linux-kernel - Re: [PATCH] ftrace/x86: Fix function graph tracer reset path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20160517070826.6b3464c53d69ba7af14d68f8@kernel.org>
Date:	Tue, 17 May 2016 07:08:26 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
	Borislav Petkov <bp@...e.de>, "H.J. Lu" <hjl.tools@...il.com>
Subject: Re: [PATCH] ftrace/x86: Fix function graph tracer reset path

On Mon, 16 May 2016 09:58:33 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> 
> Nice work Masami!
> 
> On Mon, 16 May 2016 21:32:50 +0900
> Namhyung Kim <namhyung@...nel.org> wrote:
> 
>     
> > >     -/* This is global to keep gas from relaxing the jumps */
> > >     -ENTRY(early_idt_handler)
> > >     +/* This is weak to keep gas from relaxing the jumps */
> > >     +WEAK(early_idt_handler)
> > >      	cld
> 
> > So IIUC, this -mshared option disables the optimization on branch
> > instructions and generates slightly bigger code.  Not sure how much
> > affected by this though.
> > 
> > Steve, do you think it's better to use this option?
> 
> Can we solve this by doing the same thing it did for the kernel?

Looks good to me :)

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks!

> 
> -- Steve
> 
> diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S
> index ed48a9f465f8..e13a695c3084 100644
> --- a/arch/x86/kernel/mcount_64.S
> +++ b/arch/x86/kernel/mcount_64.S
> @@ -182,7 +182,8 @@ GLOBAL(ftrace_graph_call)
>  	jmp ftrace_stub
>  #endif
>  
> -GLOBAL(ftrace_stub)
> +/* This is weak to keep gas from relaxing the jumps */
> +WEAK(ftrace_stub)
>  	retq
>  END(ftrace_caller)
>  


-- 
Masami Hiramatsu <mhiramat@...nel.org>