linux-kernel - Re: [PATCH] x86, ftrace: Fix compiler warning in ftrace.c

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Message-ID: <1305648241.5456.743.camel@gandalf.stny.rr.com>
Date:	Tue, 17 May 2011 12:04:01 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	hpa@...or.com, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] x86, ftrace: Fix compiler warning in ftrace.c

On Thu, 2011-05-12 at 23:33 +0600, Rakib Mullick wrote:
> Due to commit dc326fca2b64 (x86, cpu: Clean up and unify the NOP selection infrastructure), we get the following warning:
> 
> arch/x86/kernel/ftrace.c: In function ‘ftrace_make_nop’:
> arch/x86/kernel/ftrace.c:308:6: warning: assignment discards qualifiers from pointer target type
> arch/x86/kernel/ftrace.c: In function ‘ftrace_make_call’:
> arch/x86/kernel/ftrace.c:318:6: warning: assignment discards qualifiers from pointer target type
>  
> ftrace_nop_replace() now returns const unsigned char *, so change its associated function/variable to its compatible type to keep compiler clam.
> 
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
> ---
> 
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 0ba15a6..d2d82cf 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -266,8 +266,8 @@ static const unsigned char *ftrace_nop_replace(void)
>  }
>  
>  static int
> -ftrace_modify_code(unsigned long ip, unsigned char *old_code,
> -		   unsigned char *new_code)
> +ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
> +		   unsigned const char *new_code)
>  {
>  	unsigned char replaced[MCOUNT_INSN_SIZE];
>  
> @@ -290,7 +290,7 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
>  		return -EINVAL;
>  
>  	/* replace the text with the new text */
> -	if (do_ftrace_mod_code(ip, new_code))
> +	if (do_ftrace_mod_code(ip, (void *)new_code))

Instead of typecasting, why not make new_code const void *?

This would probably trickle down to change __probe_kernel_write() which
would not be a bad thing.

-- Steve

>  		return -EPERM;
>  
>  	sync_core();
> @@ -301,7 +301,7 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
>  int ftrace_make_nop(struct module *mod,
>  		    struct dyn_ftrace *rec, unsigned long addr)
>  {
> -	unsigned char *new, *old;
> +	unsigned const char *new, *old;
>  	unsigned long ip = rec->ip;
>  
>  	old = ftrace_call_replace(ip, addr);
> @@ -312,7 +312,7 @@ int ftrace_make_nop(struct module *mod,
>  
>  int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
>  {
> -	unsigned char *new, *old;
> +	unsigned const char *new, *old;
>  	unsigned long ip = rec->ip;
>  
>  	old = ftrace_nop_replace();
> 


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