[PATCH] modules: Fix build error in moduleloader.h

[PATCH] modules: Fix build error in moduleloader.h

[Steven Rostedt]

Fengguang Wu's build bot detected that if moduleloader.h is included in
a C file (used by ftrace and kprobes to access module_alloc() when
available), that it can fail to build if CONFIG_MODULES and
CONFIG_MODULES_USE_ELF_REL is not defined.

This is because there's a printk() that dereferences struct module to
print the name of the module. But as struct module does not exist when
CONFIG_MODULES is not defined we get this error:

   include/linux/moduleloader.h: In function 'apply_relocate':
>> include/linux/moduleloader.h:48:63: error: dereferencing pointer to incomplete type  
     printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
                                                                  ^
Avoid the printk if CONFIG_MODULES is not set.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 560ca53..d9da807 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -45,7 +45,10 @@ static inline int apply_relocate(Elf_Shdr *sechdrs,
 				 unsigned int relsec,
 				 struct module *me)
 {
+/* me->name only exists if modules are enabled */
+#ifdef CONFIG_MODULES
 	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
+#endif
 	return -ENOEXEC;
 }
 #endif

Re: [PATCH] modules: Fix build error in moduleloader.h

[Masami Hiramatsu]

(2014/07/03 22:21), Steven Rostedt wrote:
> Fengguang Wu's build bot detected that if moduleloader.h is included in
> a C file (used by ftrace and kprobes to access module_alloc() when
> available), that it can fail to build if CONFIG_MODULES and
> CONFIG_MODULES_USE_ELF_REL is not defined.
> 
> This is because there's a printk() that dereferences struct module to
> print the name of the module. But as struct module does not exist when
> CONFIG_MODULES is not defined we get this error:
> 
>    include/linux/moduleloader.h: In function 'apply_relocate':
>>> include/linux/moduleloader.h:48:63: error: dereferencing pointer to incomplete type  
>      printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
>                                                                   ^
> Avoid the printk if CONFIG_MODULES is not set.

Looks OK to me. BTW, CONFIG_KPROBES depends on CONFIG_MODULES,
so currently kprobes itself doesn't hit that problem.

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you, :)

> 
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
> index 560ca53..d9da807 100644
> --- a/include/linux/moduleloader.h
> +++ b/include/linux/moduleloader.h
> @@ -45,7 +45,10 @@ static inline int apply_relocate(Elf_Shdr *sechdrs,
>  				 unsigned int relsec,
>  				 struct module *me)
>  {
> +/* me->name only exists if modules are enabled */
> +#ifdef CONFIG_MODULES
>  	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> +#endif
>  	return -ENOEXEC;
>  }
>  #endif
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com

Re: [PATCH] modules: Fix build error in moduleloader.h

[Rusty Russell]

Steven Rostedt <rostedt@goodmis.org> writes:
> Fengguang Wu's build bot detected that if moduleloader.h is included in
> a C file (used by ftrace and kprobes to access module_alloc() when
> available), that it can fail to build if CONFIG_MODULES and
> CONFIG_MODULES_USE_ELF_REL is not defined.
>
> This is because there's a printk() that dereferences struct module to
> print the name of the module. But as struct module does not exist when
> CONFIG_MODULES is not defined we get this error:

First, we have module_name() for exactly this.

Second, there are two places like this: you hit
CONFIG_MODULES_USE_ELF_REL and not CONFIG_MODULES_USE_ELF_RELA.

(We could uninline them, and put them in module.c, but I think having
them in the header is nice and self-documenting.)

So does this work for you?

Thanks,
Rusty.
PS.  Masami Hiramatsu, your review should have caught the second case,
     at least :(

Subject: modules: Fix build error in moduleloader.h

Fengguang Wu's build bot detected that if moduleloader.h is included in
a C file (used by ftrace and kprobes to access module_alloc() when
available), that it can fail to build if CONFIG_MODULES and
CONFIG_MODULES_USE_ELF_REL is not defined.

