linux-kernel - Re: [PATCH 1/3] x86/entry: Fix idtentry unwind hint

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Date:   Wed, 25 Oct 2017 14:07:38 -0700
From:   Andrei Vagin <avagin@...tuozzo.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>, torvalds@...ux-foundation.org,
        peterz@...radead.org, hpa@...or.com, tglx@...utronix.de,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 1/3] x86/entry: Fix idtentry unwind hint

Hi Josh,

Here is one more warning:
[    5.852094] WARNING: can't dereference iret registers at ffffb6ce01b7ffe0 for ip entry_SYSCALL_64_fastpath+0xa/0xc2

[avagin@...top linux]$ git describe tip/auto-latest
v4.14-rc6-471-g376214a8543d

On Fri, Oct 20, 2017 at 11:21:33AM -0500, Josh Poimboeuf wrote:
> This fixes the following ORC warning in the 'int3' entry code:
> 
>   WARNING: can't dereference iret registers at ffff8801c5f17fe0 for ip ffffffff95f0d94b
> 
> The ORC metadata had the wrong stack offset for the iret registers.
> 
> Their location on the stack is dependent on whether the exception has an
> error code.
> 
> Reported-and-tested-by: Andrei Vagin <avagin@...tuozzo.com>
> Fixes: 8c1f75587a18 ("x86/entry/64: Add unwind hint annotations")
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> ---
>  arch/x86/entry/entry_64.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 49167258d587..f6cdb7a1455e 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -808,7 +808,7 @@ apicinterrupt IRQ_WORK_VECTOR			irq_work_interrupt		smp_irq_work_interrupt
>  
>  .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
>  ENTRY(\sym)
> -	UNWIND_HINT_IRET_REGS offset=8
> +	UNWIND_HINT_IRET_REGS offset=\has_error_code*8
>  
>  	/* Sanity check */
>  	.if \shift_ist != -1 && \paranoid == 0
> -- 
> 2.13.6
>