Re: [PATCH] firmware_loader: re-export fw_fallback_config into firmware_loader's own namespace

[Greg KH]

On Thu, Apr 23, 2020 at 08:31:40PM +0000, Luis R. Rodriguez wrote:
> From: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> 
> 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@xxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Fixes: "firmware_loader: remove unused exports"
> Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> ---
>  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