linux-kernel - [PATCH] modpost: fix acpi MODULE_DEVICE_TABLE built with mismatched endianness

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Message-ID: <20241103124824.943659-1-masahiroy@kernel.org>
Date: Sun,  3 Nov 2024 21:46:50 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] modpost: fix acpi MODULE_DEVICE_TABLE built with mismatched endianness

When CONFIG_SATA_AHCI_PLATFORM=m, modpost outputs incorect 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_ALIAS() 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: 26095a01d359 ("ACPI / scan: Add support for ACPI _CLS device matching")
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 scripts/mod/file2alias.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 99dce93a4188..16154449dde1 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -567,12 +567,12 @@ 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;
 
@@ -580,10 +580,10 @@ static int do_acpi_entry(const char *filename,
 		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;
-- 
2.43.0