Re: [PATCH tracing/kprobes 1/7] x86/ptrace: Fix regs_get_argument_nth() to add correct offset

From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
	Ingo Molnar <mingo@elte.hu>, lkml <linux-kernel@vger.kernel.org>,
	systemtap <systemtap@sources.redhat.com>,
	DLE <dle-develop@lists.sourceforge.net>,
	Jim Keniston <jkenisto@us.ibm.com>,
	Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	Andi Kleen <ak@linux.intel.com>,
	Christoph Hellwig <hch@infradead.org>,
	"Frank Ch. Eigler" <fche@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Jason Baron <jbaron@redhat.com>,
	"K.Prasad" <prasad@linux.vnet.ibm.com>,
	Lai Jiangshan <laijs@cn.fujitsu.com>,
	Li Zefan <lizf@cn.fujitsu.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Tom Zanussi <tzanussi@gmail.com>
Subject: Re: [PATCH tracing/kprobes 1/7] x86/ptrace: Fix regs_get_argument_nth() to add correct offset
Date: Thu, 10 Sep 2009 21:43:06 -0400	[thread overview]
Message-ID: <1252633386.18996.60.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20090910235306.22412.31613.stgit@dhcp-100-2-132.bos.redhat.com>

On Thu, 2009-09-10 at 19:53 -0400, Masami Hiramatsu wrote:

> ---
> 
>  arch/x86/kernel/ptrace.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
> index a33a17d..caffb68 100644
> --- a/arch/x86/kernel/ptrace.c
> +++ b/arch/x86/kernel/ptrace.c
> @@ -150,7 +150,7 @@ static const int arg_offs_table[] = {
>  unsigned long regs_get_argument_nth(struct pt_regs *regs, unsigned int n)
>  {
>  	if (n < ARRAY_SIZE(arg_offs_table))
> -		return *((unsigned long *)regs + arg_offs_table[n]);
> +		return *(unsigned long *)((char *)regs + arg_offs_table[n]);

That definitely looks like a bug.

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve

>  	else {
>  		/*
>  		 * The typical case: arg n is on the stack.
> 
> 