linux-kernel - Re: [PATCH] firmware_loader: re-export fw_fallback_config into firmware

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Date:   Fri, 24 Apr 2020 11:21:19 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     akpm@...ux-foundation.org, josh@...htriplett.org,
        rishabhb@...eaurora.org, kubakici@...pl, maco@...roid.com,
        andy.gross@...aro.org, david.brown@...aro.org,
        bjorn.andersson@...aro.org, linux-wireless@...r.kernel.org,
        keescook@...omium.org, shuah@...nel.org, mfuzzey@...keon.com,
        zohar@...ux.vnet.ibm.com, dhowells@...hat.com,
        pali.rohar@...il.com, tiwai@...e.de, arend.vanspriel@...adcom.com,
        zajec5@...il.com, nbroeking@...com, markivx@...eaurora.org,
        broonie@...nel.org, dmitry.torokhov@...il.com, dwmw2@...radead.org,
        torvalds@...ux-foundation.org, Abhay_Salunke@...l.com,
        jewalt@...innovations.com, cantabile.desu@...il.com, ast@...com,
        andresx7@...il.com, dan.rue@...aro.org, brendanhiggins@...gle.com,
        yzaikin@...gle.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] firmware_loader: re-export fw_fallback_config into
 firmware_loader's own namespace

On Thu, Apr 23, 2020 at 08:31:40PM +0000, Luis R. Rodriguez wrote:
> From: Luis Chamberlain <mcgrof@...nel.org>
> 
> Christoph's recent patch "firmware_loader: remove unused exports", which
> is not merged upstream yet, removed two exported symbols. One is fine to
> remove since only built-in code uses it but the other is incorrect.
> 
> If CONFIG_FW_LOADER=m so the firmware_loader is modular but
> CONFIG_FW_LOADER_USER_HELPER=y we fail at mostpost with:
> 
> ERROR: modpost: "fw_fallback_config" [drivers/base/firmware_loader/firmware_class.ko] undefined!
> 
> This happens because the variable fw_fallback_config is built into the
> kernel if CONFIG_FW_LOADER_USER_HELPER=y always, so we need to grant
> access to the firmware loader module by exporting it.
> 
> Instead of just exporting it as we used to, take advantage of the new
> kernel symbol namespacing functionality, and export the symbol only to
> the firmware loader private namespace. This would prevent misuses from
> other drivers and makes it clear the goal is to keep this private to
> the firmware loader alone.
> 
> Cc: Christoph Hellwig <hch@....de>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> Fixes: "firmware_loader: remove unused exports"
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> ---
>  drivers/base/firmware_loader/fallback.c       | 3 +++
>  drivers/base/firmware_loader/fallback_table.c | 1 +
>  2 files changed, 4 insertions(+)
> 
> diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
> index 1e9c96e3ed63..d9ac7296205e 100644
> --- a/drivers/base/firmware_loader/fallback.c
> +++ b/drivers/base/firmware_loader/fallback.c
> @@ -9,6 +9,7 @@
>  #include <linux/umh.h>
>  #include <linux/sysctl.h>
>  #include <linux/vmalloc.h>
> +#include <linux/module.h>
>  
>  #include "fallback.h"
>  #include "firmware.h"
> @@ -17,6 +18,8 @@
>   * firmware fallback mechanism
>   */
>  
> +MODULE_IMPORT_NS(FIRMWARE_LOADER_PRIVATE);
> +
>  extern struct firmware_fallback_config fw_fallback_config;
>  
>  /* These getters are vetted to use int properly */

While nice, that does not fix the existing build error that people are
having, right?

> diff --git a/drivers/base/firmware_loader/fallback_table.c b/drivers/base/firmware_loader/fallback_table.c
> index 0a737349f78f..46a731dede6f 100644
> --- a/drivers/base/firmware_loader/fallback_table.c
> +++ b/drivers/base/firmware_loader/fallback_table.c
> @@ -21,6 +21,7 @@ struct firmware_fallback_config fw_fallback_config = {
>  	.loading_timeout = 60,
>  	.old_timeout = 60,
>  };
> +EXPORT_SYMBOL_NS_GPL(fw_fallback_config, FIRMWARE_LOADER_PRIVATE);


How about you send a patch that just reverts the single symbol change
first, and then a follow-on patch that does this namespace addition.  I
can queue the first one up now, for 5.7-final, and the second one for
5.8-rc1.

thanks,

greg k-h