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

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Message-ID: <CAK7LNASW1jrO-hENgbZS1QGiZcGeAFwOwZY6M6cAx6tafOfhqQ@mail.gmail.com>
Date: Sun, 3 Nov 2024 21:56:23 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: 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: Re: [PATCH] modpost: fix acpi MODULE_DEVICE_TABLE built with
 mismatched endianness

On Sun, Nov 3, 2024 at 9:48 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> 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

This is a typo:

 DEF_FIELD_ALIAS() -> DEF_FIELD_ADDR()



> 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
>


-- 
Best Regards
Masahiro Yamada