linux-kernel - Re: [PATCH v6 6/9] modpost: Add modname to mod_device

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Message-Id: <DC26OG2L7OMH.31RE7460D4DHU@kernel.org>
Date: Thu, 14 Aug 2025 15:26:53 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Alexey Gladkov" <legion@...nel.org>
Cc: "Nathan Chancellor" <nathan@...nel.org>, "Nicolas Schier"
 <nicolas.schier@...ux.dev>, "Masahiro Yamada" <masahiroy@...nel.org>, "Petr
 Pavlu" <petr.pavlu@...e.com>, "Luis Chamberlain" <mcgrof@...nel.org>, "Sami
 Tolvanen" <samitolvanen@...gle.com>, "Daniel Gomez" <da.gomez@...sung.com>,
 <linux-kernel@...r.kernel.org>, <linux-modules@...r.kernel.org>,
 <linux-kbuild@...r.kernel.org>, "Miguel Ojeda" <ojeda@...nel.org>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>,
 <rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH v6 6/9] modpost: Add modname to mod_device_table alias

On Thu Aug 14, 2025 at 3:07 PM CEST, Alexey Gladkov wrote:
> At this point, if a symbol is compiled as part of the kernel,
> information about which module the symbol belongs to is lost.
>
> To save this it is possible to add the module name to the alias name.
> It's not very pretty, but it's possible for now.
>
> Cc: Miguel Ojeda <ojeda@...nel.org>
> Cc: Andreas Hindborg <a.hindborg@...nel.org>
> Cc: Danilo Krummrich <dakr@...nel.org>
> Cc: Alex Gaynor <alex.gaynor@...il.com>
> Cc: rust-for-linux@...r.kernel.org
> Signed-off-by: Alexey Gladkov <legion@...nel.org>
> ---
>  include/linux/module.h   | 14 +++++++++++++-
>  rust/kernel/device_id.rs |  8 ++++----
>  scripts/mod/file2alias.c | 18 ++++++++++++++----
>  3 files changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 3319a5269d28..e31ee29fac6b 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -244,10 +244,22 @@ struct module_kobject *lookup_or_create_module_kobject(const char *name);
>  /* What your module does. */
>  #define MODULE_DESCRIPTION(_description) MODULE_INFO(description, _description)
>  
> +/*
> + * Format: __mod_device_table__kmod_<modname>__<type>__<name>
> + * Parts of the string `__kmod_` and `__` are used as delimiters when parsing
> + * a symbol in file2alias.c
> + */
> +#define __mod_device_table(type, name)	\
> +	__PASTE(__mod_device_table__,	\
> +	__PASTE(__KBUILD_MODNAME,	\
> +	__PASTE(__,			\
> +	__PASTE(type,			\
> +	__PASTE(__, name)))))
> +
>  #ifdef MODULE
>  /* Creates an alias so file2alias.c can find device table. */
>  #define MODULE_DEVICE_TABLE(type, name)					\
> -static typeof(name) __mod_device_table__##type##__##name		\
> +static typeof(name) __mod_device_table(type, name)			\
>    __attribute__ ((used, alias(__stringify(name))))
>  #else  /* !MODULE */
>  #define MODULE_DEVICE_TABLE(type, name)
> diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs
> index 70d57814ff79..62c42da12e9d 100644
> --- a/rust/kernel/device_id.rs
> +++ b/rust/kernel/device_id.rs
> @@ -195,10 +195,10 @@ macro_rules! module_device_table {
>      ($table_type: literal, $module_table_name:ident, $table_name:ident) => {
>          #[rustfmt::skip]
>          #[export_name =
> -            concat!("__mod_device_table__", $table_type,
> -                    "__", module_path!(),
> -                    "_", line!(),
> -                    "_", stringify!($table_name))
> +            concat!("__mod_device_table__", line!(),

Why do we have line!() between "__mod_device_table__" and "__kmod_", while the
format is defined as "__mod_device_table__kmod_<modname>__<type>__<name>" above?

The previous logic was to create a unique name with
using "<module_path>_<line>_<table_name>" as "<name>". So, I think this should
actually be:

	concat!("__mod_device_table__kmod_",
		module_path!(),
		"__", $table_type,
		"__", stringify!($table_name),
		"_", line!())

rather than the below.

> +                    "__kmod_", module_path!(),
> +                    "__", $table_type,
> +                    "__", stringify!($table_name))
>          ]
>          static $module_table_name: [::core::mem::MaybeUninit<u8>; $table_name.raw_ids().size()] =
>              unsafe { ::core::mem::transmute_copy($table_name.raw_ids()) };