALIAS("acpi' drivers/ata/ahci_platform.mod.c
  MODULE_ALIAS("acpi*:APMC0D33:*");
  MODULE_ALIAS("acpi*:010601:*");

However, when building a little-endian kernel on a big-endian machine
(or vice versa), the output is incorrect:

  $ grep 'MODULE_ALIAS("acpi' drivers/ata/ahci_platform.mod.c
  MODULE_ALIAS("acpi*:APMC0D33:*");
  MODULE_ALIAS("acpi*:0601??:*");

The 'cls' and 'cls_msk' fields are 32-bit.

DEF_FIELD() must be used instead of DEF_FIELD_ADDR() to correctly handle
endianness of these 32-bit fields.

The check 'if (cls)' was unnecessary; it never became NULL, as it was
the pointer to 'symval' plus the offset to the 'cls' field.

Fixes: 26095a0 ("ACPI / scan: Add support for ACPI _CLS device matching")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Author: masahir0y

scripts/mod/file2alias.c

@@ -567,23 +567,23 @@ static int do_acpi_entry(const char *filename,
 			void *symval, char *alias)
 {
 	DEF_FIELD_ADDR(symval, acpi_device_id, id);
-	DEF_FIELD_ADDR(symval, acpi_device_id, cls);
-	DEF_FIELD_ADDR(symval, acpi_device_id, cls_msk);
+	DEF_FIELD(symval, acpi_device_id, cls);
+	DEF_FIELD(symval, acpi_device_id, cls_msk);
 
 	if (id && strlen((const char *)*id))
 		sprintf(alias, "acpi*:%s:*", *id);
-	else if (cls) {
+	else {
 		int i, byte_shift, cnt = 0;
 		unsigned int msk;
 
 		sprintf(&alias[cnt], "acpi*:");
 		cnt = 6;
 		for (i = 1; i <= 3; i++) {
 			byte_shift = 8 * (3-i);
-			msk = (*cls_msk >> byte_shift) & 0xFF;
+			msk = (cls_msk >> byte_shift) & 0xFF;
 			if (msk)
 				sprintf(&alias[cnt], "%02x",
-					(*cls >> byte_shift) & 0xFF);
+					(cls >> byte_shift) & 0xFF);
 			else
 				sprintf(&alias[cnt], "??");
 			cnt += 2;