linux-kernel - Re: [PATCH v2 09/11] x86/unwind/orc: Prevent unwinding before ORC initialization

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Date:   Sat, 25 Apr 2020 05:12:47 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        Dave Jones <dsj@...com>, Jann Horn <jannh@...gle.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 09/11] x86/unwind/orc: Prevent unwinding before ORC
 initialization

On Sat, Apr 25, 2020 at 05:03:08AM -0500, Josh Poimboeuf wrote:
> If the unwinder is called before the ORC data has been initialized,
> orc_find() returns NULL, and it tries to fall back to using frame
> pointers.  This can cause some unexpected warnings during boot.
> 
> Move the 'orc_init' check from orc_find() to __unwind_init(), so that it
> doesn't even try to unwind from an uninitialized state.
> 
> Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Reviewed-by: Miroslav Benes <mbenes@...e.cz>

I got a weird error when sending this one:

  4.7.1 Error: too much mail from 10.10.114.29

If anybody didn't get it, let me know and I can bounce it.

> ---
>  arch/x86/kernel/unwind_orc.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> index e9f5a20c69c6..cb11567361cc 100644
> --- a/arch/x86/kernel/unwind_orc.c
> +++ b/arch/x86/kernel/unwind_orc.c
> @@ -148,9 +148,6 @@ static struct orc_entry *orc_find(unsigned long ip)
>  {
>  	static struct orc_entry *orc;
>  
> -	if (!orc_init)
> -		return NULL;
> -
>  	if (ip == 0)
>  		return &null_orc_entry;
>  
> @@ -591,6 +588,9 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
>  void __unwind_start(struct unwind_state *state, struct task_struct *task,
>  		    struct pt_regs *regs, unsigned long *first_frame)
>  {
> +	if (!orc_init)
> +		goto done;
> +
>  	memset(state, 0, sizeof(*state));
>  	state->task = task;
>  
> -- 
> 2.21.1
> 

-- 
Josh