This is because there's a printk() that dereferences struct module to
print the name of the module. But as struct module does not exist when
CONFIG_MODULES is not defined we get this error:

   include/linux/moduleloader.h: In function 'apply_relocate':
>> include/linux/moduleloader.h:48:63: error: dereferencing pointer to
>> incomplete type  
     printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
								  ^
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Based-on-the-true-story-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 560ca53a75fa..7eeb9bbfb816 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -45,7 +45,8 @@ static inline int apply_relocate(Elf_Shdr *sechdrs,
 				 unsigned int relsec,
 				 struct module *me)
 {
-	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
+	printk(KERN_ERR "module %s: REL relocation unsupported\n",
+	       module_name(me));
 	return -ENOEXEC;
 }
 #endif
@@ -67,7 +68,8 @@ static inline int apply_relocate_add(Elf_Shdr *sechdrs,
 				     unsigned int relsec,
 				     struct module *me)
 {
-	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
+	printk(KERN_ERR "module %s: REL relocation unsupported\n",
+	       module_name(me));
 	return -ENOEXEC;
 }
 #endif

Re: [PATCH] modules: Fix build error in moduleloader.h

[Masami Hiramatsu]

(2014/07/08 8:40), Rusty Russell wrote:
> Steven Rostedt <rostedt@goodmis.org> writes:
>> Fengguang Wu's build bot detected that if moduleloader.h is included in
>> a C file (used by ftrace and kprobes to access module_alloc() when
>> available), that it can fail to build if CONFIG_MODULES and
>> CONFIG_MODULES_USE_ELF_REL is not defined.
>>
>> This is because there's a printk() that dereferences struct module to
>> print the name of the module. But as struct module does not exist when
>> CONFIG_MODULES is not defined we get this error:
> 
> First, we have module_name() for exactly this.
> 
> Second, there are two places like this: you hit
> CONFIG_MODULES_USE_ELF_REL and not CONFIG_MODULES_USE_ELF_RELA.
> 
> (We could uninline them, and put them in module.c, but I think having
> them in the header is nice and self-documenting.)
> 
> So does this work for you?
> 
> Thanks,
> Rusty.
> PS.  Masami Hiramatsu, your review should have caught the second case,
>      at least :(

Oops, sorry, I missed the second one ... and this version seems good to me.

Thank you,

> 
> Subject: modules: Fix build error in moduleloader.h
> 
> Fengguang Wu's build bot detected that if moduleloader.h is included in
> a C file (used by ftrace and kprobes to access module_alloc() when
> available), that it can fail to build if CONFIG_MODULES and
> CONFIG_MODULES_USE_ELF_REL is not defined.
> 
> This is because there's a printk() that dereferences struct module to
> print the name of the module. But as struct module does not exist when
> CONFIG_MODULES is not defined we get this error:
> 
>    include/linux/moduleloader.h: In function 'apply_relocate':
>>> include/linux/moduleloader.h:48:63: error: dereferencing pointer to
>>> incomplete type  
>      printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> 								  ^
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Based-on-the-true-story-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> 
> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
> index 560ca53a75fa..7eeb9bbfb816 100644
> --- a/include/linux/moduleloader.h
> +++ b/include/linux/moduleloader.h
> @@ -45,7 +45,8 @@ static inline int apply_relocate(Elf_Shdr *sechdrs,
>  				 unsigned int relsec,
>  				 struct module *me)
>  {
> -	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> +	printk(KERN_ERR "module %s: REL relocation unsupported\n",
> +	       module_name(me));
>  	return -ENOEXEC;
>  }
>  #endif
> @@ -67,7 +68,8 @@ static inline int apply_relocate_add(Elf_Shdr *sechdrs,
>  				     unsigned int relsec,
>  				     struct module *me)
>  {
> -	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> +	printk(KERN_ERR "module %s: REL relocation unsupported\n",
> +	       module_name(me));
>  	return -ENOEXEC;
>  }
>  #endif
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com

Re: [PATCH] modules: Fix build error in moduleloader.h

[Steven Rostedt]

On Tue, 08 Jul 2014 09:10:09 +0930
Rusty Russell <rusty@rustcorp.com.au> wrote:
 
> Subject: modules: Fix build error in moduleloader.h
> 
> Fengguang Wu's build bot detected that if moduleloader.h is included in
> a C file (used by ftrace and kprobes to access module_alloc() when
> available), that it can fail to build if CONFIG_MODULES and
> CONFIG_MODULES_USE_ELF_REL is not defined.
> 
> This is because there's a printk() that dereferences struct module to
> print the name of the module. But as struct module does not exist when
> CONFIG_MODULES is not defined we get this error:
> 
>    include/linux/moduleloader.h: In function 'apply_relocate':
> >> include/linux/moduleloader.h:48:63: error: dereferencing pointer to
> >> incomplete type  
>      printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> 								  ^
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Based-on-the-true-story-by: Steven Rostedt <rostedt@goodmis.org>

Confirms-rustys-story-ends-the-same-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve


> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
>