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Subject: Re: [PATCH tracing/kprobes 1/7] x86/ptrace: Fix  regs_get_argument_nth() to add correct offset
From: Steven Rostedt <rostedt@goodmis.org>
Reply-To: 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>
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Date: Fri, 11 Sep 2009 01:43:00 -0000
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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.
> 
>