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

From: Masahiro Yamada
Date: Sun Nov 03 2024 - 07:48:55 EST


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@xxxxxxxxxx>
---

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