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

From: Steven Rostedt
Date: Tue May 17 2011 - 12:04:09 EST


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 âftrace_make_nopâ:
> arch/x86/kernel/ftrace.c:308:6: warning: assignment discards qualifiers from pointer target type
> arch/x86/kernel/ftrace.c: In function âftrace_make_callâ:
> 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@xxxxxxxxx>
> ---
>
> 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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