linux-kernel - Re: [PATCH] powerpc/interrupt: Do not call single_step

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Date:   Thu, 12 Aug 2021 20:01:08 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        fthain@...ux-m68k.org, Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>, userm57@...oo.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/interrupt: Do not call single_step_exception()
 from other exceptions

Excerpts from Christophe Leroy's message of August 11, 2021 2:13 am:
> single_step_exception() is called by emulate_single_step() which
> is called from (at least) alignment exception() handler and
> program_check_exception() handler.
> 
> Redefine it as a regular __single_step_exception() which is called
> by both single_step_exception() handler and emulate_single_step()
> function.
> 

Reviewed-by: Nicholas Piggin <npiggin@...il.com>

> Fixes: 3a96570ffceb ("powerpc: convert interrupt handlers to use wrappers")
> Cc: stable@...r.kernel.org
> Cc: Stan Johnson <userm57@...oo.com>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Finn Thain <fthain@...ux-m68k.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/kernel/traps.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index dfbce527c98e..d56254f05e17 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -1104,7 +1104,7 @@ DEFINE_INTERRUPT_HANDLER(RunModeException)
>  	_exception(SIGTRAP, regs, TRAP_UNK, 0);
>  }
>  
> -DEFINE_INTERRUPT_HANDLER(single_step_exception)
> +static void __single_step_exception(struct pt_regs *regs)
>  {
>  	clear_single_step(regs);
>  	clear_br_trace(regs);
> @@ -1121,6 +1121,11 @@ DEFINE_INTERRUPT_HANDLER(single_step_exception)
>  	_exception(SIGTRAP, regs, TRAP_TRACE, regs->nip);
>  }
>  
> +DEFINE_INTERRUPT_HANDLER(single_step_exception)
> +{
> +	__single_step_exception(regs);
> +}
> +
>  /*
>   * After we have successfully emulated an instruction, we have to
>   * check if the instruction was being single-stepped, and if so,
> @@ -1130,7 +1135,7 @@ DEFINE_INTERRUPT_HANDLER(single_step_exception)
>  static void emulate_single_step(struct pt_regs *regs)
>  {
>  	if (single_stepping(regs))
> -		single_step_exception(regs);
> +		__single_step_exception(regs);
>  }
>  
>  static inline int __parse_fpscr(unsigned long fpscr)
> -- 
> 2.25.0
> 
>