linux-kernel - Re: [PATCH 18/25] dynamic_debug: Introduce global fake module param $module.dyndbg

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Date:	Wed, 07 Dec 2011 11:31:55 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	jim.cromie@...il.com, jbaron@...hat.com
Cc:	greg@...ah.com, joe@...ches.com, bart.vanassche@...il.com,
	linux-kernel@...r.kernel.org, Jim Cromie <jim.cromie@...il.com>,
	Thomas Renninger <trenn@...e.de>
Subject: Re: [PATCH 18/25] dynamic_debug: Introduce global fake module param $module.dyndbg

On Tue,  6 Dec 2011 12:11:28 -0700, jim.cromie@...il.com wrote:
> From: Jim Cromie <jim.cromie@...il.com>
> 
> Rework Thomas Renninger's $module.ddebug boot-time debugging feature,
> from https://lkml.org/lkml/2010/9/15/397

This worked out pretty neatly.  Thanks!

A few questions from your patches:

> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> index 7e3c53a..b77f43b 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -39,11 +39,16 @@ struct _ddebug {
>  int ddebug_add_module(struct _ddebug *tab, unsigned int n,
>  				const char *modname);
>  
> +struct kernel_param;
> +
>  #if defined(CONFIG_DYNAMIC_DEBUG)
>  extern int ddebug_remove_module(const char *mod_name);
> +
>  extern __printf(2, 3)
>  int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...);

struct kernel_param def belongs in future patch?  And whitespace change
is kind of annoying.

> diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
> index 7939f63..91bd56a 100644
> --- a/include/linux/moduleparam.h
> +++ b/include/linux/moduleparam.h
> @@ -292,7 +292,7 @@ extern int parse_args(const char *name,
>  		      char *args,
>  		      const struct kernel_param *params,
>  		      unsigned num,
> -		      int (*unknown)(char *param, char *val));
> +		      int (*unknown)(char *param, char *val, const char *modname));

Do you really want the modname here, or a struct module?  I wonder if we
should make this a standard opaque void *.  Of course, we'd have to
modify parse_args callers, but you're abusing "name" arg here a bit
anyway.

> @@ -2893,7 +2893,8 @@ static struct module *load_module(void __user *umod,
> 	  mutex_unlock(&module_mutex);
> 
> 	  /* Module is ready to execute: parsing args may do that. */
> -	err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL);
> +	err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
> +			 ddebug_dyndbg_param_cb);
> 	  if (err < 0)
> 		  goto unlink;

You have to 



> @@ -510,8 +510,7 @@ asmlinkage void __init start_kernel(void)
>  	printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
>  	parse_early_param();
>  	parse_args("Booting kernel", static_command_line, __start___param,
> -		   __stop___param - __start___param,
> -		   &unknown_bootoption);
> +		   __stop___param - __start___param, &unknown_bootoption);
>  
>  	jump_label_init();

Gratuitous whitespace change.

> +int ddebug_dyndbg_param_cb(char *param, char* val, const char* modname)
> +{
> +	if (strcmp(param, "dyndbg")) {
> +		pr_warn("bogus param %s=%s received for %s\n",
> +			param, val, modname);
> +		return -EINVAL;
> +	}

This is already done in parse_args(); don't add a pr_warn here.

Thanks,
Rusty.
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